Veterinary Anatomy: Canine & Feline Abdomen

Small Animal Abdomen (Canine & Feline)

• The abdominal cavity is bordered by muscle and bone.
• It is lined by serous membranes.
• It contains viscera.
• Cranial border- diaphragm muscle
• Caudal border- pelvic inlet
• Dorsal border- vertebrae, sublumbar muscles, crura of diaphragm
• Lateral- intrathoracic = ribs and costal arch, intercostal mm.; extrathoracic = muscles of the abdominal wall
• Ventral - rectus abdominis muscle

Topographic Regions of Thorax and Abdomen

• The abdomen is divided into regions for anatomical reference.
• Regions include cranial, middle, and caudal abdominal regions.
• Other relevant thoracic and abdominal regions are listed, such as pectoral, costal arch, xiphoid, hypochondriac, umbilical, lateral, inguinal, and pubic regions.

Blood Supply

• Caudodorsal Quadrant: Deep circumflex iliac a. (arises from the aorta)
• Craniodorsal Quadrant: Phrenicoabdominal a. (caudal phrenic a. and cranial abdominal a.) (arises from the aorta)
• Caudoventral Quadrant: Caudal epigastric a., caudal superficial epigastric a., right external iliac
• Cranioventral Quadrant: Cranial epigastric a., cranial superficial epigastric a.
• Additional arteries and their sources are detailed.

Innervation (Nerve Supply)

• Spinal nerves T13-L4 supply innervation to the abdominal wall.
• Lateral cutaneous branches are off the lateral branches.
• Medial branches are also noted.
• Additional nerves are described.

Lumbar Spinal Nerves

• The ventral branches of lumbar spinal nerves (and T13) innervate the abdominal wall.
• Relevant nerves, such as costoabdominal n. (T13), cranial iliohypogastric n. (L1), caudal iliohypogastric n. (L2), ilioinguinal n. (L3), and lateral cutaneous femoral n. (L3/L4) are described.

The Abdominal Aorta

• The abdominal aorta has several paired arterial branches.
• These branches include lumbar aa. (segmental), phrenicoabdominal aa., renal aa., testicular/ovarian aa., deep circumflex iliac aa., external iliac aa., and internal iliac aa.

Peritoneum

• The peritoneum is a mesothelial layer with three components.
• These components are parietal peritoneum (lines the body wall), visceral peritoneum (covers the organs), and connecting peritoneum (mesenteries, omenta or ligaments).

Connecting Peritoneum

• Omentum (extended mesogastrium)- attaches the stomach to body wall or other organs.
• Greater omentum - from the stomach greater curvature to the ventral body wall.
• Mesoduodenum - origin dorsal abdominal wall and root of mesentery.
• Mesentery (mesojejunoileum) - attachment: abdominal wall opposite the second lumbar (L2) vertebra.
• Additional ligaments and attachments of the peritoneum are detailed.

Connecting Peritoneum (cont.)

• Falciform ligament - fold of peritoneum which attaches from the umbilicus to the diaphragm.
• Median ligament of the urinary bladder - fold of peritoneum caudal to the umbilicus and umbilical arteries (in the free border of the median ligament of the UB) in the fetus.
• Lesser omentum - from the lesser curvature of the stomach to the liver and diaphragm.

Connecting Peritoneum (cont.)

• The greater omentum (epiploon) encloses a space called the omental bursa (11).
• The epiploic foramen opens to the main peritoneal cavity.

Abdominal Contents (Digestive System)

• Gastrointestinal tract (stomach, small intestine, large intestine)
• Accessory organs of digestion (liver, gallbladder, pancreas)

Abdominal Contents (Immune, Endocrine, Urinary, and Reproductive)

• Immune organs (spleen)
• Endocrine organs (adrenal glands, pancreas)
• Urinary organs (kidneys, ureters, urinary bladder)
• Reproductive organs (ovaries, uterus)

Gastrointestinal Tract

• The gastrointestinal tract begins at the pylorus and continues to the anus.
• The tract contains the small intestine and the large intestine
• Additional details about the parts of the G.I. tract are provided.

Stomach

• Stomach- largest dilation of the alimentary canal.
• The stomach is musculoglandular, stores, and mixes food.

Duodenum

• Duodenum is the initial portion of the small intestine.
• It's closely attached to the abdominal roof by mesoduodenum.

Jejunum and Ileum

• Jejunum and ileum lie on the abdominal floor in multiple coils.
• They are suspended by mesojejunoileum.

ILEUM

• The ileum opens into the large intestine at the ileocecal orifice.

The Canine Colon

• The canine colon has three regions: ascending, transverse, and descending.
• Additional details regarding the colons are listed.

Mesocolon

• Mesocolon is a peritoneal fold that connects parts of the colon to the abdominal wall.

Liver

• The liver is located in the cranial abdomen.
• It's the largest gland in the body which is exocrine (producing bile) and endocrine (metabolizing substances like fat, carbohydrates, and protein).

Liver Lobes

• The liver has six lobes (left lateral, left medial, quadrate, right medial, right lateral, and caudate).
• Features about each lobe are detailed.

Gallbladder

• The gallbladder stores and concentrates bile.
• The cystic duct, the bile duct, joins to the hepatic duct and all these ducts open at the major duodenal papilla.

Pancreas

• The pancreas is an exocrine gland which produces enzymes for protein, carbohydrates, and fats.
• It also has endocrine functions.

Spleen

• The spleen is located in the left cranial part of the abdomen.
• The gastrosplenic ligament runs from the hilus of the spleen to the greater curvature of the stomach,
• Stores and concentrates erythrocytes, filters blood and produces lymphocytes.

Medical Imaging

• Information regarding imaging findings of the abdomen is included.

Vascularization

• There are three unpaired branches of the abdominal aorta: celiac, cranial mesenteric, and caudal mesenteric arteries.
• Details about the blood supply in various regions of the GI tract are listed.

Blood Supply to Stomach

• The stomach is supplied by the three main branches of the celiac artery: hepatic, splenic, and left gastric arteries.
• Information on the various arteries and their branches are listed in the supplied text.

Blood Supply to the Small Intestine

• The cranial mesenteric artery supplies the small intestine. The various branches involved are detailed.

Blood Supply to the Duodenum

• Duodenum is supplied by the cranial and caudal pancreaticoduodenal arteries.

Blood Supply to the Jejunum

• The jejunum is supplied by arteries/branches of the mesenteric vessels.

Blood Supply to the Ileum

• The ileum is primarily supplied by branches from the cranial mesenteric and mesenteric ileal vessels (and antimesenteric ileal artery which emerges from the cecal artery).

Blood Supply to the Large Intestine

• Blood to the large intestine is via cranial and caudal mesenteric arteries.

Blood Supply to the Liver

• Liver is supplied by the hepatic artery which is a branch of the celiac artery.

Blood Supply to the Pancreas

• Information regarding the flow of blood through the pancreas regions (body, right, and left lobes).

Blood Supply to the Kidneys

• The kidneys are supplied by paired renal arteries.

Adrenal Glands

• Adrenal glands are paired and situated against the roof of the abdominal cavity.

Reproductive Organs (Ovaries and Uterus)

• Structures, and functions regarding the ovaries and uterus are described.

Lymph Nodes

• Several lymph nodes are associated with the abdominal and abdominal viscera.

Sympathetic versus Parasympathetic Supply to the Gut

• The sympathetic and parasympathetic systems have nerves that supply to the gut for homeostasis.
• The sympathetic innervation involves the sympathetic chain giving pre-ganglionic fibers to pre-vertebral ganglia, and postganglionic nerves leave to the viscera.
• The parasympathetic innervation involves dorsal and ventral vagal nerve trunks.

This quiz covers the anatomy of the abdominal cavity in canines and felines, including its borders and viscera. It also examines the topographic regions of both the thorax and abdomen, along with the blood supply to these areas. Test your knowledge of these essential veterinary concepts.