THE LOWER TRUNK

THE LIST OF TOPICS

Abdominal wall; inguinal region

Autonomic nervous system

Abdominal organs: stomach, duodenum, pancreas, liver & spleen

Abdominal organs: intestinal tracts

The kidneys, the diaphragm and the posterior abdominal wall

Pelvis and pelvic contents

Gluteal and perineal relations; perineum

Abdominal wall; inguinal region

The diaphragm:

• originates:
  • from the inner surfaces of the lower 6 ribs,
  • from 2 crura attached to 2 left or 3 right lumbar vertebrae (Clemente 250-252; Grant p. 172-174; Netter 3e 189, 255; 4e 195, 263),
  • from the medial and lateral arcuate ligaments,
  • and from the xiphoid process (Clemente 251; Grant p.174; Netter 3e 189, 4e 195)
• inserts into the central tendon.
• The right dome is higher than the left (Clemente 250; Grant p. 96-97, Netter 3e 192, 4e 196).
• The inferior surface is covered by peritoneum (except for the bare area of the liver; Clemente 216-217; Grant p. 120; Netter 3e 266, 335, 4e 287).
• is innervated by C3, 4, and 5.

During contraction of the diaphragm, the thorax volume increases, the abdomen volume decreases.

During relaxation, the thorax volume decreases. If the abdominal muscles contract at the same time, then the abdominal pressure increases (parturition, vomiting, defecation).

 

The anterior abdominal wall (Clemente 176-178; Grant p. 98-99; Netter 3e 241, 4e 247-249)

• extends from the anterior aspects of the rib cage to the pelvic girdle.
• is bounded superiorly by the xiphoid process and the costal cartilages of ribs 7 to 10.
• is attached inferiorly to the iliac crest, anterior superior iliac spine, inguinal ligament, pubic tubercle, pubic crest, and pubic symphysis.

Skin landmarks:

The umbilicus (Clemente 176; Grant p. 98; Netter 3e 260, 4e 268) is at the level of the intervertebral disc between L3-4 and it is used to divide the abdominal wall into quadrants:

• Left and right upper quadrants above the umbilicus
• Left and right lower quadrants below the umblilicus.

 

The xiphoid process is at T7 dermatome (Clemente 8; Grant p. 348; Netter 3e 157, 4e 164).

The umbilicus overlies the T10 dermatome.

The pubic symphysis is at L1 dermatome.

The umbilicus

• is tightly attached to the underlying fascia
• contains vestiges of the allantois (urachus - median umbilical ligament), umbilical arteries (medial umbilical ligaments) and vein (ligamentum teres) which can be seen on the posterior aspect of the anterior abdominal wall (Clemente 196; Grant p. 118; Netter 3e 245, 4e 253).

The inferior epigastric arteries form the lateral umbilical ligaments.

The superficial fascia

• Above the umbilicus, it contains fat and connective tissue fibers as a single layer of tissue.
• Below the umbilicus, it is divided into the subcutaneous Camper's fascia and the deeper Scarpa's fascia ( membranous deep layer of superficial fascia; Clemente 190; Grant p. 105; Netter 3e 335, 4e 249). Scarpa's fascia is continuous with the superficial perineal fascia (Colle's fascia) and attaches to the fascia lata. Scarpa's fascia is used for suturing the subcutaneous fascia in repairs of the anterior abdominal wall
• In rupture of the urethra, urine can extravasate between Scarpa's fascia and the deep fascia of the anterior abdominal wall, as high as the axilla.

Abdominal wall muscles and their relationships

Rectus abdominis (Clemente 181-183; Grant p. 102, 104; Netter 3e 242, 4e 250-251)

• is the great flexor of the trunk
• From the rib cage to the pubic bone, it , has 4 transverse tendons and is enclosed in the fascia investing the other 3 flat muscles of the anterior abdominal wall.
• also fixes the rib cage for the neck muscles (lifting head from pillow)
• fixes pelvis for hip flexors (raising legs from bed)
• is innervated by T6-T12 (segmental innervation).
• Superiorly, it is attached to the anterior surface of the xiphoid process and the adjacent 5-7 costal cartilages.
• Inferiorly, it is attached to the pubic crest and symphysis.
• The lateral margin of the right rectus abdominis overlies the gallbladder as it crosses the costal margin.
• The 2 recti abdominis are separated by the linea alba (Clemente 180; Grant p. 102-103; Netter 3e 242-243, 4e 250-251) which is an avascular insertion of the aponeuroses of the 3 flat anterior abdominal muscles. The linea alba extends from the xiphoid process to the pubic symphysis and it is a potential site for herniation.

The rectus sheath is the deep fascia investing the superficial and deep layers of the 3 flat abdominal muscles. It envelopes the rectus abdominis, but the arrangement of layers differs depending on the level:

1. Superior to the umbilicus, the 3 muscles converge on the rectus abdominis (Clemente 184; Grant p. 105; Netter 3e 244, 4e 252). The deep fascia of the external oblique and the fascia covering the anterior surface of internal oblique pass anterior to rectus abdominis. The fascia of the posterior surface of the internal oblique and the fascia of the transversus abdominis pass posterior to the rectus abdominis.

2. Inferior to the umbilicus, all of the deep fascia pass anterior to the rectus muscle.

The blood supply to the rectus abdominis is provided by the inferior epigastric artery (Clemente 187; Grant p. 103; Netter 3e 243, 245, 4e 255) which ascends on the posterior surface of the rectus within its sheath to anastomose with the superior epigastric artery, near the level of rib 8 costal cartilage.

The nerve supply, from thoracic nerves, comes from the lateral margin (Clemente 176; Grant p. 100-103; Netter 3e 249, 4e 254, 257): the surgical approach to the rectus should be from the medial margin! BUT since the linea alba is avascular and does not heal well, incision should be made in the anterior rectus sheath, on the medial side and the muscle should be retracted laterally. Then the posterior aspect of the rectus sheath is incised.

The flat muscles of the anterior abdominal wall

These are the lateral flexors and rotators of the torso. They help maintain the intraabdominal pressure and assist in expiration, micturition, defecation and parturition. They are also involved in coughing, vomiting and venous return to the heart

These muscles arise from the posterior and lateral aspects of the abdominal wall and pass anteriorly to end in aponeuroses at the lateral margin of the rectus. The aponeuroses join with the rectus sheath and insert into the linea alba at the midline. Motor nerves and arteries are found between the 2nd and 3rd layers of muscle (Grant p. 103; Netter 3e 249, 4e 255, 257).

External oblique (Clemente 178; Grant p. 100-105; Netter 3e 241, 4e 249)

• arises from the external aspects of lower 8 ribs. Its superior and lateral portions are muscular whereas the medial and inferior portions are aponeurotic. Fibers are oriented inferomedially, with the most superior being horizontal and the most inferior almost vertical (from rib 12 to the iliac crest).
• The superior 1/2 of the muscle inserts into the anterior aspect of the rectus sheath and then cross fibers with the opposite muscle in the linea alba (Clemente 184; Grant p. 105; Netter 3e 241, 4e 252). The inferior half of the muscle inserts into the iliac crest, tubercle, anterior superior iliac spine, inguinal ligament and pubic bone. The lowermost fibers insert into the external lip of the iliac crest posteriorly, and more superior fibers insert into more anterior aspects of the iliac crest.
• The free inferior border of the external oblique between the anterior superior iliac spine and the pubic tubercle is the inguinal ligament (Clemente 179; Grant p. 106; Netter 3e 241, 4e 250). A reflection of this ligament onto the pectineal line of the pubic bone is the lacunar ligament (Clemente 179; Grant p. 106; Netter 3e 251, 4e 259). The opening in the external oblique aponeurosis close to the pubic tubercle is the superficial inguinal ring.

Internal oblique (Clemente 180-182; Grant p. 104-105; Netter 3e 242, 4e 250)

• is deep to the external oblique and its fibers are oriented perpendicular to the external oblique fibers. The internal oblique is muscular in its inferior and lateral aspects, and aponeurotic in its superior and medial aspects.
• It arises from the intermediate line of the iliac crest and the lateral half of the inguinal ligament.
• The most posterior fibers ascend to the costal cartilages of ribs 9-12. More anterior fibers run superomedially and contribute to the anterior and posterior layers of the rectus sheath, before inserting into the linea alba. Fibers arising from the lateral half of the linea alba arch over the inguinal canal and insert into the pubic tubercle and pectineal line of the pubis. This insertion is combined with that of the transversus abdominis and is called the conjoint tendon or inguinal falx (Clemente plate 165; Grant p. 107-109; Netter 251).

Transversus abdominis (Clemente 181, 183; Grant p. 103-104; Netter 3e 246, 4e 254)

• has horizontal fibers. It has a wide origin with the most superior fibers arising from the lower 6 costal cartilages. Intermediate fibers arise from an aponeurosis  attached to the tips of the transverse processes of the lumbar vertebrae and inferior fibers arise from the inner lip of the iliac crest and the lateral half of the inguinal ligament.
• The majority of the fibers contribute to the linea alba. Fibers arising from the lateral half of the inguinal ligament join with fibers from the internal oblique to form the conjoint tendon (falx inguinalis). The conjoint tendon fuses with the underlying transversalis fascia reinforcing the wall posterior to the superficial inguinal ring.

Cremaster muscle (Clemente 190; Grant p. 107; Netter 3e 243, 251, 4e 259) invests the spermatic cord within the inguinal canal. It is derived from muscle fibers of the internal oblique arching over the spermatic cord within the inguinal canal. The cremaster muscle elevates the testes in the scrotum (Clemente 190; Grant p. 112-113; Netter 3e 242-243, 4e 387) and is innervated by the genital branch of the genitofemoral nerve (L1,2 - not under voluntary control).

The anterior rami of T7-T12 innervate the anterior abdominal wall. They are mixed nerves and run between internal oblique and transversus abdominis muscles.

Layers in the walls of abdomen (match to the list below; Clemente 193; Grant p. 115; Netter 3e 253, 370, 4e 249, 260, 387) :

1. Skin

2. Superficial fascia (Camper's and Scarpa's)

3. External oblique aponeurosis

4. Internal oblique

5. Transversus abdominis

6. Fascia transversalis

7. Extraperitoneal fat

8. Peritoneum

Layers in the walls of the scrotum (match to the list above):

1. Skin

2. Dartos muscle and fascia

(1&2 SCROTUM)

3. External spermatic fascia

4&5. Cremaster muscle

6. Internal spermatic fascia

(3-6 COVERINGS OF THE SPERMATIC CORD)

7. Areolar tissue

8. Tunica vaginalis

(7&8 CONSTITUENTS OF THE SPERMATIC CORD)

The spermatic cord contains a neurovascular bundle supplying testes and cremaster muscle (Clemente 192; Grant p. 116; Netter 3e 241-243, 4e 387). The tunica vaginalis of the peritoneum lies adjacent to the testes and its neurovascular pedicle. The spermatic cord lies within the inguinal canal (Clemente 179; Grant p. 108; Netter 3e 253, 4e 260).

The inguinal canal

• As the descending testis moves from the extraperitoneal fatty tissue and traverses the abdominal wall, it first encounters the abdominal wall layer formed by the fascia transversalis which becomes the internal spermatic fascia (Clemente 193; Grant p.109; Netter 3e 253, 370, 4e 260, 387). The proximal opening of the inguinal canal in the transversalis fascia is the deep inguinal ring (above the mid-point of the inguinal ligament, lateral to the inferior epigastric artery; Clemente 303; Grant p. 108; Netter 3e 253, 4e 260).
• Next the internal oblique and its fascia gives rise to the cremaster muscle and its cremasteric fascia (Clemente 196; Grant p. 112; Netter 3e 370, 4e 387).
• The external oblique aponeurosis gives rise to the external spermatic fascia continous with the superficial inguinal ring which is at the pubic tubercle (Clemente 179; Grant p. 106; Netter 3e 370, 4e 260).

The inguinal canal

• is between the superficial and deep inguinal ring and is about 2 inches long.
• The anterior wall is formed by the external oblique aponeurosis (Clemente 179; Grant p. 106; Netter 3e 253, 4e 260).
• The floor is also formed by the external oblique aponeurosis and is part of the inguinal ligament and lacunar ligament.
• The posterior wall of the inguinal canal is formed by the fascia transversalis (Clemente 184; Grant p. 108; Netter 3e 253, 4e 260).
• The roof of the inguinal canal is formed by the arching fibers of the internal oblique and transversus abdominis running from the lateral 1/2 of the inguinal ligament to the conjoint tendon or inguinal falx (Clemente 181; Grant p. 108; Netter 3e 253, 4e 259).
• The deep inguinal ring is reinforced anteriorly by the internal oblique and the aponeurosis of the external oblique (Clemente 181; Grant p. 108; Netter 3e 253, 4e 260).
• The superficial inguinal ring is reinforced posteriorly by the conjoint tendon (Clemente 181; Grant p. 108-109; Netter 3e 253, 4e 259).

INGUINAL HERNIAS

• The indirect inguinal hernia enters the deep inguinal ring. It is surgically defined as lying lateral to the inferior epigastric artery and invested in internal spermatic fascia (Grant p. 115; Netter 3e 254, 4e 261).
• The direct inguinal hernia protrudes through the superficial inguinal ring. This occurs when the conjoint tendon fails and the hernia lies medial to the inferior epigastric artery, covered by external spermatic fascia (Grant p. 115; Netter 3e 251).

The nerves related to the inguinal canal are the ilioinguinal, iliohypogastric and genitofemoral nerves.

• The ilioinguinal nerve (L1) pierces the internal oblique and runs in the inguinal canal as a sensory nerve (Clemente 188, 190; Grant p. 103, 107; Netter 3e 240, 4e 257). It leaves the canal by the superficial inguinal ring and contributes to the innervation of the skin in the L1 dermatome (Clemente 8; Grant p. 101; Netter 3e 150, 4e 164). Its territory overlaps with the S2,3 dermatome. Terminal branches innervate the anterior skin of scrotum (anesthesia for vasectomy) in the male and the skin of the anterior aspect of the labium majus in the female.
• The iliohypogastric nerve (L1) is sensory as it pierces the external oblique aponeurosis above the superficial inguinal ring (Clemente 188, 190; Grant p. 100-103; Netter 3e 240, 4e 257).
• The genital branch of the genitofemoral nerve is motor to the cremaster muscle and elicits the cremasteric reflex over the L1,2 dermatomes (medial aspect of the thigh; Clemente 188; Grant p. 112; p.309, fig.5.7A; Netter 3e 240, 4e 257).

TESTES, SPERMATIC CORD AND GUBERNACULUM

• In prenatal life, the gubernaculum connects the inferior pole of the developing gonad with the skin of the developing scrotum (labium majus).
• In the male the gubernaculum also draws the processus vaginalis and the vas deferens into the inguinal canal with the testis. The gonad descends into the iliac fossa during the 3rd prenatal month, traverses the inguinal canal during the 7th month and reaches the bottom of the scrotum after birth.
• In the female, the ovaries stay within the pelvis but the round ligament of the ovary and the round ligament of the uterus attach the inferior pole of the ovary to the labium majus (Clemente 188; Grant p. 110-111; Netter 360). These round ligaments are the equivalent of the gubernaculum testis.

The scrotum

• is a double cavity sac divided by a partition. Its wall contains the dartos muscle (Clemente 192; Grant p. 115; Netter 3e 370, 4e 387) which is smooth and innervated by the sympathetic nerves. It is derived from the right and left labioscrotal folds (in the female, these form the labia majora). It contains the testes and keeps them at below-body temperature.
• The anterior scrotum (or labium majus) is innervated by the ilioinguinal nerve (L1). The posterior scrotum (labium majus in female) is innervated by S2,3,4.
• Vascularization is provided by branches of the external (Clemente 368; Grant p. 370; Netter 3e 247, 4e 500) and internal pudendal arteries (Clemente 319; Grant p. 261; Netter 3e 383, 4e 405) and veins. The external pudendal arteries are derived from the femoral artery and the internal pudendal arteries are derived from the internal iliac arteries (Grant p. 224-225; Netter 3e 383, 4e 403). Corresponding veins run with the arteries.
• Lymphatic drainage of the scrotum is to the superficial inguinal nodes (Clemente 369; Grant p. 366-367; Netter 3e 388, 4e 546). Lymphatic drainage of the testes follows testicular arteries and veins along the spermatic cord to the abdominal lymph nodes (Clemente 257, Grant p. 228; Netter 3e 388, 4e 406).

The spermatic cord is made up of external spermatic, cremasteric and internal spermatic fasciae.

The spermatic cord contains:

Layer 1

a. Processus vaginalis (from the parietal peritoneum). The portion in the canal becomes obliterated whereas the inferior portion becomes the tunica vaginalis (Clemente 195; Grant p. 113; Netter 3e 370, 4e 387). The underlying cavity is known as that of the tunica vaginalis and accumulation of fluid in this area is called a hydrocele.

b. Loose connective tissue continuous with the extraperitoneal loose connective tissue.

Layer 2

a. Vas (ductus) deferens (Clemente 194; Grant p. 117; Netter 3e 371, 4e 390) is the spermatic duct and is a continuation of the epididymis. It runs from the testis, through the inguinal canal, around the inferior epigastric artery (Clemente 303; Grant p. 108; Netter 3e 252, 4e 363) to reach the posterior aspect of the bladder and the seminal vesicle (Clemente 304; Grant p. 214; Netter  3e 348, 4e 384).

b. Testicular artery (Clemente 194; Grant p. 111; Netter 3e 252, 4e 390) and sympathetic nerves

c. Pampiniform plexus of veins (forming single testicular vein in the abdomen; Clemente 243; Grant p. 116; Netter 3e 370, 4e 390, 401).

d. Lymphatics

e. Artery of the ductus deferens (Clemente 194; Grant p. 117; Netter 3e 370, 4e 403) and accompanying veins and sympathetic nerves.

3. The genital branch of the genitofemoral nerve (Clemente 188; Grant p. 116; Netter 3e 370, 4e 257).

The testis

• is covered by the tunica vaginalis except around the epididymis and where the spermatic cord enters the testis (Clemente 193; Grant p. 113; Netter 3e 370, 4e 387,,390).
• has an outer covering called the tunica albuginea which is called the mediastinum testis posteriorly.
• is divided by septa into ~250 pyramidal compartments which contain the seminiferous tubules. The latter are connected to the rete testis via the straight tubules. The rete testis is connected to the head of the epididymis by the efferent ductules (6-12).

The epididymis is divided into a head, body and tail (Clemente 193; Grant p. 117; Netter 3e 371, 4e 390).

The testicular artery arises from the abdominal aorta at L2 (Clemente 243; Grant p. 175; Netter 3e 256-257, 4e 401), pierces the mediastinum testis and anastomoses with the artery of the vas deferens (derived from the inferior vesical branch of the internal iliac artery) and the cremasteric artery (a branch of the inferior epigastric artery).

The pampiniform plexus of veins forms the testicular vein superiorly. The right vein joins the inferior vena cava and the left vein drains into the left renal vein (Clemente 243; Grant p. 175; Netter 3e 257, 4e 401). Varicocele may result in the testicular veins.

Lymphatics of the testis end in lymph nodes between the common iliac and renal vessels (Clemente 257; Grant p. 228; Netter 3e 388, 4e 406).

Lymphatics of the scrotum and penis drain into the inguinal nodes.

Innervation (Grant p. 231; Netter 3e 389, 4e 410)

The testis is sympathetically innervated from T6-T10 vasomotor fibers.

Afferent fibers accompany the sympathetic fibers and is referred to T8-T10 dermatomes (pit of the stomach).

The ductus deferens is innervated by sympathetic fibers derived from the inferior hypogastric plexus made up of fibers from T11,12, and L1.

updated 09/22/2008

Autonomic nervous system

The autonomic nervous system is not under voluntary control and carries out its actions even when you are asleep. Some parts are under conscious control: focusing of the eye by the ciliary muscles and stimulation of the lacrimal gland to produce tears.

The autonomic N.S. is divided into the sympathetic and parasympathetic systems. The sympathetic system is for "fight or flight" and the parasympathetic system takes over during relaxation.

A general idea of the distribution of sympathetic nerves can be acquired by studying your own reactions before the next exam:

• The face is pale because of cutaneous vasoconstriction.
• The pupils are dilated.
• The heart rate and blood pressure are increased
• The digestive glands cease to secrete (dry mouth)
• The skin is sweaty (palms of the hand).
• A prickly sensation over the skin is due to contraction of the arrectores pili muscles ("hair standing on end").
• The bronchial smooth muscles are relaxed as is the smooth muscle of the gut, except for the sphincters (although this is not as noticeable).

General organization of the autonomic nervous system

• Preganglionic sympathetic fibers are short and postganglionic sympathetic fibers are long. The ganglia are seen in the dissecting room.
• Preganglionic parasympathetic fibers are long and postganglionic parasympathetic fibers are short. The ganglia are seen in the histology laboratory (except for 4 in the head which can be seen in the dissecting room).
• Sympathetic preganglionic fibers leave the spinal cord at T1-L2,3, travel in the anterior primary rami and reach the sympathetic ganglia as white rami communicantes (Clemente plate 155; Grant p. 20; Netter 3e 161, 315; 4e 167, 228).
• Parasympathetic preganglionic fibers are carried in a cranial and sacral outflow. The cranial outflow is carried by cranial nerves 3, 7, 9, 10 and 11. The sacral outflow is carried by sacral nerves 2, 3 and 4 (Grant p. 246; Netter 4e 168).

SYMPATHETIC NERVOUS SYSTEM

The sympathetic trunk or paravertebral chain of sympathetic ganglia extends the whole length of the trunk on each side of the midline from base of skull to tip of coccyx:

• In the cervical region, it lies on bodies of vertebrae posterior to the carotid sheath (Clemente plate 452; Grant p. 774; Netter 3e 124; 4e 130),
• In thoracic region, it lies along the heads of the ribs, outside of the pleura (Clemente plates 115, 117; Grant p. 80-85; Netter 3e 222, 226-227; 4e 209),
• In the lumbar region, along the anterior border of the psoas major muscle (Clemente plate 241; Grant p. 172-173; Netter 3e 259; 4e 344).
• In the sacral region, just medial to the sacral foramina.
• The sympathetic trunk ends near the coccyx in the midline ganglion impar (Clemente plate 241; Grant p. 172-173; Netter 3e 259; 4e 167).

Developmentally, there was the same number of ganglia as spinal nerves but many of them fused.

In the neck, 3 cervical ganglia:

• a superior cervical ganglion connected for outflow to the first 4 cervical nerves (Clemente plates 526, 527; Grant p. 774-775; Netter 3e 124; 4e 130),
• a middle cervical ganglion connected for outflow to C5 and 6 (Clemente plate 554; Grant p. 774-775; Netter 3e 124; 4e 130),
• an inferior cervical ganglion connected for outflow to C7 and 8 (Grant p. 774-775; Netter 3e 124; 4e 130).

In the thorax, there are 10-12 ganglia but the first usually fuses with the inferior cervical ganglion to form the cervicothoracic or stellate ganglion (Clemente plate 554; Grant p. 84-85; Netter 3e 236; 4e 130, 226-227).

There are usually 4 lumbar and 4 sacral ganglia (Clemente plate 239; Grant p. 176-177; Netter 3e 330; 4e 324).

Preganglionic sympathetic fibers may synapse in a ganglion at the same level, at different levels (up or down) or may pass through the sympathetic trunk and synapse with some outlying ganglion.

There are no white rami communicantes above T1 or below L2.

Postganglionic sympathetic fibers may:

• follow a spinal nerve,
• follow an artery,
• pass directly to a viscus (cardiac branches of cervical ganglia).

Sympathetic supply for the limbs may run along larger arteries, then limb nerves and then back along arteries.

Cranial sympathetic:

• Mainly carried by the internal carotid nerve which is a superior prolongation of the superior cervical ganglion along the internal carotid artery (carotid plexus; Clemente plate 491 fig. 771; Grant p. 717; Netter 3e 125; 4e 130-131). This continues as plexuses around the anterior and middle cerebral arteries (Clemente plate 491; Grant p. 646; Netter 3e 132; 4e 131) and opthalmic arteries (Clemente plate 491; Grant p. 657; Netter 3e 81; 4e 121).
• This is supplemented by a plexus around the vertebral artery originating from the cervicothoracic ganglion (Clemente plate 554; Grant p. 776; Netter 3e 124; 4e 130).
• Branches from the superior cervical ganglion are carried by the external carotid artery to the face and scalp (Clemente plate 490 fig. 769; Grant p. 764; Netter 3e 124; 4e 130).
• Cranial sympathetic system supplies blood vessels and sweat glands, dilator pupillae, smooth muscle in the levator palpebrae superioris.
• With a ganglionectomy, there will be anhidrosis (absence of sweating), ptosis (drooping of the upper eye lid) and myosis (constriction of the pupil). The eyeball will be less prominent than usual (enophthalmos) because of paralysis of some smooth muscle within the orbit. This is Horner syndrome.

Cervical sympathetic

• Grey rami are distributed to all cervical nerves and arteries in the vicinity.
• Branches to the larynx and pharynx are mainly for the blood vessels.
• Cardiac branches (Clemente plate 117; Grant p. 774; Netter 3e 222; 226-227) descend into the thorax to join the cardiac plexus.
• The sympathetic supply of the salivary glands has an unknown function since the secretomotor fibers are derived from the parasympathetic system.

Thoracic sympathetic

• Each intercostal nerve is connected to the sympathetic trunk by at least one white ramus and 2 grey rami (Clemente plate 152; Grant p. 80; Netter 3e 205; 4e 228).
• Grey rami pass to the aorta and its branches, especially the posterior intercostal arteries, the pulmonary plexus (ganglia 2-4; Clemente plate 151; Grant p. 42; Netter 3e 206; 4e 209-210) and to the cardiac plexus (upper 5 ganglia).
• Largest branches are the preganglionic greater (T 5-9), lesser (T10-11) and least (T12) splanchnic nerves (Clemente plates 148, 150; Grant p. 85; Netter 3e 205; 4e 318, 321), which pass along the sides of the vertebrae, enter the abdomen through the crura of the diaphragm (T12-aortic hiatus) and synapse in the celiac ganglia. Some preganglionic fibers even continue on through to synapse in the suprarenal medulla.

Lumbar sympathetic

• White rami pass from L1, L2 (and L3) to sympathetic ganglia and all ganglia send gray rami to the lumbar nerves (Clemente plate 239; Grant p. 178; Netter 3e 308; 4e 324). Lumbar splanchnic nerves (Clemente plate 215; Grant p. 176-179; Netter 3e 314; 4e 324) connect the ganglia to the celiac plexus. Further branches join the aortic and iliac plexuses and others pass in front of the common iliac vessels to join the superior hypogastric plexus (Clemente plate 215, 227; Grant p. 176-177; Netter 3e 330; 4e 324).
• The celiac ganglia and associated plexuses surround the celiac artery and sends branches along the branches of the aorta and the ventral gut arteries (celiac, superior and inferior mesenteric; Clemente plate 227; Grant p. 176-179; Netter 3e 330; 4e 324). Postganglionic fibers innervate intestines and associated structures.

Pelvic sympathetic

• The sympathetic ganglia send grey rami to the sacral nerves and to local arteries.
• The superior hypogastric plexus lies in front of the promontory of the sacrum between the 2 common iliac arteries and is sometimes called the presacral nerve (Clemente plate 227; Grant p. 176-177; Netter 3e 330; 4e 323). It divides into the right and left inferior hypogastric plexuses. They are joined by the pelvic splanchnic nerves (which are parasympathetic!) and give vascular branches and branches to the pelvic viscera.

THE PARASYMPATHETIC SYSTEM

Preganglionic parasympathetic fibers travel in oculomotor (III), facial (VII), glossopharyngeal (IX), vagus (X) and cranial portion of the accessory (XI) nerves.

The 4 "large" parasympathetic ganglia are the ciliary (Clemente plates 511, 512; Grant p. 822, 840; Netter 3e 115; 4e 121, 168), otic (Clemente plate 490 fig. 769; Grant p. 835, 840; Netter 3e 119; 4e 125, 168), pterygopalatine (Clemente plate 526 fig. 834; Grant p. 826, 840; Netter 3e 116; 4e 123, 168) and submandibular ganglia (Clemente plate 479; Grant p. 829-831; Netter 3e 116; 4e 122-123, 168)

Cranial parasympathetic system in cranial nerves III, VII, and IX will supply secretomotor fibers to the salivary, lacrimal glands, ciliary muscle and constrictor pupillae in the eye.

The vagus (X) and its accessory (XI) combine to supply most of the abdominal viscera including the colon as far as the splenic flexure (attachment point of the proximal 2/3 to the distal 1/3 of the colon; the connection of the midgut to hindgut; Clemente plate 155; Grant p. 836-837; Netter 3e 120; 4e 324).

• In the neck, upper and lower cardiac branches and esophageal branches innervate smooth muscles and glands (at lower end of the esophagus).
• In the thorax, branches pass to the cardiac plexus, synapse in microscopic ganglia and supply atria, atrioventricular bundles and coronary arteries.
• The Vagus also supplies the pulmonary plexuses with synapses in microscopic ganglia to supply bronchial smooth muscle, glands and blood vessels.
• In the abdomen, anterior and posterior gastric nerves supply the stomach and via branches joining the coeliac plexus, the intestines and related structures.
• The parasympathetic system is secretomotor to the glands of the stomach and intestine, motor to the smooth muscle but inhibitory to the sphincters. In the gut, the ganglia are situated in Auerbach's and Meissner's plexuses.

The sacral outflow in S 2,3 (4) joins the inferior hypogastric plexus by means of the pelvic splanchnic nerves (Clemente plate 155, plate 296 fig. 456; Grant p. 246; Netter 3e 330; 4e 324) which supply:

• smooth muscle of the rectum and bladder with motor fibers (inhibitory fibers to the sphincters),
• the uterus with vasodilator and possibly inhibitory fibers
• and the erectile tissue of the penis and clitoris with vasodilator fibers (ejaculation is under sympathetic control).

Some parasympathetic fibers climb out of the pelvis around the inferior mesenteric artery and via its branches supply the distal part of the transverse colon and the descending and sigmoid colon.

updated 09/18/2008

Abdomen I

(Clemente 3; Grant p. 128; Netter 3e 260, 4e 268)

• Transpyloric plane (L1) lies half way between the jugular notch and pubic symphysis.
• Subcostal plane (L2) crosses the lowest part of the costal margin
• Umbilical plane (L3)
• Transtubercular plane (L4) crosses the tubercles on the iliac crest.

Clinically:

• The iliac region refers to the iliac fossa
• The hypogastrium refers to the suprapubic region
• The back of the lumbar region, in the angle between rib12 and the midline, is also called the renal angle (Clemente 246; Grant p. 97; Netter 3e 240, 4e 330).

The peritoneal cavity

The foregut, midgut and hindgut have their own arteries: coeliac, superior mesenteric and inferior mesenteric arteries (Clemente 243; Grant p. 133; Netter 3e 256, 4e 329).

The peritoneal cavity is divided into a main cavity or greater sac and an omental bursa or lesser sac (Clemente 212-213; Grant p. 120; Netter 3e 335, 4e 273).

The omental bursa

• has an opening facing to the right: the epiploic foramen (of Winslow; Clemente 212-213; Grant p. 1123-124, 126-127; Netter 3e 267, 4e 273)
• lies mainly behind the liver and the stomach (Clemente 202-203; Grant p. 120-121; Netter 3e 267, 4e 273)
• The lesser omentum (hepatogastric ligament) extends from the lesser curvature of the stomach to the liver (Clemente 212; Grant p. 120-121, 123-124; Netter 3e 267, 4e 275).
• The superior recess of the omental bursa lies posterior to the lesser omentum and the caudate lobe of the liver (Clemente 213; Grant p. 120-121; Netter 3e 264, 4e 272).

The greater omentum

• is an apron of peritoneum, fat and blood vessels hanging from the greater curvature of the stomach (Clemente 204; Grant p. 119-121; Netter 3e 261, 4e 269).
• Reflect it to see the transverse colon embedded in its posterior surface (Clemente 205; Grant p. 136; Netter 3e 261, 4e 269).
• is a double layer of peritoneum covering the front and back of the stomach, hanging down from the greater curvature and folded back on itself at the lower border (Clemente 203; Grant p. 120; Netter 3e 335, 4e 348).

The transverse mesocolon

• is the mesentery between the transverse colon and the posterior abdominal wall.
• Above the transverse mesocolon, the posterior wall of the lesser sac is formed by the "stomach bed".

After rotation of the gut and return to the abdomen, both duodenum and pancreas (except for the tail end) become fused to the dorsal abdominal wall and become retroperitoneal (Clemente 223; Grant p. 122; Netter 3e 266, 4e 274).

The ventral mesogastrium forms the lesser omentum (Clemente 202; Grant p. 120-121; Netter 3e 267, 4e 275), falciform (Clemente 202, 212; Grant p. 121-123, 126; Netter 3e 267, 4e 275), triangular (Clemente 217; Grant p. 146-148; Netter 3e 279, 4e 287) and coronary ligaments (Clemente 202, 212; Grant p. 120, 146, 148; Netter 3e 279, 4e 287).

Relationships of viscera in the upper abdomen:

The transpyloric plane is at the level of L1.

Duodenum:

• The 1st part is attached to the edge of  the lesser omentum and is mobile (Clemente 212-215; Grant p. 133-134; Netter 3e 270-271, 4e 275). The rest is retroperitoneal.
• The 2nd part descends vertically downwards to L3. The opening of the common bile duct (major duodenal papilla) into the duodenum marks the junction between the foregut and the midgut (Clemente 221, 224-225; Grant p. 133, 156; Netter 3e 271, 4e 279, 294-295).
• The 3rd part crosses the midline horizontally;
• The 4th part ascends to the left of the midline to the level of L2.
• The head of the pancreas is enclosed in the C-shaped duodenum (Clemente 223-224; Grant p. 133-135; Netter 3e 270, 4e 278-279).
• The 2nd part of the duodenum overlies the hilum of right kidney (renal pelvis and renal vessels)
• The tail of the pancreas crosses the hilum of the left kidney.
• The adrenal (suprarenal) glands sit on top of the kidney. The right one is posterior to the inferior vena cava (Clemente 223; Grant p. 133; Netter 3e 270, 4e 278).
• The aorta lies in the midline, in contact with the bodies of the vertebrae posteriorly and the inferior vena cava lying to the right.
• The beginning of the transverse colon crosses the right kidney and the 2nd part of the duodenum. Then the transverse colon becomes suspended by the transverse mesocolon.
• The spleen sits on the upper lateral part of the left kidney and the tail of the pancreas reaches its hilum by the lienorenal ligament. The spleen is enclosed by peritoneum.

The foregut artery or coeliac artery (Clemente 210-211; Grant p. 130; Netter 3e 270, 4e 300-303) arises just above the upper border of the pancreas and immediately breaks up into 3 branches:

• The left gastric artery climbs toward the esophagus, turns anteriorly and inserts itself in the layers of the lesser omentum giving out esophageal branches. It runs onto the lesser curvature of the stomach and anastomoses with the right gastric artery (Clemente 208; Grant p. 129; Netter 3e 290, 4e 300).
• The splenic artery runs along the upper border of the pancreas into the splenorenal ligament and the hilum of the spleen. It gives the short gastric and the left gastroepiploic arteries.
• The hepatic artery passes to the right and then turns superiorly into the right free border of the lesser omentum and then to the liver. It gives off the right gastric artery (from which arises the cystic artery) going to the lesser curvature of the stomach and the gastroduodenal artery.

The gastroduodenal artery runs to the 1st part of the duodenum and when it reaches its lower border, divides into the right gastroepiploic artery which follows the greater curvature of the stomach (anastomosing with the left gastroepiploic artery) and the superior pancreaticoduodenal artery.

The superior pancreaticoduodenal artery runs down between the pancreas and duodenum, supplying both and anastomosing with the inferior pancreaticoduodenal artery from the superior mesenteric artery (Anastomosis between foregut and midgut arteries; Clemente 223; Grant p. 135; Netter 3e 291, 4e 301).

The superior mesenteric artery

• arises posterior to the pancreas, emerges at the lower border of this organ, and crosses the 3rd part of the duodenum.
• This artery and the aorta form a nutcracker enclosing the left renal vein (Clemente 243, Grant p. 145, fig. 2.77; Netter 3e 286, 4e 332) and the duodenum (Clemente 223, 241; Grant p. 131, fig. 2.56; Netter 3e 292, 4e 301).
• The pancreas sends an uncinate process posterior to this artery.

The superior mesenteric vein

• lies to the right of the artery and passes posterior to the pancreas (Clemente 223; Grant p. 133-134, 160-161; Netter 3e 295, 4e 301).
• is joined by the splenic vein which lies inferior to the splenic artery and thus posterior to the pancreas (Clemente 232; Grant p. 134, 160-161; Netter 3e 299-301, 4e 309, 311-313).
• These 2 veins form the portal vein posterior to the pancreas and the 1st part of the duodenum.

There is little mixing of the 2 bloodstreams from the superior mesenteric vein and splenic vein (and inferior mesenteric vein). The right side of the portal vein receives mostly blood from the superior mesenteric vein and the left side receives blood from the splenic (and inferior mesenteric) vein (Netter 4e 312).

• In the case of ingested liver poisons, their absorption from the small intestine into the tributaries of the superior mesenteric vein results in a greater concentration of the poison reaching the right side of the liver, which may show toxic changes while the left side remains normal.
• In deficiencies of substances such as choline and methionine, the inferior mesenteric vein absorbs little or none, the small intestine already having absorbed most. The left half of the liver is thus deprived of an adequate supply and exhibits cirrhosis in the absence of such changes in the right side.

The portal vein

• travels in the free border of the lesser omentum, posterior to the hepatic artery and reaches the liver (Clemente 218; Grant p. 126, 152-153, 160; Netter 3e 290, 4e 312).
• is anterior to the inferior vena cava, separated from it by the epiploic foramen (Clemente 206; Grant p. 123; Netter 3e 288, 4e 273).

THERE IS NO VALVE IN THE PORTAL SYSTEM.

Lying within the free border of the lesser omentum is the common bile duct. This leaves the liver and travels down, lying to the right of the hepatic artery and anterior to the portal vein (Clemente 211; Grant p. 152-159; Netter 3e 290, 4e 273). It runs posterior to the first part of the duodenum and the head of the pancreas and opens into the second part of the duodenum with the main pancreatic duct (Clemente 221, 224-225; Grant p. 156; Netter 3e 285, 4e 279).

Innervation of the liver

• Sympathetic branches (vasoconstrictors) from the celiac plexus follow the hepatic arteries and the portal vein to the liver (Grant p. 176-178; Netter 3e 309, 4e 319-320).
• These are joined by hepatic branches from the anterior vagal and posterior vagal trunks which run in the lesser omentum to reach the hepatic plexus.
• Sympathetic and vagal fibers end on the gallbladder, extra and intrahepatic ducts.
• A vagotomy will lead to enlargement of the gallbladder and slows its emptying.
• Visceral afferents (pain) join the celiac plexus, then the splanchnic nerves and enter the spinal cord at levels T6-T9.

Pain from the gallbladder is referred to the region of Ribs 6-9 extending to the inferior angle of the scapula on the right side.

The inferior mesenteric artery is hidden by the 3rd part of the duodenum, emerges inferior to it and gives off branches for the supply of the hindgut (Clemente plate 226; Grant p. 142-143, 163; Netter 296). Emerging from posterior to the duodenum are the testicular or ovarian arteries (Clemente plate 226; Grant p. 162-163; Netter 322).

The inferior phrenic arteries emerge superior to the coeliac artery, the right one lying posterior to the inferior vena cava.

The inferior mesenteric vein leaves the left side of the artery, running superiorly and alongside the 4th part of the duodenum, posterior to the pancreas and joins with the splenic vein (Clemente 232; Grant p. 160-161; Netter 3e 301-302, 4e 311).

The stomach bed (Clemente 223; Grant p. 120-121, 123, 125, 133; Netter 3e 288, 4e 309) is formed by the following structures:

• omental bursa,
• pancreas,
• upper left part of kidney and suprarenal gland
• coeliac artery, coeliac ganglia and spleen.

Esophagus

• Esophageal veins from the left gastric veins (Clemente plate 198; Grant p. 121, 227; Netter 3e 299, 4e 309) anastomose with the esophageal branches of the azygos veins.
• They form a portal-systemic anastomosis. They may become swollen in portal obstruction and bleed (esophageal varices). They are located around the cardiac orifice.

Stomach (Clemente 208-209; Grant p. 128-129; Netter 3e 267, 4e 276-277)

• Is divided into a:
  • Fundus, which rises to the level of 5th intercostal space;
  • Body;
  • Pylorus with a pyloric sphincter.
• contains rugae
• is innervated by vagal fibers and sympathetic branches from the celiac plexus (greater splanchnic nerve T6-9; Grant p. 178; Netter 3e 309-311, 4e 319-320).

The greater omentum

• is supplied by the right and left gastroepiploic arteries (Clemente 204-206; Grant p. 124, 130; Netter 3e 309, 4e  269, 300, 309)
• is the"policeman" of the abdomen: it forms adhesions in case of inflammation, sealing off the danger area and preventing a generalized peritonitis.

Liver

• Right lobe (Clemente 216-220; Grant p. 146-147; Netter 3e 279, 4e 286-293)
• Left lobe with caudate and quadrate lobes
• Porta hepatis and fissure for the ligamentum venosum
• The lesser omentum is attached to the liver at the fissure for the ligamentum venosum (Clemente 217; Grant p. 147; Netter 3e 279, 4e 287). The ligamentum venosum is a remnant (ductus venosus) connecting the left branch of the portal vein to the inferior vena cava.

The inferior vena cava (IVC)

• is deeply embedded in the liver before passing through the central tendon of the diaphragm (Clemente 216-217; Grant p. 147; Netter 3e 279, 4e 287).
• Large hepatic veins open into the IVC, which is retroperitoneal (Clemente 218; Grant p. 149; Netter 3e 279, 4e 287).

The gallbladder

• is a reservoir for bile, lying in a groove under the liver (Clemente 221; Grant p. 152-159; Netter 3e 285, 4e 294-295).
• has a cystic duct which joins with the common hepatic duct (formed by the union of the right and left hepatic ducts) to form the common bile duct.
• Blood supply is by the cystic artery, a branch of the right branch of the hepatic artery (Clemente 206; Grant p. 154-155; Netter 3e 285, 4e 294).

The pancreas

• Head, body and tail are supplied by the splenic artery (Clemente 223; Grant p. 134-135; Netter 3e 291, 4e 298) and a branch called the arteria pancreatica magna (greater pancreatic artery).
• The main duct opens with the common bile duct into the hepatopancreatic ampulla (of Vater; Clemente 224; Grant p. 156; Netter 3e 285, 4e 294), closed by the sphincter of Oddi.
• Innervation is by the celiac and the superior mesenteric plexuses.
• Pain is referred to T6-T10 dermatomes

The spleen

• lays opposite ribs 9 to 11. It has notches on its anterior aspect (Clemente 212-213; Grant p. 131, 135; Netter 3e 289, 4e 299).
• Its innervation is purely sympathetic

PORTAL SYSTEMIC ANASTOMOSES

• Esophageal veins
• Paraumbilical veins running with the ligamentum teres and uniting the portal vein with veins of the anterior abdominal wall. When enlarged, they form the caput medusae (Clemente 9; Grant p. 161, 227; Netter 3e 248, 4e 256, 312)
• Portal systemic anastomosis in the anal canal (see Abdomen II) .
• Anastomosis between the small veins of the portal system and veins of the diaphragm or posterior abdominal wall, in the region of the bare area of the liver (Clemente 216; Grant p. 146; Netter 3e 335, 4e 287).

updated 09/29/2008

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Abdomen II

Text:  Gross Anatomy, K. W. Chung, 6^th edition: pp. 195-210.

Reference:  Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5^th edition: pp. 265-281.

Dissector:

Clemente’s Anatomy Dissector, 2nd edition:  pp. 152 - 160

Grant’s Dissector, P.W. Tank, 14^th edition:  pp. 96-105

 

JEJUNUM AND ILEUM

• No sharp junction can be observed grossly between the jejunum and the ileum. Most of the jejunum lies in the left upper quadrant, whereas most of the ileum lies in the right lower quadrant.
• The inner circular folds, increasing the internal surface for absorption, are present in duodenum and jejunum but they diminish in size in the ileum (Grant p. 136; Netter 3e 272, 4e 280).
• The jejunum has a greater vascularity than the ileum, with long vasa recta (Clemente 230; Grant p. 140; Netter 3e 272, 4e 306).
• Remember: the ileum is NOT the ilium.
• Lymph follicles in the mucous membrane of the ileum form Peyer's patches and may be visible to the naked eye (Clemente 236; Grant p. 136; Netter 3e 272, 4e 280).
• The 20 feet (6-7 m) of jejunum and ileum are attached to the posterior body wall by mesentery (Clemente 226, 228; Grant p. 120, 140; Netter 3e 263, 4e 270-271). This is attached from the duodenojejunal flexure to the end of the ileum so that its attachment is 6 in. long. The other border is 20 feet long.
• Because of the convolutions, the loop of the intestine and its segment of the mesentery may become twisted (volvulus) so that the vessels and the gut may become obstructed.

The superior mesenteric artery (Clemente 230-231; Grant p. 140-141; Netter 3e 295, 4e 306) and vein (Grant p. 160-161; Netter 3e 300, 4e 310) having crossed the 3rd part of the duodenum enter the root of the mesentery and curve down towards the right iliac region giving off jejunal and ileal branches from the left side. The branches form arcades (up to 3 orders) and run straight to the gut wall. These arcades assure the blood supply of the gut.

The caecum: The ileum ends in the right iliac region by joining with the cecum (blind end; Clemente 236; Grant p. 139; Netter 3e 273-275, 4e 281-284).

The appendix

• is attached to the cecum.
• is about the size of an earthworm (vermiform) and may become inflamed.

The blood supply of the appendix (Clemente 237; Grant p. 139; Netter 3e 273, 4e 281).

The superior mesenteric artery ends by becoming the ileocolic artery which gives off the ileal, colic, cecal branches and the appendicular artery.

The appendicular artery

• runs behind the terminal part of the ileum and then into the free border of the mesentery of the appendix, the mesoappendix, before running alongside the appendix itself .
• may become thrombosed in appendicitis.
• Remember that appendicitis may become localized only with involvement of the parietal peritoneum, if not, the pain is referred to the umbilical region.
• Removal of the appendix may be difficult because its position is variable (Clemente 237; Grant p. 139; Netter 3e 275, 4e 283). The best guide to it are the taeniae coli which are 3 strips of longitudinal muscle running along the surface of the colon and they converge to meet at the base of the appendix.

The colon (Clemente 238-239; Grant p. 138, 142-145; Netter 3e 276, 4e 284)

has the following features:

• taeniae coli
• haustra
• epiploic appendages
• hepatic flexure
• splenic flexure

The ascending, descending colon and the rectum along with their blood vessels and lymphatics are retroperitoneal.

The transverse colon is attached by the transverse mesocolon and sigmoid colon by the sigmoid mesocolon.

The sigmoid colon leads down to the pelvis to become the rectum at the level of S3.

The rectum (Clemente 309; Grant p. 208-209; Netter 3e 335, 347, 374-375, 4e 284-285)

• follows the curve of the sacrum
• then bends back in front of the tip of the coccyx to become the anal canal.
• There are no taeniae coli, haustra or epiploic appendages along the rectum (Clemente 309; Grant p. 212; Netter 3e 267, 4e 284).
• It is covered by peritoneum anteriorly and laterally in its upper part; its lower part lies below the level of the peritoneum.

The anal canal (Clemente 309-310; Grant p. 208, 211; Netter 3e 374, 4e 392-395)

• is about 4 cm long
• passes inferiorly and posteriorly.
• is surrounded by a complex sphincter (see lectures on the pelvis).
• contains the anal valves and the anal columns (folds of the mucosa).
• The boundary between the columnar epithelium and the stratified squamous epithelium is Hilton's white line or pectinate line.

Blood supply of the large intestine.

• The midgut is supplied by the superior mesenteric artery. The terminal branch is the ileocolic artery (Clemente 230; Grant p. 140; Netter 3e 295, 4e 307).
• Other branches of the superior mesenteric artery are the right colic (retroperitoneal) and the middle colic (travels through the transverse mesocolon to reach the middle of the transverse colon).
• When the arteries reach the colon, they divide into proximal and distal branches running along the colon and anastomosing with one another. This results in a continuous chain of anastomoses along the colon (Marginal artery of Drummond; Clemente 230-234; Grant p. 142; Netter 3e 296, 4e 307-308).

The inferior mesenteric artery

• gives off the left colic artery (retroperitoneal) and the sigmoid branches (Clemente 234; Grant p. 142; Netter 3e 296, 4e 307)
• runs into the pelvis in the sigmoid mesocolon and changes its name to the superior rectal artery.

The superior rectal artery (Clemente 234; Grant p. 213; Netter 3e 378, 4e 307, 398) supplies all the rectum and the upper 1/2 of the anal canal. Its terminal branches anastomose with the inferior rectal artery.

The superior rectal vein drains via the portal system (Clemente 311; Grant p. 160; Netter 3e 379, 4e 311, 399) and the inferior rectal vein into the systemic system: this is another portal-systemic anastomosis).

Distension of the veins gives rise to hemorrhoids and the main dilated vessels are found at 4, 7, and 11 o'clock when the anal canal is viewed with the patient lying supine and the legs are flexed.

The upper 1/2 of the anal canal is derived from the embryonic hindgut whereas the lower 1/2 is derived from ectoderm from the embryonic proctodeum.

• The upper 1/2 is lined with columnar epithelium, the lower with stratified squamous epithelium.
• The upper 1/2 is supplied by the autonomic nervous system and the lower by spinal nerves (Clemente 313; Grant p. 214; Netter 3e 390, 4e 410, 412). Hemorrhoids in the lower part of the canal are extremely painful.
• The upper 1/2 drains venous blood into the portal system, the lower into the systemic system.
• Lymph from the upper 1/2 drains into the abdomen while lymph from the lower 1/2 drains into the superficial inguinal nodes.

updated 10/06/2008

The posterior abdominal wall consists of (Clemente 252; Grant p. 172; Netter 3e 255, 4e 263):

• the vertical ridge produced by the vertebral bodies,
• the psoas,
• the quadratus lumborum
• the transversus abdominis muscle
• the posterior part of the diaphragm and its crura, posteriorly.

The parietal peritoneum covers this posterior abdominal wall along with the retroperitoneal organs such as the duodenum and the kidneys lying on the vertebrae and muscles (Clemente 240; Grant p. 122; Netter 3e 266, 4e 274).

MUSCLES

Psoas major (Clemente 250; Grant p. 173; Netter 3e 478, 4e 263):

• attaches from the transverse processes and sides of the bodies and intervertebral discs of the 5 lumbar vertebrae;
• passes with iliacus (Iliacus arises from the inner surface of ilium) under the inguinal ligament
• attaches to the lesser trochanter fusing with iliacus (iliopsoas).
• innervated by L1, 2 and 3 inside the abdomen.
• flexes the hip joint.
• Because the muscle fills in the angle between the transverse processes and the sides of the bodies of the vertebrae, it covers the intervertebral foramina. The lumbar plexus thus enters the psoas major and its branches emerge from the surface of the muscle.

Psoas minor is an occasional small muscle belly with its long tendon lying over the psoas major.

Iliopsoas is covered by dense layer of fascia so that muscles and lumbar plexus are behind fascia and iliac vessels are in front of it (The femoral sheath is formed by the transversalis fascia above the inguinal ligament and the iliopsoas fascia below the ligament).

Quadratus lumborum lies lateral to psoas, running between the iliac crest and R12. It is a side flexor of the trunk and is innervated segmentally by the adjacent lumbar nerves.

The diaphragm crosses the quadratus lumborum and the psoas by the lateral and medial lumbocostal arches (arcuate ligaments) respectively (Clemente 251; Grant p. 172; Netter 3e 255, 4e 263).

Transversus abdominis arises from the thoracolumbar fascia (Anterior attachment have been described in the anterior abdominal wall; Clemente 250; Grant p. 104-105; Netter 3e 243-244, 255, 4e 263).

The abdominal aorta lies in the midline (Clemente 253; Grant p. 163; Netter 3e 256, 4e 264). It enters the abdomen under the median arcuate ligament at T12 and ends at L4, left of the midline by dividing into the 2 common iliac arteries. The main continuation of the aorta is the median or middle sacral artery.

Other branches of the abdominal aorta are subdivided into 3 groups of 3:

• ventral, to the gut
• lateral, to the 3 glands
• branches to the body wall.

1. Ventral branches are the celiac, superior and inferior mesenteric arteries to the fore-, mid- and hindgut respectively.

2. Lateral branches supply the suprarenal glands, kidneys and the gonads (Clemente 243, 253; Grant p. 165; Netter 3e 256, 264):

• The largest are the renal arteries, which receive 1/4 of the cardiac output. They arise just below the superior mesenteric artery. The right renal artery passes posterior to the inferior vena cava. They also send branches to the suprarenal glands and the renal pelvis.
• The suprarenal branch of the aorta is also called the middle suprarenal artery.
• The gonadal (ovarian or testicular) arteries arise from the aorta just below the renal arteries. They descend lying anterior to the surface of the psoas to reach the ovary or pass into the inguinal canal to go to the scrotum.

3. Branches to the body wall (Clemente 253; Grant p. 175; Netter 3e 256, 4e 264):

• The inferior phrenic arteries: branches to the suprarenal glands and ramify on the inferior surface of the diaphragm.
• The 4 lumbar arteries: gives a posterior branch going through the back and giving a spinal branch. The anterior branch runs in the anterior abdominal wall between the transversus and the internal oblique muscle.
• The median (middle) sacral artery: in the midline, anterior to the sacrum.

The INFERIOR VENA CAVA begins in front of the body L5 and ascends to the diaphragm to pierce the central tendon at T8 (Clemente 253; Grant p. 174-175; Netter 3e 257, 4e 265).

• From the renal veins upwards, veins lie anterior to the corresponding arteries. Below the level of the renal veins, the arteries lie anterior to the veins.
• Tributaries of the inferior vena cava may be deduced from branches of the aorta (Clemente 265; Grant p. 175; Netter 3e 257, 4e 265):
  • Ventral branches all drain to the portal system. Hepatic veins drain into IVC.
  • Lateral tributaries correspond to the named arteries except on the left where the suprarenal and gonadal veins open into the left renal vein.
  • Of the tributaries from the body wall, the inferior phrenic and lumbar veins drain into the IVC but the median sacral opens into the left common iliac vein.

Kidneys and ureters.

• Kidneys lie on the psoas major, quadratus lumborum and the origin of the transversus abdominis from medial to lateral (Clemente 241; Grant p. 163; Netter 3e 319, 4e 264-265).
• Superiorly, the upper part of the kidney lies against the diaphragm posterior to which is the costodiaphragmatic recess of pleura and the lower ribs (12 R; 11 and 12 L). The subcostal, iliohypogastric and ilioinguinal nerves are also posterior relations.
• Kidneys are surrounded by perirenal fat enclosed in renal fascia. The renal capsule lies directly surrounding the kidney (Clemente 245; Grant p. 164; Netter 3e 321, 4e 334).

Blood supply of the kidney

The renal artery divides into 5 segmental arteries (apical, anterosuperior, anteroinferior, posterior and inferior) supplying the corresponding segments of the kidneys (Clemente 244; Grant p. 167; Netter 3e 323, 4e 335). There is no anastomosis between these arteries. Aberrant arteries may remain from development.

Intrarenal veins do anastomose.

Internal appearance of the kidneys

The kidney has the following internal features

• Cortex and medulla (Clemente 247; Grant p. 166; Netter 3e 321, 4e 334)
• Lobes are separated by renal columns of Bertin.
• Segmental arteries give rise to lobar branches which give rise to interlobar branches and arcuate arteries running between cortex and medulla (Clemente 247; Grant p. 167; Netter 3e 323, 4e 335). From these arise the interlobular arteries radiating out to the cortex. Some of them anastomose with the capsular vessels. Corresponding veins on the surface of the kidneys are the stellate veins.
• Interlobular arteries give rise to afferent arterioles and efferent arterioles with peritubular capillaries.
• Medulla and renal papilla.
• Minor calyces and major calyces (Clemente 247; Grant p. 166; Netter 3e 321, 4e 335).

The ureter begins at the pelvis, it is lined by transitional epithelium, runs down anterior to the psoas major, retroperitoneally. It measures 25cm (10 in.) and has 3 narrow regions (Clemente 243; Grant p. 163; Netter 3e 328, 4e 329):

• at the junction with the pelvis of the kidney,
• where it crosses the brim of the pelvic bone,
• and as it enters the bladder.

Inferiorly, testicular or ovarian vessels cross over the ureter. It is well supplied by the renal artery, aorta, gonadal vessels and various pelvic vessels. In a urogram, the ureters lie approximately opposite the tips of the lumbar transverse processes (Clemente 248; Grant p. 168).

The suprarenal glands are within the renal fascia at the upper poles of the kidneys (Clemente 242-243, 245; Grant p. 163-164; Netter 3e 319, 4e 332). The right gland is less accessible because it is posterior to the bare area of the liver and has a short vein draining into the IVC (Clemente 242-243, 245; Grant p. 163; Netter 3e 322, 4e 332). The glands are divided internally into cortex and medulla. The cortex may be stimulated by adrenocorticotrophic hormone (ACTH) whereas the medulla is stimulated by the preganglionic sympathetic fibers from the celiac plexus.

The glands are well vascularized by branches from the renal and phrenic arteries and the aorta (Clemente 245; Grant p. 165; Netter 3e 322, 4e 332). Venous drainage for the left gland is by a large vein draining into the left renal vein or for the right gland by a short vein directly into the inferior vena cava.

The lumbar plexus lies in the psoas major and is formed by the anterior primary rami of L1, 2, 3, and 4 (Clemente 254-256; Grant p. 172-173; Netter 3e 259, 479, 4e 267). The sacral plexus is from L4, 5, S1, 2, 3 and 4.

• L4 is also called the nervus furcalis or lumbosacral trunk because it splits itself between the lumbar and sacral plexuses.
• The subcostal nerve is seen in the posterior abdominal wall, below R12. It emerges from under the lumbocostal arch and runs on quadratus lumborum. It slips between the transversus abdominis and the internal oblique and is distributed to the anterior abdominal wall.
• L1: the main portion is the iliohypogastric nerve. This has a lateral cutaneous branch.
• The collateral of the iliohypogastric is the ilioinguinal which has no collateral. This runs between the layers of the anterior abdominal wall, emerges from the superficial inguinal ring and supplies the skin on the medial side of the thigh and the scrotum or labium majus.
• The genitofemoral nerve (L1 and 2) emerges from the anterior surface of the psoas major, runs down deep to the psoas fascia and supplies cremaster muscle via its genital branch and a small area under the inguinal ligament by its femoral branch.
• The lateral cutaneous nerve of the thigh (L2 and 3) emerges from the lateral border of the psoas, sweeps around the iliac fossa and leaves the abdomen by passing under the inguinal ligament near its lateral attachment to the anterior superior iliac spine.

Due to the lower limb rotation, the femoral nerve is derived from dorsal divisions of the anterior primary rami of L2, 3, and 4 while the obturator nerve which supplies the medial side of the thigh is derived from ventral divisions of the anterior primary rami of L 2, 3 and 4.

The femoral nerve is large and emerges from the lateral border of psoas and may give branches to psoas and iliacus. It lies outside of the fascia covering psoas and iliacus and is therefore outside of the femoral sheath.

The obturator nerve emerges from the medial border of the psoas near the brim of the pelvis, lying posterior to the common iliac vessels. It then travels anteriorly and inferiorly, anterior to obturator internus and leaves the pelvis by passing through the superior part of the obturator foramen.

The autonomic nervous system in the abdomen

The paravertebral chain of ganglia will be found along the anterior border of the psoas (Clemente 255; Grant p. 172; Netter 3e 259, 4e 267). White rami from the first 2 lumbar nerves pass to the ganglia and all ganglia have gray fibers passing back to the lumbar nerves.

Celiac ganglia and plexuses lie around the celiac and superior mesenteric arteries (Clemente 255; Grant p. 176-177; Netter 3e 308, 4e 267). Plexuses are joined by the 3 splanchnic nerves, branches of the vagus nerves (parasympathetic) and branches from the sympathetic trunk. Postganglionic sympathetic fibers from plexuses travel with all the major arteries, along with preganglionic parasympathetic fibers to innervate viscera (except for stomach which gets its own parasympathetic innervation (anterior and posterior gastric nerves).

Plexuses around the aorta continue downward anterior to the aortic bifurcation as the superior hypogastric plexus (Clemente 313; Grant p. 176-177; Netter 3e 308, 4e 318). This divides into the right and left inferior hypogastric plexuses joined by the parasympathetic pelvic splanchnic nerves (S2,3,4). Pelvic viscera are thus supplied with sympathetic and parasympathetic fibers. Pelvic splanchnic nerves also supply the hindgut.

updated 10/06/2008

Pelvis and pelvic contents

THE SACROILIAC JOINT

This is a plane synovial joint (Clemente plates 252-257; Grant p. 196-199; Netter 3e 468; 4e 352-355, 486)  It is the strongest joint in the body and is in the line of weight transmission from the spine to the hip bone and then to the femur (only the dorsal part is involved; the ventral part acts as a tie beam preventing the ilia from being forced apart).

Ligaments are arranged to allow a small amount of movement and to resist major displacement of the sacrum (Clemente plates 254, 255, 257; Grant p. 200-201; Netter 3e 340-341; 4e 352-353).

1) Posterior or dorsal interosseous sacroiliac ligaments: posterior sacrum to posterior ilium.

2) Anterior or ventral sacroiliac ligament is weaker.

3) Sacrospinous ligament: from ischial spine to side of sacrum. Converts greater sciatic notch into a foramen.

4) Sacrotuberous ligament: from ischial tuberosity to side of sacrum. Converts lesser sciatic notch into a foramen.

5) Iliolumbar ligament from the transverse process of L5 to posterior part of iliac crest.

MUSCLES OF THE PELVIS

The obturator internus attaches from the medial wall of the pelvis, runs through the lesser sciatic foramen, and forms a right angle to the greater trochanter of the femur (Clemente plate 335; Grant p. 202, 391; Netter 3e 345-346, 477; 4e 411, 503). It is covered by the obturator fascia and is a lateral rotator of the thigh. It is innervated by the nerve to obturator internus.

The levator ani AND the coccygeus form the pelvic diaphragm, separating the pelvis from the ischiorectal fossa (Clemente plate 272 fig. 420, plate 276 fig. 426; Grant p. 203; Netter 3e 343-346; 356-361).

• The urethra, vagina and rectum pass through the pelvic diaphragm.
• The pudendal nerve and vessels go around it (Clemente plates 266, 277; Grant p. 261; Netter 3e 384-385, 391-393; 4e 357, 411)

The levator ani is the muscular floor of the pelvis and supports the viscera (Clemente plates 265, 286 fig. 439; Grant p. 203-212; Netter 3e 343-346; 4e 360-361).

• from the back of the pubis, lateral to the symphysis,
• and from the spine of the ischium,
• the muscle sweeps inferiorly, medially and posteriorly:

a) The most anterior fibers from the back of the pubis run:

1) in the male, posteriorly and inferiorly just below the prostate gland, to be inserted into the perineal body. The integrity of the perineal body is vital.

2) in the female, the muscle surrounds the vagina and forms the sphincter vaginae.

b) other fibers pass around the recto-anal junction and blends in with fibers of the anal sphincter: this is the puborectalis or recto-anal sling (Clemente plate 272 fig. 420; Grant p. 210; Netter 3e 344, 346; 4e 356-357).

c) more posterior fibers meet their opposite and form the anococcygeal raphe.

d) most posterior fibers insert into the coccyx.

The levator ani is innervated by nerve to levator ani S4 and the inferior rectal nerve.

Coccygeus is deep to the sacrospinous ligament and has similar attachments. Nerve supply is S4.

Piriformis from the 3 middle pieces of sacrum, passes through greater sciatic foramen (along with sciatic nerve, superior and inferior gluteal vessels and nerves) and inserts into greater trochanter of femur (Clemente plates 271, 335; Grant p. 202, 390; Netter 3e 343, 345, 477; 4e 358, 503).

Levator ani, coccygeus and piriformis are covered by a layer of fascia.

SACRAL PLEXUS (L4, 5, S 1, 2, 3; Clemente plate 240; Grant p. 206-207; Netter 3e 479-481; 4e 499)

The lower half of L4 joins with L5, forming the lumbosacral trunk which crosses the brim of the pelvis and joins with S1.

(Below C7, the spinal nerve lies below its corresponding vertebra).

• Sciatic nerve: tibial (L4, 5, S1, 2, 3) and common peroneal (L4, 5, S1, 2) branches
• Superior gluteal L4, 5, S1
• Inferior gluteal L5,S1,2
• Posterior cutaneous nerve of thigh S1, 2, 3
• Pudendal S2, 3, 4
• Levator ani, coccygeus and anal sphincter S4
• Also nerves to quadratus femoris, obturator internus, gemelli and piriformis.

The PELVIC VISCERA

The organization of pelvic viscera from anterior to posterior is the following:

• In the male: bladder, prostate and male genital organs and rectum (Clemente plate 289 fig. 445; Grant p. 209; Netter 3e 348; 4e 361).
• In the female: bladder, uterus and female genital organs and rectum (Clemente plate 258; Grant p. 208; Netter 3e 347; 4e 360).

The pelvic viscera are partly covered by peritoneum in their upper aspects but are extraperitoneal inferiorly.

In the male pelvis, the empty bladder is covered above by the peritoneum reflecting off the back of the anterior abdominal wall (Clemente plate 261 fig. 398, plate 286 figs. 440A and B; Grant p. 209; Netter 3e 349-353; 4e 361). When it is full, it rises above the pubic symphysis and strips the peritoneum from the anterior abdominal wall.

In the male, the peritoneum passes laterally to the side walls of the pelvis. Posteriorly, it dips down over the back of the bladder and the upper parts of the seminal vesicles before being reflected back onto the rectum to form the rectovesical pouch.

In the female, relations are similar except that it dips inferiorly to the junction between the uterine body and the cervix (internal os) to form the vesicouterine pouch (Clemente plate 258, plate 259 fig. 395, plate 261 fig. 398; Grant p. 208; Netter 3e 347; 4e 360). This is separated from the vagina by the pelvic fascia, which is called the parametrium. Posterior to the uterus, the peritoneum is reflected onto the rectum forming the recto-uterine pouch or pouch of Douglas. Laterally, the peritoneum drapes over the uterine tubes and the ovaries to form the broad ligament of the uterus and the suspensory ligament of the ovary (Clemente plate 261 fig. 399; Grant p. 233-237; Netter 3e 354-355; 4e 362, 371).

The BLADDER

is found between the 2 levator ani muscles. It has a wall of smooth muscle, the detrusor muscle arranged in 3 layers. It is lined by transitional epithelium thrown into folds except over the trigone, which is derived from the lower end of the mesonephric duct and of mesodermal origin (Clemente plate 262 fig. 400, plate 288; Grant p. 221; Netter 3e 353; 4e 367). The ureters open superiorly, and the urethra, inferiorly.

The urethral orifice has a sphincter vesicae, which, in the male, prevents semen reflux during ejaculation.

The bladder is surrounded below the peritoneum by pelvic fascia, which is thickened anteriorly to form the puboprostatic ligament in the male (Clemente plate 286 fig. 439; Grant p. 210; Netter 3e 353, 4e 361, 366) or pubovesical ligaments in the female (Clemente plate 272 fig. 419; Grant p. 232; Netter 3e 343, 4e 365, 366). Laterally, along the sides of the bladder, they are connected to the obturator fascia, forming the lateral true ligaments. The bladder receives its nerve supply from S2,3,4 via nervi erigentes (pelvic splanchnic nerves) and pudendal nerves and from the sympathetic system.

The PROSTATE

In the male, the internal urethral orifice leads directly to the prostatic urethra, the gland being immediately below the bladder (Grant p. 216-221; Netter 3e 367; 4e 366). The prostate has 15-20 ducts opening into the prostatic urethra (Grant p. 221; Netter 3e 367-368; 4e 366). It has a large amount of smooth muscle, has a capsule and is surrounded by the prostatic venous plexus. The gland is divided into 2 lateral lobes (site of carcinoma - may be felt through the rectum) and a middle lobe (the upper part is the site of benign hypertrophy).

The posterior wall of the prostatic urethra has a colliculus seminalis or verumontanum onto which open the ejaculatory ducts (Grant p. 221; Netter 3e 367; 4e 366).

The SEMINAL VESICLES

The vas deferens enters through the deep inguinal ring, runs on the side wall of the pelvis and hooks over the ureter. It then runs posterior to the bladder approaching the other vas deferens (Clemente plate 288 fig. 442; plate 291; Grant p. 220; Netter 3e 367; 4e 361, 384). The seminal vesicles secrete a fluid which contributes to the semen. The ducts of the seminal vesicles join with the vas deferens to form the ejaculatory ducts (Clemente plate 289 fig. 444; Grant p. 220; Netter 3e 367; 4e 384). The ducts bilaterally converge to open on the seminal colliculus or verumontanum on either side of the prostatic utricle (Clemente plate 290 fig. 446; Grant p. 221; Netter 3e 367; 4e 384).

The prostatic utricle is a small diverticulum entering the substance of the prostate. It is a remnant of the paramesonephric ducts. In pseudohermaphroditism, it may enlarge to form a mini-uterus and vagina.

The UTERUS and VAGINA

The uterus has a body, fundus, cervix and 2 uterine (Fallopian) tubes (Clemente plate 262 fig. 401; Grant p. 233-237; Netter 3e 356; 4e 371). It is composed of smooth muscle, powerful when hypertrophied during pregnancy (Clemente plate 238-239; Netter 3e 394; 4e 371, 414). The lumen of the cervix is smaller than that of the body and the constriction between the 2 is called the internal os. The opening of the cervix into the vagina is called the external os which is circular until the birth of the first child. After that it is a transverse slit.

The vaginal portion of the cervix protrudes into the vagina, surrounded by the anterior, posterior and lateral vaginal fornices (Clemente plate 263 fig. 402; Grant p. 235; Netter 3e 356; 4e 371).

The supravaginal portion of the cervix is above the level of the vagina and is surrounded by the pelvic connective tissue which is called the parametrium (the uterine muscle is called the myometrium and the mucosa the endometrium ( fom the Greek, metra = womb; Clemente plate 263 fig. 403; Netter 4e 371).

The upper 1/3 of the cervix gets taken up into the uterus during the first stage of labor and the obstetricians refer to it as the lower uterine segment.

The uterus is anteflexed and anteverted (Clemente plate 258; Grant p. 232-236; Netter 3e 358; 4e 374). It is less anteverted when the bladder is full.

The uterine tubes pass laterally lying in the broad ligament. Each has an infundibulum, ampulla and isthmus (Clemente plate 262; Grant p. 235; Netter 3e 356; 4e 371). The ovarian end passes over the upper pole of the ovary and down its posterior surface with the fimbria covering the medial surface of the ovary.

The broad ligament is formed by the mesosalpinx, mesovarium and mesometrium.

The suspensory ligament or infundibulopelvic ligament is a fold of peritoneum connecting the ovary and the end of uterine tube to the side wall of the pelvis (Clemente plate 261 fig. 399; Grant p. 232-237; Netter 3e 356; 4e 371).

The following structures are found between the layers of the broad ligament:

1) The round ligament of the uterus and ligament of the ovary (female gubernaculum).

2) The uterine artery runs near base of broad ligament and ascends between its layers along the side of the uterus.

3) The transverse cervical ligaments are found near the base of the broad ligament.

SUPPORT OF THE UTERUS

A prolapsed uterus is an abnormally descended uterus bulging into the vagina, perhaps due to a difficult birth. The support of the uterus depends on:

1) the integrity of the pelvic floor, which relies on the perineal body.

2) the round ligament, which helps to keep the uterus in the anteverted position.

3) the uterosacral ligaments, which lie between the cervix and the sacrum. They are enclosed in the rectouterine fold and form the lateral boundaries of the rectouterine pouch.

4) the transverse cervical ligament (also called cardinal or Mackenrodt's ligament).

5) the pubovesical ligaments also pass posteriorly to form the pubocervical ligaments.

The structures listed in #3, 4, and 5 are condensations of the pelvic fascia.

The OVARY

• Lies on the side wall of the pelvis before the first pregnancy in the angle between the external iliac vessels superiorly and the internal iliac arteries and the ureter posteriorly (Clemente plate 258; Grant p. 232; Netter 3e 347; 4e 360).
• Attached to the upper surface of the broad ligament by the mesovarium. The ovary is surrounded by a layer of germinal epithelium. When the Graafian follicle ruptures, the egg is expelled momentarily into the peritoneal cavity before entering the fimbriated end of the uterine tube. Beneath the germinal epithelium is the tunica albuginea.
• The surface of the mature ovaries is irregular (Clemente plate 263 fig. 404; Grant p. 237; Netter 3e 356; 4e 371) due to presence of immature follicles, corpora lutea and scars of old corpora lutea.

The VAGINA

The vagina passes superiorly and posteriorly from the vestibule to the cervix of the uterus (Clemente plate 258; Grant p. 232; Netter 3e 355; 4e 360). It is lined by stratified squamous epithelium and undergoes some minor variations during the menstrual cycle. It is surrounded by smooth muscle in an outer longitudinal and inner circular layer. The smooth muscle is reinforced by striated muscle fibers, the bulbospongiosus, to help form the sphincter vaginae (Clemente plate 279 fig. 430; Grant p. 255-257; Netter 3e 376; 4e 370). No glands are found in the vagina, the lubrication is provided from the cervical mucus.

The blood supply of the female internal genitalia

• The female internal genitalia are supplied by the uterine, vaginal and ovarian arteries (Clemente plate 264; Grant p. 235; Netter 3e 380; 4e 404).
• The main blood supply to the uterus is from the uterine artery, a branch from the internal iliac artery (Clemente plate 267; Grant p. 241; Netter 3e 382; 4e 402). The uterine artery hypertrophies during pregnancy. The uterine artery passes over the ureter.
• The vaginal artery (Clemente plate 269; Grant p. 241; Netter 3e 382; 4e 402) usually replaces the inferior vesical artery of the male and passes below the ureter to supply the vagina.
• The ovarian artery, coming from the aorta, passes from the side wall of the pelvis in the suspensory ligament and anastomoses with the uterine artery in the broad ligament (Clemente plate 264; Grant p. 237; Netter 3e 384; 4e 400, 404). It supplies mainly the ovary and part of the uterine tube.

BLOOD VESSELS OF THE PELVIS

The common iliac arteries divide at the brim of the pelvis into the internal and external iliac arteries (Clemente plates 266, 269 fig. 414, plate 287; Grant p. 224-225, 242-243; Netter 3e 382-383; 4e 402-403).

The internal iliac artery enters the pelvis by running inferiorly and posteriorly to the lower part of the greater sciatic foramen. It divides into anterior and posterior branches.

Anterior branches of the internal iliac artery

1) The first branch from the anterior branches of the internal iliac artery is the superior vesical artery, which is attached to the obliterated umbilical artery.

2) The next anterior branch is the obturator artery, which joins with the obturator nerve on the obturator internus and leaves the pelvis via the upper part of the obturator foramen along with its vein.

*The obturator artery may arise from the inferior epigastric artery (Grant p. 226) and run down posterior to the pubis to join the nerve. In this anatomical variation, the obturator artery is vulnerable in inguinal hernia operations because it lies posterior to the lacunar ligament.

3) The inferior vesical and middle rectal arteries are small and may arise from a common trunk. The middle rectal artery may also arise independently from the internal iliac artery or in common with the internal pudendal artery.

The inferior vesical artery is replaced by the vaginal artery in the female.

4) Next, in the female, is the uterine artery, which arises independently from the internal iliac artery.

5) 2 terminal branches leave the pelvis through the greater sciatic notch below the piriformis: the internal pudendal and inferior gluteal arteries. The internal pudendal artery crosses the spine of the ischium in the gluteal region and reenters the ischiorectal fossa below the levator ani (Clemente plate 294; Grant p. 218; Netter 3e 382-383; 4e 402-403). The inferior gluteal artery leaves the pelvis between the first and second sacral nerves and enters the gluteal region (Clemente plate 337; Grant p. 388-389; Netter 3e 382-383, 484; 4e 402-403, 502).

Posterior branches of the internal iliac artery are directed to the upper part of the greater sciatic foramen.

It breaks up into 3 nonvisceral branches leaving the pelvis by (Clemente plate 266; Grant p. 224-225, 242-243; Netter 3e 382-383; 4e 402-403):

1) climbing over the brim: the iliolumbar artery ascends in front of the sacrum and anastomoses with the lumbar arteries.

2) entering the sacral foramina: the lateral sacral artery, may be double and supplies contents of the sacral canal.

3) going through the greater sciatic foramen: the superior gluteal artery is found between the lumbosacral trunk and S1.

Relationships

• The ductus deferens (Clemente plates 265, 287; Grant p. 216; Netter 3e 383; 4e 362-363, 402-403) or round ligament of the uterus may be superimposed on the vessels lying under the peritoneum. It enters the deep ring lateral to the inferior epigastric artery and then crosses the obliterated umbilical artery, the obturator artery and the ureter.
• The ureter (Grant p. 226; Netter 3e 382, 4e 400-401) crosses the external iliac vessels and anterior branches of the internal iliac artery, lying close to the internal iliac artery at first. It then runs medially, passing superior to the lateral fornix of the vagina and enters the bladder.
• The ovarian fossa is framed by the external iliac vessels superiorly, the obliterated umbilical artery anteriorly, the ureter and internal iliac vessels posteriorly. Obturator nerve and vessels are lateral to the ovarian fossa.

updated 10/07/2008

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Gluteal and perineal relations; perineum.

The Triangle of Marcille

• The medial border is formed by the side of L5 vertebra.
• The lateral border, by the medial border of psoas major.
• The inferior border, by the upper border of the sacrum.
• The floor of triangle, by the iliolumbar and lumbosacral ligaments.

The PERINEUM

The ischiorectal (ischioanal) fossa is the space below the levator ani and is the fossa between ischium and rectum and extending anteriorly to the back of the body of the pubis (Clemente plates 276, 300; Grant p. 212, 259; Netter 3e 361, 364, 4e 366, 396).

Bones and ligaments of the perineum

The skeletal basis is the outlet of the pelvis, bounded anteriorly by the symphysis, the inferior ramus of the pubis and the ramus of the ischium. Posteriorly it is bound by the lower part of the sacrum and the coccyx connected to the ischial tuberosity by the sacrotuberous ligament. The outlet is diamond-shaped and can be divided into 2 triangles: the anal triangle and the urogenital triangle (Clemente plate 273 fig. 421, plate 300 fig. 463; Grant p. 255; Netter 3e 342, 361, 363-364; 4e 354, 380).

The superficial part of this region is called the perineum including the external genitalia (in the urogenital triangle) and the anus (in the anal triangle). It is also called the pudendal region, being supplied by the pudendal nerves and vessels.

Muscles of the perineum

The ischiorectal fossa is the space between the obturator fascia, the fascia of the under surface of the levator ani and the outer surface of the sphincter ani externus (Clemente plates 276, 300; Grant p. 258, 259; Netter 3e 360, 363, 4e 392, 395). It is filled mostly with fat.

• Since the obturator internus and the levator ani extend to the back of the body of the pubis, the ischiorectal fossa must extend to the back of the pubis.
• An ischiorectal abcess may rupture internally into the anal canal and externally onto the skin so that a fistula is formed.

The main part of the fossa is limited posteriorly by the sacrotuberous ligament and the origin of gluteus maximus from this ligament.

The fossa is crossed by the inferior rectal vessels and nerves which are distributed to the anal canal ( not the rectum). They are branches of the internal pudendal vessels and the pudendal nerve, lying enclosed in a fascial tunnel called the pudendal canal (Clemente plates 277, 301; Grant p. 261; Netter 3e 391, 393, 4e 392, 411, 413). The fascia is continuous with the obturator internus fascia.

The sphincter ani externus and internus

The sphincter ani externus is formed by the voluntary muscle fibers surrounding the anal canal and, along with the smooth muscle of the sphincter ani internus, is responsible for continence. Both muscles form the anorectal ring, which is usually divided into subcutaneous, superficial and deep (Clemente plate 293; Grant p. 262; Netter 3e 375, 4e 393-395).

• The subcutaneous part surrounds the lower portion of the canal, below the edge of internal sphincter. The intersphincteric groove lies between the 2 sphincters.
• The superficial part is attached to the coccyx posteriorly and the perineal body anteriorly.
• The deep part blends in with the puborectal portion of the levator ani.

*The anorectal ring cannot be cut because the result will be incontinence.

The urogenital triangle

The perineal membrane (triangular ligament of surgeons) or inferior fascia of urogenital diaphragm. This is a strong triangular membrane stretching across the urogenital triangle from the rami of the pubis and the ischium. A small gap at the apex of the triangle, posterior to the pubic symphysis, exists for passage of the deep dorsal vein and the dorsal nerve of the penis (clitoris; Clemente plate 278 fig. 429, plate 299 fig. 462; Grant p. 254; Netter 3e 366, 4e 383). The perineal membrane is pierced by the urethra, by the vagina in the female, by the ducts of the bulbourethral glands and by the deep and dorsal arteries of the penis (clitoris).

The superficial perineal (Colle's) fascia is separated from the perineal membrane by a superficial perineal pouch (Clemente plate 289 fig. 445; Grant p. 255, 258; Netter 3e 366, 4e 383). It contains the roots of the penis and muscles.

The penis consists of a corpus spongiosum and 2 corpora cavernosa (which contain erectile tissue; Clemente plate 303; Grant p. 266-267; Netter 3e 365, 4e 381, 382).

• The corpus spongiosum is enlarged at the end to form the glans of the penis (Clemente plate 303; Grant p. 266; Netter 3e 365, 4e 382) and the penile (spongiose) urethra (Clemente plate 306 fig. 471, plate 307 fig. 473; Grant p. 267; Netter 3e 368, 4e 382) runs through it to open at the external urethral orifice. The whole is enclosed in the fascia penis and supported by the suspensory ligament, which is attached between the fascia penis and pubic symphysis (Clemente plate 302 fig. 466; Grant p. 264; Netter 3e 348, 4e 250).
• The superficial dorsal vein is in the midline and drains skin, into a tributary of the saphenous vein on one or the other side.
• The deep dorsal vein is in the fascia penis, in the midline and drains the deep structures. It passes through the gap of the perineal membrane and joins the prostatic venous plexus. It is flanked by the paired deep dorsal arteries and nerves (NAV). The skin of the penis is thin and loose and the fold over the glans is the prepuce (Clemente plate 302 fig. 467; Grant p. 264; Netter 3e 364, 4e 381).

The superficial perineal pouch

• The roots of the penis are posterior continuations of the corpora cavernosa and they are known as the crura. The continuation of the corpus spongiosum is the bulb of the penis (Clemente plate 303; Grant p. 252; Netter 3e 365, 4e 382, ).
• The crura are attached to the inferior ramus of the pubis and the ramus of the ischium while the bulb is attached to the undersurface of the perineal membrane. The urethra pierces the membrane in order to enter the bulb (Clemente plate 305; Grant p. 255, 266-267; Netter 3e 366, 4e 383).
• The crura are surrounded by the ischiocavernosus muscle and the bulb by the bulbospongiosus,which expels the last drop of urine (Clemente plate 300 fig. 464; Grant p. 255, 261; Netter 3e 364, 4e 381).
• The transversus perinei superficialis extends from the ischium to the perineal body.
• Scrotal (labial; Clemente plate 301; Grant p. 261, 271; Netter 3e 384-385, 4e 403-405) vessels are also contained within the superficial perineal pouch.

The deep perineal pouch

• between the perineal membrane and the superior fascia of the urogenital diaphragm.
• It contains the:
  • membranous urethra (Clemente plate 289; Grant p. 258-259; Netter 3e 366, 4e 368, 385,) surrounded by the sphincter urethrae (a small, striated muscle);
  • bulbourethral (Cowper's) glands (Clemente plates 298, 299; Grant p. 258; Netter 3e 366, 4e 383), the ducts of which pierce the perineal membrane to open into the urethra in the bulb of the penis (Clemente plate 290; Grant p. 255; Netter 3e 366, 4e 383).
• The transversus perinei profundus (Grant p. 257; Netter 3e 366, 4e 383) is in the deep pouch, in a position corresponding to the superficial transversus perinei.

The female perineum

The female perineum has the following characteristics:

• The labia majora (Clemente plate 274; Grant p. 253, 269; Netter 3e 359, 4e 377) and labia minora
• The clitoris
• The vestibule between the labia minora has the openings of the urethra and the vagina. The hymen is a fold of mucosa (Netter 3e 359, 4e 377).
• The bulb of the vestibule (Clemente plate 279; Grant p. 255, 272; Netter 3e 361, 4e 379) is equivalent to the bulb of the penis, but is in two parts on either side of the vestibule.
• The greater vestibular (Bartholin's) glands are the equivalent of the bulbourethral glands. They lie towards the posterior ends of the bulbs of the vestibule and open into the vestibule just below the hymen.

The urethra has prostatic, membranous and penile (spongiose) portions in the male (Clemente plate 290; Grant p. 258; Netter 3e 368, 4e 385).

The female urethra (Grant p. 259; Netter 3e 352, 4e 360) is shorter and simpler, running posterior to the pubic symphysis, embedded in the anterior wall of the vagina. It opens 2 cm posterior to the clitoris.

The urogenital diaphragm

• resembles a triangular double-decker sandwich
  • The bottom layer is formed by the superficial perineal (Colle's) fascia (Clemente plates 258-259; Grant p. 197; Netter 3e 363, 4e 383)
    • The roots of the penis or clitoris and associated muscles and vessels are found in the superficial perineal pouch.
  • The middle layer is formed by the perineal membrane or urogenital diaphragm (Clemente plate 298; Grant p. 254; Netter 3e 361, 366, 4e 383)
    • The membranous urethra (Clemente plates 278, 299; Grant p. 258; Netter 3e 366, 4e 384), bulbo-urethral glands and sphincter urethrae are found in the deep perineal pouch.
  • The superior layer is the superior fascia of the urogenital diaphragm.
  • The apex of the urogenital diaphragm lies posterior to the symphysis pubis and the sides are attached to the pubis and ischium (Grant p. 254; Netter 3e 366, 4e 383).

Note that the ischiorectal fossa continues anteriorly above the urogenital diaphragm, on either side of the prostate.

Vessels and nerves of the perineum

From the lower end of the greater sciatic notch emerge from medial to lateral, the pudendal nerve, the internal pudendal artery and the nerve to obturator internus (Clemente plate 330; Grant p. 388-89; Netter 3e 484, 4e 503). They cross the spine of ischium and enter the perineum through the lesser sciatic foramen.

• The internal pudendal artery and pudendal nerve enter the pudendal canal medial to the obturator internus (Clemente plates 277, 301; Grant p. 261; Netter 3e 391, 393, 485, 4e 392). They both give an inferior rectal branch, which leaves the pudendal canal, passes medially through the ischiorectal fossa and supplies the lower part of the anal canal and its muscles. The inferior rectal nerve is sensory to the lower half of the anal canal, motor to the sphincter ani externus and levator ani. These muscles are also innervated by a separate branch from S4.
• The pudendal nerve divides into a dorsal nerve of the penis (clitoris) and the perineal nerve lying on either side of the pudendal artery.
• The dorsal nerve of the penis (clitoris) enters the deep perineal pouch, staying lateral, pierces the perineal membrane and passes onto the dorsum of the penis (Clemente plate 278 fig. 429, plate 302; Grant p. 265; Netter 3e 250-251, 253, 366, 389, 4e 383, 409).
• The perineal artery gives rise to scrotal (Clemente plate 301; Grant p. 261; Netter 3e 385, 4e 403, 405) or labial (Clemente plate 277; Grant p. 269; Netter 3e 384, 4e 404) branches and then enters the deep perineal pouch. It supplies the bulb, of the penis (clitoris) and the urethra and ends by dividing into dorsal and deep arteries of the penis (clitoris; Clemente plate 278 fig. 429, plate 299 fig. 462; Grant p. 264-265; Netter 3e 384-385, 4e 381, 383).

LYMPHATICS OF THE ABDOMEN AND PELVIS

Lymph nodes are closely related to the main arteries.

1) Preaortic nodes are related to the 3 ventral branches of the aorta. All lymph vessels converge to form the intestinal trunks leading to the cisterna chyli (Clemente plates 156, 157; Grant p. 182; Netter 3e 305, 4e 316).

• The preaortic nodes include the celiac (Clemente plate 243; Grant p. 182, 184-185; Netter 3e 304, 4e 316), gastric, pancreaticosplenic, hepatic (Clemente plate 206 fig. 308; Grant p. 184-185; Netter 3e 307, 4e 314-315), pyloric and gastroepiploic (gastro-omental) nodes
• The stomach is divided into 4 sectors draining into nearest appropriate group. The lymph flow tends to run from right to left along the lesser curvature and from left to right along the greater curvature.
• The liver drains mainly into the hepatic group. Part of the upper surface drains into nodes around the inferior vena cava and the left lobe drains into the left gastric group.
• The pancreas drains into the pancreaticosplenic nodes but also into the superior mesenteric nodes (Clemente plate 213; Grant p. 184-185; Netter 3e 307, 4e 315).
• The superior mesenteric and inferior mesenteric nodes drain along the major arteries (Clemente plate 215; Gra