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Abdomen, Pelvis, and Perineum - Written Examination September 22: Part V - Essay

*Note: This is an outline of topics to be covered. It is not the "answer key." It is an answer guide. *

External Oblique Muscle

Define the origin(s), insertion(s) and relationships of the external abdominal oblique muscle, including any aponeurotic/derivations/ligamentous terminations. Discuss the innervation, vasculature, and lymphatics of this muscle.
  • The external oblique is a digastric muscle having the linea alba as its central tendon. Each belly is quadralateral in shape. It has superior attachments to the external surface of the ribs. Inferior attachments to the ilium and pubis. Anterior attachments to the rectus sheath and linea alba. The posterior aspect of the external oblique has a free border near the lateral extent of the thoracolumbar fascia.
  • Origins
    • Anterior, lateral, and external surfaces of Ribs 5 - 12
    • Paired digastric muscle with linea alba as central tendon
  • Insertions
    • Anterior and lateral iliac crest
    • Anterior superior iliac spine
    • Inguinal ligament - free edge of the aponeurosis
    • Pubic tubercle, crest, and symphysis
    • Pectin line by way of pectineal ligament
  • Relationships
    • Continuous with external intercostals and forms outer muscle layer of anterior abdominal wall
    • Interdigitates with serratus anterior and with latissimus dorsi
    • Superficial to the internal oblique muscle
    • Deep to tela subcutanea, campers fascia, and Scarpa's fascia
    • Attachments of Scarpa's fascia define potential space, fundiform ligament
    • Inguinal ligament provides site of attachment for the internal oblique and for the transversus abdominis
  • Derivations
    • Rectus sheath
      • anterior lamina
      • linea semilunaris
    • Linea alba
    • Lumbar triangle
    • Inguinal canal
      • Inguinal ligament - inferior
      • Aponeurosis - anterior
      • Arcades - superior
      • Superficial ring - distal opening
    • Superficial inguinal ring
      • Inguinal ligament
      • Medial crus
      • Lateral crus
      • Intercrural fibers
      • Reflected inguinal ligament
      • External spermatic fascia
    • Femoral ring
      • Inguinal ligament - anterior
      • Lacunar ligament - medial
      • Pectineal ligament - Posterior
  • Innervation
    • Lower 6 intercostal nerves and the subcostal nerve
    • Iliohypogastric nerve
  • Vasculature
    • Lower 6 intercostal arteries and the subcostal artery
    • Lumbar arteries
    • Iliolumbar artery
    • Deep circumflex iliac arteries
    • Inferior and superior epigastric arteries
    • Superficial epigastric and superficial circumflex iliac arteries and veins
  • Lymphatics
    • Below the level of the umbilicus there is superficial drainage into superificial inguinal nodes by way of lymph vessels traveling with superficial epigastric and superficial circumflex iliac veins.
    • Above the level of the umbilicus there is superficial drainage into parasternal, pectoral, subscapular, and axillary nodes.
    • Deep drainage is into common iliac nodes (deep circumflex iliac vessels and inferior epigastric vessels)
    • para-aortic nodes (lumbar and intercostal vessels), intercostal nodes, internal iliac nodes (iliolumbar vessels)
    • Parastenal nodes (superior epigastric vessels)

Stomach

Review the structure of the stomach. Include the anatomy of the stomach, supporting elements, vasculature, lymphatic drainage, innervation, and relationships to surrounding structures and spaces.
  • General
    • The stomach is located in the left upper quadrant of the abdominal cavity.
    • Extends toward the right to reach the level of the umbilical region
    • Adult capacity of about 1500 ml
    • Intervenes between the esophagus and the duodenum
    • The most superior extent of the fundus is at T9
    • The most inferior extent of the antrum is at L2
  • External Structure
    • Cardiac incisor
    • Body
    • Fundus - projects into the left dome of the diaphragm as high as the 5th intercostal space
    • Antrum
    • Pyloric canal - 1-2 cm in length
    • Pylorus - sphincter into duodenal cap
    • Lesser curvature - to the right between the cardiac incisura and the pyloric sphincter, lesser omentum, ventral mesentery
    • Greater curvature - gastrolieno ligament, greater omentum, dorsal mesentery, as high as the 5th intercostal space
  • Internal Structure
    • Gastric rugal folds of mucosa
    • Longitudinal folds
    • Pyloric orifice
  • Support
    • Lesser omentum (hepatogastric and hepatoduodenal ligament)
    • Greater omentum - gastrocolic ligament
    • Gastrolieno ligament
    • Lienorenal ligament
    • Esophageal hiatus
  • Vasculature
    • Lesser curvature - right and left gastric arteries from hepatic artery and celiac trunk, lesser omentum
    • Cardiac region - esophageal artery from left gastric, vein is implicated in esophageal varices in the case of portal hypertension
    • Fundus - short gastric arteries from splenic artery, gastrolieno ligament
    • Greater curvature - left and right gastroepiploic arteries from splenic and gastroduodenal arteries, greater omentum
    • Venous drainage directly into portal vein and indirectly by way of superior mesenteric vein
  • Lymphatic drainage
    • Nodes named for the arterial supply drain into celiac nodes
    • Splenic nodes, pancreatic nodes, infrapyloric nodes,
  • Innervation
    • Preganglionic parasympathetic - vagus nerve branches to celiac plexus follow arterial supply to the stomach
    • Postganglionic parasympathetic - intrinsic ganglia within the stomach
    • Preganglionic sympathetic - IMLCC of T5-9 ventral root - spinal nerves - white ramus communican - thoracic sympathetic trunk - splanchnic nerves - greater splanchnic nerve - pierce right crus diaphragm - enter celiac ganglion
    • Postganglionic sympathetic - celiac ganglion - celiac plexus - follow arterial supply to stomach
    • Sensory (low threshold homeostatic) celiac plexus to anterior and posterior vagal trunks
    • Sensory (high threshold pain) celiac plexus through celiac ganglion - greater splanchnic nerves - splanchnic nerves - sympathetic trunk - ramus communican - spinal nerve - dorsal root - cord levels T5-9
    • Superior mesentric ganglia and the plexus are sometimes said to contribute. Thus T10-11 levels may be involved.
  • Relationships
    • Anterior surface
      • Faces greater sac
      • Left - diaphragm, spleen, intercostal spaces 5 - 9
      • Right - quadrate lobe of liver
      • Inferior - transverse colon
      • Superior - dome of the diaphragm
    • Posterior surface
      • Faces lesser sac
      • Right - left crus diaphragm and diaphragm proper, left inferior phrenic artery and suprarenal gland,
      • Intermediate posterior - pancreas, splenic artery, transverse colon
      • Left - left colic flexure, spleen, superior pole left kidney
    • Spaces
      • Subphrenic space

Ovary

Discuss the anatomy of the ovary and include relationships (6 directions), structure, surfaces, supports, vasculature, innervation, and lymphatic drainage.
  • Structure
    • The ovary is roughly cylindrical about 3 cm long and 1 cm in diameter.
  • Surfaces
    • The visceral peritoneum covering the ovary gives way to a specialized germinal epithelial cell layer. *The egg is able to penetrate this layer and enter the peritoneal cavity.
  • Support
    • The ovary is suspended from the posterior lamina of the broad ligament by the mesovarium -- a peritoneal ligament.
    • Supporting the superior pole of the ovary to the pelvic brim is the suspensory ligament of the ovary.
    • Supporting the inferior pole of the ovary to the lateral uterus is the ovarian ligament.
  • Vasculature
    • The arterial supply is mostly from the ovarian arteries. These are paired arteries arising from the anterolateral surface of the aorta near the level of the third lumbar vertebra. The ovarian veins arise from the IVC on the right and the left renal vein on the left. Additional blood supply is by ascending branches of the uterine vessels (ovarian br.) that anastomose with the ovarian vascular supply.
  • Innervation
    • Parasympathetic preganglionic cell bodies are located in the central gray of the spinal cord (IMLCC) at levels S2-4. Preganglionic fibers enter the inferior hypogastric plexus by way of the pelvic splanchnic nerves. The inferior hypogastric plexus contributes a uterine plexus and then to the ovarian plexus. Postganglionic parasympathetic cell bodies are located in intrinsic ganglia of the ovary. The above pathway assumes that the uterovaginal plexus reaches the ovary. This is not known for certain. Parasympathetic pregangionic contributions from the vagus n. may also follow the ovarian plexus.
    • Sympathetic preganglionic cell bodies are located in the interomedial lateral cell column at cord levels T10 (and perhaps T11-12). Preganglionic fibers follow the lesser and least splanchnic nerves to aortic ganglia near (and including) the superior mesenteric ganglion and the aorticorenal ganglion. Postganglionic fibers from these ganglia enter the aortic plexus and extend along the ovarian artery as the ovarian plexus. Visceral afferent pathways follow the sympathetic pathways up to the T10 spinal level. Additional visceral pathways follow parasympathetic pathways back to the S3-4 spinal levels.
  • Lymphatic drainage
    • Lymph drainage is primarily along the embryological decent of the ovary. This includes upper lumbar nodes in the vicinity of the renal arteries. Much of the vascular supply reaches the ovary through the suspensory ligament.
    • Lymph drainage to superficial inguinal nodes follows the ovarian and round ligament.
    • Internal iliac nodes and ovarian fossa
  • Relationships
    • superior to the ovary is the pelvic brim and suspensory ligament
    • inferior to the ovary is the uterine wall and the ovarian ligament
    • anterior to the ovary is the broad ligament, uterine tube, and fimbria of uterine tube
    • posterior to the ovary is the rectum and pelvic floor
    • medial to the ovary is the pararectal fossa, rectouterine pouch, fundus of the uterus
    • lateral to the ovary is the ovarian fossa (internal iliac a. and ureter), psoas major muscle, and obturator n.

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-- LorenEvey - 27 Sep 2008

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