Equine G.I. Anatomy

Oral Cavity / Esophagus

100

What is your diagnosis? "Dull, darker areas of the secondary dentine, with pitting and food pocketing into the pulp chamber"

What is pulpar exposure

200

What are FOUR diagnostic imaging modalities available to evaluate the esophagus?

- Standard Radiography - Ultrasound - Endoscopy - Barium contrast esophagography

300

Describe the length and 3D anatomical dimension of the esophagus (cranial 1/3rd, middle 1/3rd, caudal 1/3rd)

Length: 125 to 200cm (49 to 78 inches) Cranial 1/3rd - lies dorsal to trachea on midline Middle 1/3rd - deviates to the left side of the medial plane Caudal 1/3rd - becomes ventral to trachea at thoracic inlet

400

Comment on the blood supply and neuromuscular innervation of the esophagus. Any considerations for surgery?

Blood supply - carotid a., bronchoesophageal a., gastric a., - arcuate, segmental and has poor collateral circulation - preservation of blood supply is essential during surgery Neuromuscular innervation - C.N. 9 - C.N. 10 - Sympathetic trunk - G.P. disease can influence = chronic choke

500

How many pulp chambers do 06s have? How many pulp chambers do 07s have? How many pulp chambers do 08s have? How many pulp chambers do 09s have? How many pulp chambers do 10s have? How many pulp chambers do 11s have?

06s = 6 PCs 07 to 10s = 5 PCs 11s = 6 or 7 PCs

Stomach / Spleen

100

What are the two most valuable diagnostic imaging modalities for evaluating the spleen?

- Ultrasound - Laparoscopy

200

Describe the anatomical position of the stomach in the abdomen as precisely as possible. Comment on rib spaces, position of pylorus, dorsal to ventral direction, attachment to diaphragm etc.

- On the left side of the abdomen - Greater curvature is most caudal, extends to rib 14 to 15 - Pylorus is to the right of midline - Dorsal position, even when distended does not contact ventral body wall - Cardia attached to diaphragm by gastrophrenic ligament

300

What 3 ligaments help suspend the spleen?

- Phrenicosplenic ligament - Renosplenic ligament - Gastrosplenic ligament

400

Define: epithelial restitution (in the context of gastric ulcers)

Superficial ulcer erosions can be rapidly covered by migration of epithelium adjacent to the wound.

500

Spleen anatomy: - Is the cranial border concave or convex? - Is the caudal border concave or convex? - Is the parietal border concave or convex? - Is the visceral border concave or convex? - Where and what is the hills?

Cranial = concave Caudal = convex Parietal = convex Visceral = concave Hilus present on the medial surface. Longitudinal ridge. Contains nerves and vascular supply (splenic artery).

Small Intestine

100

How long (in meters or feet) is the small intestine? How long is the duodenum? How long is the ileum?

Range 10 to 30 meters Average is 25 meters 25 meters = 82 feet Duodenum = 1 meter or 3.2 feet Ileum = 0.7 meter or 2.2 feet

200

Describe the location and attachment of the duodenocolic ligament:

- Immediately caudal to the right kidney - Attaches to the transverse colon

300

Describe in detail the vascular arcade of the jejunum. Start at aorta:

Aorta -> Cranial Mesenteric Artery -> Major Jejunal Vessel -> Arcuate Vessel -> Vasa Recta -> Intestinal Wall - Arcuate Vessels form loops that help connect major jejunal vessels.

400

Which of these drugs disrupt myoelectrical activity? - Xyaline? - Atropine? - Banamine? - Dipyrone? - Metaclopromide? - Butorphanol? - Isoflurane?

- Xyaline? YES - Atropine? YES - Banamine? NO - Dipyrone? NO - Metaclopromide? NO - Butorphanol? YES - Isoflurane? YES

500

Explain the pathophysiology of strangulated small intestinal segments?

- Thin walled veins are occluded first due to strangulation - Increases edema and net secretion of fluid - Edema leads to increased vascular resistance to arterial blood flow - Overall reduced blood flow - Can also have indirect occlusion of arterial blood flow from pressure (i.e., displacement of large colon pushing on small intestine) - Altered capillaries, erythrocytes extravagate = intramural hemmorhage or hemorrhagic infarction - Ischemia is hypoxia, which leads to morphological changes to the tissue Villus tip sloughs off first - Epithelial barrier is lost - Bacteria can transverse into the peritoneum or be absorbed into circulation - End result = endotoxemia

Cecum / Large Intestine

100

Describe the anatomical location of the cecum, in detail, within the abdomen:

- Base is located in right iliac / sub lumbar region - Greater curvature dorsally and lesser curvature ventrally - Extends to 14th to 15th rib, narrowing and terminating at an apex that sits on midline of the ventral abdomen - Cecal base is attached dorsally to ventral surface of right kidney and right pancreas - Cecal base is attached medially to the transverse colon and mesenteric root

200

- How many bands does the cecum have? Any clinical relevance? - How many bands does the left dorsal, right dorsal, left ventral, right ventral colon and pelvic flexure have? - How many bands does the small colon have?

- Cecum: Four, lateral, medial, dorsal, ventral. - Lateral = cecocolic ligament - Dorsal = ileocecal ligament - Large colon - Left dorsal =1 - Right dorsal = 2 - Left Ventral = 4 - Right Ventral = 4 - Pelvic Flexure = 1 - Small Colon = 2

300

Describe cecal motility in terms of the four patterns. How often is pattern IV heard?

Pattern I - cecal apex and moves up to cecal base Pattern II - caudal cecal base to apex Pattern III - cranial cecal base to apex Pattern IV - cecal apex up to cecal base, and into right ventral colon (occurs once every 3 minutes, strongest on auscultation of right flank)

400

Describe the blood supply to the ascending colon:

Aorta -> cranial mesenteric artery & ileocecocolic artery Ileocecocolic artery -> Colic branch -> Ventral Colon Cranial mesenteric artery -> right colic artery -> fuses with colic branch of ileocecocolic artery at pelvic flexure Cranial mesenteric artery -> middle colic artery -> supplies transverse colon and start of small colon

500

What is the anatomy of the transverse and small colon?

Transverse colon from right dorsal colon - Begins at 17th or 18th rib, dorsally - Passes from right to left - Cranial to the cranial mesenteric artery - Connected dorsally to the pancreas Small colon - Often in left caudal-dorsal quadrant of abdominal cavity - Approximately 3.5m long - Suspended by own mesocolon - 2 bands

Random

100

How does the wall layers of the esophagus compared to the small intestine differ?

Same: Mucosa, submucosa, muscularis Different: Adventicia (esophagus) Serosa (small intestine)

200

What way does the spleen contribute to the immune system?

- Filtering, phagocytic activity - Site of production of IgM - Site of maturation of B Cells - Reserve for immunocompotent lymphocytes

300

What are the four borders of the epiploic foramen?

- Potential opening in the greater omentum - Cranially, caudate lobe of liver - Caudally, pancreas - Dorsally, caudal vena cava - Ventrally, portal vein

400

Describe the difference between true/indirect, false/direct hernias:

- True/indirect: occurs through a normal aperture (i.e., inguinal) and has peritoneal covering present - False/direct: does not occur through normal aperture (i.e., body wall defect from trauma or surgery)

500

What is the blood supply to the small colon?

Aorta -> caudal mesenteric artery -> anastamosis with cranial mesenteric artery, middle rectal artery, caudal rectal artery Caudal mesenteric artery divides into -> cranial rectal artery and left colic artery Left colic artery innervates proximal 3/4 of small colon -> branches into 4-8 arcuate arteries -> cranial and caudal branch (parallel to small colon) -> marginal arteries