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The Structural Basis of Medical Practice (SBMP) - Human Gross Anatomy, Radiology, and Embryology
Answer Guide for Abdomen, Pelvis, and Perineum Essay Examination (48 pts) - September 20, 2002
The College of Medicine at The Pennsylvania State University
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[ Spermatic Cord ] [ Pancreas ]
[ Prostate ] [ Pelvic Diaphragm ]
Note. The following is a guide to answering the questions and is not the "answer."
Discuss the anatomy of the spermatic cord; include contents, coverings, fascial boundaries, relationships, vasculature,
innervation, and lymphatics. Additionally, explain the pathway, and location of hernial contents associated with an indirect
hernia that descends into the scrotum. (12 pts)
- General. The spermatic cord is the pedicle of testis. Beginning at the deep ring, the spermatic cord transmits the contents of the
deep ring from the abdominopelvic cavity to the scrotum. The pathway from the deep ring to the scrotum marks the "descent" of the
testis. A peritonealized surface of the testis causes a trailing diverticulum know as the processes vaginalis. Applied to
the anterior aspect of the testis is the visceral layer of tunica vaginalis. The deep
ring marks the beginning of the inguinal canal and is located: at the midinguinal point; lateral to the inferior
epigastric artery; and slightly more than 1 cm superior to the inguinal ligament. At the deep ring the
spermatic cord receives the internal spermatic fascia derived from transversalis fascia. Within
the inguinal canal the internal oblique contributes the cremasteric fascia. The cord exits the inguinal canal by
way of the superficial ring. The superficial ring, a defect in the external oblique aponeurosis, contributes the external
spermatic fascia. The testis, at
the distal extent of the cord, ultimately resides within the scrotum. It is tethered to the most inferior aspect of the scrotum
by the scrotal ligament. The
external spermatic fascia (deep fascia) is opposed to dartos fascia (superficial fascia).
- Structures that pass through the deep ring reside within the internal spermatic fascia.
- processes vaginalis - a trailing diverticulum of peritoneum that accompanies the testis during the "descent."
- Distally, within the scrotum, the processes vaginalis opens into the tunica vaginalis
- Extraperitonial connective tissue
- Testicular artery - paired branches from lumbar aorta near renal arteries
- Testicular vein - proximally the testicular vein consists of 3-4 veins
- Distally the testicular surrounds the testicular artery forming the pampinifrom plexus veins numbering 10 to 12 veins
- Left testicular vein drains into left renal vein and the right testicular vein drains into the IVC near the renal artery
- Testicular lymphatics - provide drainage to upper lumbar nodes, to lumbar lymph ducts, to cysterna chyli
- Testicular autonomic plexus - sympathetic preganglionic cell bodies in IMLCC T10(11-12)
- - Symmpathetic postganglionic cell bodies in superior mesenteric ganglion
- - Parasympathetic preganglionic fibers derived from the vagus nerve
- Afferent "pain" fibers following sympathetic pathways to spinal levels T10(11-12)
- Vas deferens - under sympathetic control, the walls (2-3 mm thick) of the vas deferens contract to discharge spermatozoa
- Within the cord the Vas deferens lies posterior to the testicular artery
- Distally, the Vas deferens forms the tail of the epididymis at the posterior inferior pole of testis
- Further distally the tail gives way to the body and then to the head of the epididymis at the posterior superior pole
- Deferential artery - branch of the internal iliac artery vascularizes the vas deferens and anastomoses with the testicular artery
- Deferential autonomic plexus - derived from the superior/inferior hypogastric autonomic plexus to prostatic plexus
- - Parasympathetic preganglionic fibers possibly derived from pelvic splanchnics (S2-4)
- Afferent "pain" fibers following sympathetic pathways to spinal levels T10(11-12)
- Deferential lymphatics - drainage to internal iliac nodes, to lumbar lymph ducts, to cysterna chyli
- The cremesteric fascia is superficial to the internal spermatic fascia and deep to the external spermatic fascia
- Derived from internal oblique muscle, the cremesteric fascia contributes to the cord within the inguinal canal
- Genital branch of the genitofemoral nerve - provides somatic motor supply
- Cremesteric artery - branches provide vascularization to the cremesteric fascia
- The external spermatic fascia is superficial to the cremesteric fascia and is the outer most tunic
- Derived from the external oblique, the external spermatic fascia extends to the cord beyond the superficial ring
- Within the scrotum the external spermatic fascia is deep to dartos tunic
- Path of indirect inguinal hernia
- An indirect hernia follows the embryologic "descent" of the testis indirectly out the superficial ring by way of the deep ring.
- A patent processes vaginalis allows herniated material to pass through the deep ring lateral to the inferior epigastric artery
- Herniated material passes through the inguinal canal and out the superficial ring - superior and medial to pubic tubercle
- Distally, the hernia is arrested by the tunica vaginalis
- In the case of herniated intestine, visceral peritoneum is directly opposed to visceral and parietal tunica vaginalis
- Palpation of the hernia occurs at the anterior aspect of the testis within the scrotum
- The long and curvaceous path of an indirect hernia make strangulation a distinct possibility
Indicate your understanding of the pancreas providing structure, relationships, vasculature, innervation, and
lymphatic drainage. (12 pts)
- Structure. The pancreas is a tear-drop shaped finely lobulated glandular structure associated with the duodenum. Named parts
include the head, uncinate process, neck, body, and tail. It lies transversely to the anterior surface of the aorta with the neck and
uncinate process on the anterior surface of the aorta and IVC. The tail extends laterally to left as far as the leinorenal ligament. The
longitudinal extent is about 6 - 8 inches. The width at the head is 2 - 3 inches. The chief and accessory pancreatic ducts discharge
digestive enzymes into the duodenum at the major and minor duodenal papilla. The chief pancreatic duct runs the transverse length of the
pancreatic tissues and drains toward the ampulla of Vater. In turn, discharge from the ampulla is regulated by the sphincter of Oddi.
The accessory pancreatic duct drains the superior aspect of the head.
- The pancreas is located retroperitoneal and forms much of the floor of the lesser sac
- The head extends from the right side of the L1-3 lumbar vertebrae
- The head is cradled by all parts of the duodenum in the comfortable embrace of a "C"
- The head, neck crosses the IVC, the anterior vertebral bodies of L1-3 and the aorta
- The body crosses the duodenojejunal junction
- The neck, body, and tail extend to the left as far the the hilum of the spleen
- The uncinate process creates the pancreatic incisure at the inferior border of the head
- The pancreatic incisure "takes a bite" out of the superior mesenteric vein and artery (vein to right of artery)
- The uncinate process lies posterior to the superior mesenteric vein and artery
- Transverse mesocolon crosses lower aspect of head and inferior margin of neck and body
- Anterior surface faces lessor sac and stomach - incision of gastrocolic ligament provides surgical access
- Anterior surface of head touches all four parts of duodenum
- Posterior to the head is the hilum of the right kidney along with the right renal vessels
- Posterior to the head is the common bile duct on the right and the portal vein to the left
- Posterior to the neck is the IVC and the aorta
- Posterior to the body is the left kidney, suprarenal gland, and right crus of the diaphragm
- The celiac trunk is immediately superior to the upper margin of the head and neck
- The splenic artery runs retroperitoneal along the superior margin of the neck, body, and crosses anterior to tail
- The common hepatic artery crosses the anterior surface of the upper margin of the head to the right side
- The splenic vein runs directly posterior to the neck and body
- The inferior mesenteric vein crosses the posterior surface of the lower margin of the neck
- Head - arterial arcades from the celiac (foregut) and supermesenteric arteries (midgut)
- - the superior anterior and posterior pancreaticoduodenal arteries from the gastroduodenal artery
- - the inferior anterior and posterior pancreaticoduodenal arteries from the superior mesenteric artery
- Neck - dorsal pancreatic artery from aorta
- Body - great pancreatic artery from splenic artery
- Tail - caudal pancreatic arteries from splenic artery
- The inferior pancreatic artery, an anastomotic network within the pancreas, provides all tissues
- Venous drainage follows arterial channels to eventually drain into the SMV, splenic vein, and portal vein
- Lymphatic drainage of the pancreas
- Lymphatics tend to follow blood vessels
- Superior margin of head into celiac nodes
- Inferior margin of head into superior mesenteric nodes
- Anterior surfaces into pyloric nodes
- Body and tail into pacreaticolienal nodes along spenic vessels in turn into celiac nodes or upper lumbar nodes
- Paraaortic nodes drain into lumbar lymph ducts and then into cysterna chyli
- Innervation of the pancreas
- Celiac plexus innervates superior head and neck as well as the body and tail
- Superior mesenteric plexus innervates the inferior head
- Sympathetic preganglionic cell bodies - IMLCC of T5-9 to fibers in greater splanchnic nerve
- Sympathetic postganglionic cell bodies - celiac ganglion to fibers in celiac plexus
- Sympathetic preganglionic cell bodies - IMLCC of T10-11 to fibers in lesser splanchnic nerve
- Sympathetic postganglionic cell bodies - superior mesenteric ganglion to fibers of superior mesenteric plexus
- Parasympathetic preganglionic cell bodies - dorsal motor nucleus vagus nerve to fibers of celiac and superior mesenteric plexuses
- Visceral afferent pain - follow thoracic splanchnic nerves to spinal levels T5-11
Review the anatomy of the prostate. Include structure, supports, relationships, vascularization, innervation,
and lymphatic drainage. (12 pts)
- Structure of the prostate
- The prostate, a walnut sized structure located superior to the pelvic floor and inferior to the neck of the bladder,
is uniquely in the male. The glandular structure is encapsulated in a shiny capsule that is, in turn, surrounded by a
thickened periprostatic fascia derived from pelvic visceral fascia. The posterior aspect of this fascia is especially
thickened and is named the fascia of Denonvillier. A considerable amount of smooth muscle within the stroma adds
firmness to the gland. Glandular follicles drain by way of 15 - 20 prostatic ducts into the prostatic sinuses of
the prostatic urethra.
- The median lobe of the prostate is posterior to the prostatic urethra. This lobe includes the ejaculatory ducts,
seminal colliculus, urethral crest, and most distal aspect of the uvula. Benign prostatic hypertrophy commonly affects
the median lobe. In addition to the median lobe, there designated two lateral lobes and an anterior lobe. There are no anatomical
landmarks delineating the lobes.
- The prostatic urethra occupies about 2.5 cm of the central prostate. The superior posterior wall receives a projection of
the uvula that becomes the urethral crest within the prostatic urethra. Approximately one-third of the way into the prostatic
urethra the urethral crest widens for 2-4 mm to form the seminal colliculus. The ejaculatory ducts empty into the prostatic urethra on
either side of the seminal colliculus. Lateral to the seminal colliculus the posterior wall deepens posteriorly to the form
the prostatic sinuses receiving the prostatic ducts. The utrical, thought to be a vestigial uterus in the male, might be
visible on the anterior surface of the seminal colliculus.
- Puboprostatic ligament - Condensation of pelvic visceral fascia secures prostate to anterior pelvic wall
- lateral ligaments - Condensation of pelvic visceral fascia secures prostate to lateral pelvic wall
- Median umbilical ligament - obliterated urachus secures bladder, and thus prostate, to anterior abdmoninal wall
- Levator prostatae muscle - fibers of pubococcygeus insert into the prostatic fascia and capsule
- Relations of the prostate
- Inferior - superior fascia fascia of the pelvic diaphragm located at the urogental hiatus of the urogenital diaphragm
- Superior - neck of the bladder and the uvula
- Anterior - inferior aspect of the pubic symphysis
- Posterior - rectum, rectovesical space
- Posterior/superior - ampulla of ductus deferens, ureter, seminal vesical
- Lateral - pelvic diaphragm, superior aspect of conjoint rami, pelvic wall
- The arterial supply to the prostate is derived from the inferior vesical, middle rectal, and inferior rectal
(internal pudendal) arteries. Each of these arteries is a branch of the internal iliac artery
- The prostatic venous plexus is superficial to the capsule and deep to prostatic fascia. It receives the deep dorsal
vein of the penis and the vesical venus plexus. Venus drainage to internal iliac veins follow the aforementioned arterial
pathways. There is free drainage by the lateral sacral veins into the internal vertebral venus plexus. This drainage is
thought to account for the propensity of prostatic cancers to metastasize to the vertebral column.
- The prostatic autonomic plexus is derived from the inferior hypogastric plexus. Preganglionic sympathetic cell
bodies are located in the IMLCC of L1-2. Preganglionic fiber pathways involve the superior hypogastric plexus and
the right and left hypogastric nerves. Further, preganglionic fibers can follow the common iliac plexus to the
internal iliac plexus and arrive at the prostatic plexus by way of the arterial supply. Postganglionic sympathetic cell
bodies are thought to be located in unnamed ganglia distributed throughout the inferior hypogastric plexus. Additionally,
preganglionic fibers within the sacral sympathetic trunk contribute sacral splanchnics to the
inferior hypogastric plexus.
- Parasympathetic preganglionic cell bodies are located in the IMLCC of S2-4. Pelvic splanchnic nerves convey
preganglionic fibers to the inferior hypogastric plexus. Postganglionic cell bodies are located in enteric ganglia at
the target location.
- The inferior hypogastric plexus form extensions that spread out over the pelvic organs. The prostatic autonmomic
plexus froms a collection of nerves the run along the lateral aspect of the prostate and onto the the membranous urethra
to enter the cavernous tissue of the perineum. The cavernous nerves provide the parasympathetic innervation to the
helecine arteries. To avoid impotency, it is essential that the cavernous nerves are preserved during prostatic surgery.
- Lymphatic drainage of prostate
- The internal tissues of the prostate have relatively litte lymphatic drainage. For this reason, it is thought that
metastatic desease reaches the vertral column through venous channels (see above).
- The prostatic capsule and fascia drain into internal iliac nodes to common iliac, to lumbar, to cysterna chyli.
Discuss the anatomy of the pelvic diaphragm. Include structure, fascial coverings, relationships, vascularization,
innervation, and lymphatic drainage. (12 pts)
- Structure and fascial coverings of the pelvic diaphragm
- The pelvic diaphragm is a thin sheet of muscle. The urethra, vagina, and anal canal pass through the pelvic diaphragm at the
urogenital hiatus. Posterior to the vagina and anterior to the anal canal, the urogenital hiatus is filled by the perineal body
and the pubococcygeus muscle. The pelvic diaphragm functions in micturation and defecation by controlling intra-abdominal pressure and the
anatomical properties of functional sphincters -- uvula and puborectal sling.
- The anterior aspect of the pelvic diaphragm is made up of the pubococcygeus, iliococcygeus, and the puborectalis. Collectively,
these three muscles constitute the levator ani. Its lateral halves slope inferiorly medially from the arcus tendineus to
meet at the midline of pelvic floor. The pubococcygeus and especially the ilococcygeus, upon contracting, raise the
pelvic floor. These two muscles are tethered to the coccyx by the anococcygeal raphe and insert upon the lateral aspects of the
urethra, prostate, vagina, and anal canal.
- The puborectalis arises from the pubic bones near the superior aspect of the symphysis. It lies on the inferior surface of the
pubococcygeus muscle. Posteriorly, the puborectalis muscle circles the anorectal junction. It is not tethered by the anococcygeal
raphe. Thus, when contracted, the puborectalis pulls the rectum anterior and thereby promotes fecal continence.
- The posterior wall of the pelvic diaphragm is defined by the ischiococcygeus muscle. This muscle is not antomically favored to
directly elevate the pelvic and, thus, is not included as part of levator ani. However, the ischiococcygeus muscle, by virtue of its
attacments to the ischial spine and the coccyx acts of approximate these two structures and indirectly assists in elevating the pelvic
- The superior surface of the pelvic diaphragm is covered by parietal pelvic fascia. This fascia is continuous with the transversalis
fascia of the abdominal cavity. The inferior surface of the pelvic diaphragm is covered by the inferior fascia. This fascia is
continuous with deep fascia of the perineum.
- Relations of the pelvic diaphragm
- Superior - immediate is pelvic visceral fascia then the pelvic viscera and the abdominal cavity
- Inferior anterior - superior fascia urogenital diaphragm
- Inferior posterior - posterior recess of ischiorectal fossa including fat, gluteus maximus, and perineal skin
- lateral - arcus tendineus and obturator internus fascia (oburator nerve, external iliac artery and vein)
- anterior - superior aspect of the conjoint rami near pubic symphysis
- Posterior - piriformis muscle and sacrum (sacral plexus, sacral sympathetic trunk, middle sacral artery, effluents of sciatic foramina)
- Vasculature of pelvic diaphragm
- The pelvic diaphragm recieives arterial supply from the internal iliac. In particular, the inferior vesical arteries, the middle rectal
arteries, the internal pudendal arteries, and the inferior rectal arteries all supply the pelvic diaphragm. Similarly,
veins if the same name provide venus drainage.
- Innervation of pelvic diaphragm
- The levator ani is innervated by the nerve to levator ani derived from S3-4. Additionally, the perineal surface of the levator
ani receives innervation from inferior rectal branches of the pudendal nerve.
- The ischiococcygeus is supplied by the nerve to coccygeus derived from S4-5.
- Lymphatic drainage of pelvic diaphragm
- Lymphatic drainage of pelvic diaphragm follows branches of the interanl iliac artery to internal iliac nodes, then to upper lumbar
nodes, lumbar lymph ducts, and the cysterna chyli. Other drainages include the sacral nodes and the common iliac nodes.
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