VESSELS AND NERVES OF THE PELVIS/PERINEUM II. Blood Supply The internal iliac artery furnishes most of the blood supply to the pelvis. It originates and descends from the region of the lumbosacral articulation to the greater sciatic notch and divides into Anterior Branch - has 3 parietal branches and all branches to pelvic cera (from which arises the superior, middle, and inferior vesical eries; middle rectal; obturator; internal pudendal; inferior gluteal; rine; and vaginal arteries). Posterior Branches - has only parietal branches (iliolumbar, lateral ral, and superior gluteal arteries). Veins of the pelvis correspond to the named arteries and arise from ous plexuses. Nerve Supply Arises mainly from the sacral and coccygeal spinal nerves (with a small contribution from the lumbar spinal nerves). Each of the five spinal sacral nerves and the spinal coccygeal nerve divides into a dorsal and ventral ramus in the central canal. The dorsal rami supply the back. The ventral rami are arranged as follows LN4 (lower division) + LN5 = Lumbosacral Trunk SN1, SN2, SN3, SN4 (upper division) + Lumbosacral Trunk = Sacral Plexus SN4 (lower division) + coccygeal N = Coccygeal Plexus AUTONOMIC NERVOUS SYSTEM (ANS) The sympathetic part of the ANS reaches the pelvis via two routes as a downward continuation of the sympathetic trunks and as a downward continuation of the aortic plexus. The parasympathetic part of the ANS arises from pelvic splanchnic nerves SN-2, SN-3, SN-4 (nervi erigentes). 1. All of the following are true of the internal iliac artery EXCEPT it supplies most of the blood supply to the pelvis it crosses in front of the ureter it is divided into two main divisions it arises from the common iliac in front of the sacroiliac joint it is separated from the sacroiliac joint by the lumbo-sacral nerve trunk Right. No, the answer is B. 2. All of the following are posterior branches of the internal iliac arteries EXCEPT iliolumbar lateral sacral superior gluteal inferior gluteal Right. No, the answer is D. However, sometimes the superior and inferior gluteals may arise by a common stem above the origin of the internal pudendal artery. 3. Necrosis of the rectal mucosa usually will not result from occlusion of the inferior mesenteric artery because an important arterial supply to the rectum is from anastomotic connections from the superior mesenteric artery the inferior rectal artery, a branch of the external iliac artery, is a major supplier of the rectum the middle rectal artery, a branch of the internal iliac, is a major supplier to the rectum the left colic artery provides a major arterial supply to the rectum the inferior mesenteric is not a supplier of the rectum Very good. No, the answer is C. The rectum receives blood from the paired middle and inferior rectal arteries and from the superior rectal artery. The superior rectal is a continuation of the inferior mesenteric artery. The middle and inferior rectal arteries are branches of the internal iliac and will supply the rectum if the inferior mesenteric is occluded. 4. This artery arises below the inferior gluteal artery as a parietal branch of the internal iliac superior gluteal iliolumbar obturator umbilical internal pudendal Correct. No, the answer is E. 5. After birth, the part of each umbilical artery between its last branch and the umbilicus becomes a fibrous remnant called ductus arteriosus lateral umbilical folds ligamentum teres median umbilical fold medial umbilical ligaments Correct. No, the answer is E. Median umbilical fold peritoneum over former urachus. Medial umbilical folds peritoneum over the medial (lateral) umbilical ligaments, which are the former umbilical arteries. Lateral umbilical folds peritoneum over the inferior epigastric arteries. 6. This artery runs under the ureter, and in the female under the round ligament of the uterus or, in the male under the ductus deferens inferior gluteal internal pudendal obturator superior gluteal iliolumbar Right. No, the answer is C. 7. This artery gives rise to the superior vesical arteries, as well as, in the male, to the ductus deferens artery lateral sacral umbilical artery inferior gluteal internal pudendal obturator Correct. No, the answer is B. 8. While usually a branch of the internal iliac, this artery may also arise as a branch of the external iliac or inferior epigastric obturator superior vesical internal pudendal uterine vaginal Very good. No, the answer is A. When the obturator arises from the inferior epigastric it is called an abnormal obturator. In this condition, care must be taken during inguinal hernia repair not to sever the abnormal obturator since it is in a vulnerable area posterior to the spermatic cord. 9. Which of the following is INCORRECT concerning the internal pudendal artery? has anastomotic connections with the middle rectal (hemorrhoidal) artery leaves the pelvis via the greater sciatic foramen enters the perineum via the lesser sciatic foramen supplies the superior rectal arteries travels in the pudendal canal with the pudendal nerve Right. No, the answer is D. The internal pudendal artery gives off the inferior rectal artery. Other branches of the internal pudendal are labial (or scrotal), perineal, artery of the bulb of the penis (or vestibule), and urethral artery. Its terminal branches are the deep and dorsal arteries of the clitoris (or penis). 10. Which of the following is INCORRECT about the uterine artery? it is homologous to the artery of the ductus deferens in the male it passes in front of and above the ureter it ends with an ovarian branch it anastomoses with the ovarian artery it gives rise to the inferior vesical artery Correct. No, the answer is E. If the uterine artery is occluded during pregnancy, the ovarian arteries have sufficient anastomoses to maintain adequate blood supply to the uterus. 11. Important collateral circulation after the internal iliac artery has been obstructed results from anastomoses with branches of the opposite internal iliac between parietal branches and branches of the femoral artery between the superior and middle rectal arteries between the internal pudendal and vaginal artery Correct. No. The first three foils are correct. 12. When the portal vein is obstructed (e.g. hepatic cirrhosis), portosystemic shunts develop. These include those between gastric and esophageal veins between superior and inferior mesenteric veins between superior and middle (or inferior) rectal veins between the renal and uterine veins Very good. No. The first and third foils are correct. The anastomoses between the superior and middle (or inferior) rectal veins can result in rectal hemorrhoids. Chronic bleeding from these may result in anemia. 13. The spermatic cord contains the following blood vessels artery and vein of the ductus deferens testicular artery pampiniform plexus of veins cremasteric artery Very good. No. All foils are correct. 14. Which of the following is (are) true concerning the blood supply to the penis? branches of the internal pudendal supplying the penis are the deep and dorsal arteries of the penis some of the branches of the penile arteries end as helicene arteries which open into the cavernous spaces filling of the cavernous spaces causes erection blood is trapped in the penis during erection due to penile muscular constriction. Correct. No. The first three foils are correct. Erection is due to mechanical engorgement of the cavernous sinuses. This increase in size of the sinuses produces compression of the deep veins of the penis and traps the blood in the sinuses. There is a direct connection between the penile and prostatic veins and the vertebral veins via Batson's vertebral plexus. This is a direct route for metastasis of cancer from pelvis to brain. 15. Blood supply to the ureters is derived from renal arteries gonadal arteries common iliac arteries superior vesical arteries Very good. No. All foils are correct. 16. Cross the pelvic brim ovarian vessels testicular vessels both neither Very good. No, the answer is A. Ovarian vessels have a course similar to testicular vessels as far as the pelvic brim, then dissimilar thereafter. 17. All of the following are true regarding the sacral plexus of nerves except? the lumbosacral trunk which contributes to the sacral plexus is made up of the lower part of LN-4 and all of LN-5 SN-1, SN-2, SN-3, and the upper part of SN-4 combine with the lumbosacral trunk to make the sacral plexus the sacral plexus is made up of the dorsal rami of the spinal nerves the sacral plexus lies in front of the piriformis muscle the sacral plexus lies posterior to the internal iliac vessels and the ureters Correct. No, the answer is C. The dorsal rami of the spinal nerves supply the muscles of the back. The ventral rami form the sacral plexus. 18. All of the following branches of the sacral plexus pass through the greater sciatic foramen below the piriformis muscle except superior gluteal nerve inferior gluteal nerve pudendal nerve posterior femoral cutaneous nerve sciatic nerve Correct. No, the answer is A. This nerve leaves the sciatic foramen above the piriformis. 19. The pudendal nerve can be distinguished from the inferior gluteal nerve because while both leave via the greater sciatic foramen, only the pudendal returns via the lesser sciatic foramen carries motor fibers, sensory fibers, and postganglionic sympathetic fibers runs in the pudendal canal with the pudendal artery gives off the ventral nerve of the clitoris (penis) Very good. No. The first three foils are correct. The pudendal nerve gives off the inferior rectal nerve, the perineal nerve and the dorsal nerve of the clitoris (penis). The pudendal nerve furnishes most of the innervation to the perineum. 20. Which of the following muscles and innervations are correctly matched? (Question is considered a preview to gluteal portion of lower limb) inferior gluteal nerve - gluteus maximus superior gluteal nerve - gluteus minimus & medius, & tensor fasciae latae nerve to obturator internus - superior gemellus muscle nerve to quadrator femoris - inferior gemellus muscle Very good. No. All foils are correct. 21. The coccygeal plexus of nerves is larger than the sacral plexus is made of the ventral rami of the lower part of SN-4, all of SN-5, and the coccygeal nerve gives rise to the sciatic nerve supplies the sacrococcygeal joint, the coccyx, and skin over the coccyx Very good. No. The second and fourth foils are correct. 22. The sympathetic innervation of the pelvis reaches the pelvis via two routes arises partly from SN-2, SN-3, SN-4 nerves (nervi erigentes) arises partly from the downward continuation of the aortic plexus is responsible for bladder contraction and sphincter relaxation Correct. No. The first and third foils are correct. The sympathetic trunk and downward continuation of the aortic plexus are the two routes of sympathetic innervation. 23. The sacral part of the sympathetic trunks descend paravertebrally, cross the brim of the pelvis, and descend on the anterior sacrum the two trunks join to form the ganglion impar contribute fibers to the inferior hypogastric plexus are connected to spinal nerves LN-4 through SN-4 via white rami communicantes Very good. No. The first three foils are correct. There are no preganglionic sympathetic fibers originating in the sacral part of the spinal cord. Remember, the sympathetic part of the ANS is known as thoracolumbar division. Preganglions are myelinated (white rami communicantes) and postganglionics from the sympathetic trunk are unmyelinated (gray rami communicantes). 24. The superior hypogastric plexus of nerves is made of sympathetic fibers receives fibers from the lumbar splanchnic nerves is a continuation of the aortic plexus divides in front of the sacrum to form the right and left hypogastric nerves Very good. No. All foils are correct. 25. The inferior hypogastric plexus contains postganglionic sympathetic fibers preganglionic parasympathetic fibers sensory fibers preganglionic sympathetic fibers Very good. No. The first three foils are correct. The postganglionic sympathetic fibers come from the superior hypogastric plexus and also directly from the sympathetic trunk. 26. Subdivisions of the inferior hypogastric plexus accompany the visceral branches of the internal iliac arteries have limited intercommunication with one another supply the pelvic organs include the ganglion impar Correct. No. The first and third foils are correct. The subdivisions freely communicate. They are the middle rectal plexus, prostatic plexus, cavernous nerves of the clitoris (or penis), vesical plexus, and uterovaginal plexus. 27. If during a pelvic dissection for rectal carcinoma, the inferior hypogastric plexus was ablated, all of the following deficits would result except inability to ejaculate lessened sensation in external genitalia inability to achieve erection urinary retention lessened peristalsis in the descending colon Correct. No, the answer is B. 28. Which of the following is INCORRECT regarding male erection and ejaculation? the parasympathetic nervous system primarily controls erection the CNS can have inhibitory or excitatory effects on erection erection can occur after complete bilateral sympathectomy ejaculation is under control of the sympathetic nervous system orgasm has no psychic component Correct. No, the answer is E. Orgasm is a cortical sensory phenomenon. 29. All of the following are true regarding normal bladder function except the detrusor muscle innervated by sympathetics provides the propulsive force for emptying the bladder the smooth muscle of the trigonal area is innervated by the sympathetic nervous system the external urethral sphincter and perineal nerves are under involuntary control the spinal voiding reflex is mediated via pelvic nerves to SN-2, SN-3, and SN-4 the cortical centers suppress the sacral spinal reflex arc controlling bladder emptying Correct. No, the answer is C. When the bladder is distended the sacral reflex arc is stimulated resulting in reflex emptying unless suppressed by higher cortical centers. Normal micturition is initiated by voluntary relaxation of the external sphincter.