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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 (36 pts) - September 22, 2005
The College of Medicine at The Pennsylvania State University
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Present a comprehensive review of the ischiorectal fossa. Include boundaries, fascial specializations, relationship to the superficial
and deep pouches, and provide explanation why infections in the ischiorectal fossa might not enter the superficial or deep pouches. (12 pts)
- General
- Wedge shaped area located between the ischial tuberosites and the anorectal canal and consisting of a posterior
recess and an anterior superior recess.
- Boundaries of Anterior Superior Recess
- Superior - inferior fascia of the pelvic diaphragm, most lateral and superior is arcus tendineous
- Inferior - superior fascia of the urogenital diaphragm
- Anterior - fusion of superior fascia urogenital diaphragm (transverse perineal ligament) with inferior fascia of pelvic diaphragm at the pubic bone
- Posterior - open into the posterior recess of the ischiorectal fossa
- Lateral - inferior - conjoint ramus, intermediate - oburtator internus muscle
- Medial - fusion of the inferior fascia of the pelvic diaphragm with superior fascia urogenital diaphragm at urogenital hiatus
- Boundaries of Posterior Recess
- Superior - inferior fascia of the pelvic diaphragm
- Inferior - medial: perianal skin, lateral: gluteus maximus
- Anterior - superior to posterior free edge urogenital diaphragm: anterior superior recess of the ischiorectal fossa,
inferior to posterior free edge of urogenital diaphragm: superficial perineal fascia (Dartos)
- Posterior - gluteus maximus
- Lateral - gluteus maximus
- Medial - anal canal
- Fascial specializations
- Arcus tendineus - thickening of obturator internus fascia, faces pelvic cavity on superior aspect and ischiorectal fossa on inferior aspect
- Pudendal canal - thickened covering of obturator internus fascia over falciform edge along medial ischial tuberosity forms
osseofibrous pudendal canal from lesser sciatic foramen to the posterior free edge of the urogenital diaphragm at the conjoint ramus
- Contents and relationships
- Loose areolar fat - accomodate distention
- Anal canal
- Pudendal nerve and branches - inferior rectal, perineal, posterior scrotal, dorsal nerve
- Internal pudendal artery and branches - inferior rectal, perineal, posterior scrotal, dorsal artery, deep artery, artery to the bulb
- What fascial barriers prevent spread of infection into the superficial pouch
- Infection does not spread from the ischiorectal fossa into the superficial pouch because Scarpa's fascia attaches to the posterior
free edge of the UG diaphragm. This attachment provides part of the anterior border of the ischiorectal fossa at levels inferior
to the posterior free edge of the urogenital diaphragm.
- What fascial barriers prevent spread of infection into the deep pouch
- Infection does not spread from the ischiorectal fossa into the deep pouch because the superior fascia of the urogenital diaphragm
provides a fascial barrier between the anterior superior recess of the ischiorectal fossa and the deep pouch.
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Review the anatomy of the liver and the gall bladder. Include structure, supporting elements,
peritoneal relationships, vasculature, lymphatic drainage, innervation (e.g., preganlionic,
postganglionic, afferent innervation and pathways), and relationships to surrounding
structures and spaces. (12 pts)
- General
- Largest and most vascular organ in the body
- Weighs 1-2 Kg
- Smooth diaphragmatic surface
- The "H" on the visceral surface: right stem is filled by gall bladder and IVC, left stem is marked by fissures for the round ligament and the ligamentum venosum, cross line is the portahepatis
- The boundary between the right and left lobes is marked by falciform ligament
- The quadrate lobe and part of the caudate lobe are considered to belong to the left lobe
- intraperitoneal
- Structure
- Left lobe
- Right Lobe
- Quadrate lobe
- Caudate lobe
- Porta hepatis
- Gall Bladder - storage for bile, spiral folds in the cystic duct
- Supporting elements
- Falciform ligament and ligamentum teres secure liver to anterior abdominal wall and diaphragm
- Coronary ligament, right triangular ligament, left triangular ligament, and the IVC secure the liver to the diaphragm
- Hepatorenal ligament secures the liver to the posterior abdominal wall and diaphragm
- ligamentum venosum provides site of attachment for the hepatogastric ligament
- Hepatogastric ligament tethers the liver to the stomach and spleen
- Hepatoduodenal ligament tethers the liver to the duodenum and pancreas
- Gall bladder is secured to the liver by peritoneum and small veins between the gall bladder and the liver bed
- Peritoneal relationships
- Lesser sac is to the left of the right lobe, inferior to left lobe, and posterior to lesser omentum
- Caudate lobe faces into lesser sac
- Posterior right lobe faces the hepatorenal recess
- The bare area is between the reflection of the anterior and posterior lamina of the coronary ligament (allows for IVC)
- Inferior right lobe faces the right paracolic gutter - communicates with hepatorenal recess and with epiploic foramen
- Gall bladder faces the greater sac - possible to have floating gall bladder (intraperitoneal)
- Cystic duct and common bile duct are, in part, within the hepatoduodenal ligament
- Relationships
- Superior - Diaphragm
- Inferior - right kidney, duodenum, transverse colon, transverse mesocolon, spleen, pancreas, stomach
- Anterior - diaphragm
- Posterior - diaphragm, right kidney, suprarenal gland, IVC, aorta, pancreas
- Lateral left - duodenum, head of pancreas, spleen, stomach
- Lateral right - diaphragm, right colic flexure, right kidney, costodiaphragmatic recess,
- Vasculature and Lymphatics
- Liver - Right and left hepatic arteries from the common hepatic artery derived from celiac trunk
- Liver - Right and left hepatic veins drain into the IVC
- Gall bladder - Cystic artery from right hepatic
- Liver receives portal vein
- Right and left hepatic ducts form common hepatic duct - join cystic duct to from common bile duct
- Lymphatic drainage to hepatic nodes to celiac nodes to intestinal lymph trunk to cysterna chyli
- Bare area drains to posterior mediastinal lymph nodes
- Some lymphatic drainage to parasternal and intercostal nodes by way of diaphragm drainages
- Innervation - motor and sensory
- Preganglionic parasympathetic - vagus nerve branches to celiac plexus follow hepatic arteries and a separate hepatic branch
- Postganglionic parasympathetic - intrinsic ganglia within the liver
- Preganglionic sympathetic - IMLCC of T5-9 ventral root - spinal nerver - white ramus communican - thoracic trunk - splanchnic nerves -
greater splanchnic nerve - pierce right crus diaphragm - enter celiac ganglion
- Postganglionic sympathetic - celiac ganglion - celiac plexus - follow arterial supply to liver
- Sensory (low threshold homeostatic) celiac plexus to anterior and posterior vagal trunks
- Sensory (high threshold pain) celiac plexus to celiac ganglion - greater splanchnic nerves -
splanchnic nerves - sympathetic trunk - ramus communican - spinal nerve - dorsal root - cord levels T5-11 (maybe T12 and L1)
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Review the anatomy of the rectum. Include relationships to peritoneum and surrounding structures,
innervation (e.g., preganglionic, postganglionic, afferent innervation and fiber pathways), vasculature, and
lymphatic drainage. What structures can be palpated upon rectal examination of the male? (12 pts)
- General Anatomy
- rectosigmodal junction at S3 extending to tip of coccyx and ending at anorectal junction (pelvic floor)
- 12 cm long with two convexities to right and one to left (transverse folds)
- teneia coli broaden
- no haustra or appendices epiploica
- smooth mucosa
- distensible
- Peritoneal coverings and relations
- upper 1/3 covered front and sides
- middle 1/3 covered front
- lower 1/3 not peritonealized
- peritoneal pouches and fossa
- ant: rectouterine or rectovesical pouch
- lateral: pararectal fossae
- Relations to surrounding structures
- Anterior - bladder, vagina, uterus, prostate, seminal vesical, vasdeferens, ureters
- Posterior - presacral space, sacrum, sacral foramina, sacral plexus, sacral sympathetic trunk, piriformis, middle and lateral sacral arteries
- lateral (left and right) - inferior hypogastric plexus, pelvic wall and associated structures, appendix on right
- Superior - sigmoid colon, false pelvis
- Inferior - anal canal, pelvic floor
- Ligaments and support
- Rectovesical - part of the pubosacral ligamentous complex (derived from pelvic visceral fascia)
- Rectosacral - part of the pubosacral ligamentous complex (derived from pelvic visceral fascia)
- Innervation (no somatic for rectum proper)
- sympathetic
- Preganglionic: IMLL L1-3 - white rami - lumbar sympathetic trunk - lumbar splanchnics - aortic plexus - inferior mesenteric ganglion
- Postganglionic: inferior mesenteric plexus - superior rectal aa - rectal plexus
- parasympathetic
- Preganglionic: pelvic splanchnic nerves leave ventral rami of S2-4 spinal nerves to enter the pelvic plexus on either side of the rectum (inferior hypogastric plexus)
- an extension of the pelvic plexus either independently or via the left hypogastric nerve contributes to rectal plexus
- postganglionic: cell bodies and fibers are located in enteric (intrinsic) ganglia
- Vasculature Supply
- superior rectal aa pair on lateral posterior rectum - derived from single continuation of inferior mesenteric a - provides superior aspect of rectum
- superior rectal vein - drains most of the entire venus plexus of the rectum
- middle rectal artery - from internal iliac - provides inferior aspect of rectum
- inferior rectal artery - from pudendal artery - anastomosis with middle rectal artery - not directly to rectum proper
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The Structural Basis of Medical Practice - Human Gross Anatomy
The College of Medicine
of the The Pennsylvania State University
Email: lae2@psu.edu
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