Lesson 81 & 82: Small Intestine and Pancreas Anatomy

ileum

p

duodenum

w

jejunum

e

descending duodenum

1

- most fixed part

- located on the right of the median plane

- contact with right abdominal wall

descending duodenum

red arrows

transverse duodenum

2

- aka caudal flexure of duodenum

- mostly along the roof of the abdominal cavity

ascending duodenum

3

- located on the left side, mostly along the roof

duodenojejunal flexure

- sharp bend where the ascending duodenum becomes the jejunum

mesoduodenum

connecting peritoneum of the duodenum

cranial duodenal flexure

yellow circle

major duodenal papilla

Descending duodenum:

2

- opening of the common bule duct and major/main pancreatic duct

minor duodenal papilla

Descending duodenum:

1

- opening of the lesser/accessory pancreatic duct

- inconstant in cats, present in only 20% of cats

jejunum

4

- remains free in the abdominal cavity and forms bulk of the intestine

mesojejunum/jejunal mesentery/great mesentery/mesentery

connecting peritoneum of the jejunum

root of the mesentery

purple circle

- start of the mesojejunum

- jejunal lymph nodes located here

jejunal lymph nodes at the root of the mesentery

red circle

ileum

- shortest portion of small intestine

- located in caudal abdominal cavity

- slightly thicker wall than the jejunum

ileocecocolic junction

connects the ileum to the cecum

antimesenteric ileal artery

8

used to demarcate the ileum from the jejunum

ileocolic junction

- where the ileum opens into the ascending colon

ileum

dog:

1

cecum

dog:

2

ascending colon

dog:

3

ileal orifice

dog:

4

cecocolic orifice

dog:

5

cranial pancreaticoduodenal artery

Blood supply to the duodenum:

red arrow

jejunal arteries

Blood supply to the jejunum:

9

jejunal arcades

anastomotic branches of the jejunal arteries for collateral blood circulation

cranial mesenteric artery

Blood supply to the jejunum:

2

common trunk/ileocolic artery

Blood supply to the ileum:

3

mesenteric ileal artery

Blood supply to the ileum:

7

antimesenteric ileal artery

Blood supply to the ileum:

8

cranial pancreaticoduodenal vein

8

gastroduodenal vein

3

cranial mesenteric vein

4

vagus nerve

parasympathetic innervation of small intestine

intussusception (telescoping)

common disorders of the small intestine

duodenum

horse small intestine:

yellow

ileum

horse small intestine:

orange

cecum

horse small intestine:

dark green

colon

horse small intestine:

light green

descending duodenum

horse

red arrows

jejunum

horse

6

- most found within the left dorsal part of the abdomen (doesn't make contact with abdominal floor)

ileum

horse

- opens into the cecum (in ruminants and pigs too)

ileal papilla

horse

1

cecocolic orifice

horse

2

spiral colon

ruminant:

1

- modified large intestine

jejunum

ruminant:

2

ascending duodenum

ruminant small intestine:

1

descending duodenum

ruminant small intestine:

2

spiral colon

ruminant small intestine:

3

jejunum

ruminant small intestine:

4

jejunum

pig:

- mostly on the right side of the abdominal cavity when the stomach is distended fully

- topography changes with the condition of the stomach (shifts to the left temporarily)

left lobe of pancreas

red circle

right lobe of pancreas

green circle

- ventral to right kidney

amylase

Exocrine pancreas:

- breaks down carbs into simple sugars

lipase

Exocrine pancreas:

- aids in fat digestion by breaking triglycerides into fatty acids and glycerol

protease

Exocrine pancreas:

- break down proteins into peptides and amino acids

right lobe of pancreas

1

- ventral to right kidney

left lobe of pancreas

2

body of pancreas

3

cranial pancreaticoduodenal artery

1

caudal pancreaticoduodenal artery

2

pancreas

Ruminant:

- closely related to the duodenum, stomach, liver, and hepatic portal vein

pancreas

Horse:

- closely related to the duodenum, stomach, liver

- Hepatic portal vein perforates the __________

cats

Species differences of the pancreas:

- pancreatic duct large, small accessory pancreatic duct present in some (20%) of individuals

dogs

Species differences of the pancreas:

- pancreatic duct, accessory pancreatic duct larger

cows

Species differences of the pancreas:

- pancreatic duct extremely rare, accessory pancreatic duct

horses

Species differences of the pancreas:

- pancreatic duct large, accessory pancreatic duct small

pigs

Species differences of the pancreas:

- accessory pancreatic duct