Lecture Notes - Peritoneal Cavity & Intestines
  1. Abdominal Cavity: The major part of the abdominopelvic cavity, bounded by the thoracic diaphragm and the pelvic inlet. It includes both the peritoneal cavity and the retroperitoneal space.
    Peritoneal Cavity: That part of the abdomen surrounded by peritoneum. It is a potential space between the parietal and visceral layers of peritoneum.

    Retroperitoneal Space: The area behind (posterior to) the peritoneum. Retroperitoneal organs are located in this space.
  2. Abdominal Contents:
    Peritoneum - A mesothelial lining of the abdominal cavity. The peritoneum has visceral and parietal layers, just like the pleural cavity.
    Parietal - covers the abdominal wall
    Visceral - forms surfaces of organs, the serosa.
    Mesenteries: Portions of the peritoneum that suspend the gut and its derivatives and provide path for blood vessels and nerves to viscera.

    Organs
    Intraperitoneal: peritonealized organs having a mesentery, such as the stomach, small intestine (jejunum and ileum), transverse colon, liver and gallbladder.

    Retroperitoneal: organs without a mesentery and associated with posterior body wall, such as the aorta, inferior vena cava, kidneys and suprarenal glands.

    Secondarily retroperitoneal: organs which had a mesentery once and lost it during development, such as the pancreas, duodenum, ascending and descending colons.
  3. Basic embryological considerations of gut development:
    Gut development
    Foregut - develops around celiac trunk: stomach to mid-duodenum, liver, pancreas, spleen
    Midgut - develops around superior mesenteric artery: mid-duodenum to left colic flexure
    Hindgut - develops around inferior mesenteric artery: left colic flexure to rectum
    Primitive mesenteries
    Derivatives of the dorsal mesogastrium: the greater omentum (omental apron, gastrosplenic, gastrophrenic, gastrocolic, and splenorenal "ligaments")
    Derivatives of the ventral mesogastrium: lesser omentum (hepatoduodenal and hepatogastric ligaments) and falciform ligament
    Derivatives of the dorsal common mesentery: the mesentery, transverse mesocolon, sigmoid mesocolon, mesoappendix and mesocolon for ascending and descending colon (not in the adult).
    Rotation of the gut
    Development of the omental bursa, omental (epiploic) foramen, fusion fascias, peritoneal regions and gutters such as subphrenic, para-, supra- and inframesocolic spaces and final peritoneal relationships of organs.
  4. The small intestine (small bowel): duodenum, jejunum and ileum
    Duodenum: secondarily retroperitoneal.

    Jejunum and ileum
    The mesentery
    Vessels: Intestinal branches of superior mesenteric artery and vein, arcades and vasa rectae
    Structural features: duodeno-jejunal flexure and suspensory ligament (of Treitz); circular folds; Meckel's diverticulum
  5. Large intestine (large bowel): Ascending, transverse, descending and sigmoid colon
    Hepatic and splenic flexures
    Ascending and descending colons: secondarily retroperitoneal
    Mesenteries: transverse and sigmoid mesocolons, mesoappendix
    Vessels:
    • superior mesenteric - ileocolic, right and middle colic
    • inferior mesenteric - left colic, sigmoid and superior rectal
    • marginal artery
    Structural features: Cecum, appendix, ileocecal valve, tenia, haustra and omental (epiploic) appendages
  6. Nerves and Lymphatics:
    Nerves: Preaortic autonomic plexuses and pelvic splanchnics
    Lymphatics: Intestinal nodes draining to intestinal lymph trunk to cisterna chyli