Anatomy of Abdominal and Pelvic Structures

Aponeurosis and Rectus Sheath

  • The aponeurosis layers encompass the rectus abdominis, pulling the top and bottom parts and ultimately fusing to create the rectus sheath.

  • The rectus sheath is a fibrous structure that surrounds the rectus abdominis muscle, formed from the tendons of several abdominal muscles.

Key Components of Rectus Sheath

  • Aponeurotic tendons from:

    • External abdominal oblique

    • Internal abdominal oblique

    • Transversus abdominis

Deep Fat Layer

  • The layer of deep fat is referred to as mining (though likely a miscommunication—correct term is not clear).

  • The deep fascia lining the abdominal and pelvic cavities is known as transversalis fascia.

Cross-Sectional Anatomy of the Dog

  • A cross-section through the body shows various organs and muscles, including:

    • Lumbar vertebrae

    • Sublumbar muscles

    • Diaphragm

    • Abdominal muscles

  • The abdominal cavity contains all abdominal organs and also includes the peritoneal cavity.

Peritoneal Membranes

  • The serous membrane within the abdominal-pelvic cavity is called the peritoneum.

  • Visceral peritoneum: Adheres directly to the surface of organs like the stomach and liver.

  • Parietal peritoneum: Lines the abdominal cavity and is on the internal surfaces of the abdominal wall.

Types of Connecting Peritoneum

  • As one moves caudally in the abdominal cavity, reflections of the peritoneum occur.

  • Three types of folds of peritoneum include:

    1. Omentum: A double-layered fold attached to the stomach.

    2. Ligaments: Narrower than omenta, these are double-layered folds that help support organs.

    3. Mesentery: Broad sheets that convey blood vessels and connect to the body wall.

Specific Examples of Peritoneal Structures

  • Greater omentum: Extends from the greater curvature of the stomach, containing fat and connecting to the abdominal organs.

  • Lesser omentum: Connects the liver to the lesser curvature of the stomach and extends between the liver, the cranial part of the duodenum, and encloses the bile duct.

  • The great mesentery, mesoduodenum, and mesocolon are specific examples of mesentery.

Gastro-Splenic Ligament

  • The gastro-splenic ligament connects the stomach to the spleen and is part of the greater omentum.

  • The omental veil suspends the spleen and extends from the dorsal wall.

Clinical Considerations

  • Intestinal anatomy is subject to intestinal incarceration or epiploic entrapment where the intestines may twist and cause blood vessel collapse, leading to necrosis.

  • The greater omentum is critical for providing insulation and managing space between abdominal organs, regulating blood flow to ensure proper functionality of organs.

  • In surgeries, it is important to avoid damaging the greater omentum to preserve its protective and functional roles.

Liver Anatomy

  • The liver lobes in cats and dogs include:

    • Left lateral, left medial, quadrate, right medial and lateral lobes with a caudate lobe that has both caudate process and papillary process.

  • Coronary ligament: Reflects from the cranial surface of the liver onto the ventral surface of the diaphragm.

Gallbladder and Bile Ducts

  • The gallbladder functions similarly to a balloon, with:

    • Fundus: The apex of the gallbladder.

    • Body: Middle section leading to the neck.

    • Cystic duct: Where bile flows from the gallbladder to the duodenum.

  • Bile duct: Formed from the cystic duct and the common hepatic duct; carries bile from the liver to the duodenum.

  • Bile aids in emulsifying fats during digestion, resulting in its release upon eating.