Answer Guide for the Pancreas, Ischiorectal Fossa, Anterior Abdominal Wall - September 15, 2011

Note. The following is a guide to answering the questions and is not the "answer."

Ischiorectal Fossa - September 15, 2011

Discuss the boundaries and contents of the ischiorectal fossa, fascial specializations, vascularization, innervation, lymphatic drainage, the relationship of the ischiorectal fossa to the superficial and deep pouches, and provide an explanation of your observation that urine does not accumulate in the superficial pouch. (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

Fascial Barriers to 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.

Fascial Barriers to 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.

arrowbupTop

Pancreas - September 15, 2011

Review the anatomy of the Pancreas. Include structure, supports, relationships, vascularization, innervation, and lymphatic drainage. (12 pts)

General

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.

Structure

  • 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

Relationships

  • 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

Vasculature

  • 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

arrowbupTop

Anterior Abdominal Wall - September 15, 2011

Review the anatomy of the anterior abdominal wall. Include structure, supports, relationships, vascularization, innervation, and lymphatic drainage. (12 pts)

General

  • Between the costal margins and the bony pelvis
  • Muscular - relaxes on distension and contracts on compression
  • Compression raises intra-abdominal pressure to stabilize vertebral column - increasing muscle tone is a treatment for back pain
  • Compression protects abdominopelvic viscera from injury
  • Forced expiration of the lungs and evacuation of pelvic viscera
  • Neurovascular plane - between internal oblique and transversus abdominis

Muscles

  • External oblique - origin: iliac crest for trunk flexion (ribs for compression), insertion: lower 7 ribs (iliac crest for compression), inferior free edge is inguinal ligament, anterior half is aponeurosis contributing to rectus sheath and linea alba and attaching to pubic crest
  • Internal oblique - orgin: lateral two-thirds inguinal (different accounts), iliac crest, and thoracolumbar fascia, insertion: lower 3 ribs, anterior half is aponeurosis contributing to rectus sheath and conjoined tendon
  • Transversus abdominis - origin: inquinal ligament lateral to internal oblique, inner lip iliac crest, thoracolumbar fascia, lower six costal cartilages, inserts upon itself by way of the rectus sheath and linea alba
  • Rectus abdominis - origin: pubic crest, insertion: 5, 6, and 7 costal cartilages, tendinous intersections divide muscle into sections, pyramidalis

Ligaments

  • Linea alba - midline raphe: intertwining of aponeurotic fibers from external oblique, internal oblique, and transversus abdominis
  • Inguinal ligament - inferior aspect of the external oblique aponeurosis
  • Lacunar ligament - external oblique, medial boundary of femoral ring
  • Pectineal ligament - external oblique, posterior boundary of femoral ring
  • Conjoint tendon - fusion of internal oblique and transverses abdominis to pectin pubis, guards against direct inguinal hernia
  • Median umbilical ligament - obliterated urachus
  • Lateral umbilical ligaments - obliterated umbilical arteries
  • Fundiform ligament - derived from Scapa's fascia and supporting the dorsum of the penis/clitoris to the inferior aspect of linea alba
  • Medial and lateral crua - contribute to anterior wall of inguinal canal and to the margin of the superficial ring, external oblique, external oblique
  • Intercrural fibers - contribute to anterior wall of inguinal canal and aproximate the medial and lateral crura, external oblique
  • Reflected inguinal ligament - posterior/inferior wall of superficial ring, external oblique

Fascia and Fascial Specializations

  • The rectus sheath surrounds the rectus abdominis muscle. Boudaries - superior: costal cartilages, inferior: pubic crest, anterior: anterior lamina rectus sheath, posterior: posterior lamina rectus sheath, medial: linea alba, lateral: linea semilunaris. Contained with the rectus sheath are the rectus abdominis, superior and inferior epigastric vessels, anterior branches of intercostal, subcostal, and iliohypogastric nerves, tendinous intersections.
  • Superficial to deep lateral to rectus sheath: epidermis - dermis - campers fascia (fatty) - Scarpa's fascia (membranous) - deep fascia - external oblique - internal oblique - transversus abdominis - transversalis fascia - extraperitoneal connective tissue - parietal peritoneum
  • Superficial to deep at rectus sheath superior to arcuate line: epidermis - dermis - campers fascia (fatty) - Scarpa's fascia (membranous) - deep fascia - external oblique aponeurosis - internal oblique aponeurosis anterior layer - rectus abdominis - internal oblique aponeurosis posterior layer - transversus abdominis aponeurosis - transversalis fascia - extraperitoneal connective tissue - parietal peritoneum
  • Superficial to deep at rectus sheath inferior to arcuate line: epidermis - dermis - campers fascia (fatty) - Scarpa's fascia (membranous) - deep fascia - external oblique aponeurosis - internal oblique aponeurosis anterior and posterior layers fused - transversus abdominis aponeurosis - rectus abdominis - transversalis fascia - extraperitoneal connective tissue - parietal peritoneum
  • The superifical fascia, starting superior at the level of the umbilicus and extending inferior, is made up of two layers - a fatty layer (Camper's) and a membranous layer (Scarpa's). Scarpas fascia is attached to deep fascia along the linea alba and extends inferiorly onto the penis (Colle's), scrotum (Dartos), or labia majora (superficial perineal fascia). Scarpa's fascia contributes the fundiform ligament from the anterior abdmominal wall to the dorsum of the penis/clitoris. Most inferiorly, Scarpa's fascia or its derivatives attach to the posterior free edge of the urogenital diaphragm and to the fascia lata about one inch inferior to the inguinal ligament.
  • The rectus sheath does not have a aponeurotic posterior lamina at levels inferior to the arcuate line and superior to the insertions of the internal oblique. Thus, the posterior lamina is non-muscular inferior to the approximate mid-point between umbilicus and pubic crest and is, again, non-muscular superior to the xiphoid process.

Nerves and innervation

  • Motor - lower intercostal nerves (T6-11), subcostal, iliohypogastric - travel in neurovascular plane and pierce linea semilunaris
  • Sensory - lower intercostal nerves (T6-11), subcostal, iliohypogastric - travel in neurovascular plane and pierce linea semilunaris, anterior intercostal nerves, T8 at xiphysternal region, T10 at umbilicus, and T12 at suprapubic region, subcostal at pubic ridge

Vasculature Supply

  • Supeficial veins - portal system: paraumbilical veins, caval system: lateral thoracic, thoracoepigastric, superficial epigastric, superficial circumflex iliac vein
  • Superficial arteries - superficial circumflex iliac, superficial epigastric, superficial pudendal
  • Caput Medusa - paraumbilical veins (portal system) reverse flow, dilate, and shunt to caval system at inferior vena cava (great saphenous - femoral - external iliac - IVC)and superior vena cava (axillary - subclavian - brachiocephalic - SVC)
  • Vessels in the neurovascular plane (deep the internal oblique and superficial to transversus abdominis) - intercostal arteries and veins from lower thoracic levels and lumbar arteries, musculophrenic, deep circumflex iliac artery, iliolumbar artery
  • Vessels within the rectus sheath - superior and inferior epigastric arteries and veins
  • Anterior aortic shunt - subclavian - internal thoracic - superior epigastric - inferior epigastric - external iliac

arrowbupTop

Comments

 

arrowbupTop

-- LorenEvey - 21 Sep 2011

key Access Control:
  • Set DENYTOPICVIEW =

This topic: Main > WebHome > AbdomenPelvisPerineumExams > AbdomenPelvisPerineumExamEssay2011
Topic revision: 21 Sep 2011, UnknownUser
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding Structural Basis of Medical Practice? Send feedback