Lesson 81 - Small Intestine Structure

What are the three parts of the small intestine?

duodenum, jejunum, ileum

What are the parts of the duodenum?

descending, transverse, ascending

What is important about the jejunum?

jujunal folds/loops, highly flexous

What animal has a 4m small intestine?

dog

What animal has a 1.72m small intestine?

cat

What animal has a 22m small intestine?

horse

What animal has a 18m small intestine?

pig

What animal has a 46m small intestine?

bovine

What animal has a 26m small intestine?

small ruminant

What is different about the ileum?

straight segment and thicker wall

How does the small intestine assist with digestion of food?

digestive enzymes from pancreas and intestinal mucosa break down carbohydrates, proteins, fats

What happens to carbohydrates in the small intestine?

broken down into monosaccharides and absorbed

What happens to proteins in the small intestine?

broken down into amino acids and peptides and absorbed

What happens to lipids in the small intestine?

emulsified by bile, broken down by lipases, absorbed as fatty acids or monoglycerides

What does the small intestine help with in ruminants?

continues digestion of microbial proteins from the rumen

What happens with fat-soluble vitamins in the small intestine?

require bile for absorption

What happens to water-soluble vitamins in the small intestine?

absorbed directly

What happens to minerals in the small intestine?

absorbed passively or actively

What are the fat-soluble vitamins?

A, D, E, K

What are the water soluble vitamins?

B-complex, C

What assists with moving the chyme in the small intestine?

peristalsis and segmentation

What is segmentation?

mixing contractions that help enhance digestion and absorption

What are the immune functions of the small intestine?

GLAT, peyer's patches, secretory IgA

Where are Peyer's patches located?

especially in the ileum

What does the small intestine do with water?

absorbs a large portion of water from digestive secretions

What electrolytes do the small intestine try to balance?

sodium, chloride, potassium

What are ruminant specific adaptations of the small intestine?

absorbs microbial proteins and volatile fatty acids

What are horse specific adaptations of the small intestine?

protein and fat absorption, but the hindgut takes care of the fiber with fermentation

What are carnivore specific adaptations of the small intestine?

highly adapted for protein and fat digestion

What are pig & omnivore specific adaptations of the small intestine?

efficient digestion of both plant and animal matter

What is the connecting peritoneum of the duodenum?

mesoduodenum

What is important about the location of the duodenum?

right side mostly, fairly fixed and attached to the body wall

What is the proximal part of the small intestine?

duodenum

What is the most fixed part of the duodenum and small intestine?

descending duodenum

What does the descending duodenum contact?

right abdominal wall

Where are the major and minor papillae located?

descending duodenum

What opens at the major duodenal papilla?

common bile duct and major/main pancreatic duct

What opens at the minor duodenal papilla?

lesser/accessory pancreatic duct

What acts as the sphincter for the major and minor papilla?

modified circular muscle in the small intestine wall

What papilla is present in only 20% of cats?

minor duodenal papilla

What is the transverse duodenum also called?

caudal flexure of the duodenum

Where is the transverse duodenum?

crosses the median plane mostly along the roof

Where is the ascending duodenum?

on the left side mostly along the roof

What is the term for where the duodenum becomes the jejunum?

duodenojejunal flexure

What does the duodenojejunal flexure look like?

sharp bend

What is the duodeno-colic fold?

fold of mesentery connect the ascending duodenum and descending colon

What does the jejunum look like?

long, coiled loops with a thin, flexible wall

What is the connecting peritoneum of the jejunum?

mesojejunum/jejunal mesentery

What remains free in the abdominal cavity?

jejunum

What part of the small intestine is more ventral?

jejunum

What is the mesentery?

peritoneum that connects the small intestine to the dorsal wall of the

Where do the vessels for the small intestines travel?

through the mesentery

Where would you cut into the small intestine?

where the mesentery doesn't attach becuase less blood vessels

What is the mesenteric side?

side of the organ that the mesentery attaches to

What is the antimesenteric side?

the side of the organ opposite of where the mesentery attaches to

What is the root of the mesentery?

attachment of the mesentery to the dorsal abdomen

What structures may be located towards the root of the mesentery?

jejunal lymph nodes/mesenteric lymph node

What is the shortest component of the small intestine?

ileum

What is the area where the ileum and colon join?

ileocecocolic junction/ileocolic junction

What can be used to demarcate the ileum from the jejunum?

antimesenteric artery

What are the structures in the ileocecocolic junction?

ileal orifice, ileal papilla, ileocolic sphincter

What is the ileal papilla?

projection of the ileum into the ascending colon

What forms the ileocolic sphincter?

circular muscle fibers of the wall

What are the two main arteries coming from the aorta for the small intestines?

celiac and cranial mesenteric arteries

What branch comes from the celiac artery?

gastroduodenal artery

What branch comes from the cranial mesenteric arteries?

jejunal arteries and ileocolic artery

What supplies the jejunum?

jejunal arteries

What supplies the ileum?

ileocolic artery

What are the branches of the gastroduodenal artery?

right gastroepiploic and cranial pancreaticoduodenal artery

What supplies the cranial part of the duodenum?

cranial pancreaticoduodenal artery

What supplies the caudal part of the duodenum?

caudal pancreaticoduodenal artery

Where does the caudal pancreaticoduodenal artery come from?

cranial mesenteric artery

What are some branches of the cranial mesenteric artery?

jejunal arteries and common trunk/ileocolic artery

What do the jejunal arteries form?

jejunal arcades forming a collateral blood circulation

What branches come from the ileocolic artery?

mesenteric ileal artery and cecal branch

What artery comes from the cecal branch?

antimesenteric ileal artery

What are the two main veins draining into the portal vein?

gastroduodenal vein and cranial mesenteric vein

What vein drains into the gastroduodenal vein?

cranial pancreaticoduodenal vein and right gastroepiploic vein

What veins drain into the cranial mesenteric vein?

jejunal vein, ileocolic vein, caudal pancreaticoduodenal vein

Where does sympathethic innervation come from?

thoracic spinal cord (T5-T12)

What nerves are sympathetic innervation from thoracic spinal cord?

greater and lesser splanchnic nerves

Where are the preganglionic fibers synapsing for sympathetic?

prevertebral ganglia

What does the prevertebral ganglia include?

celiac ganglia, cranial mesenteric ganglion

Where does the parasympathetic nerves originate from?

dorsal motor nucleus in the medulla oblongata

What nerve is for parasympathetic?

vagus nerve

What trunk of the vagus nerve supplies the duodenum and pancreas?

ventral vagal trunk

What trunk of the vagus nerve supplies the jejunoileum?

dorsal vagal trunk