THE UPPER TRUNK
THE LIST OF TOPICS
Deep back and suboccipital triangle
Gross Anatomy, K. W. Chung, 6th edition: pp. 293-320
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 478-553; 6th edition: pp. 440-507
Anatomy Dissector, 2nd edition: pp. 280-302
Dissector, P.W. Tank, 14th edition: pp. 5-18
The vertebrae are held together by the (Clemente 343-352; Grant p.
3e 146, 4e 158):
- intervertebral discs
- and synovial joints between the articular processes.
Movement between 2 vertebrae is slight but movement of
the vertebral column as a whole is over quite a range (Grant p. 292-293).
The thoracic vertebra (Clemente 347; Grant p. 300-301; Netter 3e 147, 4e
- The body of the vertebra is the weight-bearing part and
contains red bone marrow, drained by basivertebral veins (Clemente 361; Grant p. 309; Netter
3e 166, 4e 173).
- The neural arch and the processes exist:
- for the protection of the spinal cord (Clemente 360; Grant p. 304-305; Netter
3e 163, 4e 170)
- for attachment of muscles
- for articulation with ribs (long transverse processes)
- and for regulation of movements.
- Superior and inferior articular facets form synovial
joints with the adjoining articular facets (Clemente 348; Grant p. 291, 300; Netter
3e 147, 4e 154).
- The spinous process is downturned so as to overlap the
The cervical vertebra (Clemente 342-344; Grant
p. 294-295; Netter 3e 16, 4e 18-19):
- has a smaller body which carries less weight and overlaps
the lower vertebra anteriorly (Clemente 343, Grant p.
295; Netter 3e 16, 4e 19).
- has a bifid spinous process
- The transverse process has (Clemente 342; Grant p. 294; Netter
3e 16, 4e 18):
- anterior and posterior tubercles
- and a transverse foramen.
- All vertebrae have costal elements (Grant p. 290), but in the cervical, lumbar and sacral regions, they are
incorporated into the vertebrae. Thus, in the cervical vertebrae, the posterior
tubercle is the true transverse process and the anterior tubercle
is the costal element.
C7 costal element may form a cervical rib. C7 is the vertebra
prominens (but is usually less prominent than T1).
- C1 (Atlas) and C2 (Axis)
are atypical (Clemente 342; Grant p. 297;
Netter 3e 15, 4e 17).
- The dens of C2 protrudes through the ring of the atlas
(Clemente 343; Grant p. 297; Netter 3e 15, 4e 17) and
is held in place by a transverse ligament (Clemente 344;
Grant p. 299; Netter 3e 18, 4e 22).
- The upper articular facets of C1 are concave (for the
occipital condyles - "YES" joint) and the lower articular facets
of C1 are flatter ("NO" joint; Clemente 342;
Grant p. 299; Netter 3e 15, 4e 17).
The lumbar vertebrae (Clemente 350-351; Grant p.
302-303; Netter 3e 148-149, 4e 155-156)
- are the most massive vertebrae, with increasing body
- The lumbar spines are massive and project posteriorly.
Since they do not overlap, lumbar pucture may be performed at this level.
- is formed by 5 sacral vertebrae fused into one (Grant
p. 313; Netter 3e 150, 4e 157).
- has 4 intervertebral foramina modified into anterior
and posterior sacral foramina, transmitting anterior and posterior primary
rami of sacral nerves (Clemente 353; Grant p. 313; Netter 3e 150, 4e 157).
- The lower opening of the sacral canal may be used for
introduction of anesthetic into the vertebral canal.
- Auricular surfaces are found at the sides for articulation
with the ilium (Clemente 353; Grant p. 313;
Netter 3e 150, 4e 157).
The intervertebral joints are symphyses between
the vertebral bodies (Clemente 352, Grant p. 304-305; Netter 3e 148, 4e 158).
- A layer of hyaline cartilage and fibrocartilage (anulus
fibrosus) forms the intervertebral disc (Clemente 352;
Grant p. 305; Netter 3e 148, 4e 155).
- The intervertebral disc has a high water content. The
nucleus pulposus is rich in glycosaminoglycans.
- The intervertebral discs are compressed by the weight
of the body resulting in differences in height between the beginning and
end of the day.
Pathological problems associated with the intervertebral
disc (Grant p. 308; Netter 3e 156, 4e 152):
- Herniated disc.
- Schmorls's node: the upward
herniation erodes the body of the adjacent vertebra.
Ligaments of the vertebrae:
2 ligaments per component of the vertebra, i.e., paired components are each
joined by one ligament and unpaired components are joined by 2.
- The vertebral spines are joined by supraspinous and interspinous
ligaments (Clemente 351; Grant p. 308; Netter
3e 152, 4e 158).
- The vertebral bodies are joined by the anterior and posterior
longitudinal ligaments (Clemente 348-349, 351; Grant p. 306-307; Netter 3e 151-152,
- The paired articular processes are joined by the capsular
ligaments of the synovial (zygapophyseal) joints (Clemente 350; Grant p. 304; Netter
3e 151, 4e 158).
- The transverse processes are joined by the intertransverse
- The laminae are joined by the ligamenta flava (Clemente
349; Grant p. 306; Netter 3e 151, 4e 158).
There is no ligament between the pedicles because of
the intervertebral foramina and the emergence of spinal nerves.
Flexures (curvatures) of the vertebral column (Clemente 346;
Grant p. 287; Netter 3e 146, 4e 153):
- Cervical flexure (support of head)
- Thoracic flexure (original fetal curve)
- Lumbar flexure (support of trunk for standing and walking).
Movements of the vertebral column are anterior flexion,
extension, lateral flexion (Grant p. 307) and rotation.
Rotation is free in the thoracic region because the superior
articular facets face postero-laterally. But in the lumbar region, it is
almost nonexistent because the superior articular facets face almost medially
(Clemente 347, 350; Grant p. 303; Netter 3e 147-148, 4e 154-155).
On a flexed trunk, the spines of most vertebrae are palpable
except for the first 6 because of the anterior cervical flexure. So C7,
T1, etc..are palpable vertebral spines.
- The scapula lies between T2-T7.
- The supracristal plane runs between the 2 highest point
of the iliac crest through L4.
- The posterior superior iliac spines lie at the level
The spinal cord ends in the adult at L1 and the subarachnoid
space at S2 (Clemente 356-357; Grant p. 344; Netter
3e 154, 4e 160-161).
A lumbar puncture is performed at the level of L3-4.
The needle passes (Clemente 351, 360; Grant
p. 308; Netter 3e 151, 4e 163):
- through/along the supra- and interspinous ligaments,
- through/along the ligamenta flava,
- and finally the dura and arachnoid into the subarachnoid
MUSCLE LAYERS OF THE BACK are
organized into 3 layers.
- A superficial group (see lecture notes on the Superficial
- An intermediate group
- A deep group
The intermediate group
- is formed by the serratus posterior superior and inferior
(Clemente 332; Grant p. 322; Netter 3e 167, 4e 174-175).
- has respiratory functions. They elongate the thoracic
cavity and are thus muscles of inspiration.
- are innervated by the ventral rami of intercostal nerves.
The deep group are intrinsic muscles
of the back. When acting jointly, they extend the vertebral
joints (they prevent/regulate flexion at these joints). Unilaterally, they
laterally bend and rotate the spinal column.
The splenius capitis and cervicis (Clemente 332;
Grant p. 323; Netter 3e 167-168, 4e 174)
- attach from the inferior 1/2 of the ligamentum nuchae
and spines of T1-5.
- Splenius capitis attaches to the superior nuchal line
and mastoid process (along with the sternocleidomastoid).
- Splenius cervicis attaches to the transverse processes
of C1-4 (along with levator scapulae).
The thoracolumbar fascia (Clemente 332; Grant p. 321;
Netter 3e 167, 4e 174)
- The lumbar portion is the dorsal aponeurosis of the transversus
- The superficial layer attaches to the lumbar spines.
- The deep layer attaches to the tips of the lumbar transverse
- The thoracic portion attaches from the vertebral spines
to the angle the ribs, over the deep dorsal muscles.
The erector spinae:
- fill the grooves between the spines of the vertebrae
(Clemente 327; Grant p. 324; Netter 3e 172, 179),
the transverse processes and the ribs (they form the edible part of the
- start from the sacral region, enlarge and are powerful
in the lumbar region (Clemente 331; Grant p. 323;
Netter 3e 168, 4e 175-176).
- splits into columns of separate muscles attaching to
spines, transverse processes and ribs in the thoracic region (Clemente
332; Grant p. 323; Netter 3e 168, 4e 175).
- The longest bundle is most superficial and the shortest
is deep, in contact with the bone.
The erector spinae are also called sacrospinalis.
They attach from the pelvis to the skull.
They split near rib 12 into:
- The iliocostalis attaches to the angles of the
ribs and C4-6 transverse processes.
- The longissimus (thoracis, cervicis and capitis)
attach into the lumbar accessory and transverse processes, thoracic transverse
processes and parts of T2-12. Bundles arising from T1-4 attach to C2-6.
- The spinalis is found only in thoracic regions.
Oblique muscles: The transversospinalis
group is deep to the erector spinae, run from transverse processes to spines
and are disposed in 3 layers (Clemente 335, 337; Grant p. 325, 328; Netter 3e 169,
Semispinalis (Clemente 335; Grant p. 328; Netter 3e 168, 4e
- forms the superficial layer.
- has a more vertical course (from near the tips of transverse
processes to the tips of spinous processes)
The semispinalis capitis attaches from the transverse processes
of T1-5 and the articular processes of C4-7 to the occipital bone (Clemente
333; Grant p. 328; Netter 3e 168, 4e 175).
The large uppermost muscle is the semispinalis capitis
which forms the ridges on either side of the posterior midline of the neck,
covered by trapezius. It is innervated by the dorsal primary rami of all
Multifidus (Clemente 335; Grant p. 328;
Netter 3e 169, 4e 176)
- attach from the dorsal sacrum between the spinous and
transverse crests from all transverse processes (up to C4) and from adjacent
ligaments and fascia of erector spinae,
- to the inferior border of C2-L5 spinous processes.
Rotatores (Clemente 335; Grant p. 329;
Netter 3e 169, 4e 176)
- originate from the inferior transverse process,
- attach to the superior spinous process or lamina.
Interspinales (Clemente 335; Grant p. 328; Netter
3e 169, 4e 176) and intertransversarii.
- are well developed in cervical and lumbar regions but
absent from thoracic regions.
- Interspinales unite bifid tubercles of adjacent cervical
spinous processes and adjacent border of lumbar spines.
- Intertransversarii (anterior and posterior) unite adjacent
anterior tubercles and adjacent posterior tubercles of cervical transverse
SPINAL CORD AND MENINGES
- At birth, the spinal cord is at L3.
- In the adult, at L1 (Clemente 356; Grant p.
344; Netter 3e 154, 4e 160-161).
The upper cervical nerves pass horizontally from cord to
intervertebral foramina but the nerve roots become more oblique inferiorly.
They become vertical at L1 forming the cauda equina which is composed
of anterior and posterior nerve roots (Clemente 358; Grant p. 334;
Netter 3e 154, 4e 161).
The true end of the spinal cord is the conus medullaris,
which is attached by the filum terminale to provide vertical stability
to the spinal cord (Clemente 359; Grant p. 334; Netter 3e 153-154,4e 161).
The denticulate ligaments are formed by reflections
of pia mater and are responsible for the lateral stability of the spinal
cord (Clemente 358; Grant p. 335; Netter 3e 162, 4e 169).
The subarachnoid space ends at S2 (Clemente 357;
Grant p. 337; Netter 3e 154, 4e 161). The filum terminale pierces the
dura and runs to the posterior aspect of coccyx as the coccygeal ligament.
The dura mater is prolonged along spinal nerves for a short
DORSAL RAMI OF SPINAL NERVES (Clemente 361;
Grant p. 20, 338; Netter 173)
- are typical except for the first 2 and the last 3.
- typically originate lateral to the spinal ganglion and
pass dorsally on the side of the superior articular process (dorsal sacral
rami use dorsal sacral foramina).
- supply skin and deep muscles of the back medial to the
angles of the ribs (Clemente 329; Grant p. 20; Netter
3e 173, 4e 177).
- innervate the articular facets of vertebrae which are
synovial joints and may, in time,be affected by arthritis.
Some cutaneous branches travel further:
- C2 (greater occipital nerve) to scalp (Clemente 338; Grant p. 330; Netter
3e 170, 4e 178).
- T2 (intercostobrachial nerve;
- L1, 2, 3 to the gluteal region.
Each dorsal ramus divides into medial and lateral branches
(except C1, S4, S5 and Co1) and either one ends as a cutaneous branch (except
for C1, C6, C7, C8, L4 and L5).
VENOUS PLEXUS (Clemente plate 433 fig. 689; Grant p.
309; Netter 166)
The vertebral column has a dense plexus of thin-walled
valveless veins surrounding the spinal dura mater.
The plexus communicates superiorly with the occipital and
basilar sinuses of the cranium (Clemente plate 489; Grant p. 639; Netter 97, 98).
The vertebral venous plexus (Clemente 361; Grant
p. 309; Netter 3e 166, 4e 173):
- is divided into anterior and posterior longitudinal
- receives a vein from the spinal cord and a
basivertebral vein from the body of a vertebra at each segment.
- is drained by intervertebral veins passing through the
intervertebral (sacral) foramina to the vertebral, intercostal, lumbar
and lateral sacral veins.
There is also an anterior external vertebral plexus
formed by veins from the body of the vertebrae and a posterior external
vertebral plexus formed by veins passing through the ligamenta flava
(Clemente 359, 361; Grant p. 305; Netter 3e 166, 4e 173).
The suboccipital triangle
The apex of the posterior triangle of the neck is formed
by the posterior border of the sternocleidomastoid and the anterior border
of the trapezius (Clemente 338; Grant p. 332; Netter
3e 167, 4e 178).
Under the trapezius is the semispinalis capitis (Clemente
338; Grant p. 330; Netter 3e 167, 4e 178) which is attached
to the skull between the superior and inferior nuchal lines (Clemente
516; Grant p. 332; Netter 3e 8, 167, 4e 8).
The occipital artery emerges from under cover of the splenius
capitis and breaks into branches to supply the back of scalp.
2 nerves emerge through the semispinalis capitis and supply
the skin of scalp:
1) The greater occipital nerve (dorsal primary ramus of
2) The third occipital nerve (dorsal primary ramus of
The suboccipital triangle is deep to C3.
- The superior and inferior nuchal lines on the occipital
- C1 (atlas) has a posterior tubercle (It has no spine
to allow for head extension in looking up), and long transverse processes
(for use as levers in rotation of the head and C1 on the dens; Clemente
342; Grant p. 297; Netter 3e 15, 4e 17).
- The spine of the axis.
Muscles (Clemente 339-341; Grant p. 330-331; Netter 3e 168-169,
- Rectus capitis posterior (RCP) major attaches from the spine of the axis to below the inferior nuchal
line, lateral to RCP minor.
- RCP minor attaches from the
posterior tubercle of the Atlas to below the inferior nuchal line, bilaterally.
- Obliquus superior attaches
from the transverse process of the Atlas to the area between the nuchal
lines lateral to semispinalis.
- Obliquus inferior attaches
from the spine of the Axis to the transverse process of the Atlas.
The vertebral artery
- runs through the transverse foramina of the upper 6 cervical
vertebrae (Clemente 490; Grant p. 333; Netter 3e 17, 4e 21).
- emerges onto the upper surface of the Atlas, passes posteriorly,
closely related to the articular facet to reach a deep groove on the superior
aspect of the posterior arch of the atlas (Clemente 339;
Grant p. 332; Netter 3e 171, 178)
- passes into the foramen magnum to meet with the opposite
vertebral artery and to form the basilar artery.
*If the vertebral artery is affected by atheroma (atherosclerosis),
movements of head and neck may affect movement of blood through it and cause
faintness or unconsciousness.
- emerges from the spinal cord
- lies in the groove between artery and bone.
- the dorsal primary ramus (named the suboccipital nerve)
enters the suboccipital triangle and innervates the muscles (Clemente
339; Grant p. 330-331; Netter 3e 171, 4e 178).
- the ventral primary ramus runs forward, lateral to the
superior articular facet and joins the hypoglossal nerve (cranial nerve
XII; Grant p. 839; Netter 3e 67, 122, 4e 128).
C2 emerges between the Atlas
and the Axis (Clemente 640; Grant p. 330-331; Netter
171) and travels superiorly over the suboccipital triangle to form the
greater occipital nerve.
C3 emerges between axis and
Thorax and lungs
Anatomy, K. W. Chung, 5th edition: pp. 131-145
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 75-135; 6th edition : pp. 72-127
Anatomy Dissector, 2nd edition: pp. 76-96
Dissector, P.W. Tank, 14th edition: pp. 54-64
- is flattened anteroposteriorly in the adult.
- is covered by upper limb muscles (Clemente 102;
Grant p. 3; Netter 3e 176, 4e 188-189).
The thoracic spinal nerves supply thoracic as well as the
abdominal wall (Clemente 176; Grant p. 101-104; Netter 3e 249, 4e 188).
The ribs enclose and protect some of the abdominal viscera
(Clemente plates 188-189; Grant p. 96-97; Netter 260).
The 12 thoracic vertebrae (Clemente 109; Grant
p. 300-301; Netter 3e 147, 4e 268) have the following landmarks:
- The body or centrum is flattened, on the left side, from
T6 down due to the impression of the descending aorta.
- The pedicle
- The transverse processes
- The spinous processes
- The articular processes (synovial joints)
- The laminae, which are removed during a laminectomy to
gain access to the spinal cord.
- The vertebral foramen forms the vertebral canal with
the vertebral foramina from other vertebrae.
- The intervertebral foramina formed by vertebral notches
are the exit points for the spinal nerves.
The 12 pairs of ribs (Clemente 103-109; Grant p.
10-11; Netter 3e 178-179, 4e 185-187)
- rib + cartilage = costa
- Ossification begins around 9th prenatal week and spreads
in both directions.
- Epiphyses capping the head and tubercle fuse by year
- Ribs 1-7 are classified as vertebrosternal.
- Ribs 8-10 are classified as vertebrochondral.
- Ribs 11 and 12 are classified as vertebral (floating).
The different parts of the ribs have the following articulations:
- The head articulates with the sides of bodies of 2 vertebrae
(at the same and superior levels; Clemente 347-349; Grant p.
14-15; Netter 3e 180, 4e 187), except for rib 1, 11, and 12. It is attached
to the intervertebral disc by an intraarticular ligament, but not ribs 1, 11, and 12.
- The neck
- The articulating tubercle attaches to the transverse
process of vertebra at the same level (rib 6 is attached to T6); this is
a synovial joint called the costotransverse joint.
Costotransverse joints (Clemente
347-348; Grant p. 15, 17; Netter 3e 180, 4e 187)
- The superior joints (ribs1-7) permit mostly rotation
of the rib and the inferior ones (ribs 8-10) permit mostly gliding movement
for the articulated rib.
- Attachments are by medial (neck) and lateral (tubercle)
costotransverse ligaments. The superior costotransverse ligament descends
from the superior transverse process to the crest of inferior rib.
The rib has the following landmarks (Clemente 106; Grant p. 13-14; Netter
3e 179, 4e 186):
- The crest for attachments of the superior costotransverse
- The angle
- The body
- The costal groove
The costovertebral articulation is formed by the
joint of the head and the joint of the tubercle of the rib (Clemente
347; Grant p. 15; Netter 3e 180, 4e 187).
The sternocostal articulation: the joint cavity
is divided into 2 by an intraarticular ligament and closed ventrally by
ligaments radiating from the perichondrium to the sternum (Clemente 104, 107; Grant p. 12; Netter
3e 179, 4e 186).
Interchondral joints exist
between the costal cartilages of ribs 7, 8, and 9 (Clemente 104; Grant p. 12; Netter
3e 179, 4e 186)
The sternum contains red bone marrow and is thus used for
sternal punctures in diagnosing blood diseases.
The manubrium (Clemente 104-105; Grant p. 12; Netter 3e 179,
- has the jugular (suprasternal) notch.
- articulates with the clavicle at the sternoclavicular
joint (the only bony attachment point of the upper limb to the trunk),
rib 1 and half of rib 2.
- forms the attachment points for the pectoralis major,
sternocleidomastoid, sternohyoid and sternothyroid muscles.
The sternal angle (of Louis) or manubriosternal joint is
a cartilaginous joint and is at the same level as: (Clemente 130; Grant p.
26, 27, 29; Netter 3e 178, 192, 4e 233)
- the 2nd rib and T4, 5 vertebrae
- the carina of trachea.
- the aorta crossing from right to left.
The second intercostal space is used for listening to aortic
(right) and pulmonary (left) valves (Clemente 129; Grant
p. 44, Netter 213).
The body of the sternum (Clemente 104; Grant p. 10: Netter
3e 179, 4e 186)
- develops from bilateral sternal bars. If they fail to
fuse, a sternal foramen (Grant p. 16) or bifid xiphisternum
- 4 fused sternebrae (ossify during the 3rd trimester of
- articulates with half of the head of rib 2 and the heads
of ribs 3-7.
- contains red bone marrow.
- forms the attachment site for the pectoralis major
plate 11; Grant p. 4; Netter 3e 182, 4e 188), and transversus thoracis posteriorly (Clemente
110; Grant p.
21, 23; Netter 3e 184, 4e 191).
The xiphoid process (Clemente 105, 8; Grant p. 348; Netter
3e 157, 4e 185-186, 164)
is at the level of the 6th thoracic dermatome on the anterior
surface of the body.
The thoracic inlet is located
superiorly and is the site of entrance of the viscera and vessels from the
head, neck and upper limb into the thorax (Clemente 113;
Grant p. 25; Netter 3e 190, 4e 198).
The thoracic outlet is closed
by the diaphragm, pierced by the inferior vena cava (T8), aorta (T12) and
esophagus (T10), and innervated by the phrenic nerves (C3, 4, 5; Clemente
156-157, 163; Grant p. 25, 73; Netter 3e 188, 229, 4e 194232-233).
- Paraplegic (2-limb paralysis)
- Quadriplegic (4-limb paralysis)
- Pentaplegic (involvement of the diaphragm due to a lesion
affecting C3, 4, 5).
Muscles of the thoracic wall (Clemente 110; Grant p.
17-18, 21-24; Netter 3e 182-185, 4e 188-189, 191-192)
- The external intercostal muscles project inferiorly
in a posterior to anterior direction. They are replaced in the front by
the external intercostal membrane. They are most active in INSPIRATION
- The internal intercostal muscles project superiorly
in a posterior to anterior direction (perpendicular to fibers of external
intercostals). They are replaced in the back by the internal intercostal
They are most active in EXPIRATION.
- The innermost intercostal muscles include the transversus thoracis. The transversus thoracis arises from the back of the sternum
and the xiphoid process and inserts onto costochondral junctions from ribs
3-6. Innermost intercostal muscles can bridge more than one intercostal space.
The primary role of the intercostal muscles is to act together
to stiffen the chest wall, preventing paradoxical motion during descent
of the diaphragm in inspiration.
- In a healthy adult with a vital lung capacity of 4.5
litres, about 3 liters is accounted for by diaphragmatic excursion
after high spinal injury where there is flaccid paralysis of the entire
trunk and only the diaphragm is left functioning, the vital lung capacity
falls to 300 milliliters although the diaphragm is moving maximally. Some
2.7 litres are lost by paradoxical incursion of the flaccid chest wall as
the diaphragm descends.
- Within several weeks, the paralysis becomes spastic,
stiffening the chest wall, and the vital lung capacity rises to its phrenic
limit of about 3 litres.
Intercostal vein, artery and nerve form a neurovascular
bundle lying between internal intercostals and innermost intercostals (Clemente
158-159; Grant p. 17-20; Netter 3e 184-187, 4e 192).
Intercostal nerves are mixed nerves containing both motor
and sensory fibers (Clemente 163; Grant p. 20; Netter
3e 187, 4e 192).
- Posterior (dorsal) rami innervate back muscles between
the angle of the ribs and the spinous processes of the vertebrae, with
cutaneous branches innervating the overlying skin.
- Anterior (ventral) rami innervate intercostal musculature,
periosteum of the ribs and skin of the thorax (dermatome).
- T7, 8, 9 , 10 and 11 innervate the abdominal wall (Clemente
176; Grant p. 100-101; Netter 3e 249, 4e 257).
- T12 (the subcostal nerve) and L1 innervate the region
above the pubis.
Intercostal arteries and veins
- Intercostal vessels bifurcate in intercostal spaces and
have branches running in the intercostal groove as well as collateral branches
above the body of the subjacent rib (Clemente 158; Grant p. 17-18; Netter
3e 187, 4e 192).
- The posterior intercostal arteries in the first 2 intercostal
spaces arise from the costocervical trunk, branching from the subclavian
artery (Clemente 158; Grant p. 75; Netter 3e 29, 4e 33).
- Other posterior intercostal arteries are branches of
the thoracic aorta.
- The posterior intercostal veins drain into right azygos
and left hemiazygos system. The superior veins also drain into the brachiocephalic
veins (Clemente 159; Grant p. 76; Netter 3e 226-227, 4e 238).
- Anterior intercostal arteries and veins arise from the
internal thoracic vessels (Clemente 111; Grant p. 22-23; Netter
3e 183-184, 4e 191) and anastomose with the posterior vessels
in the intercostal spaces around the midclavicular line (Grant p. 20,
Netter 3e 187, 4e 192). They also supply the skin over the sternum by perforating
The internal thoracic artery:
- is a branch of the subclavian artery.
- runs between the transversus thoracis and the sternum.
- terminates inferiorly by dividing around the xiphisternal
joint into the superior epigastric artery (which enters the rectus sheath
inferiorly; Clemente 111; Grant p. 103; Netter
3e 176, 4e 192-193) and the musculophrenic artery (which follows the attachment of
the diaphragm to the ribs).
- also sends branches to the thymus, bronchi and pericardium.
The parasternal lymph nodes (Clemente 7; Grant
p. 9; Netter 3e 177, 4e 184) drain this anterior region and also the
medial aspect of the breast. Examination is required if a tumor is found
in the medial 1/2 of the breast.
The thoracic cavity contains:
- right and left pleural cavities (Clemente 113;
Grant p. 26; Netter 3e 192-193, 4e 198).
- right and left lungs.
- the mass of the mediastinum in the middle (Clemente 130; Grant p. 29; Netter
3e 198, 4e 212).
The mediastinum contains (Clemente 126-127, 130;
Grant p. 48-49; Netter 3e 190, 4e 211-212, 230-232):
- the heart
- the pericardium and associated great vessels.
- the trachea and the structures traversing the thorax
such as the esophagus, the vagus nerves, the phrenic nerves and the thoracic
A change in the pressure in one pleural cavity may deflect
the mediastinum to the opposite side. This can be checked by the position
of the trachea at the root of the neck.
The lungs and heart are contained within separate pleural
and pericardial cavities and are separated from the abdomen by the diaphragm
(Clemente 113; Grant p. 25, 28; Netter 3e 190, 4e 212-213).
An imaginary line joining the manubriosternal joint and
T4-T5 subdivides the mediastinum into superior and inferior parts (Clemente
130; Grant p. 29; Netter 3e 227, 4e 230-231, 233).
The visceral pleura
- is a layer of simple squamous epithelium over surface
- is not innervated and thus is insensitive to pain
- provides a moistened and lubricated surface for lung
Adhesions with the parietal pleura may result from infections,
inflammatory reactions and lung immobility.
The parietal pleura (Clemente 114-116; Grant
p. 28, 30-31; Netter 3e 192-193, 4e 196-197)
- is attached to the costal, diaphragmatic and mediastinal
surfaces by the endothoracic fascia.
- projects into the root of the neck as the cupula. This
area is vulnerable to wounds and needles and its perforation will result
in equalization of external and pleural pressures, i.e. a pneumothorax.
The pressure in the pleural cavity is slightly below atmospheric pressure
but is referred to as "negative pressure".
- is innervated by free sensory nerve endings of the intercostal
and phrenic nerves. Pain may be referred to dermatomes served by
specific thoracic intercostal and phrenic nerves. Severe pain caused possibly
by adhesions is called pleurisy.
Visceral and parietal pleurae are continuous at the root
of the lungs, where pulmonary artery and vein, and bronchus penetrate the lung (Clemente
120; Grant p. 28, 34-35;
Netter 3e 195, 4e 199). The pulmonary ligament found inferior to the root of the
lungs is a segment of reflected pleura which forms a sleeve.
The parietal pleura:
- on the costal surface, is continuous with the mediastinal
pleura anterior to the vertebral column (vertebral reflection).
- is continuous with the mediastinal pleura posterior to
the sternum (sternal reflection).
- and is continuous with the diaphragmatic pleura near
the thoracic wall (costal reflection).
The parietal pleurae (Clemente 114-116; Grant
p. 30-31; Netter 3e 192-193, 4e 196-197):
- touch at the level of ribs 2-4.
- are separated between ribs 4-6 due to the heart indentation.
The base of the parietal pleurae is found:
- at the level of the 8th costal cartilage in the midclavicular
- at the level of the 10th costal cartilage in the midaxillary
- at the level of rib 12 dorsally.
The pleural cavity contains pleural fluid.
- Costodiaphragmatic recesses:
sampling of pleural fluids between ribs 8-10 is possible without lung penetration.
This is the costophrenic angle of radiologists. The costal and diaphragmatic
pleurae are in contact during expiration.
- Sternocostal recesses
- Costomediastinal recesses
over the heart and pericardium.
The lungs (Clemente 118-121; Grant p. 32, 34-35; Netter 3e 195,
- have rounded posterior borders shaped by the ribs and
sharp anterior borders fitting between the heart and the chest.
- have concave bases. The dome of the diaphragm is higher
on the right (T8) than on the left (T8/T9), due to the underlying mass
of the liver, so the right lung is shorter.
The base of the lungs (Clemente 114-116; Grant
p. 30-31; Netter 3e 192-193, 4e 196-197)
- is found:
- at the level of the 6th costal cartilage in the mid-clavicular
- at the level of the 8th costal cartilage in the mid-axillary
- at the level of rib 10 dorsally.
- Due to the position of the heart, the base of the right
lung is broader than that of the left lung (Clemente 201; Grant
p. 28; Netter 3e 190, 4e 120-121).
The lungs have the following landmarks (Clemente 118, 120; Grant p. 32, 34-35, Netter
3e 195, 4e 199):
- The apex forms the cupula.
- The costal surface
- The medial surface has vertebral and mediastinal parts.
- The vertebral part is posterior and round with the costal
surface, occupying the thoracic gutters.
- The mediastinal part of the medial surface lies anterior
to the vertebral column. It contains the root or hilus of the lung. The
cardiac impression is anterior to the hilus and larger on the left than
on the right.
The hilus (root of the lung) is the point of entry
of vessels, nerves, and bronchi.
- The uppermost structure in the hilus is the pulmonary
artery (Artery Above).
- The most posterior structure is the bronchus (Bronchus
Relationships to the hilus:
- The phrenic nerve is the only structure traversing the
thorax which passes anterior to the hilus (Clemente 126-127;
Grant p. 80-81; Netter 3e 226-227, 4e 230-231).
- On the right side, the azygos arch passes from posterior
to anterior above the right hilus, to reach the superior vena cava.
- On the left side, the arch of the aorta passes from anterior
to posterior above the left hilus.
THE RIGHT LUNG (Clemente 118, 120; Grant p. 32, 34; Netter
3e 193, 4e 199-201).
- The right lung has 3 lobes demarcated by the oblique
fissure (between superior and inferior lobes). The oblique fissure is in
line with rib 6 and the medial border of the scapula (when the arm is raised).
- Examination of the superior lobe is done on the anterior
chest wall, whereas examination of the inferior lobe is done posteriorly
below the scapula (Clemente 115-116; Grant p. 30;
Netter 3e 188, 4e 197).
- The superior lobe of the right lung is further divided
from the middle lobe by a horizontal fissure (in line with rib 4, from
the midaxillary line to the attachment of rib 4 to the sternum).
THE LEFT LUNG
- has a superior and inferior lobe divided by an oblique
fissure. It also has a large cardiac notch found on the mediastinal surface.
The lingula which is an anterior projection of the superior lobe overlies
the anterior aspect of the heart.
- Examination of the superior lobe is done anteriorly and
of the posterior lobe posteriorly, below the level of rib 6.
THE BRONCHIAL TREE (Clemente 117, 122-125; Grant
p. 36-40; Netter 3e 190, 191, 4e 202-205)
- It is formed by the branching of the trachea at the level
- The primary bronchus is in the mediastinum and it enters
the hilus of the lung. The primary bronchus divides into secondary or lobar
bronchi (3 - upper, middle, lower - for the right lung and 2 - upper and
lingular, lower - for the left lung). The lobar bronchi divide into the
tertiary or segmental bronchi which supply bronchopulmonary segments of
the lung. The tertiary bronchus is joined by a tertiary division of the
pulmonary artery (Clemente 124; Grant p. 33, 41; Netter 3e 201, 4e 205).
Bronchopulmonary segments (Clemente 117, 119, 121; Grant
p. 36-38; Netter 3e 196-197, 4e 200-201, 203)
- A bronchopulmonary segment can be resected with less
physiological loss than a lobectomy or pneumonectomy and thus the pattern
of bronchopulmonary segments is important.
- The right lung has 10 bronchopulmonary segments and the
left lung has 8.
Body positions for lung drainage
- To drain the base of the lung, the patient must have
the head down.
- To drain the upper lobe, the patient must be sitting
Aspiration of foreign bodies
- Objects aspirated into the trachea from a vertical position
tend to be found in the right lung (the posterior basal segment is most
likely) because the right bronchus is almost in line with the trachea.
- With patient lying on the right side, the object would
be in the bronchopulmonary segments of the right posterior or middle lobes.
- With patient lying on the left side, it would be in the
superior or inferior bronchopulmonary segments of the lingula.
- With the patient lying supine, it would be in the superior
bronchopulmonary segment of the lower lobe.
The upper respiratory tract insures the patency of the
airways, via bony and cartilaginous structures.
2 PULMONARY ARTERIES
- are derived from the bifurcated pulmonary trunk (Clemente
206; Grant p. 41; Netter 3e 202, 4e 124).
- lie anterior to the bronchi as they enter the hilus.
The right pulmonary artery:
- is crossed over by the azygos vein whereas the left one
is crossed over by the arch of the aorta at T5 (Clemente 126-127; Grant p. 66-68; Netter
3e 226-227, 4e 230-231).
- divide into lobar branches
- and then tertiary branches which have a close relationship
with the tertiary bronchi in the bronchopulmonary segments (Grant p.
33; Netter 3e 197, 201, 4e 205).
- bring deoxygenated blood which will be oxygenated at
the level of the terminal alveolar ducts and the bronchial sacs. Oxygenated
blood is returned to the heart by pulmonary veins.
4 PULMONARY VEINS (Clemente 126-127; Grant p. 41;
Netter 3e 202, 4e 206)
- 2 lower pulmonary veins from the veins of the inferior
lobe of each lung, return to the left atrium of the heart.
- The upper right pulmonary vein comes from the superior
and middle lobe of the right lung.
- The upper left pulmonary vein comes from the superior
lobe of the left lung.
- The pulmonary veins also drain oxygenated blood supplied
to the lungs by the bronchial arteries.
BRONCHIAL ARTERIES (Clemente
157, 158; Grant p. 75; Netter 3e 203, 4e 207) arise from the
descending aorta or 3rd intercostal
branch and supply oxygenated blood to the lung tissue.
Lymphatics (Clemente 134; Grant p. 43; Netter
3e 204, 4e 208)
- are extensive and follow the vascular tree.
- At the hilus of the lung, they are filtered by the pulmonary
lymph nodes and then enter the right lymphatic duct, on the right side.
The latter join with the intersection of the right subclavian and right
internal jugular veins (Clemente 168-169).
- On the left side, lymph vessels enter the thoracic duct
which returns lymph at the intersection between the left subclavian and
the left internal jugular veins.
Nerves (Clemente 166-167; Grant p. 42; Netter
3e 205-206, 4e 210)
- The bronchopulmonary plexus supplies both para- and sympathetic
nerves to the bronchial and vascular trees.
- Parasympathetic fibers are preganglionic vagal and secretomotor
to glands in the bronchial mucosa.
- Sympathetic fibers are postganglionic fibers and vasomotor
to arterial system.
*Bronchodilatation can be achieved by epinephrine
which mimics the sympathetic nervous system.
Heart and Mediastinum
Gross Anatomy, K. W. Chung, 6th edition: pp. 135 -136, 146 - 160
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 135 - 169; 6th edition: pp. 127-160
Anatomy Dissector, 2nd edition: pp. 97 - 108
Dissector, P.W. Tank, 14th edition: pp. 64 - 75
The pericardium is a fibrous sac lining a serous
sac invaginated by the heart and great vessels during development (Clemente
112; Grant p. 25; Netter 3e 208, 211, 4e 211-212).
- The visceral pericardium (epicardium) lines the
surface of the heart.
- The parietal pericardium lines the inner surface
of the fibrous sac.
- The pericardial cavity contains fluid. Increased amount
of fluid results in cardiac tamponnade, requiring opening of the
- The pericardium is continuous with the connective tissue
of the central tendon of the diaphragm inferiorly and that of the great
vessels superiorly (Clemente 135; Grant p. 51;
Netter 3e 211, 4e 212). It defines the mediastinum (Clemente 130; Grant p. 25,
3e 207, 4e 230-231, 233).
has 4 chambers
- left and right atria
- left and right ventricles
Atria and ventricles are separated by the coronary (atrioventricular)
sulcus (Clemente 132-133; Grant p. 46; Netter 3e 210, 4e 214).
The ventricles are separated from each other by the anterior
and posterior interventricular sulci (Clemente 132-133; Grant p.
46-49; Netter 3e 210, 4e 212, 214).
The base of the heart
- is posterosuperior;
- is most stationary during heartbeats;
- is formed by the left atrium and the 4 pulmonary veins
(Clemente 133; Grant p. 47; Netter 3e 210, 4e 214);
- The visceral pericardium is continuous with the parietal
pericardium at this point and forms the oblique pericardial sinus (Clemente
135; Grant p. 51; Netter 3e 211, 4e 215).
The apex of the heart
- is most moveable
- is located in the left 5th intercostal space (Clemente
129; Grant p. 45; Netter 3e 192, 4e 213).
Surfaces of the heart are:
- anterior (right sternocostal)
- left sternocostal
- inferior diaphragmatic.
- The anterior interventricular sulcus is on the left sternocostal
- The posterior interventricular sulcus is on the diaphragmatic
- Coronary vessels are found in the coronary sulcus and
their branches are found in the anterior and posterior interventricular
sulci (Clemente 139; Grant p. 46-52;
Netter 3e 212, 4e 216-217).
SURFACE ANATOMY (Clemente 109; Grant p. 28, fig.
1.23; Netter 3e 184, 4e 198)
- The right subclavian vein, under the right clavicle,
joins with right internal jugular vein at the sternoclavicular joint, forming
the right brachiocephalic vein (Clemente 113; Grant p. 48; Netter 3e 207-208,
- The left brachiocephalic vein joins with the right posterior
to the right side of the sternum, superior to the sternal angle.
- The Superior Vena Cava (SVC)
descends posterior to the right of the sternum to rib 3 costal cartilage
where it enters the right atrium.
- The Inferior Vena Cava (IVC)
pierces the diaphragm at T8 (at the level of the xiphisternal joint) and
enters the right atrium at the level of rib 6 costal cartilage (Clemente
135; Grant p. 51; Netter 3e 228, 4e 206).
- The right ventricle forms most of the anterior (sternocostal)
surface of the heart, posterior to the inferior portion of sternum and
the costal cartilages of ribs 4 and 5 (Clemente 134; Grant p.
49; Netter 3e 208, 4e 212-213).
- The apex of the heart is the tip of left ventricle, related
to the left 5th intercostal space, 10 cm from the sternal midline.
- The left margin of the heart extends in an oblique line
from the left 5th to the 2nd intercostal spaces (Clemente 129;
Grant p. 45; Netter 3e 192, 4e 213).
- The left ventricle is found along the inferior left margin
of the heart on an oblique line .
- The tip of the left auricle is on the left margin posterior
to rib 3.
*The ascending aorta and pulmonary artery were embryonically
a single vessel forming the truncus arteriosus. They eventually become
divided to form the outlet vessels for the right and left ventricles (Clemente
151; Grant p. 46, 49; Netter 3e 210, 4e 229).
- is in the 2nd intercostal space.
- overlaps posteriorly with the descending aorta.
- pierces pericardium and divides into the right and left
pulmonary arteries (Clemente 132-133; Grant p. 46;
Netter 3e 211, 4e 214-215).
Pulmonary arteries (Clemente 134-135; Grant p.
66; Netter 3e 208, 4e 215)
- The right pulmonary artery is longer and runs
behind the ascending aorta to enter the lung.
- The left pulmonary artery enters the left lung
by running anterior to the descending aorta.
- The pulmonary arteries in the middle mediastinum lie
between the bronchi anteriorly and the pulmonary veins posteriorly.
- Between the left proximal pulmonary artery and the aortic
arch is the ligamentum arteriosum. The ligamentum arteriosum is
the vestigial ductus arteriosus which bypassed the collapsed lungs to provide
blood to the rest of the fetus.
The ascending aorta
- is continuous with the arch of aorta at the sternal angle
(Clemente 129; Grant p. 45; Netter 3e 208, 4e 233).
- crosses posteriorly and to the left over the hilus of
the left lung, forming the aortic knuckle on radiographs (Clemente 128; Grant p. 27; Netter
3e 209, 4e 213).
AORTIC AND PULMONARY SEMILUNAR VALVES
- Both pulmonary trunk and ascending aorta have a semilunar
valve (Clemente 136, 143, 145; Grant p. 60-61; Netter 3e 218-219, 4e
222-224) to prevent reflux into the ventricles during systole and diastole
(ventricular contraction and relaxation).
- The semilunar valves are formed by 3 cusps (valvules).
A nodule is present in the middle of the free edge and the portion
below the free edge is the lunule (Clemente 143-145; Grant p. 61; Netter 3e 219,
- During diastole, the closing of the valves can be heard
over the right 2nd intercostal space for the aorta and over the left 2nd
intercostal space for the pulmonary trunk (Clemente 129;
Grant p. 44; Netter 4e 213).
- Each valve has 3 sinuses to prevent the valvules from
sticking to the vessel walls.
- The aortic valve has right (with the ostium for the right
coronary artery), posterior (noncoronary) and left (with the ostium for
the left coronary artery) sinuses associated with the cusps (Clemente
145; Grant p. 61; Netter 3e 219, 4e 223).
- The pulmonary valve has right, left and anterior cusps.
BLOOD SUPPLY OF THE HEART
Coronary refers to arterial
vessels whereas cardiac refers to venous vessels.
Right and left coronary arteries arise from right and left
coronary sinuses of the aortic valve (Clemente 145; Grant p. 52; Netter 3e 214-215,
The left coronary artery (Clemente 136-140; Grant p. 54; Netter
3e 215, 4e 216-217, 219)
- passes anterior between the pulmonary trunk and the tip
of the auricle of the left atrium. It divides on the anterior aspect of
the heart into the anterior interventricular branch (1) and the
circumflex branch (2).
- (1) descends in the anterior interventricular sulcus
to the inferior margin of the heart and continues into the posterior interventricular
sulcus on the diaphragmatic surface. It supplies the anterior aspects of
the right and left ventricles and the anterior 1/2 of the interventricular
- (2) runs to the left in the atrioventricular sulcus between
the left atrium and ventricle. It gives off a marginal branch for
the lateral margin of the left ventricle and continues onto the posterior
aspect of the heart. It forms an anastomosis with the arteries (derived
from the right coronary artery) in the posterior interventricular sulcus.
The right coronary artery (Clemente 136-141;
Grant p. 52, 54-55; Netter 3e 214, 4e 216-218)
- runs in the coronary sulcus between the right atrium
and right ventricle.
- gives off a nodal artery which passes onto the posterior
aspect of the right atrium and supplies the area of the sinoatrial (SA)
- then gives off a marginal branch (smaller than the left
one) to supply the right ventricle.
- terminates in the posterior interventricular sulcus as
the posterior interventricular artery, supplying mainly the posterior aspect
of the right and left ventricles as well as the posterior 1/2 of the interventricular
The cardiac veins (Clemente 136-137; Grant p. 53;
Netter 3e 212-213, 4e 216-217)
- accompany coronary arteries and their branches.
- lie superficial to the arteries in the sulci.
- Most of the veins drain into the coronary sinus.
The coronary sinus
- is derived from the sinus venosus (the primitive
receiving chamber of the developing heart).
- lies in the coronary sulcus between the left margin of
the heart and the posterior interventricular sulcus. It drains into the
right atrium by an opening to the left of the entrance of the inferior
The great cardiac vein
- forms in the anterior interventricular sulcus
- joins the coronary sinus near the left margin of the
The middle cardiac vein
- occupies the posterior interventricular sulcus
- enters the coronary sinus near the entrance to the right
The small cardiac vein
- follows the right marginal branch of the right coronary
- joins the coronary sinus near the junction with the middle
The oblique vein drains from the left atrium into the coronary
sinus along with posterior ventricular veins draining the diaphragmatic
surface of the left ventricle.
The anterior cardiac veins
- drain the anterior surface of the right ventricle.
- open directly into the right atrium.
Venae cordis minimae or thebesian veins
- are tiny veins draining the heart wall.
- open directly into the chambers.
Chambers of the heart
Right atrium (Clemente 142; Grant p. 56; Netter 3e 216, 4e
- forms the right margin of the heart with the right auricle
projecting superiorly and anteriorly over the base of the ascending aorta.
The superior vena cava drains into the superior margin. The inferior vena
cava and coronary sinus drain via the posterior surface (Clemente 137; Grant p. 50; Netter
3e 210, 4e 214).
- contains a roughened area with musculi pectinati,
derived from the embryonic atrium which is now represented by the auricle
(Clemente 142; Grant p. 56; Netter 3e 216, 4e 220). These
merge with the crista terminalis. The crista terminalis extends
from the superior vena cava to the inferior vena cava and on the exterior
side, it is marked by the sulcus terminalis. The sinuatrial node
is located in the floor of the sulcus terminalis near the superior vena
cava (Clemente 225; Grant p. 64; Netter 3e 221, 4e 149).
- The smooth area of the right atrium is derived from the
sinus venarum cavarum (primitive receiving chamber of the developing
- The inferior vena cava opening contains a fenestrated,
non-functional valve in the adult.
- The coronary sinus also contains a valve and its opening
is located between the inferior vena cava and the tricuspid.
- The fossa ovalis is a depression on the interatrial
wall superior to the opening of the inferior vena cava and used to be the
opening in the developing prenatal heart shunting blood from right atrium
to left atrium, bypassing the pulmonary system.
- Superior to the fossa ovalis is the annulus which
is the inferior border of the rigid superior part of the interatrial wall;
thus the mobile inferior wall opens when the pressure is higher in the
right atrium and closes when the left atrial pressure is higher, sealing
the foramen ovale.
- The right atrioventricular or tricuspid valve
is located anteriorly and closes during ventricular contraction.
The left atrium (Clemente 144; Grant p. 58;
Netter 3e 58, 4e 221)
- forms 2/3 of base of heart. The auricle is visible anteriorly
from the left side of the pulmonary trunk.
- lies superior to the coronary sulcus.
The right and left superior and inferior pulmonary veins
drain into the left atrium and the portion of the atrium derived from these
vessels is smooth. The auricle contains musculi pectinati capable of contraction.
The left atrioventricular (or bicuspid or mitral
valve) is located anteriorly.
The ventricles (Clemente 143-145, 147-149; Grant p. 57, 59; Netter
3e 216-217, 4e 220-224)
- Right and left ventricles lie anterior to their atria.
- The right ventricle forms most of the anterior sternocostal
part of the heart and the inferior margin posterior to sternum.
- The left ventricle forms the left margin of the heart
and most of the diaphragmatic base.
The right ventricle works against pulmonary pressure (4/25
mm Hg) whereas the left ventricle works against systemic pressure (80/120
The left ventricular wall is about 5 times thicker than
the right one (Clemente 143-145; Grant p. 64; Netter 3e 220, 4e 224)
and the thickness of the interventricular septum approximates that of
the left. The interventricular wall is fleshy except for its superior part
where the membrane is continuous with the membranous spiral septum which
divided the primitive truncus arteriosus into the pulmonary trunk and the
Ventricular walls are lined with trabeculae carnae.
Some form papillary muscles arising from the anterior and posterior
walls (Clemente 147; Grant p. 57-59, 63; Netter 3e 219-220, 4e 220-224). The right ventricle also has septal papillary muscles. The apex
of a papillary muscle is attached to the cusp of an atrioventricular valve
by the chordae tendinae.
In each ventricle, the portions below the pulmonary trunk
and the ascending aorta are called the conus arteriosus (infundibulum;
Clemente 143; Grant p. 62; Netter 3e 216, 4e 220) and the aortic
vestibule, respectively. They are noncontractile.
In the atrioventricular valves, the
chordae tendinae from each papillary muscle control the contiguous margins
of 2 cusps (Clemente 142-145; Grant p. 63; Netter 3e 219, 4e 223),
preventing eversion during ventricular contraction.
On the chest, an oblique line from the 3rd intercostal
to the 6th intercostal spaces will have all 4 valves of the heart lined
up: Pulmonary, Aortic, Mitral, and Tricuspid.
Listen for heart sounds at
the left 2nd intercostal space (pulmonary), right 2nd intercostal space
(aortic), left 5th intercostal space (mitral) and right 5th intercostal
space (tricuspid; Clemente 129-131; Grant p. 44; Netter 4e 213).
CONDUCTION SYSTEM OF THE HEART (Clemente 148-149; Grant p. 64; Netter
3e 221, 4e 225)
The sinoatrial (SA) node
- is the pacemaker
- is vascularized by the nodal branch of the right
coronary artery (Clemente 138-139; Grant p. 52;
Netter 3e 214, 4e 218).
- is innervated by fibers from the vagus (parasympathetic)
and the sympathetic chain of ganglia.
The atrioventricular (AV) node is located in the wall of
the right atrium anterior to the mouth of the coronary sinus.
The atrioventricular bundle (of His) connects atria to
ventricle in the interventricular septum and divides into right and left
bundle branches (crura).
The rigth crus is visible in the right ventricle as the
septomarginal trabecula (moderator band) running to the anterior
The heart innervation:
- The SYMPATHETIC innerviation is via 1-3 cervical cardiac
branches, 2-3 cervicothoracic branches from the stellate (cervicothoracic)
ganglion, and 2-4 thoracic branches from the upper 4 thoracic levels. They
are cardiac accelerators.
- The VAGUS innervation (Clemente 635; Grant p.
42, 65; Netter 3e 223, 4e 227) is via a single cervical branch, 1-2
cervicothoracic cardiac branches from the main nerve at the thoracic inlet
(Grant p. 65) or from the right recurrent laryngeal branch),
and 2-4 thoracic cardiac branches from the thoracic part of the vagus nerve
(or left recurrent branch). They are inhibitory to the cardiac rate.
All the branches fuse into a cardiac plexus which courses
around the right pulmonary artery to the posterior aspect of the atria.
They distribute to the SA and AV nodes and to the coronary plexuses.
Visceral afferent (sensory)
fibers are chemosensitive to ischemic byproducts (lactic acid) and pain
from ischemic heart muscle. They enter the spinal cord at level of T1 and
thus angina pectoralis may manifest itself as referred pain on the T1 dermatome
of the left arm (Grant p. 346, 348; Netter 3e 157, 4e 227)
Superior and posterior mediastinum
Gross Anatomy, K. W. Chung, 6th edition: pp. 160 - 180
Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th edition:
pp. 169 - 191; 6th edition: pp. 160 - 180
Anatomy Dissector, 2nd edition: pp. 109-117
Dissector, P.W. Tank, 14th edition: pp. 73 - 77
Mediastinum (Clemente 130; Grant p. 25-29; Netter
3e 192-194, 4e 211-212)
- divides the thoracic cavity
- contains all the thoracic viscera, except for the lungs.
- from the posterior aspect of the sternum anteriorly to
the thoracic vertebrae posteriorly (Clemente 126-127; Grant
p. 25, 29; Netter 3e 194, 226-227, 4e 230-231)
- from the thoracic inlet superiorly to the diaphragm inferiorly.
A line through the sternal angle and the intervertebral
disc T4/5 subdivides the mediastinum into the superior and inferior
mediastinum (Clemente 130; Grant p. 29, Netter 213).
The inferior mediastinum is further divided into the anterior, middle and
- The anterior mediastinum contains fatty and thymic
- The middle mediastinum contains the heart and
- The posterior mediastinum contains viscera traversing
the thorax and going to abdomen.
CONTENTS OF THE SUPERIOR MEDIASTINUM
- The thymus gland
- The great veins
- The vagus and phrenic nerves
- Tje retrosternal structures
The thymus (Clemente 112-113;
Grant p. 66; Netter 207)
- is derived from the 3rd pharyngeal pouch similarly to
the inferior parathyroid glands.
- lies posterior to the manubrium sterni.
- The costomediastinal recesses are on either side, and
the left brachiocephalic vein and aortic arch lie posteriorly.
The left brachiocephalic vein (Clemente plates 101,
119; Grant p. 26, 48, 67; Netter 194)
- is formed by the left jugular and the left subclavian
veins, posterior to the left sternoclavicular joint.
- joins with the right brachiocephalic vein and they form
the superior vena cava at the level of the 1st right intercostal space.
- The left brachiocephalic vein passes anterior and superior
to the 3 great branches of the aortic arch.
The right brachiocephalic vein
- is formed by the union of the right internal jugular
and right subclavian veins posterior to the right sternoclavicular joint.
- forms the superior vena cava with its left counterpart.
- The superior vena cava enters the right atrium at the
level of the 3rd right costal cartilage (Clemente 129; Grant p.
26; Netter 3e 208, 4e 213). It receives the arch of the azygos system
on its posterior surface (Clemente 126; Grant p. 80;
Netter 3e 226, 4e 230) and the right phrenic nerve runs with it.
Both vagus and phrenic nerves descend posterior to the
brachiocephalic veins bilaterally in the superior mediastinum. The phrenic
nerve passes anterior to the root of the lung whereas the vagus nerve passes
posterior to the root of the lung (Clemente plates 115, 117; Grant p.
80-81; Netter 226-227).
The esophagus lies posterior to the trachea (Clemente
155; Grant p. 67; Netter 3e 226, 4e 232-233)
- begins below the larynx (below the cricoid cartilage)
at the level of C6 (Clemente 586-587; Grant p. 750; Netter
3e 229, 4e 233).
- Half is in the neck and half is in the superior mediastinum.
- bifurcates at the level of T4/5, at the carina.
- lies in the median plane and inferiorly it is displaced
to the right by the aortic arch.
- Its right relationships are the brachiocephalic artery,
the right vagus (Clemente 126, 155; Grant p. 68; Netter 3e 228, 4e 230, 232), and the azygos arch.
- To the left are the left common carotid and left subclavian
arteries, left vagus, and left recurrent laryngeal nerve between the trachea
and the mediastinal pleura (Clemente 127, 155; Grant p. 68-69; Netter 3e 228,
- The lymph nodes are found in the 3 bifurcation angles
of the trachea (Clemente 156; Grant p. 68; Netter 3e 204, 4e 208, 239).
They drain into the right lymphatic duct and the thoracic duct (Clemente
168-169; Grant p. 76; Netter 3e 204, 4e 208).
The cardiac plexus
- contains sympathetic and vagal fibers located anterior
to the bifurcation of the trachea, inferior to the bifurcation of the pulmonary
trunk and the arch of the aorta.
- has extensions as the right and left pulmonary plexus
(Clemente 130; Grant p. 68; Netter 3e 205, 222, 4e 209, 226)
cervical, cervicothoracic and thoracic cardiac branches; anterior and
posterior vagal and sympathetic nerves at the hilus) and the plexus of
the thoracic aorta.
Preganglionic sympathetic nerves (Clemente 165; Grant p.
346; Netter 3e 223,
4e 210, 227)
- originate at T1-T4 lateral horn of spinal cord.
- enter the paravertebral sympathetic chain of ganglia
via the white rami communicantes
- may synapse in the upper ganglia or as high up as the
- Postganglionic fibers produce tachycardia and
vasodilation of the coronary arteries.
Separate visceral afferent fibers carry visceral
reflexes and visceral pain sensation to the spinal cord.
- The cell bodies are in the dorsal root ganglion and fibers
enter the spinal cord at the level of T1-T2.
- Thus pain due to myocardial ischemia can be referred
to T1 and T2 dermatomes of left arm and chest.
Preganglionic vagal fibers
- arise from cell bodies in the brainstem
- reach the heart via the right and left vagus nerves.
- The ganglia are confined to the atria and the interatrial
septum near the roots of the great vessels.
- Efferent vagal fibers produce bradycardia.
- Afferent vagal fibers from the heart, aorta and great
vessels are for chemo- and baroreception. The cell bodies are in the inferior
ganglion of the vagus nerve.
The aortic arch and its 3 great branches (Clemente 161; Grant p. 68-69; Netter
3e 228, 4e 232).
- The inferior aspect of the aortic arch lies on a line
from the sternal angle through the T4/5 intervertebral disc.
- The ascending aorta is posterior to the right margin
of the sternum. It arches over the right pulmonary artery and left bronchus,
curves to the left (Clemente 127; Grant p. 67; Netter
3e 202, 4e 231-232) and becomes the descending aorta to the left of the T5 vertebral
- The aortic arch lies anterior
to the end of the trachea, left recurrent laryngeal nerve (Clemente
127, 155, 158; Grant p. 67; Netter 3e 228, 4e 231-233), superior portion of
the esophagus and the thoracic duct.
- The left vagus, left phrenic nerves, and left superior
intercostal vein cross it anteriorly.
Branches of the aorta (Clemente 161; Grant p.
70; Netter 3e 228, 4e 232)
- All the branches arise from the superior aspect of the
- They are the brachiocephalic trunk, the left common carotid
and the left subclavian arteries.
- The left brachiocephalic vein crosses them anteriorly
(Clemente 159; Grant p. 67; Netter 3e 202, 4e 212).
The brachiocephalic trunk (Clemente 155; Grant
p. 26; Netter 3e 192, 4e 212)
- arises posterior to the manubrium
- divides posterior to the right sternoclavicular joint
into the right subclavian and the right common carotid arteries.
The left common carotid courses
into the head in the carotid sheath
The left subclavian artery arches
over the apex of the left lung, posterior to rib 1 costal cartilage and
enters the axilla.
The inferior aspect of the aortic arch contains the ligamentum
arteriosum (Clemente 136; Grant p. 49; Netter 3e 202, 4e 212, 231), vestige of the ductus arteriosus.
- The ductus arteriosus shunted blood from the pulmonary
system in prenatal life.
- With expansion of the lungs and a decrease in resistance
in the pulmonary arterial system postnatally, it closes.
The ligamentum arteriosum is intimately associated with
the course of the left recurrent laryngeal nerve.
The vagus nerves
- descend in the neck on the post. aspect of the common
carotid arteries in the carotid sheath (Clemente 479; Grant p.
48; Netter 3e 222, 4e 71).
- enter the thoracic inlet posterior to rib 1.
- pass anterior to the arterial system (subclavian artery on
the right side and aortic arch on the left side (Clemente 126-127; Grant p. 67; Netter
3e 222, 4e 230-231).
- The 2 vagi then course posterior to the roots of the
lung giving out branches to the cardiac and pulmonary plexuses.
The left recurrent laryngeal nerve (Clemente 127, 158;
Grant p. 67; Netter 3e 228, 4e 231, 232)
- branches from the left vagus,
- passes below the ligamentum arteriosum and the arch of
- ascends between the trachea and the esophagus into the
root of the neck.
The right recurrent laryngeal nerve (Clemente 126, 158; Grant p. 67; Netter
3e 228, 4e 230, 232)
- arises from the right vagus anterior to the rigth subclavian
- courses around the artery
- ascends in the neck.
- Both recurrent nerves provide vagal innervation to the
trachea and esophagus before innervating the larynx.
The phrenic nerves (Clemente 126, 127; Grant
p. 67; Netter 3e 218, 219, 4e 230-231)
- arise from anterior rami of C3,4,and 5.
- enter the thoracic inlet, coursing medially.
- The left phrenic nerve crosses the left vagus anteriorly
(Grant p. 42, 67).
- descend anterior to the root of the lungs, between the
lateral wall of the fibrous pericardium and the mediastinal pleura.
- The right phrenic nerve is associated with the superior
vena cava in its upper course and pierces the diaphragm with the inferior
vena cava (Clemente 126; Grant p. 80; Netter 3e 226, 4e 230).
- The left phrenic nerve pierces the diaphragm at the margin
of the fibrous pericardial attachment to the central tendon (Clemente
127; Grant p. 81; Netter 3e 227, 4e 231).
- from the left side of the body of T5, descends on the
left of the vertebral column posterior to the root of the left lung (Clemente
156; Grant p. 81; Netter 3e 228, 4e 231).
- is in the midline at T8
- passes through the aortic hiatus at T11/12 (Clemente
155; Grant p. 74; Netter 3e 229, 4e 233).
- The greater splanchnic nerve from the sympathetic trunk
joins the descending aorta and enters the abdomen with it (Clemente
158; Grant p. 81; Netter 3e 236, 4e 240).
The visceral branches of the descending aorta are
(Clemente 156, 158; Grant p. 75; Netter 3e 233, 4e 207, 237):
- 1-3 bronchial arteries
- 1-3 esophageal arteries
- branches to pericardium and diaphragm.
The parietal (thoracic) branches are:
- the right and left posterior intercostal arteries from
the 3rd intercostal space to the subcostal arteries below rib 12.
- The right posterior intercostal arteries from T3-T8 cross
the vertebral column anteriorly. They anastomose with the anterior intercostal
arteries of the internal thoracic artery at the midclavicular line.
- The 1st and 2nd intercostal spaces are supplied from
the costocervical trunk of the subclavian arteries.
The thoracic duct (Clemente 159; Grant p. 76-77; Netter 235)
- begins at the cisterna chyli, posterior to the abdominal
aorta, inferior to the diaphragm (Clemente 159; Grant p. 83; Netter
3e 305, 4e 266).
- enters the thorax posterior to the descending aorta.
- stays on the right of the vertebral column.
- At T8, the thoracic duct lies posterior to the esophagus
and ascends to T5.
- It then crosses the vertebral column and enters the root
of the neck on the left side, terminating at the junction between the left
subclavian and left internal jugular veins.
- It drains all the lymph of the body except for the right
thorax, right upper limb and right side of the head and neck.
- These remaining areas drain into the right lymphatic
duct which joins the junction of the right internal jugular and right subclavian
The azygos and hemiazygos venous systems (Clemente 159; Grant p. 78-79; Netter
3e 234, 4e 238)
- drain the posterior thoracic wall from the 3rd intercostal
space to the subcostal veins.
- The posterior intercostal veins on the left side drain
into the hemiazygos veins. They join with the azygos sytem in the mid-thorax
by passing anterior to the vertebral column .
- The azygos system ascends on the right side of the vertebral
column and arches over the right bronchus to enter the posterior aspect
of the superior vena cava at the level of the costal cartilage of rib 3
(Clemente 126; Grant p. 80; Netter 3e 234, 4e 230).
- The right superior intercostal vein joins the azygos
after draining the 2nd, 3rd, 4th right intercostal spaces.
- The left superior intercostal vein joins the left brachiocephalic
vein by crossing the anterior aspect of the aortic arch.
- The highest posterior intercostal veins drain the 1st
intercostal space and join the brachiocephalic veins.
- The anterior intercostal veins drain into the internal
thoracic veins (Clemente 111; Grant p. 23; Netter 3e 184, 4e 191).
- extends from the posterior aspect of the pharynx at the
level of C6 (Clemente 155; Grant p. 788; Netter 3e 229, 4e 233) to the stomach, below the left dome of the diaphragm.
- pierces the diaphragm at the level of the rib 7 costal
cartilage at the level of T10.
- is constricted in 4 regions:
- C6 (upper esophageal sphincter-voluntary),
- T2/3 (crossing of aortic arch),
- T4/5 (crossing of left primary bronchus),
- T10 (diaphragm).
- Obstructions may occur at these levels. These levels
are respectively 15 cm, 22 cm, 27 cm and 40 cm from the incisor teeth.
- lies anterior to the vertebral bodies of C7-T8
- swings to the left in the lower thorax, in front of the
descending aorta to pass through the left dome at T10.
- is anterior to the thoracic duct, right posterior intercostal
arteries (T3-T7), azygos and hemiazygos systems in the midthoracic region.
- The trachea is anterior to the esophagus from C7 to T4
(Clemente 155; Grant p. 74; Netter 3e 229, 4e 233). Then the
esophagus lies posterior to the base of the heart (left atrium; Clemente
156; Grant p. 65; Netter 3e 229, 4e 233).
The superior esophageal sphincter is the cricopharyngeus
(a voluntary muscle; (Grant p. 787; Netter 3e 229, 4e 233).
The inferior esophageal cardiac sphincter is under
the control of vagal (opener) and sympathetic fibers (closer).
The recurrent laryngeal nerves
In the cervical region, both recurrent laryngeal nerves
lie between the trachea and the esophagus (Clemente plate 554; Grant
p. 788-789; Netter 228).
The vagus nerves
- inferior to the root of the lung, the left vagus lies
anterior to the esophagus (Clemente 127; Grant p. 81; Netter 3e 228, 4e 231) and the right vagus lies posterior.
- Their branches form the anterior and posterior esophageal
plexuses (Clemente 126-127, 167; Grant p. 80-81; Netter 3e 236, 4e 232)
which form single nerves to pierce the diaphragm at the esophageal
- Below the diaphragm they are renamed the anterior and
posterior gastric nerves.
- Vagal branches induce peristalsis in the esophagus and
are secretomotor to mucous glands.
Sympathetic nerves are vasomotor
to blood vessels.
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