Unit 6 - Large Animal Pancreas and Intestinal Tract

What are the parts of the pancreas?

- Right lobe

- Left lobe

- Body

Where does the pancreas sit in the abdomen of the horse?

- Sits transversely on the dorsal wall of the abdomen at the 17th thoracic vertebra

Where is the right lobe of the pancreas located in the horse? The left lobe?

- Right lobe located within the mesoduodenum

- Left lobe located within the deep layer of the greater omentum

Where does the pancreatic duct of the equine pancreas drain? What about the accessory pancreatic duct?

- Drains at the major duodenal papilla (also known as the hepatopancreatic ampulla) in the duodenum along with the common hepatic duct

- Accessory pancreatic duct drains at the minor duodenal papilla

Where do the right and left lobes of the ruminant liver sit in the abdomen?

- Right lobe located within the mesoduodenum

- Left lobe located within the dorsal attachment of the greater omentum at the root of the mesentery

Where does the pancreatic duct drain in ruminants?

- Drains at the major duodenal papilla in the duodenum along with the common bile duct

Where does the accessory pancreatic duct drain in ruminants?

- Drains at the minor duodenal papilla

What is the main pancreatic duct present in the in small ruminants? The ox?

- Small ruminants: Pancreatic duct is main duct and the accessory pancreatic duct is not present

- Ox: Accessory pancreatic duct is main duct and the pancreatic duct is occasionally present

What is the length of the equine small intestine?

- Approximately 22 m

What is the length of the equine duodenum?

- Approximately 1 m

What are the parts of the equine duodenum?

- Cranial part

- Cranial duodenal flexure

- Descending duodenum

- Caudal duodenal flexure

- Ascending duodenum

- Duodenojejunal flexure

Where does the caudal duodenal flexure course in the horse?

- Courses caudal to the cranial mesenteric artery

Where is the mesoduodenum located in the horse?

- Between the cranial part of the duodenum and the liver, the descending duodenum and right dorsal colon, and ascending duodenum and the base of the cecum and right kidney

Where is the duodenocolic fold located in the horse?

- Between the ascending duodenum and descending colon

What is the major duodenal papilla or hepatopancreatic ampulla in the horse?

- Site of drainage of the common hepatic duct and pancreatic duct

What is the minor duodenal papilla in the horse?

- Site of drainage of the accessory pancreatic duct

Describe the jejunum of the equine small intestine.

- Numerous coils located mainly in the dorsal part of the left half of the abdomen

Where does the mesojejunum course in the equine small intestine?

- Courses between the dorsal abdominal wall (around the cranial mesenteric artery at L1) and the jejunum

What is the mesojejunum composed of in the horse?

- Two layers of peritoneum - Contains vessels, nerves and lymph nodes

Describe the flow of ingesta from the ileum to the colon in the horse.

- Ingesta flows from the ileum to the cecum via the ileocecal orifice at the ileal papilla

Do horses have an ileocolic orifice?

- No

Where does the ileocecal fold course?

- Courses between the antimesenteric surface of the ileum and the dorsal cecal band

What is the approximate length of the equine large intestine?

- 7.5-8 m in length

What are teniae (bands)?

- Smooth muscle and elastic fibers oriented longitudinally

What are haustra?

- Sacculations

Explain the number of bands in each section of the equine large intestine.

- Cecum: 4

- Right ventral colon: 4

- Left ventral colon: 4

- Left dorsal colon: 1

- Right dorsal colon: 3

- Transverse colon: 2

- Descending colon: 2

What is the approximate length of the equine cecum? What is its capacity?

- 1.25 m in length

- 25-30 L

What are the regions of the equine cecum? Where are they each located?

- Base: Located int he right paralumbar fossa and medial to last few ribs

- Body: Dorsal portion located against the right flank; courses medially and ventrally

- Apex: Located on the floor of the abdomen near the xiphoid cartilage

What are the equine cecal orifices and what are they between?

- Ileocecal orifice: Between the ileum and cecum

- Cecocolic orifice: Between the cecum and right ventral colon

What are the equine cecal teniae/bands?

- Dorsal cecal band

- Ventral cecal band

- Medial cecal band

- Lateral cecal band

What extends from the dorsal cecal band?

- Ileocecal fold, coursing between the ileum and cecum

What extends from the lateral cecal band? What is found within it?

- Cecocolic fold, coursing between the cecum and the right ventral colon

- Lateral cecal artery and vein

What is the approximate length of the equine ascending colon? The descending colon? The rectum?

- Ascending colon: 3-3.7 m

- Descending colon: 3.5 m

- Rectum: 30 cm

What are the parts of the equine ascending colon?

- Right ventral colon

- Sternal (ventral diaphragmatic) flexure

- Left ventral colon

- Pelvic flexure

- Left dorsal colon

- Diaphragmatic (dorsal diaphragmatic) flexure

- Right dorsal colon

What is the midway point of the equine ascending colon?

- Pelvic flexure

Where does the equine transverse colon course?

- Courses right to left cranial to the cranial mesenteric artery

What are differences between the equine jejunum and small colon?

- Jejunum: No teniae, no haustra, lymph nodes located at root of mesentery, less fat in mesentery, and vasa recti (straight vessels) are longer and further apart

- Small colon: Teniae, haustra, lymph nodes located along mesocolic attachment, More fat in mesentery, and vasa recti shorter and closer together

What fixed structures can be palpated on the left side of the equine abdomen via rectal palpation?

- Spleen

- Renosplenic ligament

- Left kidney

- (Vaginal ring)

What non-fixed structures can be palpated on the left side of the equine abdomen via rectal palpation?

- Left ventral colon

- Pelvic flexure

- Left dorsal colon

- Descending colon

- Jejunum

- Ileum

What fixed structures can be palpated on the right side of the equine abdomen via rectal palpation?

- Caudal duodenal flexure

- Ileocecal junction

- Base of cecum

- (Vaginal ring)

What non-fixed structures can be palpated on the right side of the equine abdomen via rectal palpation?

- Jejunum

- Ileum

- Descending colon

What are common sites for blockage in the equine digestive tract?

- Caudal duodenal flexure

- Cecum

- Ileocecal orifice

- Sternal flexure

- Pelvic flexure

- Transverse colon

- Rectum

What is the approximate length of the bovine small intestine? The small ruminant?

- Ox: 40 m

- Small ruminant: 25 m

How long is the bovine duodeum?

- 1 m

What are the parts of the bovine duodenum?

- Cranial part

- Cranial duodenal flexure

- Descending duodenum

- Caudal duodenal flexure

- Ascending duodenum

- Duodenojejunal flexure

Where does the caudal duodenal flexure course?

- Courses caudal to the cranial mesenteric artery

What is the function of the mesoduodenum?

- Supports the descending duodenum and caudal duodenal flexure

Where is the duodenocolic fold located?

- Between the ascending duodenum and descending colon

Describe the bovine jejunum.

- Numerous coils located mostly in the supraomental recess on the right side of the rumen

Where does the bovine mesojejunum course?

- Courses between the dorsal abdominal wall (around the cranial mesenteric artery) and jejunum

What is the bovine mesojejunum composed of?

- Two layers of peritoneum - Contains vessels, nerves and lymph nodes

Describe the flow of ingesta from the bovine ileum.

- Ingesta flows from the ileum to the junction of the cecum and colon via the ileal orifice

Where does the bovine ileocecal fold course?

- Courses between the antimesenteric surface of the ileum and the cecum

What is the approximate length and capacity of the bovine cecum? The bovine colon? The small ruminant colon?

- Cecum: 75 cm; 8 L

- Bovine colon: 10 m

- Small ruminant colon: 4-5 m

What are the parts of the bovine ascending colon? What are the segments of the large intestine that follow?

- Proximal loop

- Spiral colon: Centripetal coils, central flexure, centrifugal coils

- Distal loop

- Transverse colon

- Descending colon

- Rectum

The bovine descending colon has a __________ ____________.

- Sigmoid flexure

Where can the jejunal (mesenteric) lymph nodes be found in the ruminant large intestine?

- In the mesentery near the jejunum

Where is the last centrifugal coil of the small ruminant large intestine?

- Located in the mesentery near the jejunum

What fixed structures can be palpated on the left side of the bovine abdomen via rectal palpation?

- Rumen

- Left kidney

- (Vaginal ring)

What non-fixed structures can be palpated on the left side of the bovine abdomen via rectal palpation?

- Body and apex of cecum

- Jejunum

- Ileum

What fixed structures can be palpated on the right side of the bovine abdomen via rectal palpation?

- Caudal duodenal flexure

- Base of cecum

- Spiral colon

- (Vaginal ring)

What non-fixed structures can be palpated on the right side of the bovine abdomen via rectal palpation?

- Jejunum

- Ileum

What are the significant parts of the camelid intestinal tract?

- Small greater omentum

- Duodenal ampulla

- Spiral colon

Where is the base of the porcine cecum located?

- Located on the left side

How many teniae are found on the porcine colon? How many on the cecum?

- Colon: 2

- Cecum: 3

The spiral colon of swine is _________-shaped.

- Cone

Organs caudal to what landmark are palpable rectally?

- The root of the mesentery

The equivalent of the central flexure in the ox is what in the horse?

- Pelvic flexure (midpoint of colon)