INTRODUCTION TO THE SKULL
Gross Anatomy, K. W. Chung, 6th edition: pp. 352-357
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 886-905; 6th edition: pp. 822-842
Development of the skull
- The base of the skull develops by endochondral
- The brain and cranial nerves develop before the skull,
so when the chondrocranium develops, its components form around
the nerves and form foramina.
- The chondrocranium ossifies from a number of centers.
- The last piece of cartilage to ossify is between the
body of the sphenoid bone and the occipital bone, just anterior to the
foramen magnum: this is the spheno-occipital synchondrosis. Its
epiphyseal plate exists for the growth in length of the base of the skull
and it ossifies at age 25.
The bones of the calvarium ossify by intramembranous
- The bones of the calvarium also ossify from separate
centers and they meet to form sutures (Clemente plate 482 fig. 756;
Grant p. 608-609; Netter 3e 2-11; 4e 2-12). The process is completed at about
The bones of the face are partly basal and partly calvarial
bones so they ossify both by intramembranous and endochondral ossification.
The bones of the cranium and the underlying lobes of the
brain have the same name (Clemente plate 481 fig. 754; Grant p. 610-615,
3e 2-7, 4e 4 &105):
- The frontal bone (which houses the frontal lobe
of the brain) ossifies from 2 centers and there are right and left frontal
bones at birth (Clemente plates 484-485; Grant p. 608-609;
Netter 3e 11, 4e 12). The metopic suture separating the 2 frontal bones
normally ossifies, leaving one large frontal bone.
- The parietal bones are separated from each other
by the sagittal suture (Clemente plate 482 fig. 756; Grant p. 614-615; Netter
3e 7, 4e 7) and from the frontal bone by the coronal suture
(Clemente plate 482 fig. 756; Grant p. 612-613; Netter 3e 4; 4e 4-7).
At birth, the anterior fontanelle (Clemente plate 485
fig. 762; Grant p. 608-609; Netter 3e 11, 4e 12) is a diamond-shaped area
between the 2 frontal bones and the 2 parietal bones. It pulsates and bulges
when the baby cries. It closes by 18 months to 2 years and is then known
as the bregma (Clemente plate 482 fig. 756; Grant p. 614; Netter 3e 7,
- The parietal bones and the occipital bone meet
at the posterior fontanelle (Clemente plate 485; Grant p. 609;
Netter 3e 11; 4e 12) which becomes lambda, along the lambdoid suture
in the adult (Clemente plate 482 fig. 756; Grant p. 614; Netter 3e 7,
- The side wall of the skull is completed by the squamous
part of the temporal bone and the greater wing of the
sphenoid bone, at the pterion (Clemente plate 481; Grant
p. 612-613; Netter 3e 4, 4e 4).
- This is located 4 cm above the midpoint of the zygomatic
arch and is the site of surgical exploration for the middle meningeal
artery (Grant p. 635, Netter 3e 6, 4e 6).
- The flat bones of the skull (frontal, parietal, temporal
and occipital) are formed by a sandwich of diploë (cancellous
bone containing red bone marrow) between 2 layers of compact bone (Clemente
plate 486 fig. 765; Grant p. 634; Netter 3e 96, 4e 102).
- The bones are drained by diploic veins; there are usually
4 on each side: frontal, anterior temporal, posterior temporal and
occipital (Clemente plate 486 fig. 764; Grant p. 634;
Netter 3e 94, 4e 99 & 102) which open into the nearest convenient venous sinus.
- The flat bones of the skull are also pierced by emissary
foramina transmitting emissary veins connecting veins of the
scalp with the dural venous sinuses inside the skull (this is a possible
route for the spread of infection). They may be seen in the parietal bone
or in the temporal bone posterior to the external auditory meatus (Grant
785; Netter 3e 94, 96; 4e 7, 99 & 102).
In an X-ray of the skull, it is necessary to differentiate
the following normal structures from fractures (Grant p. 620-621; Netter 3, 5):
- the sutures (possible metopic suture),
- the diploic veins,
- and the middle meningeal artery.
The pineal gland near the center of the brain may contain
corpora aranaceae (calcareous granules) and it can be used to detect
displacement of the brain.
- The occipital bone (Clemente plate 482 fig. 757;
Grant p. 614; Netter 3e 8, 4e 6 & 8):
- The external occipital protuberance is located
inferior to lambda.
- The superior nuchal lines run lateral from the
external occipital protuberance and the inferior nuchal lines are
The cranial fossae (Clemente plates 496-497; Grant p.
618-619; Netter 9):
From anterior to posterior, 3 fossae form 3 successive
steps leading down to the foramen magnum.
1) Anterior cranial fossa:
- Orbital plate of the frontal
- Lesser wing of the sphenoid
- The cribriform plate of the ethmoid with the crista
galli transmits olfactory nerves from the upper
part of the nasal cavity; this is a possible route for infection or escape
route for CSF in skull fractures.
- Optic canal for transmission
of optic nerve.
- Anterior clinoid processes
projecting posteriorly to the posterior clinoid processes of the
2) Middle cranial fossa
- is formed by the greater wing of the sphenoid
bone and the temporal bone. It is occupied by the temporal lobe
of the brain.
- The greater wings and the body of the sphenoid bone form
a butterfly shape.
- The most posterior tip of the greater wing contains the
- Anterior to the foramen spinosum is the foramen ovale
and then the foramen rotundum. The foramen rotundum leads to the
- The superior orbital fissure is a gap between
the lesser wing and the greater wing of the sphenoid leading to the orbit,
just lateral to and below the optic nerve.
- The body of the sphenoid bone contains the hypophyseal
fossa for the pituitary gland. This fossa is also called the sella
turcica and it is shaped like a 4-poster bed (clinoid processes; clinical
= patient is in bed).
- Its maximum length is 14 mm and its depth is 8 mm. Measurements
are important because pituitary tumors cause ballooning of the sella.
- The foramen lacerum is located lateroposterior
to the sella.
The middle meningeal artery enters the skull through
the foramen spinosum and its groove can be traced laterally and anteriorly
on the squamous portion of the temporal bone before dividing into anterior
and posterior (frontal and parietal) branches.
- The anterior branch crosses the greater wing at the pterion
and then breaks up into branches that run superiorly and posteriorly.
- The posterior branch runs posteriorly supplying bone
3) Posterior cranial fossa
- is formed by the temporal bone and the occipital bones.
- houses the cerebellum.
The posterior cranial fossa contains:
- the foramen magnum for the
lower end of the medulla.
- The clivus, anterior to the
foramen magnum, which leads up to the body of the sphenoid bone.
- The transverse sinus
- The sigmoid sinus which ends
at the jugular foramen.
- The hypoglossal canal (anterior condylar) canal and the posterior condylar canal.
- The internal auditory meatus
on the posterior aspect of petrous temporal bone.
- The arcuate eminence on the
petrous portion of the temporal bone, marking the position of the superior
The superior sagittal sinus
(Grant p. 613; Netter 97-98) is continuous with
the right transverse sinus whereas the smaller straight sinus
is continuous with the left transverse sinus. The right jugular foramen
is thus usually larger than the left.
The exterior base of the skull (Clemente plate
498; Grant p. 616-617; Netter 8).
- Recognize the above- mentioned foramina from the exterior.
- The spine of the sphenoid
bone is near the foramen spinosum.
- The jugular foramen is occupied by the jugular bulb
(for expansion of the internal jugular vein) in life.
- The styloid process, the mastoid process and the stylomastoid
foramen between the 2 processes.
- Anterior to the jugular foramen and in the petrous portion
of the temporal bone lies the carotid canal.
- The spine of the sphenoid bone lies medial to the mandibular
fossa. The mandibular fossa articulates with the head of the mandible
to form the temporomandibular (TMJ) joint.
- The foramen ovale lies at
the base of the lateral pterygoid plate.
- The medial pterygoid plate
(with the pterygoid hamulus at its base) and the lateral pterygoid
plate are parts of the sphenoid bone.
- The inferior orbital fissure leads anteriorly
from the pterygoid region to the orbit.
- The hard palate is formed
by the palatine process of the maxilla and by the horizontal
plate of the palatine bone. There are 3 foramina in the horizontal
plate, the larger being the greater palatine foramen.
- The vomer bone in the posterior
opening (the choanae) of the nasal cavity is attached by a fibrous
joint to the undersurface of the body of the sphenoid.
The internal carotid artery (Clemente plate 491 fig.
772, plate 497; Grant p. 644-645; Netter 3e 130, 4e 136):
- enters the carotid canal,
- runs anteromedially to the foramen lacerum
- and then runs superoanteriorly to enter the cranium through
the internal orifice of the foramen lacerum.
- It then turns anteriorly and lies on the side of the
sella turcica. It now lies in the cavernous sinus.
- It then turns superoposteriorly, medial to the anterior
clinoid process and breaks up into 3 branches.
THE SKELETON OF THE FACE
The following structures are found in the orbit (Clemente plate
480; Grant p. 650; Netter 3e 2, 4e 2 &4):
- the superior orbital fissure
- the optic canal
- The greater and lesser wings of the sphenoid.
- The zygomatic bone and the (hollow) maxilla are
in the lateral wall of the orbit.
- The ethmoid bone and the small fragile lacrimal
bone are in the medial wall .
The supraorbital, infraorbital and mental foramina
(Clemente plate 480; Grant p. 610-611; Netter 2) lie on
a vertical line and transmit the ophthalmic, maxillary and
mandibular divisions of the trigeminal (Vth cranial) nerve (Clemente
plate 542; Grant p. 630-631; Netter 3e 116, 4e 122).
SUPERFICIAL FACE AND SCALP
Gross Anatomy, K. W. Chung, 6th edition: pp. 337 – 344, 347-348
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 906-908; 933-957; 6th edition: pp. 842-865
Anatomy Dissector, 2nd edition: pp. 303-315
Dissector, P.W. Tank, 14th edition: pp. 199-210
2 main groups of muscle are located on the face:
- muscles of facial expression
innervated by the facial nerve (cranial nerve VII)
- and muscles of mastication supplied by the mandibular
division of the trigeminal nerve (cranial nerve V).
Muscles of facial expression (innervated by the facial
nerve) are superficial muscles which can move skin
and fascia in various directions. They are also dilators and sphincters
for the various orifices in the face region. The 2 major groups are around
the eye and the mouth.
Around the eye:
The sphincter is the orbicularis oculi (Clemente
plate 462 fig. 728; Grant p. 626, 628-629; Netter 3e 22, 4e 26) which has:
- a palpebral part in the eye lid (closes eye gently)
- and an orbital part which surrounds the orbit
and blends in with the anterior belly of occipitofrontalis (closing the
eye forcibly). The orbital part causes radiating skin wrinkles from the
lateral corner of the eye.
The dilator is the levator palpebrae superioris (Clemente
plate 509 fig. 801; Grant p. 654--655; Netter 3e 77, 4e 84) innervated
by the oculomotor nerve (cranial nerve III) and postganglionic sympathetic
fibers from the superior cervical ganglion.
Around the mouth:
The sphincter is the orbicularis oris (Clemente
plate 462 fig. 728; Grant p. 630; Netter 3e 22, 4e 26) which closes
the lips but can also protrude the lips as in whistling, or kissing.
The dilators are:
- Levator labii superioris alaeque nasi ("Grace"
muscle; Clemente plate 462 fig. 728; Grant p. 629; Netter 3e 22, 4e
- Levator labii superioris
- Levator anguli oris
- Zygomaticus minor
- Zygomaticus major
- Platysma (risorius; Clemente plate 463 fig. 729; Grant
p. 746; Netter 3e 22, 4e 26)
- Depressor anguli oris
- Depressor labii inferioris
The buccinator (Clemente plates 466-467; Grant
p. 666; Netter 3e 22, 50, 4e 26) is the
main muscle of the cheek and it keeps the cheeks in contact with the gums
so that food does not accumulate in the vestibule of the mouth.
*Bell's Palsy: lesions of the
facial nerve (Cranial nerve VII)
- Drainage of tears and dribbling of saliva due to paralysis
of the 2 main orbicularis muscles. Paralysis of buccinator will lead to
accumulation of food in the vestibule.
- Test by asking patients to screw up the eye (loss of
muscle tone causes the normal skin folds to disappear on the side of the
lesion), to smile or to whistle.
- Muscles must be supported during recovery or they will
stretch under gravity and cause a permanent asymmetry of the face.
Muscles of mastication (Grant p. 672-673; Netter 3e 50, 4e 54-55) developed
from the first branchial arch and are innervated by branches from
the anterior branch of the mandibular division of the trigeminal nerve (Grant p.
3e 116, 4e 122):
- The masseter (Clemente plate 466; Grant p. 626-627;
Netter 3e 50, 4e 54) muscle attaches to the zygomatic arch and the
outer surface of the mandible near the angle. It is composed of a superficial
and deep part. The masseter closes the jaw and is innervated by the masseteric
nerves passing through the mandibular notch.
- The temporalis muscle attaches from the
lateral side of the skull below the temporal line to coronoid process and
anterior border of the ramus of the mandible almost as far as the third
molar tooth (Grant p. 666-667; Netter 3e 50, 4e 54). The temporalis muscle closes the jaw and is innervated by
the deep temporal nerves.
- The lateral pterygoid muscle (Clemente plate 470;
Grant p. 670; Netter 3e 51, 4e 55) attaches from the lateral surface
of the lateral pterygoid plate to the neck of mandible and the intraarticular
disc of the temporomandibular joint. It is the only muscle
in this group to open the jaw.
- The medial pterygoid is attached from the medial
surface of the lateral pterygoid plate to the deep surface of the mandible
(at the angle of the mandible) opposite to the attachment of the masseter
muscle. The angle of the mandible thus lies between these 2 muscles. The
medial pterygoid muscle closes the jaw.
- Both pterygoid muscles are innervated by the pterygoid
The facial artery (Clemente 468,
474; Grant p. 632; Netter 3e 19, 4e 23):
- provides the main blood supply.
- passes over the lower border of mandible at the anterior
border of the masseter (feel the pulse).
- has a tortuous course to allow for movement of the face,
first to the angle of the mouth and then up at the side of the nose to
the medial angle of the eye.
- gives off upper and lower labial branches as well as
numerous other branches to the face. Free anastomoses on the same side
as well as across the midline.
The facial vein has a straighter path and communicates
with deeper veins such as veins of the orbit (leading to the cavernous sinus
within the skull (Clemente plates 468, 475; Grant p. 633; Netter 3e 19,
81, 4e 23, 85) at the medial angle of the eye and the pterygoid venous
plexus. The central face area is thus a "danger area" for an infection
on the face to travel into the skull or into the deep face.
The superficial temporal artery (Clemente 468, 474;
Grant p. 626-627, 632; Netter 3e 19, 4e 23) is a branch of the external
carotid artery. Its pulse can be felt in front of the tragus of the ear.
Above the ear it divides into anterior and posterior branches. It anastomoses
with the facial artery.
Parotid gland (Grant p. 627; Netter 3e 19, 4e 25, 61)
- This major salivary gland becomes inflamed with the mumps.
It is enclosed in a split layer of deep cervical fascia so that swelling
of the gland leads to increase in pressure and pain. The medial thickening
in this capsule forms the stylomandibular ligament (Clemente
plate 468, plate 472 fig. 740; Grant p. 674; Netter 3e 12, 14, 4e 16).
- The duct (Clemente plate 466; Grant p. 627;
Netter 3e 17, 4e 25) leaves the anterior border, crosses the masseter muscle,
turns around the anterior border of the muscle and pierces the buccinator
muscle to enter the mouth opposite the 2nd upper molar tooth. It can be
rolled under the fingers when the masseter is contracted by clenching the
teeth. It is in line with the tragus of the ear.
- The gland occupies the space between the sternocleidomastoid
and the back of the mandible and molds itself to all adjacent structures.
3 important structures passes through the parotid gland
from superficial to deep: the facial nerve, the retromandibular vein and
the external carotid artery.
The facial nerve (Clemente plate 469; Grant p.
627, 830; Netter 3e 21, 4e 25):
- from the stylomastoid foramen,
- gives off a posterior auricular branch to the occipital
belly of occipitofrontalis,
- divides within the parotid gland forming an intraglandular
- 5 branches emerge from the anterior border of the gland:
temporal, zygomatic, buccal, marginal mandibular and cervical (Palm
of hand on parotid gland with 5 fingers spread onto the face).
- *The marginal mandibular branch runs below the
border of the mandible to supply the muscles of the chin. Incision should
always be made a finger's width below it.
The retromandibular vein (Clemente plate 477; Grant
p. 633; Netter 3e 66, 4e 61)
- is formed in the gland by the union of the maxillary
and superficial temporal veins,
- emerges from the gland near the angle of the mandible
- divides into 2 with the anterior branch joining the facial
vein and draining into the internal jugular vein,
- the posterior branch joins with the small posterior
auricular vein to form the external jugular vein (Clemente plate
475; Grant p. 662; Netter 3e 66, 4e 61).
The external carotid artery (Clemente plate 477;
Grant p. 632; Netter 3e 65, 4e 61 & 69)
- divides in the substance of the parotid gland into the
maxillary and superficial temporal arteries,
- The maxillary artery runs deep to the neck of mandible
to enter the infratemporal region,
- The superficial temporal artery lies in front of the
ear and divides into anterior (frontal - side of forehead) and posterior (parietal
- side of
scalp) branches (Clemente plate 474; Grant p. 626-627; Netter 3e 19, 4e 23).
The scalp is attached to the zygomatic arch laterally
(Clemente plate 466; Grant p. 626; Netter 3e 22, 4e 4 & 26).
- S = skin
- C = connective tissue
- A = aponeurosis referring
to the Galea aponeurotica (epicranial aponeurosis). This aponeurosis
belongs to the occipitofrontalis muscle located antero- and
posteriorly. The posterior attachment of this muscle is to the occipital
bone above the superior nuchal line.
- L = space, this is a plane
of cleavage for injury and the spread of blood which can travel as far
as the zygomatic arch and into the upper eyelids. The first 3 layers of
scalp remain attached to each other in case of cleavage.
- P = periosteum
Blood vessels and nerves of the scalp.
Anastomoses in the scalp are formed by the following arteries
from anterior to posterior (Clemente plates 468, 469; Grant p. 632; Netter 3e 19,
- Supratrochlear artery
- Supraorbital artery
- Superficial temporal artery
- Posterior auricular artery
- Occipital artery
The scalp is extremely vascular and bleeds profusely when
cut. Due to anastomoses, there is no single vessel to compress but bleeding
may stop by direct pressure on or around the wound.
Emissary veins (valveless) may spread infections from the
scalp to the intracranial cavity. Normal blood flow is from inside to outside
of the skull.
The following nerves innervate the scalp from anterior
to posterior (Clemente plate 469; Grant p. 634; Netter 3e 20, 4e 24):
- 2 branches from the ophthalmic division of the trigeminal
nerve (cranial nerve V): the supratrochlear and suprorbital nerves
- 1 branch from the maxillary division of the trigeminal
nerve: the zygomaticotemporal nerve
- 1 branch from the mandibular division of the trigeminal
nerve: the auriculotemporal nerve
Branches of the trigeminal nerve lie anterior to the external
ear or auricle
Posterior to the auricle:
- The lesser occipital nerve (C2,3)
- The greater occipital nerve (C2)
- The third occipital nerve (C3)
THE PAROTID REGION AND THE
Gross Anatomy, K. W. Chung, 6th edition: pp. 344-352
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 976-987; 6th edition: pp. 914-928
Anatomy Dissector, 2nd edition: pp. 316-327
Dissector, P.W. Tank, 14th edition: pp. 210-214
The zygomatic bone has processes related to the frontal,
maxillary and temporal bones (Clemente plates 480, 481; Grant p. 610-613; Netter
3e 2, 4e 4)
Bony landmarks on the mandible (Grant p. 664-665; Netter 3e 4,
13, 4e 15):
- The body is formed by the fusion of the right and left sides
at 2 years (Clemente plate 484 fig. 760).
- 2 rami.
- Alveolar process for the teeth.
- Coronoid process.
- Condylar process with head (in temporomandibular joint)
and neck (Clemente plates 481, 542, 543; Grant p. 664-665;
Netter 3e 14, 4e 16).
- Mandibular notch.
- The mandibular foramen and canal lie medial to the mandibular
angle. They contain the inferior alveolar nerve (V3) and vessels.
- The lingula serves as attachment point for the sphenomandibular
The PAROTID BED (Clemente plate 468; Grant p.
662-663; Netter 19) is defined:
- Posteriorly by the mastoid
process with the origins of the sternocleidomastoideus and the posterior
belly of the digastric (Clemente plate 476; Grant p. 662; Netter 3e 23,
- Medially by the styloid process
of the temporal bone and the stylohyoid muscle (Clemente plates 472
fig. 740, plate 476; Grant p. 663; Netter 3e 23, 4e 27). Styloglossus
(Clemente plate 538; Grant p. 788-789; Netter 3e 55, 4e 59)
and stylopharyngeus are also medial to the parotid bed within the lateral
- Anteriorly by the sphenomandibular
and stylomandibular ligaments (Clemente plate 472; Grant p. 674; Netter
3e 14, 4e 16) as well as the fasciae of the medial pterygoid
(Clemente plates 470, 471; Grant p. 668; Netter 3e 51, 4e 55) and
masseter muscles (Clemente plates 468, 469; Grant p. 666-667; Netter 3e 50,
- Superiorly by the zygomatic
- Inferiorly by the posterior
belly of the digastric.
*The deep cervical fascia (Clemente plate 446;
Grant p. 747; Netter 3e 31, 4e 24, 35) envelops the parotid gland and
is weakest between the styloid process and spine of the sphenoid:
- Infections may spread from the parotid fascia into the
lateral pharyngeal space which communicates with the retropharyngeal space
(Clemente plate 549; Grant p. 747; Netter 3e 31, 4e 35) between
the pharynx and prevertebral musculature.
- Infections may track inferiorly through the neck and
into the thorax, along the course of the carotid sheath, between visceral
and prevertebral fasciae.
The parotid gland is innervated by the lesser
petrosal branch (secretomotor) of the IXth (glossopharyngeal) nerve
(Clemente plate 527 fig. 836; Grant p. 835; Netter 3e 119, 4e 125).
Preganglionic parasympathetic fibers from the tympanic
plexus in the middle ear (Clemente plate 527; Grant p. 835;
Netter 3e 89, 119, 4e 125, 134):
- enter the middle cranial fossa by a hiatus on the anterior
aspect of the petrous bone,
- run through the periosteal dura
- and exit the middle cranial fossa through the foramen
ovale with V3.
- The preganglionic fibers synapse in the otic ganglion
on the medial aspect of V3.
- The postganglionic fibers join with the auriculotemporal
nerve to run to the parotid gland.
- The auriculotemporal nerve thus carries secretomotor
fibers of IXth and sensory fibers of V3 for pain in the gland.
The sympathetic innervation is from the superior
cervical ganglion via the arteries and it controls the fluid content of
The INFRATEMPORAL REGION (Clemente
plates 478, 479; 481 fig. 755; Grant p. 664-665; Netter 3e 8, 4e 8, 10, 14) is:
- inferior to the temporal fossa and zygomatic arch
- and deep to the ramus of the mandible.
- It stretches from the parotid fascia posterior to the
mandibular ramus to the tuberosity of the maxilla.
The lateral wall is formed
by the medial aspect of ramus of the mandible
The anterior wall is formed
- Body and tuberosity of the maxilla, deep to zygoma and
zygomatic process of the maxilla.
- The pterygomaxillary fissure or
sphenopalatine foramen (Clemente plate
481 fig. 755; Grant p. 665; Netter 3e 12, 4e 14) may be seen in the
medial aspect of this anterior wall, opening into the more medial pterygopalatine
- The inferior orbital fissure may also be seen.
- Inferior to the pterygomaxillary fissure is the hamulus
serving as attachment point for the pterygomandibular raphé.
It serves as the common site of origin for the buccinator and the superior
constrictor muscle and runs from the hamulus to the upper 1/5 of the mylohyoid
The medial wall is formed by
- lateral pterygoid plate,
- superior constrictor muscle,
- levator and tensor palati muscles.
The roof of the infratemporal fossa is formed by:
- the greater wing of the sphenoid anteriorly
- and the squamous portion of the temporal bone posteriorly.
The infratemporal crest is on the anterior aspect
of the undersurface of the greater wing of the sphenoid and serves as an
attachment site for the upper head of the lateral pterygoid. Posterior to
this infratemporal crest are:
- The foramen ovale for transmission of V3 and the
lesser petrosal nerve (from IXth) from the middle cranial fossa to the
infratemporal fossa (Clemente plates 498, 499; Grant p. 669;
Netter 8, 10);
- The foramen spinosum for transmission of the middle
meningeal artery from the infratemporal fossa to the middle cranial fossa.
Contents of the infratemporal fossa
The key structure for orientation is the lateral pterygoid
muscle (Clemente plate 478; Grant p. 668; Netter 3e 51, 4e 55).
This muscle has 2 heads (Clemente plate 470; Grantp.
668, 672; Netter 3e 51, 4e 55):
- from the infratemporal crest to the capsule of the interarticulating
disc of the TMJ
- and from the lateral aspect of the lateral pterygoid
plate to the neck of the mandible.
*Protrusive actions of the lateral pterygoid muscle are
used to test V3: deviation is TOWARDS the side of the lesion.
The maxillary artery lies lateral to the lateral
pterygoid muscle (Clemente plates 478, 479; Grant p. 668-670;
Netter 3e 36, 4e 40).
- From the external carotid artery in the parotid gland,
the artery enters the posterior aspect of the infratemporal fossa by passing
deep to the neck of the mandibular condyle.
- It crosses the lateral side of the lateral pterygoid
muscle and enters the pterygomaxillary fissure.
- It is divided into a first or mandibular part, second
or pterygoid part and third or pterygopalatine part.
- The mandibular and pterygoid parts are associated with
the infratemporal fossa
- and the pterygopalatine part is associated with the deep
face and the nasal region.
The mandibular division of the maxillary artery
has 5 branches, all entering a canal:
- The middle meningeal artery is the principal artery
to periosteal dura of the cranial cavity.
- The inferior alveolar artery runs into
the mandibular foramen and supplies the teeth and the mandible. The angle
of the mandible is poorly supplied and may suffer from alveolar osteitis
- The deep auricular artery supplies the auditory
- The anterior tympanic artery accompanies the chorda
tympani through the petrotympanic fissure to reach the middle ear.
- The accessory meningeal branch (inconsistent)
enters the foramen ovale and supplies the trigeminal ganglion and the surrounding
The pterygoid portion of the maxillary artery has
5 branches supplying muscles of mastication in the infratemporal
- 2 deep temporal branches,
- a masseteric branch,
- a pterygoid branch,
- and a buccal branch.
The pterygoid plexus of veins (Clemente plate
477; Grant p. 613; Netter 3e 66, 4e 70) follows the maxillary
artery in the infratemporal fossa, lying mostly lateral to the artery.
- This is a route for infection: the veins have connections
with the cavernous sinus via the deep facial, inferior ophthalmic
and emissary veins in the sphenoid bone.
- Veins of the head have NO valves.
Branches of V3 (Mandibular division of the trigeminal
I. Anterior division (Clemente plates 478, 479; Grant
p. 667-669, 671; Netter 3e 42, 67, 4e 46, 71):
- Masseteric branches
- Posterior and anterior temporal branches to the temporalis
- The nerve to the medial pterygoid
- The nerve to the lateral pterygoid
- The buccal nerve
The buccal nerve of V3 :
- passes between the 2 heads of the lateral pterygoid muscle.
- continues into the cheek on the lateral surface of the
- is the terminal branch of the anterior division
- is sensory to the mucosa of the inside of the cheek and
the lower gums around the molar teeth.
- does not supply the motor innervation of the buccinator.
II. Posterior division:
- leaves V3 just inferior to the foramen ovale and projects
posteriorly in the infratemporal fossa parallel to the roof.
- The initial segment encircles the middle meningeal artery
as the artery ascends to enter the foramen spinosum and receives postganglionic
parasympathetic fibers from the otic ganglion which are secretomotor to
the parotid gland.
- Passes medial to the head of the mandibular condyle and
sends a sensory branch to the TMJ.
- Enters the deep portion of the parotid gland giving sensory
branches as well as parasympathetic postganglionic fibers from the otic
- Its terminal portion accompanies the superficial temporal
artery and innervates the upper half of pinna of the ear and part of the
temporal region (Pain and general sensation).
Inferior alveolar (dental) nerve (Clemente plate 542
fig. 866; Grant p. 828-829; Netter 3e 67, 4e 71)
- From the foramen ovale to the mandibular foramen on the
medial aspect of the ramus of the mandible, lying between the medial and
lateral pterygoid muscles and just posterior to the lingual nerve (Clemente
plate 478; Grant p. 669, 671; Netter 3e 67, 4e 71).
- The branch to mylohyoid and to the anterior belly of
the digastric is the only branch in the infratemporal fossa.
It first lies in the mylohyoid groove, and then on the inferior aspect
of the mylohyoid to reach the anterior belly of the digastric muscle (Clemente plate 479;
Grant p. 681; Netter 3e 67, 4e 71).
- The portion of the inferior alveolar nerve in the ramus
of the mandible is entirely sensory to lower teeth, lower gums and the
mucosa of the lower lips.
- It exits the mandible as the mental nerve (Clemente
plate 542; Grant p. 630, 671; Netter 3e 67, 4e 71) to innervate the mucosa
and gum adjacent to the lower lip.
Lingual nerve (Clemente
plate 479; Grant p. 668-669; Netter 3e 67, 4e 71)
- lies anterior to the inferior alveolar nerve and remains
medial to mandible.
- receives the chorda tympani in the infratemporal
fossa. The chorda tympani reaches the infratemporal fossa via the petrotympanic
fissure (Clemente plate 527 fig. 835, plate 565 fig. 919; Grant
p. 625; Netter 3e 42, 4e 46). The chorda tympani contains preganglionic
parasympathetic secretomotor fibers of VII from the tympanic plexus and
special sensory fibers for taste from the anterior 2/3 of the tongue. The
taste fibers have their cell bodies in the geniculate ganglion of VII.
- Terminal distribution of the lingual nerve and associated
fibers which mediate general sensation (pain, touch temperature and pressure)
is to the floor of the mouth and the anterior 2/3 of the tongue.
Mandibular block technique:
- Injection of anesthetic is performed in the fascial compartment
defined by the fascial covering of the medial pterygoid and the medial
aspect of the ramus of the mandible (Clemente plate 477; Grant p. 678; Netter
3e 51, 4e 55).
- The anesthetic diffuses to the lingual and inferior alveolar
Temporomandibular joint (TMJ; Clemente plate 473; Grant
p. 674-675; Netter 3e 14, 4e 16)
- Head of mandible
- Mandibular fossa and articular tubercle of the temporal
- Synovial joint with intraarticular disc dividing joint
into a lower compartment (hinge rotation for mandibular head) and
upper compartment (sliding joint for protrusion).
Minor supportive elements of the TMJ:
- Lateral temporomandibular ligament (thickening of the joint capsule; Clemente plate 472; Grant
p. 674-675; Netter 3e 14, 4e 16)
- Stylomandibular ligament (between
parotid and submandibular glands;
- Sphenomandibular ligament
Major supportive elements of the TMJ: MUSCLES OF MASTICATION
Movements of the mandible:
INTRACRANIAL CAVITY AND MENINGES;
Gross Anatomy, K. W. Chung, 5th edition: pp. 352-372
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 908-933, 1124-1154; 6th edition: pp. 865-878, 1054-1082.
Anatomy Dissector, 2nd edition: pp. 354-365
Dissector, P.W. Tank, 14th edition: pp. 215-227
The cranial cavity is a rigid box containing brain, important
blood vessels and CSF. It communicates with the vertebral canal through
the foramen magnum (Clemente plate 498; Grant p. 642;
Netter 3e 5, 4e 5) and with tissues outside the cranium via foramina. Because
it is a rigid box, extensive bleeding or a growing tumor inside the cranium
has little room for expansion and an early rise in intracranial pressure
Structure of intracranial blood vessels:
- To avoid collapse of the veins during a rise in pressure
(systole), the veins have rigid walls composed of dura and are called venous
sinuses (Clemente plates 488, 489; Grant p. 639; Netter 3e 100, 4e 102-104).
- Intracranial arteries have thin walls because when the
arteries are distended during systole, the effect is counteracted by a
rise in intracranial pressure. However, the arteries are prone to localized
distension (aneurysm) and when the vessel breaks, this may lead
to a fatal hemorrhage.
- Dura mater (pachymeninx)
- The subarachnoid space continues through the foramen
magnum, around the spinal cord.
- Pia mater (closely adherent to the brain)
*Arachnoid and pia mater are also called leptomeninges.
2 layers (Clemente plate 486 fig. 765; Grant p. 636; Netter
3e 96, 4e 102):
- An outer fibrous layer
- and an inner serous layer, which parts from the fibrous
layer to form the venous sinuses.
The dura is supplied by small arteries and the middle
meningeal artery (Clemente plate 487; Grant p. 635; Netter
3e 95, 4e 100). The vein runs with the artery.
Intracranial partitions of the dura mater:
- The falx cerebri (Clemente plate 488; Grant
p. 638; Netter 3e 97, 4e 103) with the superior sagittal sinus,
starts at the crista galli.
- The tentorium cerebelli incompletely roofs over
the posterior cranial fossa.
- At this level, the midbrain runs superiorly through the
opening to join with the diencephalon (Grant p. 640; Netter
3e 98, 100, 4e 104, 106). The sharp edges of dura may have fatal consequences when
the brain is displaced by force or a space-occupying lesion.
The flow of the cerebrospinal fluid in the venous sinuses
is from the superior sagittal sinus to the right transverse sinus
to the sigmoid sinus to the internal jugular
vein (Clemente plates 488, 489; Grant p. 639; Netter 3e 97, 98, 4e 103-104
The arachnoid villi drain CSF from the subarachnoid space
to the venous sinuses. With age, the arachnoid villi become clumped together
to form the arachnoid granulations (Clemente plate 486 fig. 765,
plate 487; Grant p. 637; Netter 3e 94 - 96, 4e 100, 102).
The inferior sagittal sinus is in the free edge
of the falx cerebri and receives part of the drainage of the great cerebral
vein (of Galen) and becomes the straight sinus (Grant p. 639; Netter 3e 97,
4e 103-104). This passes to
the left and forms the left transverse sinus, left sigmoid sinus
and left internal jugular vein.
*Because the flow from the larger superior sagittal sinus
tends to go to the right transverse sinus, the right jugular foramen is
usually bigger than the left (Clemente plate 498; Grant p. 615; Netter 3e 7,
4e 104). But, at other times, the ends of the superior sagittal
sinus and the straight sinus join together to form the confluence of
the sinuses and the jugular foramina will be even in size.
The cavernous sinuses, are found on either side
of the sella turcica (pituitary gland; Clemente plates 489, 494; Grant
p. 639; Netter 3e 98, 4e 104):
- Anteriorly, the superior and inferior opthalmic
veins open into them.
- Posteriorly, minor venous sinuses (superior and inferior
petrosal sinuses) also open into them. The inferior petrosal sinus
communicates at its other end with the internal jugular vein at the jugular
- The cavernous sinuses are joined across the midline by
intercavernous sinuses lying anterior and posterior to the pituitary
gland. The pituitary fossa is roofed in by the diaphragma sellae
through which runs the pituitary stalk (Clemente plate 492 fig. 773;
Grant p. 640; Netter 3e 98, 4e 104). Superoanteriorly, lies the
- Veins from the lower parts of the brain also drain into
the cavernous sinuses.
- The cavernous sinus contains cranial nerves III, IV,
V, and VI, and the internal carotid artery (Clemente plate 490 fig. 770;
Grant p. 644; Netter 3e 98, 4e 104).
Blood supply of the brain
After passing through the cavernous sinus, the internal
carotid artery turns superiorly (Clemente plate 458, plate 493; Grant
p. 643-649; Netter 3e 130, 132, 133, 4e 136, 138, 140):
- it then gives out the opthalmic artery (which runs into
the optic canal with the optic nerve),
- and terminates as the anterior and middle cerebral
arteries and the posterior communicating artery.
- Before it breaks up into terminal branches, it gives
out small branches to the pituitary gland and adjacent structures.
The vertebral artery (Grant 647; Netter 4e 138-139) goes through the foramen magnum
and gives off:
- the anterior spinal artery
- the posterior spinal artery,
- the posterior inferior cerebellar artery
- and finally joins with the opposite artery to form the
The basilar artery lies ventral to the pons of the brainstem,
on the clivus. The basilar artery sends out :
- branches to the brainstem,
- the anterior inferior cerebellar artery
- and terminates as the superior cerebellar and
posterior cerebral arteries.
Terminal branches of the internal carotid and the vertebral
arteries form the circle of Willis.
Cranial nerves within the cranium
The cranial nerves all leave the brain on its ventral surface
except for the IVth cranial (trochlear) nerves (Clemente plate 495; Grant
p. 642, 644; Netter 3e 112 4e 114-115).
Ist cranial (olfactory)
nerve: The cell bodies from the olfactory epithelium lie in the olfactory
mucosa and their axons travel upwards to reach the olfactory bulb through
the cribrifrom plate (Clemente plate 524 fig. 830; Grant p. 813, 818; Netter
3e 113, 4e 119).
IInd cranial (optic) nerves
(Clemente plate 495; Grant p. 819-820; Netter 3e 114, 4e 120) develop
as optic stalks which are prolongations of the brain, surrounded by the
meninges: The cerebrospinal fluid may extend as far as the back of the eyeball
(Grant p. 647; Netter 83, 4e 87) and rise in intracranial pressure
will affect the optic nerve and the optic disk (Clemente plate 520 fig.
822; Grant p. 651; Netter 3e 86, 4e 90).
- Nerve fibers of the optic nerve will not regenerate if
- Optic nerves leave the eyeballs posteriorly, enter the
cranium through the optic canal and form the optic chiasma.
Note (Grant p. 820; Netter 3e 114, 4e 120):
- the pattern of nerve fibers in the optic nerve, chiasma
and optic tract.
- The difference between blindness, bitemporal hemianopia
and homonymous hemianopia.
IIIrd, IVth and VIth cranial
nerves innervate the muscles of the eyeball (LR6, SO4)3
(Clemente plate 510-512; Grant p. 821; Netter 3e 115, 4e 121)
- VIth cranial (abducens) nerve for the abductor
- IVth (trochlear) nerve for the superior
- IIIrd cranial (oculomotor) nerve for all other
muscles including the levator palpebrae superioris.
The IIIrd cranial nerve:
- passes between the superior cerebellar and posterior
cerebral arteries (Clemente plate 493; Grant p. 644, 646; Netter
3e 136, 4e 143)
- pierces the dura posterior to the clinoid process
- travels high up in the lateral wall of the cavernous
sinus (Clemente plate 490 fig. 770, plate 492 fig. 773; Grant p. 644; Netter
3e 98, 4e 104)
- enters the orbit via the superior orbital fissure
- divides into upper and lower branches (Clemente plates
511, 513; Grant p. 822-823; Netter 3e 115, 4e 121).
The IVth cranial nerve
- passes around the midbrain from its dorsal aspect (Clemente
plate 495; Grant p. 644; Netter 3e 108, 4e 114),
- pierces the dura posterior to the IIIrd cranial nerve
(Clemente plate 492 fig. 773; Grant p. 644; Netter 3e 98, 4e 104),
- lies in the lateral wall of the cavernous sinus below
the IIIrd cranial nerve (Clemente plate 490 fig. 770; Grant p. 644; Netter
3e 98, 4e 104).
- However, the IVth cranial nerve enters the superior portion
of the orbital fissure to reach the upper border of the superior oblique
(Clemente plate 510; Grant p. 821; Netter 3e 98, 4e 86).
The VIth cranial nerve
- leaves the brain at the lower border of the pons in the
posterior cranial fossa (Clemente plate 495; Grant p. 646, 812-813;
Netter 3e 108, 115, 4e 104).
- pierces the dura on the clivus,
- runs over the ridge of the petrous portion of the temporal
- enters the cavernous sinus (Clemente plate 490; Grant
p. 644; Netter 3e 98, 4e 104).
- It lies lateral to the internal carotid artery before
entering the orbit via the lower part of the superior orbital fissure (Clemente
plate 513; Grant p. 821; Netter 3e 115, 4e 83, 121).
The Vth cranial (trigeminal) nerve (Clemente
plate 514; Grant p. 644-645, 824-829; Netter 3e 116, 4e 122)
- starts in the posterior cranial fossa,
- crosses the petrous temporal bone, carrying with it a
diverticulum of dura (cavum trigeminale or Meckel's cave) from the
posterior cranial fossa,
- enlarges to form the ganglion in the middle cranial fossa
over the roof of the carotid canal.
Anteriorly, its 3 branches (ophthalmic, maxillary and mandibular)
pierce the dura in the cavernous sinus.
- The ophthalmic division pierces the dura and enters the
orbit via the superior orbital fissure and divides into frontal, lacrimal
and nasociliary divisions (Clemente plates 510, 512; Grant p. 825; Netter
3e 81, 4e 86).
- The maxillary nerve leaves the cranium via the foramen
rotundum (Clemente plate 510; Grant p. 826; Netter 3e 98, 4e 122).
- The mandibular nerve leaves the cranium via the foramen
ovale accompanied by the lesser petrosal nerve (Clemente plate 511;
Grant p. 828-829; Netter 3e 41, 4e 46).
The VIIth cranial (facial) nerve and the
VIIIth cranial (vestibulocochlear) nerve run into the internal auditory
meatus (Clemente plate 494; Grant p. 642, 813; Netter 3e 98, 4e 104).
Parasympathetic fibers which will form the chorda tympani and
the greater petrosal nerve travel in the nervus intermedius lying
between VII and VIII (Clemente plate 574; Grant p. 813; Netter
3e 98, 118, 4e 104, 123).
The VIIIth cranial (vestibulocochlear) nerve
enters the internal auditory meatus and divides into vestibular and
cochlear branches (Grant 832; Netter 124).
The IXth cranial (glossopharyngeal) nerve arises
from the medulla of the brain and immediately enters the jugular foramen
to exit the cranium (Clemente plates 494, 495; Grant p. 642;
Netter 98, 119, 125).
The Xth cranial (vagus) nerve passes through
the jugular foramen accompanied by the cranial portion of the XIth cranial
The XIth cranial (accessory) nerve:
- The spinal portion arises from the side of the
upper 5 segments of the spinal cord and enters the cranium via the foramen
- It joins with the cranial portion and X to pass through
the jugular foramen and immediately leaves to supply sternocleidomastoideus
- The cranial portion joins with X to be distributed
with its branches.
The XIIth cranial (hypoglossal) nerve (Clemente
plate 495; Grant p. 839; Netter 3e 122, 4e 128) is a purely motor nerve
arising from the side of the medulla to pass through the hypoglossal (anterior
condylar) canal (Clemente plate 494; Grant p. 813; Netter
3e 7, 4e 8, 104).
EYE AND ORBIT
Gross Anatomy, K. W. Chung, 6th edition: pp. 375-387
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 957-977; 6th edition: pp. 889-914
Anatomy Dissector, 2nd edition: pp. 366-379
Dissector, P.W. Tank, 14th edition: pp. 227-233
- The margin of the orbit is formed by the frontal,
zygomatic and maxillary bones (Clemente plate 480; Grant p. 650; Netter 2).
- The medial wall of the orbit is formed by the
lacrimal and ethmoid bones.
- The lateral wall of the orbit is formed by the
- The floor of the orbit is formed by the maxillary
- The roof of the orbit is formed by the orbital
plate of the frontal bone.
- Deep in the orbit, the greater
and lesser wings of the sphenoid bone are separated by the superior orbital
- The inferior orbital fissure is a gap between the maxillary
bone and the greater wing of the sphenoid bone.
- The optic canal lies in the root of the lesser wing of
the sphenoid bone.
The medial walls of the orbit are parallel, whereas the
lateral walls diverge (Clemente plate 509 fig. 802; Grant p. 652-653; Netter 3e 79,
4e 83): the long axis of the orbit is at an angle to the
long axis of the eyeball.
The fibromuscular cone:
- All the recti muscles
of the eyeball originate from a fibrous ring that includes the
lower part of the inferior orbital fissure and the optic canal (Clemente
plate 517 fig. 815; Grant p. 656; Netter 3e 79, 4e 83-84).
- From this fibrous ring, the recti muscles spread out to attach
around the periphery of the eyeball (Clemente plate 516; Grant p. 658; Netter
3e 80, 4e 84).
- The superior oblique muscle arises from the body of the
sphenoid bone, superomedial to the optic canal and to the tendinous
attachment of the rectus superior. Distally, it ends in a tendon which
loops through the trochlea and attaches to the superolateral posterior
quadrant of the eyeball, between the superior and lateral recti muscles.
The inferior oblique muscle arises from the orbital surface of the maxilla,
lateral to the nasolacrimal groove. It ascends laterally between the
inferior rectus and the orbital floor, and then between the eyeball and the
lateral rectus. It attaches to the inferolateral posterior quadrant of
the eyeball between the inferior rectus and superior oblique.
A fascial sheath is continuous around and between the
muscles, forming a fibromuscular cone.
- The interior of the cone is filled with fat and contains
the optic nerve (Clemente plate 517 fig. 816; Grant p. 655;
Netter 3e 79, 4e 83).
The levator palpebrae superioris muscle (Clemente
plate 509 fig. 801; Grant p. 654-655; Netter 3e 77, 80, 4e 84):
- Superior to the cone, outside of it, lies the levator
palpebrae superioris muscle attaching anteriorly to the upper eyelid.
- From the back of the orbit, above the fibrous ring, it
lies under the roof of the orbit.
- It is supplied both by the IIIrd cranial nerve and sympathetic
nerves (loss of either innervation will lead to ptosis).
Muscles of the eyeball (Clemente plate 516; Grant p. 658-659; Netter 3e 80,
The lateral rectus (LR) on the lateral wall
of the orbit, is an abductor (Clemente plate 515 fig. 809; Grant p. 653; Netter
3e 79, 4e 84) and turns the pupil laterally.
The medial rectus (MR) lies along the medial
wall of the orbit and turns the pupil medially. Left and right medial recti
muscles contract simultaneously to cause convergence of the gaze (for focusing
on a near object).
The superior rectus (SR) turns the pupil superiorly
and medially (Clemente plate 514 fig. 808; Grant p. 659; Netter
3e 80, 4e 84).
The inferior rectus (IR) turns the pupil inferiorly
The superior oblique (SO) runs along the medial
wall to reach the trochlea (Clemente plate 515 fig. 810; Grant p. 657; Netter
3e 81, 4e 84). It then loops posteriorly through a fascial
sling before being attached to the eyeball. Its action are incyclotorsion
(primary), depression (secondary) and abduction (tertiary).
The inferior oblique (IO) arises from the floor
of the orbit and travels laterally below the eyeball, attaching to the eyeball
laterally (Clemente plate 515 fig. 810; Grant p. 654, 656; Netter
3e 80, 4e 84). Its actions are excyclotorsion (primary), elevation
(secondary) and abduction (tertiary).
The secondary actions of the superior and inferior oblique
muscles are best demonstrated with the eye adducted.
Movements of the eyeball:
- Looking straight up: SR and IO
- Looking straight down: IR and SO
- Looking left: left LR and right MR
The movements of the eyeball are finely coordinated and
may be easily disturbed (influence of alcohol).
The ophthalmic artery arises from the internal carotid
artery (Clemente plate 513; Grant p. 657; Netter 3e 81, 4e 85).
The ophthalmic artery gives out the central artery of
the retina which:
- is an end artery.
- enters the optic nerve
- travels near its center towards the eyeball (Clemente
plate 520, plate 521 fig. 824; Grant p. 657, 660-661; Netter 3e 83, 4e 90).
- divides within the eye into superior temporal and
inferior temporal branches. These in turn give rise to nasal (medial)
and temporal (lateral) branches accompanied by corresponding
veins. These can be observed with an ophthalmoscope (Clemente plate
520 fig. 822; Grant p. 661; Netter 3e 86, 4e 90).
In the orbit, the ophthalmic artery crosses to the medial
side, above the optic nerve (Clemente plate 512, 513; Grant p. 657; Netter 3e 81,
4e 85). It then travels anteriorly along the medial wall of
the orbit and ends by dividing into dorsal nasal and supratrochlear
arteries, emerging onto the face .
Other branches of the ophthalmic artery in the orbit are:
- The lacrimal artery, which follows the lateral
wall of the orbit, supplies the lacrimal gland and ends on the face by
supplying the eyelids.
- The long (2) and short (many) posterior ciliary
arteries (Clemente plate 518 fig. 817; Grant p. 661;
Netter 3e 86, 4e 91) which enter the eyeball to supply the choroid.
- The short arteries supply the back of the eyeball.
- The long arteries enter the back of the eyeball but will
break up into branches only at the corneoscleral junction.
- The long and/or short posterior ciliary arteries may
give out an anterior ciliary artery to the front of the eyeball.
- The supraorbital artery lies below the roof of
the orbit and runs out superiorly to supply the scalp (Clemente plate
512, plates 504-505; Grant p. 632, 652, 657; Netter 3e 19, 81, 4e 85).
- The anterior and posterior ethmoidal arteries
enter canals in the ethmoid bone to supply the ethmoidal air cells and
the posterior ethmoidal artery continues into the nasal cavity.
Veins accompany all the arteries but they drain into the
superior and inferior ophthalmic veins (Clemente plates
475, 494; plate 514 fig. 807; Grant p. 656; Netter 3e 81, 4e 85),
which communicate with the cavernous sinus and the pterygoid plexus of veins.
The IVth cranial nerve enters the orbit above the fibrous
ring (Clemente plate 510; Grant p. 656; Netter 3e 79, 4e 83) and
therefore lies outside of the muscular cone, crosses to the medial side
and enters the upper border of the superior oblique muscle (Clemente
plate 511; Grant p. 652-653; Netter 3e 82, 4e 86).
The VIth cranial nerve enters within the fibrous ring (Clemente
plates 510-513; Grant p. 656; Netter 3e 79, 4e 85) and immediately
turns laterally to enter the lateral rectus.
The IIIrd cranial nerve divides into 2 divisions lying
above and below the nasociliary nerve within the cone:
- The superior branch travels upward to reach the superior
rectus and the levator palpebrae superioris muscles (Clemente plate
511; Grant p. 822; Netter 3e 115, 4e 121).
- The inferior branch (Clemente plate 513; Grant p.
822; Netter 3e 115, 4e 121) breaks up to supply the medial rectus, the
inferior rectus and the inferior oblique muscles.
- The nerve to the inferior oblique carries parasympathetic
fibers from the Edinger-Westphal nucleus in the midbrain. They travel
in a branch to the ciliary ganglion where they synapse. The short
ciliary nerves travel to the back of the eyeball. They supply the ciliaris
muscle and the sphincter pupillae (Grant p. 650, 805;
Clemente plate 823; Netter 3e 82, 83-85, 4e 86, 121).
Sensory nerves are all branches of the ophthalmic division
of the trigeminal (Vth cranial) nerve: the frontal and
lacrimal nerves enter the orbit above the fibrous ring and the nasociliary
The frontal nerve (Clemente plate 510; Grant
p. 652; Netter 3e 82, 4e 86) is directly below the roof of the orbit,
lying on the levator palpebrae superioris. It divides into the supraorbital
and supratrochlear nerves leaving the orbit at its upper border
and supplies the scalp (Clemente plates 504-505; Grant p. 634;
Netter 3e 20, 4e 24).
The lacrimal nerve travels along the lateral wall
of the orbit to supply the skin of the eyelids (Clemente plate 507 fig.
797; Grant p. 652-653; Netter 3e 82, 4e 86) and it also carries parasympathetic
secretomotor fibers to the lacrimal gland (Clemente plate 507 fig.
797; Grant p. 825; Netter 3e 116, 4e 122).
The nasociliary nerve has similar branches to the
ophthalmic artery, except that:
- short ciliary nerves are derived from the ciliary ganglion,
not the nasociliary nerve
- and the lacrimal nerve is a separate branch from
the ophthalmic division.
The nasociliary nerve gives off 2 long ciliary nerves entering
the back of the eyeball, which carry sympathetic fibers to the dilator
pupillae (Clemente plate 512; Grant p. 823; Netter 3e 82, 4e 121)
and sensory fibers to the cornea (Grant p. 823). Along
the medial wall of the orbit, the nasociliary nerve gives out a posterior
ethmoidal nerve and ends by turning into the anterior ethmoidal nerve,
giving off a small infratrochlear nerve (Clemente plate 513; Grant p.
653; Netter 3e 82, 4e 86).
NOSE, NASAL CAVITIES AND PARANASAL SINUSES
Text: Gross Anatomy,
K. W. Chung, 6th edition: pp. 400-406
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
Clemente’s Anatomy Dissector, 2nd
Grant’s Dissector, P.W. Tank, 14th edition: pp.
- The nerve supply to the skin of the nose is by V1 (infratrochlear
nerve) and V2 (infraorbital nerve; Clemente plate 504; Grant p.
630; Netter 3e 20, 4e 24).
- The innervation of the tip of the nose is by the external
nasal nerve, an anterior ethmoidal branch of the nasociliary nerve
(V1) running from the root of the nose to the tip of the nose.
Loss of sensation to the tip of the nose may be due
to an intracranial, intraorbital or ethmoidal air sinus disorder affecting
V1 pathway from the trigeminal ganglion.
- The paired nasal bones articulate with the frontal
bone and frontal processes of the maxillary bones (Clemente plate 522
fig. 825; Grant p. 690; Netter 3e 32, 4e 36).
- The central septal cartilage connects with the
superior lateral cartilages articulating with the nasal bones (Clemente
plate 524 fig. 829; Grant p. 690; Netter 32, 4e 36).
- Alar cartilages are supported
by the septal cartilage.
- The nares (nostrils) open into the right and left
nasal cavities separated by the septum.
- The choanae are the posterior apertures leading
to the nasopharynx (Clemente plate 552; Grant p. 616, 790-791; Netter 3e 33,
Floor of nasal cavity:
- palatine processes of the maxilla
- and horizontal plates of the palatine bone.
Roof of nasal cavity is composed
of (Clemente plate 523; Grant p. 691; Netter 3e 34-35, 4e 38-39):
- Anterior part: slope of the nasal bones
- Intermediate part: cribriform plate of ethmoid bone
- Posterior part: anterior and inferior aspects of the
body of the sphenoid bone.
Nasal septum (Clemente plate 524 fig. 829; Grant p. 691;
Netter 3e 35, 4e 39):
- The perpendicular plate of the ethmoid bone and the vomer
bone may articulate with each other posteriorly.
- The septal cartilage intervenes between bony elements
of the septum, forming support for the midline ridge of the nose, tip and
columella (between nares from tip of the nose to anterior nasal
spine of the maxilla).
- Deviation of the nasal septum is most frequent between
the vomer and the septal cartilage.
Lateral wall (Clemente plate 525; Grant p. 691; Netter 3e 34,
- Superior, middle and inferior nasal conchae and
their corresponding meatuses.
- Sphenoethmoid recess lies
superior to the superior concha.
- Vestibule, just inside each
naris, is lined by skin.
- Atrium, inferior to nasal
bones, is lined by mucoperiosteum.
The inferior concha
- is a separate bone articulating with maxilla, lacrimal
and palatine bones on the lateral wall of the nasal cavity (Clemente plate
523; Grant p. 691; Netter 3e 34, 4e 38).
- Its meatus contains the opening of the nasolacrimal
duct draining tears from medial aspect of the orbit into the nasal
cavity (Clemente plate 507 fig. 798; Grant p. 695; Netter 3e 34, 78, 4e
37-38, 82 ).
The posterior extent of the nasal cavity is adjacent to
the opening of the auditory tube in the nasopharynx (Clemente plate 525;
Grant p. 695; Netter 3e 33, 4e 37).
The middle concha is a process
of the ethmoid bone (Clemente plate 523; Grant p. 691; Netter
3e 33, 4e 38) and it overlies the middle meatus.
Paranasal air sinuses open
into this meatus: the hiatus semilunaris (Clemente plate 522 fig.
826; Grant p. 695; Netter 3e 33, 4e 37) opens on the wall of the middle meatus between the unciform process of the ethmoid bone and the ethmoid
- Frontal sinus drains into
the superior aspect of the hiatus semilunaris (Clemente plate 522 fig. 826;
Grant p. 695; Netter 3e 33, 4e 37).
- Anterior and middle ethmoidal
air sinuses drain through openings of the ethmoidal bulla on superoposterior
aspect of the hiatus semilunaris.
- Maxillary air sinus has its
ostium directly inferior to the ethmoid bulla within the hiatus semilunaris.
The superior concha is also
a process of the ethmoid bone (Clemente plate 523; Grant p. 691; Netter 3e 34,
- It overlies the superior meatus receiving the opening
of the posterior ethmoidal air cells (Clemente plate 525 fig.
832; Grant p. 695; Netter 3e 32, 33, 4e 38).
Superior to the superior concha is the spheno-ethmoidal recess where the sphenoid air cells drain into nasal cavity.
NERVE SUPPLY TO THE NASAL CAVITY
The mucosa of upper nasal cavity is innervated by the olfactory
(I) and trigeminal (V1; anterior ethmoidal) nerves (Clemente plate
524 fig. 830; Grant p. 692; Netter 3e 38-39, 4e 42-43).
The anterior ethmoidal nerve carries general sensation
(pain, temperature, touch and pressure).
Most of the general sensation of the lateral wall and nasal
septum is mediated by V2, which is associated with the pterygopalatine ganglion
(Clemente plate 526; Grant p. 692; Netter 3e 39, 4e 43).
- The pterygopalatine ganglion receives the preganglionic
parasympathetic fibers of the superficial (greater) petrosal nerve
(VII; Clemente plate 527; Grant p. 692, 700, 831; Netter 3e 39, 117, 4e 43, 123).
- The postganglionic parasympathetic neurons send secretomotor
fibers to glands above the floor of the mouth.
Terminal branches of the infraorbital nerve (Grant p. 692; Netter
3e 38, 4e 42) also enter the vestibule
of the nose from the skin covering the nares.
A small branch from the anterior superior alveolar nerve
also innervates the anterior nasal mucosa of the inferior meatus (Grant
p. 692; Netter 3e 38, 4e 42).
The mucosa on the lateral wall of the nose is innervated
by branches of the descending greater palatine nerve from the inferior
pole of the pterygopalatine ganglion.
Superior and inferior posterior
lateral nasal nerves run in the mucoperiosteum covering the conchae
and the meatus.
The nasal septum mucosa is innervated by the nasopalatine
nerve (Clemente plate 524 fig. 830; Grant p. 692; Netter 3e 39, 4e 43).
- It enters the nasal cavity from the pterygopalatine fossa
through the sphenopalatine foramen
- and descends on the median nasal septum.
- The terminal branch leaves the nasal cavity via the incisive
foramen (Clemente plate 524 fig. 830; Grant p. 692; Netter 3e 39, 4e 43).
The sympathetic innervation of the nasal cavities comes
from the superior cervical ganglion. These postganglionic fibers reach the
nose via the nerve of the internal carotid artery (Clemente plate
527; Grant p. 701; Netter 3e 40, 4e 44) and the deep petrosal nerve
of the pterygoid canal. In the pterygopalatine fossa, they join with
terminal branches of the maxillary artery and are vasomotor to blood
vessels in the nasal cavity and palate.
BLOOD SUPPLY OF THE NASAL CAVITY
The sphenopalatine artery
- arises from the maxillary artery in the pterygopalatine
fossa (Clemente plate 526; Grant p. 693; Netter 3e 36-37, 4e 40-41).
- It enters the nasal cavity with the nasopalatine nerve
and supplies upper 2/3 of the nasal septum.
- It then anastomoses with the greater palatine artery
ascending through the incisive foramen.
The site of anastomosis is a frequent area of hemorrhage
(epistaxis or nosebleed).
The lateral walls of the nasal cavity are supplied by blood
vessels accompanying the terminal branches of the anterior ethmoidal nerve
and the greater palatine nerve and they have the same name (Clemente plate
526; Grant p. 693; Netter 3e 37, 4e 41).
The venous drainage of the nose parallels the arterial
supply and forms a network overlying the inferior and middle conchae.
The erectile tissue overlying the conchae humidifies
and warms the inspired air in the upper respiratory passage.
PARANASAL AIR SINUSES
- The sphenoid (Clemente plate 522 fig. 826; Grant p.
694; Netter 3e 44, 4e 48-49), ethmoid (Clemente plate 528; Grant
p. 696; Netter 3e 44-45, 4e 48-49), frontal (Clemente plate 529; Grant p. 696;
Netter 3e 44, 4e 48-49) and maxillary are paired but
- They are lined with respiratory epithelium which becomes
converted to stratified squamous epithelium with chronic respiratory irritation.
This may lead to chronic sinusitis.
Sphenoid air sinuses drain
into the sphenoethmoidal recess (Clemente plate 525 fig. 832; Grant p.
696; Netter 3e 45, 4e 37). A surgical approach to the pituitary may
be done through these air sinuses and the nasal cavities.
Ethmoidal air sinuses (anterior,
middle and posterior).
- Anterior and middle drain into middle meatus by openings
of the ethmoidal bulla (Clemente plate 522 fig. 826; Grant p. 695; Netter
3e 34, 4e 37).
- Posterior ethmoidal air cells drain into the superior
Frontal sinus drains via the
infundibulum into the superior extension of the hiatus semilunaris (Clemente
plate 525 fig. 832; Grant p. 695; Netter 3e 45, 4e 37).
Maxillary sinus drains into
the middle meatus through the hiatus semilunaris. The air sinus has a floor
at the level of the hard palate (Clemente plate 529; Grant p. 698; Netter 3e 45,
4e 49) and since the ostium is more superiorly located
plate 525 fig. 832; Grant p. 696, 698; Netter 3e 45, 4e 49), there is often
drainage problems. The nerve supply is by the posterior and middle superior
alveolar nerves (V2; Clemente plate 527 fig. 836; Grant p. 700; Netter 3e 41,
Mastoid air sinuses (Clemente
plate 527 fig. 836; Grant p. 710; Netter 3e 89, 4e 94) drain into
the nasal cavity via the middle ear and auditory tube.
THE ORAL CAVITY AND CONTENTS
Text: Gross Anatomy, K. W. Chung, 6th edition: pp.
Reference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th
edition: pp. 987-1010; 6th edition: pp. 928-951
Clemente’s Anatomy Dissector, 2nd edition: pp. 403-414
Grant’s Dissector, P.W. Tank, 14th edition: pp. 249-252
- is bounded by lips and cheeks,
- is lined with non-keratinized stratified squamous epithelium.
- the parotid papilla is in the superior vestibule,
opposite the 2nd upper molar tooth (Netter 3e 47, 4e 51).
- is vascularized by the superior and inferior labial
arteries from the facial artery (Clemente plate 474; Grant p. 632;
Netter 3e 32, 4e 36) . These arteries anastomose freely with their
contralateral counterparts. Because of these profuse anastomoses, lip bleeding
is controlled by grasping the injured lip between the fingers to stop the
Nerve supply of the vestibule:
- The orbicularis oris and buccinator muscles are innervated
by cranial nerve VII (facial nerve; Clemente plate 469; Grant p. 629;
Netter 3e 21, 4e 25).
- The skin and mucosa of the upper lip, cheek and vestibule
are innervated by the anterior, middle and posterior superior alveolar
nerves from V2 (Clemente plate 527; Grant p. 700; Netter 3e 42, 4e 45).
- The skin and mucosa of lower lip and adjacent anterior
vestibule are innervated by the mental nerve (V3; Clemente plate 476;
Grant p. 630-631, 671; Netter 3e 42, 4e 46).
- The mucosa of the inferior vestibule adjacent to the
cheek is innervated by the long buccal (buccinator; Grant p. 630, 668; Netter 4e
46) nerve from the anterior
division of V3.
- The roof is formed by the hard and soft palates with
the midline uvula (Clemente plate 530 fig. 843; Grant p. 682; Netter 3e 48, 52;
- The posterior border is formed by the pillars of the
fauces (Clemente plate 530; Grant p. 676; Netter 3e 54, 4e 51, 58)
- The floor is formed by the tongue divided into anterior
2/3 and posterior 1/3 by the palatoglossal arch, the V-shaped sulcus
terminalis and circumvallate papillae (lying anterior to the
sulcus; Clemente plate 539; Grant p. 676; Netter 3e 54, 4e 58).
- The lingual frenulum (Clemente plate 532 fig.
847; Grant p. 680; Netter 3e 47, 4e 51) is found on the undersurface
of the tongue with openings of the ducts of the submandibular gland
(Clemente plate 533 fig. 850; Grant p. 680; Netter 3e 47, 4e 51).
In examination of the tongue, grasp the tip of tongue
with gauze and pull the tongue out of the mouth. Examine the lateral
aspects of the anterior 2/3 of the tongue. This is a common site for cancer
of the tongue.
FLOOR OF THE MOUTH (SUBLINGUAL REGION)
The sublingual gland (Clemente plate 532 fig. 847, plate
543; Grant p. 680-681; Netter 3e 57, 4e 61):
- lies on the lingual aspect of the body of the mandible,
deep to the plica sublingualis (sublingual fold), which is the posterolateral
continuation of the lingual frenulum.
- It has a row of 15 or 16 ("middle-teens") ducts
that empty into the floor of the mouth on the plica sublingualis.
- The duct of the submandibular gland and the lingual nerve
lie on the medial surface of the sublingual gland.
- The mylohyoid muscle lies inferior to the sublingual
- The sublingual gland is innervated by postganglionic
parasympathetic fibers reaching the gland via its sensory nerve, the lingual
nerve (V3). Preganglionic parasympathetic fibers run with the chorda
tympani (VII) synapsing in the submandibular ganglion (Clemente
plate 479; Grant p. 831; Netter 3e 41, 4e 46).
The lingual nerve
- provides the general sensory (pain, touch and
temperature) modality to the anterior 2/3 of the tongue and the floor of
the mouth (Clemente plate 532 fig. 848; Grant p. 680-681, 829; Netter 3e 55, 4e 59).
- also carries chorda tympani which has special taste fibers
and secretomotor fibers of VII.
- enters the floor of the mouth on the medial mandible
next to the 3rd molar tooth (Clemente plate 533 fig. 850; Grant p. 680-681;
Netter 3e 42, 4e 46). It is thus vulnerable in extraction of the
- Preganglionic parasympathetic fibers leave the lingual
nerve to synapse in the submandibular ganglion (Clemente plate 535 fig.
855; Grant p. 680, 840; Netter 3e 42, 4e 133). Postganglionic parasympathetic
fibers rejoin the lingual nerve to reach the sublingual salivary gland.
The submandibular ganglion is thus suspended from the main trunk of the
The lingual nerve is:
- superior to the mylohyoid
muscle in the floor of the mouth (Clemente plate 479; Grant p. 681; Netter
3e 42, 4e 46).
- lateral to the submandibular
duct (Clemente plate 479; Grant p. 680-681, 780; Netter 3e 42, 4e 46),
- and medial to the sublingual gland (Clemente
plate 479; Grant p. 680; Netter 3e 56, 4e 60).
- Subsequently, it passes inferior and then medial
to the submandibular duct to ascend into the body of the tongue (Clemente
plate 533 fig. 850; Grant p. 680-681; Netter 3e 55, 4e 59).
The chorda tympani provides taste fibers which supply
the anterior 2/3 of the tongue. The cell bodies are in the geniculate ganglion
in the middle ear (Clemente plate 573; Grant p. 709, 831; Netter
3e 117, 4e 135).
The hypoglossal nerve enters the floor of the mouth
on the lateral aspect of the hyoglossus muscle, above the hyoid bone and
the mylohyoid muscle (Clemente plate 535 fig. 855; Grant p. 681, 780; Netter
3e 55, 4e 59). Cranial nerve XII lies inferior to the lingual nerve
and is purely motor to the muscles of the tongue.
Test cranial nerve XII by protrusion of the tongue.
Deviation is toward the side of the lesion.
- allows for mastication, swallowing, speech and taste.
- The anterior 2/3 (body or oral part) is derived from
the ectodermal stomodeum.
- The posterior 1/3 (pharyngeal part or root) is derived
from the endodermal foregut.
- These 2 parts are separated by the sulcus terminalis
posterior to the circumvallate papillae (Clemente plate 539; Grant p.
676; Netter 3e 52, 4e 58).
- The sulcus terminalis is oriented posteriorly and the
foramen cecum can be found at the tip of the V-shaped sulcus terminalis.
This is the point of origin of the thyroid gland.
- Lingual tonsils are located
posterior to the sulcus terminalis.
Mucous membrane of the tongue:
- The papillae (filiform, fungiform, circumvallate and
foliate) are innervated by cranial nerve VII via the chorda tympani
(anterior 2/3) and by IX (posterior 1/3; (Clemente plate 539; Grant
p. 676; Netter 3e 54, 4e 58).
- The taste buds in the epiglottis and the pharyngeal walls
are innervated by X.
- The taste buds in the palate are innervated by cranial
nerve VII via the greater petrosal nerve. Branches from the latter are
distributed by the greater and lesser palatine nerves (Clemente plate
532 fig. 849; Grant p. 683, 831; Netter 3e 48, 4e 52).
Muscles of the tongue
1) The 3 extrinsic muscles of the tongue change the position of the tongue.
- The genioglossus attaches to the superior genial
tubercles and protrudes the tongue (Clemente plate 540; Grant p. 679-680;
Netter 3e 59; 4e 63).
- The hyoglossus depresses the tongue.
- and the styloglossus retracts the tongue.
2) The intrinsic (longitudinal, transverse and vertical)
muscles change the shape of the tongue.
The lingual artery:
- is a branch from the external carotid artery and supplies
- courses anteriorly on the middle constrictor (Clemente
plate 460 fig. 724; Grant p. 763, 781; Netter 3e 53, 4e 59, 69) parallel with
cranial nerve XII.
- The hyoglossus muscle intervenes between cranial
nerve XII (lateral) and the lingual artery (medial). The lingual artery
is the only major structure medial to the hyoglossus muscle (Clemente plate
535 fig. 855; Grant p. 679-680, 780-781; Netter 3e 55, 4e 59).
- Dorsal lingual branches from
the lingual artery are given to the dorsum of the tongue
- and deep lingual arteries are given to the body
of the tongue.
- Other terminal branches supply the genioglossus muscle
and the sublingual gland.
- Lymphatics follow arteries and drain to both right and
left jugular lymphatic trunks of the neck (Clemente plate 455; Grant p.
676, 716; Netter 3e 68, 4e 73).
In each adult jaw (Clemente plates 544, 545; Grant p.
685-689; Netter 3e 52-53, 4e 56-57):
- 4 incisors
- 2 canines
- 4 premolars
- 6 molars
Nerve supply of teeth and gums (Clemente plate 542 fig.
866; Grant p. 687; Netter 3e 41, 42, 4e 45-46):
V2 supply the teeth and gums of the maxillary arch.
- The molar teeth are supplied by the posterior
superior alveolar nerve from the pterygopalatine fossa.
- The bicuspids (premolars) are innervated by the
middle superior alveolar nerve from the infraorbital nerve.
- The canines and incisors are innervated by the
anterior superior alveolar nerve from the infraorbital nerve
- The gums on the palatal surface are innervated by the
nasopalatine nerve (incisors) and greater palatine nerve
(bicuspids and molars; Clemente plate 527; Grant p. 683; Netter 3e 39, 4e
V3 supplies teeth and gums of mandibular arch.
- The inferior alveolar (dental) nerve innervates
all the teeth in the mandible.
- The gums of the molars and bicuspids are innervated by
the long buccal nerve
- The gums of the incisors are innervated by the mental
- The lingual gums are innervated by the lingual nerve.
THE EAR AND THE TEMPORAL BONE
Text: Gross Anatomy, K. W. Chung, 6th edition: pp.
Reference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th
edition: pp. 1022-1037; 6th edition: pp. 966-980
Clemente’s Anatomy Dissector, 2nd edition: pp. 425-432
Grant’s Dissector, P.W. Tank, 14th edition: pp. 255-259
The EXTERNAL EAR
is formed by the:
- Auricle (Clemente plate 564; Grant p. 703;
Netter 3e 87-88, 4e 92-93): is made of elastic cartilage and is
continuous with the cartilage of the external acoustic meatus and the lobule
(which is formed by loose connective tissue).
- External acoustic meatus (Clemente plate 566 fig.
921; Grant p. 703; Netter 3e 87, 4e 92)
The innervation of the skin of the ear:
- The superior portion is innervated by V3 via
the auriculotemporal nerve (Clemente plate 468; Grant p. 627, 703; Netter 3e 20, 4e
- The inferior portion including lobule is innervated
by fibers of the great auricular nerve from the cervical plexus (C 2, 3);
- The external acoustic meatus and the skin surrounding
the opening (concha) are innervated by the vagus nerve (X) for
general sensation (Clemente plate 468; Grant p. 703; Netter 3e 20, 4e 24).
Neurological examination of the skin of ear can determine
the status of the upper spinal cord (great auricular nerve, C 2, 3), the medulla (vagus X) and the pons
The external acoustic meatus (Clemente plate 566 fig.
921; Grant p. 703, 705; Netter 3e 87, 4e 92):
- extends from the concha to the tympanic membrane.
- Lateral cartilaginous 1/3 (lined with hair, sebaceous
glands and ceruminous glands)
- Medial bony 2/3 (thin stratified squamous epithelium,
also lining external surface of tympanic membrane).
- The auricular branch of the vagus (X) provides
the sensory innervation (Clemente plate 479; Grant p. 703;
Netter 3e 20, 120, 4e 24, 126).
The MIDDLE EAR or TYMPANUM
Sound waves create vibrations on the tympanic membrane
moving the 3 bony ossicles (malleus, incus and stapes) which
in turn vibrate the oval window (fenestra vestibuli) on the medial
wall of the middle ear: this is an amplification system (Clemente plate
566; Grant p. 704; Netter 3e 88, 4e 93, 95).
The middle ear is a modified bony sinus in the petrous
portion of the temporal bone. It communicates with the mastoid air cells
through the aditus to the mastoid antrum(Clemente plate
569; Grant p. 710, 713; Netter 3e 89, 4e 94) and with the nasopharynx through the auditory
tube (pharyngotympanic tube; Clemente plate 566; Grant p. 704-705; Netter 3e 87, 4e 92, 94).
The tympanic cavity and its walls:
- The roof is a thin layer of petrous temporal bone (Clemente
plate 566; Grant p. 708-709; Netter 3e 87, 4e 92) separating the middle
cranial fossa from the middle ear.
- The space below the roof is the epitympanic recess
(Clemente plate 566; Grant p. 708; Netter 3e 88-89, 4e 92-93) for
the articular joint of the head of the malleus and body of
- The floor of the tympanic cavity rests upon the superior
jugular bulb (Clemente plate 569 fig. 928, plate 573 fig. 935; Grant p.
710-711; Netter 3e 87, 4e 92).
- Where the internal carotid artery (moving anteriorly)
diverges from the internal jugular vein (moving posteriorly), the cranial
nerves IX and X send branches into the bony tympanic floor (Clemente
plate 571 fig. 932; Grant p. 710; Netter 3e 89, 4e 94, 125).
- Roof and floor converge anteriorly to form the auditory
tube which is divided by the processus cochlearis (Clemente
plate 569; Grant p. 711; Netter 3e 88-89, 4e 92-94) into:
- a superior compartment containing the tensor
muscle. The tensor tympani inserts into the handle of the malleus.
- and a lower compartment which joins with the cartilaginous
portion of the auditory tube.
- The lateral wall of the tympanic cavity is closed by
the tympanic membrane.
- The ascending carotid artery is associated with
wall of the tympanic cavity, separated by a thin layer of bone (Clemente
plate 571, fig. 932; Grant p. 710; Netter 3e 89, 4e 94).
- Pulsations may be heard by the patient in some clinical
- The posterior wall of the tympanic cavity contains a
tunnel, the aditus, connecting to the mastoid antrum.
- Fluid from the mastoid air cells drain via the aditus
into the tympanic cavity and then into the auditory tube and the nasopharynx.
- Fluid may collect within the tympanic cavity if the auditory
tube is obstructed due to an upper respiratory airway infection.
- The VIIth cranial nerve enters the posterior wall
below the aditus (Clemente plate 569 fig. 928; Grant p. 708, 710;
Netter 3e 89, 4e 94) and exits from the base of the temporal bone via the stylomastoid
foramen (Clemente plate 571 fig. 932; Grant p. 616, 712-713; Netter
3e 89, 4e 94).
- The chorda tympani arises from the facial nerve
within the posterior wall of the middle ear, courses over the eardrum along
the lateral wall (Clemente plate 569; Grant p. 708, 711; Netter
3e 89, 4e 94), and exits via the petrotympanic fissure into the infratemporal
- The pyramid is also located in the posterior wall.
The apex of the pyramid has an orifice through which the tendon of the
stapedius passes to insert on the neck of the stapes (Clemente
plate 570; Grant p. 708; Netter 3e 89, 4e 93-94).
- The stapedius acts to retract the stapes from the oval
window and reflexively attenuates loud sound. It is innervated by
cranial nerve VII and Bell's palsied patients may complain of sensitivity to
loud sounds (hyperacusis).
- The medial wall of the tympanic cavity faces the inner
ear contained within the petrous portion of the temporal bone.
- It has the promontory at its center, overlying
the first turn of the cochlea. Within the mucosa covering the promontory
is the tympanic plexus where fibers of VII, IX and X intermingle
(Clemente plates 570, 571; Grant p. 708, 710; Netter 3e 89, 4e 93).
Through this plexus will pass:
- sensory fibers to the external and middle ear
- and preganglionic parasympathetic fibers for the greater
(Clemente plate 571 fig. 932; Grant p. 834-835; Netter 3e 89, 4e 123, 125)
and lesser petrosal nerves.
- Posterior and superior to the promontory are the oval
window for the foot of the stapes, the canal for the facial (VIIth cranial) nerve
and the prominence of the lateral semicircular canal (Clemente
plates 570, 571; Grant p. 708, 710; Netter 89).
- The shape of the oval window matches the footplate of
- The canal of facial nerve is horizontal and connects
the internal auditory meatus to the descending canal of VII in the posterior
Posterior and inferior to the promontory is the round
window or fenestra cochleae (Clemente plate 570 fig. 930; Grant p.710; Netter 89-91), closed by a membrane (Netter 4e 94).
The tympanic membrane
- is circular (Clemente plate 567; Grant p. 706; Netter 3e 88,
- is set in a sulcus in the tympanic bone
- is oriented laterally, anteriorly and inferiorly ("catches
sounds from the ground as one advances").
- is lined with epidermis (ectodermal) laterally and mucous
membrane (endodermal) medially.
- The handle of the malleus is attached to the tympanic
- The superior pars flaccida of the eardrum attaches
to the lateral process of the malleus.
- The chorda tympani lies posterior to this pars flaccida
and must be avoided in puncturing the eardrum to drain the middle ear.
3 bony ossicles
(Clemente plate 568; Grant p. 707; Netter
3e 88, 4e 93-94)
2 synovial joints (between malleus and incus; between incus
and stapes; may be affected by otosclerosis resulting in deafness):
- Malleus has a head, neck,
manubrium with lateral process and an inferior tip. The anterior process
of the malleus is attached to a stabilizing ligament (Clemente plate
568 fig. 926; Grant p. 708; Netter 3e 88-89, 4e 93-94).
- Incus: The body of the incus
articulates with the malleus at the malleoincudal (incudomalleolar) joint (Clemente plate
568 fig. 926; Grant p. 707; Netter 3e 88, 4e 93-94).
- Short crus (process) attaches
via a ligament to the posterior wall of the epitympanic recess (Clemente
plate 568 fig. 925; Grant p. 709; Netter 3e 89, 4e 94).
- Long crus is vertically oriented
and descends into the tympanic cavity. It has a lenticular process,
which articulates with the head of the stapes.
- Stapes has a head, neck,
posterior and anterior limbs and footplate attached to the oval window
by an annular ligament.
The role of the middle ear is to transfer vibratory
sounds from the air to a fluid (perilymph):
- Vibratory surface of eardrum is 55 mm2 .
- Footplate is 3.2 mm2 .
- Hydraulic ratio between membrane and footplate is 17:1.
Muscles of the ossicles: the
contraction of either of these muscles attenuate sound by decreasing the
movement of ossicles.
1) The tensor tympani (Clemente plates 569, 570;
Grant p. 708; ; Netter 3e 88-89, 4e 93-94) in the auditory canal runs
around the processus cochleariformis to attach to the handle of the malleus:
the contraction tenses the eardrum by pulling medially. It is innervated
by a branch of V3 as it exits foramen ovale.
2) The stapedius in the pyramid of the posterior
wall, inserts into the neck of the stapes. The contraction pulls the foot
plate away from the oval window to dampen the sound. It is innervated by
The INNER EAR
is a bony labyrinth (Clemente plates 574-575; Grant
p. 704-705, 714; Netter 3e 90-91, 4e 95) containing a membranous labyrinth.
The bony labyrinth consists of:
- the cochlea,
- the vestibule
- and the semicircular canals.
1) The cochlea is shaped like a snail shell with
2.5 turns. Vibrations from the perilymph of the vestibule is communicated
to the fluids of the cochlea stimulating the hearing receptors of
the inner ear.
2) The vestibule lies between the cochlea and semicircular
canals, communicating with both chambers. It communicates with the tympanic
cavity via the oval window (fenestra vestibuli).
3) The 3 semicircular canals: anterior (superior),
posterior and lateral (horizontal). They lie in 3 planes like the corner
of a room. Their function is to maintain balance.
The membranous labyrinth (Clemente plate 575; Grant
p. 704, 714; Netter 3e 90, 4e 95-96) is surrounded by perilymph and
is formed by the cochlear duct, saccule, utricle and 3 semicircular
The ductus endolymphaticus passes from saccule
and utricle through a canal in the petrous bone, the vestibular aqueduct, to a fissure lateral to
the internal auditory meatus. It acts as a safety expansion, the
endolymphatic sac being placed extradurally.
Fluid waves from the perilymph are communicated to the
endolymph of the cochlear duct for hearing.
Angular acceleration of endolymph in semicircular canals
shifts the endolymph in the semicircular ducts and stimulate the vestibular
receptors in the ampulla of the semicircular canal.
The utricle (for detecting movements in the sagittal
plane) and the saccule (for detecting movements in the coronal plane)
are for head movements detection. This is based on gravitational forces
acting on their receptor mechanisms.
VIIIth cranial (Vestibulocochlear) nerve
(Grant p. 715; Netter 3e 118, 4e 124):
Test hearing by using a tuning fork placed against the
- If the eardrum and bony ossicles are impaired, then the
bony conduction should be heard normally. But if VIII is impaired then
total deafness is the result.
- Test balance by having patient stand with feet together
and eyes closed. If the vestibular portion of VIII is defective
then the patient will fall to the lesioned side.
The blood supply of the inner ear enters the internal acoustic
meatus with VII and VIII: This labyrinthine artery is a branch of
the anterior inferior cerebellar artery (Clemente plate 493, 574-575; Grant
647; Netter 3e 132-133, 4e 136, 139). It may be affected by strokes
in the vertebral arterial system.
VIIth cranial (Facial) nerve:
- is the nerve of the 2nd pharyngeal arch to the muscles
of facial expression, stylohyoid, posterior belly of the digastric and
- also carries the fibers of the nervus intermedius
for taste (special sensory) and preganglionic parasympathetic fibers to
all glands of the face, except the parotid gland.
The facial (VIIth cranial) nerve:
- runs through the internal auditory meatus with VIII (Clemente
plate 574; Grant p. 709; Netter 92),
- lies above VIII in the canal, above the vestibule of
the bony labyrinth,
- bends on the medial wall of the middle ear and forms
the genu with the geniculate ganglion,
- and courses to the posterior wall to descend through
the facial canal and exit through the stylomastoid foramen (Clemente
plate 573; Grant p. 710-711; Netter 3e 89, 4e 94).
The geniculate ganglion contain the cell bodies for the
taste fibers. There is no synapse in the geniculate ganglion.
The greater (superficial) petrosal nerve (Clemente plates 574-575; Grant p. 709-710;
Netter 3e 89, 4e 94) branches from the geniculate ganglion, pierces the anterior
wall of tympanic cavity, enters the middle cranial fossa. It carries taste
fibers for the palate, and secretomotor fibers for glands in the roof of
the oral cavity, the nasal cavity and the orbit.
The descending part of VII gives off a motor branch to
the stapedius and the chorda tympani (Clemente plate 572 fig. 934; Grant p.
831; Netter 3e 89, 4e 94).
The chorda tympani runs between the handle of the
malleus and the vertical process of the incus (Clemente plate 569; Grant
p. 708; Netter 3e 89, 4e 94) to exit into the infratemporal fossa
(Clemente plate 479; Grant p. 669; Netter 3e 42, 4e 46) via the
petrotympanic fissure. It carries taste fibers from the anterior 2/3 of
the tongue and secretomotor fibers to the submandibular ganglion.
Unilateral facial muscles paralysis
1) for loss of taste in the anterior 2/3 of tongue for
the integrity of the chorda tympani.
2) for hyperacusis to test the integrity of the
nerve to stapedius.
3) for lack of lacrimation on one side for the integrity
of the greater (superficial) petrosal nerve. If this is present,
it will result in dessication of cornea, ulceration and blindness. Dessication
of cornea will result in pain sensation carried by V1.
If all 3 signs are present then the lesion is between the
brainstem and the geniculate ganglion.
Bell's palsy usually
affects only branches of the facial nerve (VII) below the stylomastoid foramen.
LYMPHATIC DRAINAGE OF THE HEAD
Lymph nodes in the head and neck are organized into 2 groups:
1) A terminal (collecting) group which:
- is related to the carotid sheath
- is also named the deep cervical group (Clemente plate
455; Grant p. 716; Netter 68-69)
- All lymph vessels from the head and neck drain directly
to this group or indirectly via the
2) Intermediary, outlying groups
The jugular trunk:
- is formed by efferents of the deep cervical group
- drains on the right into the right lymphatic duct or
at the junction between the internal jugular and subclavian vein (Clemente
plates 156, 157; Grant p. 716; Netter 204).
- drains on the left into the thoracic duct or joins the
internal jugular or subclavian vein.
The deep cervical lymphatic nodes are organized into:
1) Superior deep cervical nodes (Clemente plate 455;
Grant p. 716; Netter 68)
- which can be found next to the upper portion of the internal
- and most lie deep to the sternocleidomastoid muscle.
- drain to the lower inferior group or directly to the
The jugulodigastric node is responsible for lymphatic
drainage of the tongue. It can be found in a triangle bordered by the posterior
belly of the digastric muscle, the facial and internal jugular veins.
2) Inferior deep cervical lymph nodes (Clemente
plate 455; Grant p. 716; Netter 68) are related to:
- the deep surface of the sternocleidomastoid muscle
- the lower portion of the internal jugular vein
- the brachial plexus and subclavian vessels
The jugulo-omohyoid node (Grant p. 716; Netter 68) at the level of the intermediate tendon of the omohyoid
muscle is concerned with lymphatic drainage of the tongue.
The inferior deep cervical lymph nodes drain into the jugular
Lymphatic drainage of superficial tissues of the head
2 types of drainage exist:
- Drainage by vessels afferent to local groups of nodes,
which in turn drain to the deep cervical nodes.
- Or direct drainage to deep cervical nodes.
Superficial drainage groups
1) In the head (Clemente plate 455; Grant p. 716; Netter 68):
- retroauricular (mastoid)
- buccal (facial)
2) In the neck:
- submandibular (Clemente
plate 455; Grant p. 716; Netter 68)
- anterior cervical
- superficial cervical (Clemente plate 157 fig. 243;
Grant p. 716; Netter 68)
Lymphatic drainage of scalp and ear
Submandibular nodes receive drainage from the frontal region
above the root of the nose.
Superficial parotid nodes (anterior to the tragus, superficial
and deep to the parotid fascia; Clemente plate 455; Grant p. 716; Netter 68) receive drainage from the:
- rest of the forehead
(Clemente plate 455; Grant p. 716),
- temporal region,
- upper half of the lateral auricular aspect
- anterior wall of the external acoustic meatus
- lateral vessels from the eyelids and skin of the zygomatic
Efferent vessels drain to the upper deep cervical nodes.
Upper deep cervical nodes and retroauricular (mastoid)
nodes (Clemente plate 455; Grant p. 716; Netter 68)
receive drainage from:
- a strip of scalp above the auricle
- the upper half of the cranial aspect and margin of the
- the posterior wall of the external acoustic meatus
The retroauricular nodes are found:
- superficial to the mastoid attachment of the sternocleidomastoid
- deep to the auricularis posterior
- They drain to the upper deep cervical nodes
Superficial cervical or upper deep cervical nodes receive
drainage from the:
- auricular lobule
- floor of the auditory meatus
- skin over the mandibular angle
- skin over the lower parotid region
Superficial cervical nodes:
- are distributed along the external jugular vein superficial
- have efferents:
- going around the anterior border of the sternocleidomastoid
to the upper deep cervical nodes
- following the external jugular vein to the lower deep
cervical nodes in the subclavian triangle.
The occipital scalp is drained:
- partly to the occipital nodes.
- partly by a vessel along the posterior border of sternocleidomastoid
to the lower deep cervical nodes.
The occipital nodes are mainly found superficial
to the upper attachment of trapezius and occasionally in the superior angle
of the posterior triangle of the neck.
Lymphatic drainage of the face
Lymph vessels draining the eyelid and conjunctiva:
- start in a subcutaneous and deep plexus around the tarsal
- are divided into lateral and medial vessels
Lymph vessels from eyelids and conjunctiva are organized
1) Lateral vessels :
- drain the whole thickness of both eyelids (except for
the medial parts)
- drain all of the conjunctiva
- run to the superficial parotid nodes and deep nodes embedded
in the parotid gland (Clemente plate 455; Grant p. 716; Netter 68).
- also receive lymph from the middle ear.
2) Medial vessels:
- drain the whole thickness of the medial parts of the
- drain the caruncular lacrimalis.
- run to the submandibular nodes.
- lie deep to the cervical fascia, in the submandibular
triangle (Clemente plate 461 fig. 726; Grant p. 716; Netter 68-69).
- are usually 3 in number:
- one at the anterior pole of the submandibular gland.
- two on either side of the facial artery as it reaches
- Other nodes may be embedded in the submandibular gland
or deep to it.
- drain a wide area
(Clemente plate 455; Grant p. 716) from the :
- submental nodes
buccal (buccinator) nodes
- lingual nodes
- drain to the upper and lower deep cervical nodes.
- drain directly the:
- external nose
- upper lip and lateral part of the lower lips
- the mucosa of lips and cheeks
- A few buccal (buccinator) nodes may be present near the
facial vein and they also drain to the submandibular nodes.
The skin over the root of the nose and central forehead
drains partly to the parotid nodes and partly to the submandibular nodes.
The lateral part of the cheek drains to the parotid nodes.
- are located on the mylohyoid, between the anterior bellies
of the digastric muscles (Clemente plate 460 fig. 725; Grant p. 716; Netter
- receive bilateral afferents.
- have efferents running to the submandibular and jugulo-omohyoid
nodes (Clemente plate 455; Grant p. 716; Netter 68).
Lymphatic drainage of the neck
Superficial vessels run:
- around the sternocleidomastoid, to the superior or inferior
deep cervical nodes.
- over the sternocleidomastoid and the posterior triangle,
to the superficial cervical and occipital nodes.
The superior region of the anterior triangle drains to
the submandibular and submental nodes (Clemente plate 455; Grant p.
716; Netter 68).
The anterior cervical skin below the hyoid bone drains
to the anterior cervical lymph nodes near the anterior jugular veins.
Efferents go to the deep cervical nodes bilaterally (infrahyoid,
prelaryngeal and pretracheal groups).
An anterior cervical node may often be found in the suprasternal
LYMPHATIC DRAINAGE OF THE DEEP TISSUES OF THE HEAD AND
Deep nodes are organized into
- Superior deep cervical nodes (Clemente plate 455;
Grant p. 716; Netter 68)
- Inferior deep cervical nodes
- Retropharyngeal nodes
- Paratracheal nodes
- Infrahyoid, prelaryngeal and pretracheal nodes.
- Lingual nodes.
The retropharyngeal nodes:
- are formed by a median and 2 lateral groups. The lateral
group is found bilaterally, anterior to the lateral process of the atlas,
along the border of the longus capitis muscle.
- lie between the pharyngeal and prevertebral fasciae.
- receive afferents from the nasopharynx, eustachian tube
and joints between the occipital bone, C1 and C2 vertebrae.
- drain to the upper deep cervical nodes.
- lie on either side of the trachea and esophagus, along
the recurrent laryngeal nerves (Clemente plate 549; Grant p. 716; Netter
- drain to the upper and lower deep cervical nodes.
Infrahyoid, prelaryngeal and pretracheal nodes
- are located deep to the cervical fascia.
- infrahyoid nodes are anterior to the thyrohyoid membrane.
- prelaryngeal nodes are on the conus elasticus and cricothyroid
ligament (Grant p. 716; Netter 68).
- pretracheal nodes are anterior to the trachea near the
inferior thyroid veins.
The infrahyoid nodes:
- drain afferents from the anterior cervical nodes.
- drain to the deep cervical nodes.
- form an inconstant group.
- are found on the external surface of the hyoglossus,
and between the genioglossi.
- drain to the upper cervical nodes.
Lymphatic drainage of nasal cavity and nasopharynx
- The anterior region of the nasal cavity drains superficially
to the submandibular nodes (Clemente plate 455; Grant p. 716; Netter 68).
- The rest of the nasal cavity, paranasal sinuses, nasopharynx
and pharyngeal end of the auditory tube drain via the retrophrayngeal nodes
or directly to the upper deep cervical nodes.
- the posterior nasal floor drains to the parotid nodes.
Lymphatic drainage of the middle ear.
- The mucosa of the tympanic membrane and the antrum drain
to the parotid or upper deep cervical lymph nodes.
- The tympanic end of the auditory tube drain to the deep
cervical lymph nodes.
Lymphatic drainage of the larynx.
Laryngeal lymphatic vessels:
- form superior and inferior groups, at the level of the
- anastomose on the posterior wall.
1) Superior vessels run with the superior laryngeal vessels
to the upper deep cervical nodes.
2) Inferior vessels run:
- between the cricoid cartilage and the first tracheal
ring to the inferior deep cervical nodes.
- or through the cricothyroid ligament to the pretracheal
and prelaryngeal nodes.
Lymphatic drainage of the trachea
A dense network of lymphatic vessels (tracheal plexus)
is present in the tracheal wall.
This tracheal plexus drains to:
- the pretracheal nodes (Grant p.
- the paratracheal nodes
- or directly to the inferior deep cervical nodes.
Lymphatic drainage of the thyroid gland
Lymphatic vessels from the thyroid gland communicate with
- prelaryngeal nodes (above thyroid isthmus) via the tracheal
- pretracheal nodes,
- paratracheal nodes,
- brachiocephalic nodes (in superior mediastinum),
- deep cervical nodes via the superior thyroid vessels,
- and directly to the thoracic duct.
Lymphatic drainage of the mouth
- Gingiva drain to the submandibular nodes (Clemente
plate 455; Grant p. 716; Netter 68).
- Soft and hard palate drain to the superior deep cervical
nodes and the retropharyngeal nodes.
- Anterior part of the floor of the mouth drains via the
submental nodes or directly to the superior deep cervical nodes.
- Rest of the floor of the mouth drains to the submandibular
and superior deep cervical nodes.
Lymphatic drainage of the teeth
Lymphatics from the teeth pass to the submandibular and
deep cervical nodes.
Lymphatic drainage of the tonsil
The lymphatic drainage of the tonsil drains to the superior
deep cervical nodes:
- most to the jugulodigastric node.
- some to the small nodes on the lateral aspect of the
internal jugular vein.
Lymphatic drainage of the tongue
The lingual mucosal plexus is continuous with the intramuscular
- The anterior 2/3 of the tongue drains into the marginal
and central vessels.
- The posterior 1/3 of the tongue drains into the dorsal
Marginal vessels of the tongue
- arise from the tip of the tongue and frenulum.
- drain bilaterally to the (Clemente plate 455; Grant
p. 716; Netter 69):
- submental nodes,
- jugulo-omohyoid node,
- anterior or middle submandibular node,
- jugulo-digastric nodes.
Central vessels of the tongue
follow the lingual vein to drain to:
- deep cervical nodes (jugulodigastric and juguloomohyoid
- submandibular nodes.
Dorsal vessels of the tongue
- join with the marginal vessels
- drain into the jugulodigastric node or juguloomohyoid
Lymphatic drainage of the pharynx and cervical part of
- through the retropharyngeal or paratracheal (Clemente
- Grant p. 716; Netter 68) nodes
- or directly to the deep cervical nodes.
The epiglottis drains to the infrahyoid nodes.
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