Anatomy of the Peritoneum

Peritoneum

• The mesothelial layer is divided into three regional components: parietal peritoneum, visceral peritoneum, and connecting peritoneum (mesenteries, omenta, or ligaments).
• Parietal peritoneum lines the body wall, visceral peritoneum covers the organs, and connecting peritoneum (double sheets) extends between connecting parietal to visceral parts.

Connecting Peritoneum

• Omentum (extended mesogastrium) attaches the stomach to the body wall or other organs.
• Greater omentum attaches the greater curvature of the stomach to the dorsal body wall.
• Mesoduodenum originates from the dorsal abdominal wall and root of the mesentery and extends to the duodenum, enclosing the right lobe of the pancreas.
• Mesentery (mesojejunum) attaches the abdominal wall opposite the second lumbar (L2) vertebra by a short peritoneal attachment named the root of the mesentery.
• Lateral ligaments of the urinary bladder contain the remnants of the umbilical arteries, which are also known as the round ligaments of the bladder.

Falciform Ligament

• A fold of peritoneum from the umbilicus to the diaphragm, also attached to the liver (between left medial and quadrate lobes).
• Characteristics: fat (especially in obese specimens) and round ligament of the liver (remnant of the umbilical vein) - visible in young animals, less visible in old art.

Median Ligament of the Urinary Bladder

• A fold of peritoneum caudal to the umbilicus, containing the urachus and umbilical arteries (in the free border of the median ligament of the UB) in the fetus.

Lesser Omentum

• Extends from the lesser curvature of the stomach to the porta (vena) of the liver.
• Attaches the liver to the diaphragm, covering the papillary process of the liver, and attaches the liver to the duodenum (hepatoduodenal ligament).
• Contains the portal vein, hepatic artery, and bile duct.

Greater Omentum

• Has superficial and deep leaves, enclosing a space called the omental bursa, and has an epiploic foramen opening into the main peritoneal cavity.
• Borders of the epiploic foramen: ventrally - portal vein, dorsally - vena cava caudalis, caudally - hepatic artery, cranially - liver.

Gastrointestinal Tract

• Stomach: largest dilation of the alimentary canal, stores and partly mixes food, adds enzymes, mucus, HCl, and lies largely in a transverse plane, more to the left.
• Regions of the stomach: cardiac region, fundus, body, and pyloric region.
• Duodenum: initial portion of the small intestine, short and closely attached to the abdominal roof by mesoduodenum, lies along the right body wall.
• Jejunum and ileum: lies on the abdominal floor, multiple coils that occupy the ventral aspect of the abdomen, suspended by the mesojejunum and mesoileum.

Abdominal Contents

• Gastrointestinal tract: stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, ascending colon, transverse colon, descending colon).
• Accessory organs of digestion: liver, gallbladder, pancreas.
• Immune organs: spleen.
• Endocrine organs: adrenal glands.
• Urinary organs: kidneys, ureters, urinary bladder.
• Reproductive organs: ovaries, uterus.

Ligaments and Structures of the Abdominal Cavity

• Falciform Ligament: Contains fat, acting as a remnant of the umbilical vein, primarily visible in younger animals; encloses the round ligament of the liver.
• Median Ligament of the Urinary Bladder: A peritoneal fold located caudal to the umbilicus, containing urachus and umbilical arteries, particularly significant in fetal anatomy.
• Greater Omentum: Comprises superficial and deep leaves, forming the omental bursa between them; contains the portal vein, hepatic artery, and bile duct.
• Epiploic Foramen: Opening to the peritoneal cavity with defined borders:
  • Ventrally: Portal vein
  • Dorsally: Caudal vena cava
  • Caudally: Hepatic artery
  • Cranially: Liver

Location and Attachment Details

• Hepatoduodenal Ligament: Connects the liver to the duodenum, covering the papillary process of the liver.
• Root of the Mesentery: Located near L2, where the mesentery bunches around the origin of the cranial mesenteric artery.
• Left Triangular Ligament: Links the left crus of the diaphragm to the left lateral lobe of the liver.

Internal Organ Relations

• Gallbladder: Positioned between the right medial and quadrate lobes of the liver, related to bile storage.
• Cranial Pole of Right Kidney: Resides in the renal impression of the caudate lobe of the liver.
• Papillary Process: Sits in the lesser curvature of the stomach, showcasing the close relationship between the liver and digestive organs.

Anatomical Orientation

• Visualizations may vary based on positioning of the subject (e.g., dog in dorsal recumbency) for clarity of liver and abdominal cavity structures.

General Observations

• The presence of fat in various ligaments suggests a role in supporting and cushioning abdominal organs.
• Understanding these structures is crucial for veterinary anatomy, aiding in clinical assessments and surgical procedures.

Learn about the structure and components of the peritoneum, including parietal, visceral, and connecting peritoneum. Understand the role of omenta and ligaments in the peritoneal cavity.