Human Gross Anatomy - Answer Key for Lower Limb and Thorax Essay Examination

Human Gross Anatomy - Answer Guide for Abdomen, Pelvis, and Perineum Essay Examination (48 pts)

September 23, 2004

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

This page has been visited 7170 times since August 2, 2011.

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[ Second Part of Duodenum ] [ Ischiorectal Fossa ] [ Anterior Abdominal Wall ] [ Spermatic Cord and Indirect Inguinal Hernia ]

Discuss the anatomy of the second part of the duodenum; include structure, relationships, innervation (sensory and motor), vasculature, and lymphatics. (12 pts)
- General
  - Continues from the duodenal cap (Part 1)
  - Descends from L1-L3
  - Retroperitoneal
- Relationships
  - Superior - caudate lobe liver, superior pole of right kidney, epiploic foramen
  - Inferior - right ureter, jejunum, transverse colon
  - Anterior - transverse mesocolon, liver, peritoneum (retroperitoneal)
  - Posterior - hilum of right kidney, common bile duct
  - Lateral left - head of pancreas
  - Lateral right - right colic flexure, right kidney
- Structure
  - Beginning of plicae circulares
  - Minor duodenal papilla - accessory pancreatic duct
  - Major duodenal papilla - ampulla of Vater (chief pancreatic and common bile ducts), midpoint of descending part, hood, frenulum
- Vasculature and Lymphatics
  - Superior anterior and posterior pancreaticoduodenal arteries from gastroduodenal artery of celiac trunk (anastomosis)
  - Inferior anterior and posterior pancreaticoduodenal arteries from superior mesenteric artery (anastomosis)
  - Veins follow similar pathways and drain into the portal system
  - Lymphatic drainage to right gastroepiploic nodes and pyloric nodes to celiac nodes to intestinal lymph trunk to cysterna chyli
  - Some lymphatic to superior mesenteric nodes
- Innervation - motor and sensory
  - Preganglionic parasympathetic - vagus nerve branches to celiac plexus follow gastroduodenal and superior pancreaticoduodenal arteries
  - Postganglionic parasympathetic - intrinsic ganglia within the walls of the duodenum
  - 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
  - Preganglionic sympathetic - IMLCC of T10-11 ventral root - spinal nerver - white ramus communican - thoracic trunk - splanchnic nerves - lesser splanchnic nerve - pierce right crus diaphragm - enter superior mesenteric ganglion
  - Postganglionic sympathetic - superior mesenteric ganglion - superior mesenteric plexus - follow arterial supply
  - Sensory (low threshold homeostatic) celiac and superior mesenteric plexus to anterior and posterior vagal trunks
  - Sensory (high threshold pain) celiac and superior mesenteric plexus to celiac and superior mesenteric - greater and lesser splanchnic nerves - splanchnic nerves - sympathetic trunk - ramus communican - spinal nerve - dorsal root - cord levels T5-11 (maybe T12 and L1)
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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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Discuss the organization of the anterior abdominal wall, and include muscles, ligaments, fascia, fascial specializations, nerves, and vascular supply. Do not include the inguinal region in your answer. (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
  - 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
- 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
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Present a detailed account of the spermatic cord that includes contents, coverings, fascial boundaries, relationships, vasculature, innervation, and lymphatics. Discuss the pathway and location of an indirect inguinal 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
  - Genital branch of genitofemoral nerve - mediates efferent component of cremasteric reflex
  - Cremesteric artery - branch of inferior epigastric artery vascularizes the tunics
- 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
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Human Gross Anatomy - Answer Guide for Abdomen, Pelvis, and Perineum Essay Examination (48 pts)

September 23, 2004

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

This page has been visited 7170 times since August 2, 2011.

Discuss the anatomy of the second part of the duodenum; include structure, relationships, innervation (sensory and motor), vasculature, and lymphatics. (12 pts)

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)

Discuss the organization of the anterior abdominal wall, and include muscles, ligaments, fascia, fascial specializations, nerves, and vascular supply. Do not include the inguinal region in your answer. (12 pts)

Present a detailed account of the spermatic cord that includes contents, coverings, fascial boundaries, relationships, vasculature, innervation, and lymphatics. Discuss the pathway and location of an indirect inguinal hernia that descends into the scrotum. (12 pts)