Human Anatomy: Internal Iliac Artery and Pelvic Nerves (Lecture Notes)

HUMAN ANATOMY

INTERNAL ILIAC ARTERY AND PELVIC NERVES
(Lecture Notes)

Necdet Ersoz
Gazi University Medical School

Visceral Branches

ü  Umbilical artery (occluded part, patent part: artery to ductus deferens, ureteric branches, superior vesical artery)

ü  Inferior vesical artery (prostatic branches)

ü  Middle rectal artery (vaginal and prostatic branches)

ü  Uterine artery (helicine branches, ovarian branches, vaginal branches (azygos artery of vagina, tubal branch)

ü  Vaginal artery

ü  Internal pudendal artery (inferior rectal artery, perineal artery, posterior labial branches, posterior scrotal branches, urethral artery, artery of bulb of vestibule, dorsal artery of clitoris, dorsal artery of penis, deep artery of clitoris, deep artery of penis, perforating arteries of penis)

Parietal Branches

ü  Obturator artery (pubic branch, acetabular branch, anterior branch, posterior branch)

ü  Iliolumbar artery (lumbar branch, spinal branch, iliacus branch)

ü  Lateral sacral arteries

ü  Superior gluteal artery (superficial branch, deep branch: superior branch, inferior branch)

ü  Inferior gluteal artery (artery to sciatic nerve)

Anterior Trunk

ü  Superior vesical artery

ü  Umbilical artery

ü  Inferior vesical artery

ü  Middle rectal artery

ü  Uterine artery

ü  Vaginal artery

ü  Obturator artery

ü  Internal pudendal artery

ü  Inferior gluteal artery

Posterior Trunk

ü  Iliolumbar artery

ü  Lateral sacral artery

ü  Superior gluteal artery

Umbilical Artery: Occluded Part (Medial umbilical ligament patent part)

ü  The superior vesical artery normally originates from the root of the umbilical artery and courses medially and inferiorly to supply the superior aspect of the bladder and distal parts of the ureter.

ü  In men, it also may give rise to an artery that supplies the ductus deferens.

Middle Rectal Artery:

ü  Arises with or near the inferior vesical artery but may be absent (especially in female may be replaced by the uterine and vaginal branches).

ü  Runs toward the lower rectal wall, breaking into a leash of branches before entering it, and in the male it may give off the prostatic artery that has not arisen from the inferior vesical artery.

Inferior Vesical Artery:

ü  Arises much lower than the superior vesical artery and runs medially across the pelvic floor to supply the trigone and lower part of the bladder, the ureter, ductus deferens and seminal vesicle.

ü  Usually give rise to the prostatic artery.

ü  The vaginal artery in women is the equivalent of the inferior vesical artery in men and, descending to the vagina, supplies branches to the vagina and to adjacent parts of the bladder and rectum.

Uterine Artery:

ü  In women courses medially and anteriorly in the base of the broad ligament to reach the cervix.

ü  Along its course, the vessel crosses the ureter (2 cm lateral) and passes superiorly to the lateral vaginal fornix.

ü  Once the vessel reaches the cervix, it ascends along the lateral margin of the uterus to reach the uterine tube where it curves laterally and anastomoses with the ovarian artery.

ü  The uterine artery is the major blood supply to the uterus and enlarges significantly during prengnancy.

ü  Through anastomoses with other arteries, the vessel contributes to the blood supply of the ovary and vagina as well.

ü  Developmentally it is the homolog of the artery to the ductus deferens in the male.

Vaginal Artery:

ü  Often arises from the initial part of the uterine artery instead of arising directly from the anterior division.

ü  Is the equivalent of the inferior vesical artery in men and, descending to the vagina, supplies branches to the vagina and to adjacent parts of the bladder and rectum.

Ureter and ductus deferens crosses the obturator vessels and nerve.

ü  Courses anteriorly along the pelvic wall and leaves the pelvic cavity via the obturator canal. Together with the obturator nerve, above, and obturator vein, below, it enters and supplies the adductor region of the thigh.

ü  Corona mortis: pubic branch of the obturator artery, other side same branch and pubic branch of the inferior epigastric artery.

Internal Pudendal Artery

ü  Courses inferiorly from its origin in the anterior trunk and leaves the pelvic cavity through the greater sciatic foramen inferior to the piriformis muscle.

ü  In association with the pudendal nerve on its medial side, the vessel passes laterally to the ischial spine and then through the lesser sciatic foramen to enter the perineum.

ü  Accompanies the pudendal nerve in the pudendal canal on the lateral wall of the ischioanal fossa.

ü  One or more inferior rectal arteries originate from the internal pudendal artery in the anal triangle and cross the ischioanal fossa medially to branch and supply muscle and related skin.

ü  They anastomose with middle and superior rectal arteries from the internal iliac artery and the inferior mesenteric artery, respectively, to form a network of vessels that supply the rectum and anal canal.

ü  The perineal artery originates near the anterior end of the pudendal canal and gives off a transverse perineal branch, and a posterior scrotal or labial artery to surrounding tissues and skin.

ü  The artery of bulb of penis has a branch that supplies the bulbourethral gland and then penetrates the perineal membrane to supply the corpus spongiosum.

ü  A urethral artery also penetrates the perineal membrane and supplies the penile urethra and surrounding erectile tissue to the glans.

Near the anterior margin of the deep perineal pouch, the internal pudendal artery bifurcates into two terminal branches.

ü  A deep artery of penis penetrates the perineal membrane to enter the crus and supply the crus and corpus cavernosum of the body.

ü  The dorsal artery of penis penetrates the anterior margin of the perineal membrane to meet the dorsal surface of the body of the penis.

The vessel courses along the dorsal surface of the penis, medial to the dorsal nerve, and supplies the glans penis and superficial tissues of the penis; it also anastomoses with branches of the deep artery of penis and the urethral artery.

ü  The arteries of the bulb of vestibule supply the bulb of the vestibule and related vagina.

ü  Deep arteries of the clitoris supply the crura and corpus cavernosum of the body.

ü  Dorsal arteries of the clitoris supply surrounding tissues and the glans.

Iliolumbar Artery

ü  The iliolumbar artery ascends laterally back out of the pelvic inlet and divides into a lumbar branch and an iliac branch.

ü  The lumbar branch contributes to the supply of the posterior abdominal wall, psoas, quadratus lumborum muscles, and cauda equine via a small spinal branch that passes through the intervertebral foramen between L5 and S1.

ü  The iliac branch passes laterally into the iliac fossa to supply muscle and bone.

Lateral Sacral Arteries

ü  The lateral sacral arteries, usually two, originate from the posterior division of the internal iliac artery and course medially and inferiorly along the posterior pelvic wall.

ü  They give rise to branches that pass into the anterior sacral foramina to supply related bone and soft tissues, structures in the vertebral (sacral) canal, and skin and muscle posterior to the sacrum.

Superior Gluteal Artery

ü  The superior gluteal artery is the largest branch of the internal iliac artery and is the terminal continuation of the posterior trunk.

ü  It courses posteriorly, usually passing between the lumbosacral trunk and anterior ramus of S1, to leave the pelvic cavity through the greater sciatic foramen above the piriformis muscle and enter the gluteal region of the lower limb.

Veins

Pelvic veins follow the course of all branches of the internal iliac artery except for the umbilical artery and the iliolumbar artery. On each side, the veins drain into internal iliac veins, which leave the pelvic cavity to join common iliac veins situated just superior and lateral to the pelvic inlet. Within the pelvic cavity, extensive interconnected venous plexuses are associated with the surfaces of the viscera (bladder, rectum, prostate, uterus, and vagina). Together, these plexuses form the pelvic plexus of veins. The part of the venous plexus surrounding the rectum and anal canal drains via superior rectal veins (tributaries of inferior mesenteric veins) into the hepatic portal system, and via middle and inferior rectal veins into the caval system. The single deep dorsal vein that drains erectile tissue of the clitoris and the penis does not follow branches of the internal pudendal artery into the pelvic cavity. Instead, this vein passes directly into the pelvic cavity through a gap formed between the arcuate pubic ligament and the anterior margin of the perineal membrane. The vein joins the prostatic plexus of veins in men and the visceral (bladder) plexus of veins in women. Superficial veins that drain in the skin of the penis and corresponding regions of the clitoris drain into the external pudendal veins, which are tributaries of the great saphenous vein in the thigh.

Sacral and Coccygeal Plexuses

The sacral and coccygeal plexuses are situated on the posterolateral wall of the pelvic cavity and generally occur in the plane between the muscles and blood vessels. They are formed by the ventral rami of S1 to Co, with a significant contribution from L4-L5, which enter the pelvis from the lumbar plexus. Branches of the sacral plexus include the sciatic nerve and gluteal nerves, which are major nerves of the lower limb, and the pudendal nerve, which is the nerve of the perineum.

Coccygeal Plexus

ü  The small coccygeal plexus has a minor contribution from S4 and is formed mainly by the anterior rami of S5 and Co, which originate inferiorly to the pelvic floor.

ü  They penetrate the coccygeus muscle to enter the pelvic cavity and join with the anterior ramus of S4 to form a single trunk, from which small anococcygeal nerves originate.

ü  These nerves penetrate the muscle and the overlying sacrospinous ligaments and pass superficially to innervate skin in the anal triangle of the perineum.

Visceral Plexuses

ü  SYMPATHETIC FIBERS: enter the inferior hypogastric plexuses from the hypogastric nerves and from branches (sacral splanchnic nerves) of the upper sacral parts of the sympathetic trunks.

ü  These nerves are derived from preganglionic fibers that leave the spinal cord in the anterior roots, mainly of T10 to L2.

ü  Innervates blood vessels,

ü  Cause contraction of smooth muscle in the internal urethral sphincter in men and the internal anal sphincters in both men and women.

ü  Cause smooth muscle contraction associated with the reproductive tract and with the accessory glands of the reproductive system, and,

ü  Are important in moving secretions from the epididymis and associated glands into the urethra to form semen during ejaculation.

ü  PARASYMPATHETIC FIBERS: enter the pelvic plexus in pelvic splanchnic nerves that originate from spinal cord levels S2 to S4.

ü  Are generally vasodilator,

ü  Stimulate bladder contraction,

ü  Stimulate erection,

ü  Modulate activity of the enteric nervous system of the colon distal to the left colic flexure.

ü  Visceral afferent fibers follow the course of the sympathetic and parasympathetic fibers to the spinal cord.

ü  Afferent fibers that enter the cord in lower thoracic levels and lumbar levels with sympathetic fibers generally carry pain; however, pain fibers from the bladder and urethra may accompany parasympathetic nerves to sacral levels of the spinal cord.

Pudendal Nerve

ü  Is accompanied throughout its course by the internal pudendal vessels.

ü  Innervates the skin and skeletal muscles of the perineum, including the external anal and external urethral sphincters.

ü  Inferior anal nerves

ü  Perineal nerves supply the perineum. (Posterior labial nerves, posterior scrotal nerve, muscular branches, dorsal nerve of clitoris, dorsal nerve of penis)

Note: These notes are taken from Gazi University Faculty of Medicine Prof. Dr. Meltem BAHCELIOGLU’s anatomy lectures.