Lesson 85 - Structure of Large Intestine

What are the parts of the large intestine?

colon, rectum, cecum

Where is the large intestine?

along the roof of the abdominal cavity

What are the folds associated with the large intestine?

ileocecal fold, cecocolic fold, duodenocolic fold

What type of animals absorb more water in their large intestine?

species with large fermentation chamber

What cells secrete mucus in the large intestine?

goblet cells

What is the function of bicarbonate in the large intestine?

neutralize acidic fermentation products

Where is most gas in the horses produced?

hindgut

How is gas expelled from large intestine?

flatulence

What is the cecum?

blind sac

What does the cecum open into?

one opening into the ascending colon

What is present at the ceco-colic opening?

ceco-colic sphincter

What does the cecum in cats look like?

straight non-twisted

What does the cecum in dogs look like?

twisted

What is the importance of the dog cecum being twisted?

can trap gas

Where is the cecum located?

on the right side near the abdominal roof

What is the colon?

part of the large intestine located between the ileum and rectum

What is the mesentery called that is covering colon?

mesocolon

What is the duodenocolic fold?

tissue connecting ascending duodenum and descending colon

What are the parts of the colon?

ascending colon, transverse colon, descending colon

Where is the ascending colon?

dorsal to the right of the root of the mesentery

What is the right colic/hepatic flexure?

turn of colon between the ascending colon and transverse colon

Where is the transverse colon?

dorsal cranial to the root of the mesentery

What is the left colic/splenic flexure?

turn of the colon between the transverse and descending colon

Where is the descending colon?

dorsal on the left side until it enters the pelvis

What is the rectum?

caudal most dilated part of the large intestine

Where does the rectum begin?

pelvic inlet

What is important about the rectum and peritoneum?

part of it is retroperitoneal

What is the mesentery covering the rectum called?

mesorectum

What is the caudal part of the rectum?

anal canal

What does the mesorectum attach to and create?

roof of the pelvic cavity, creating pararectal fossa on either side

What are the zones of the anal canal?

columnar, intermediate, cutaneous zone

What does the intermediate zone contain?

anocutaneous line

What is the terminal opening of the alimentary canal?

anus

What is the anus gaurded by?

external and internal anal sphincters

What sphincter will also squeeze the anal glands when contracted?

external anal sphincter

What type of muscle makes up the internal anal sphincter?

smooth muscle

What type of muscle makes up the external anal sphincter?

skeletal muscle

What are the paranal sinuses?

anal glands

Where are the anal glands located?

between the external and internal anal sphincters

What type of secretions do the paranal sinuses release?

sebaceous secretions

What is the purpose of the paranal sinuses?

territory marking

Which gland is the 8 o'clock gland?

left gland

Which gland is the 4 o'clock gland?

right gland

What arteries coming off the aorta are the main blood supply for the large intestine?

cranial and caudal mesenteric artery

What branch comes off the cranial mesenteric for large intestine?

ileocolic artery

What branches come off the ileocolic artery?

middle colic, right colic, colic branch, cecal branch

What does the ileocolic artery continue as when the cecal branch comes off?

mesenteric ileal artery

What branch supplies the ascending colon?

colic branch

What branch supplies the right colic flexure?

right colic artery

What branch supplies the left colic flexure?

middle colic artery

What branch supplies the beginning of the descending colon?

left colic artery

What are the branches of the caudal mesenteric artery?

left colic and cranial rectal arteries

What branch supplies the rectum from the caudal mesenteric artery?

cranial rectal artery

What are the blood supplies to the rectum?

cranial rectal, middle rectal, caudal rectal

What does the middle rectal artery branch off of?

prostatic/vaginal artery

What does the caudal rectal artery branch off of?

internal pudendal artery

What does the prostatic/vaginal artery branch from?

internal pudendal artery

What does the internal pudendal artery branch from?

internal iliac artery

What veins drain directly into the caudal vena cava?

caudal and cranial rectal vein

Where do the sympathetic nervous fibers originate from?

thoracic spinal cord to sympathetic trunk

What sympathetic nerves travel from the sympathetic trunk?

greater and lesser splanchnic nerves

Where do the greater and lesser splanchnic nerves synapse?

caudal and cranial mesenteric ganglion

What sympathetic nerve travels from the caudal and cranial mesenteric ganglion to the large intestine?

hypogastric nerve

What does the hypogastric nerve innervate?

descending colon and rectum

Where do the parasympathetic fibers originate from?

dorsal motor nucleus in the medulla oblongata

What is the parasympathetic nerve from medulla?

vagus nerve which branches into dorsal and ventral vagal trunks

What vagal trunks supply the large intestine?

dorsal

What does the dorsal vagal trunk innervate?

ascending and transverse colon

What parasympathetic nerve innervates the descending colon and rectum?

pelvic nerves

Where do the pelvic nerves originate from?

sacral segments of the spinal cord

How is the large intestine modified in ruminants and pigs?

larger cecum, ileum opens into the cecum, spiral colon

How is the large intestine modified in horses?

cecum is very large, ileum opens into cecum, ascending colon is modified into four large segments

What are the inward coils?

centripetal

What are the outward coils?

centrifugal

What is the point where the inward turns to outward coils?

central flexure

What are the loops of the ascending colon in ruminants?

proximal and distal loop

Where is the large intestine in ruminants?

supraomental recess; on right side

What are the parts of the cecum?

body, apex, base

What does the cecum look like in ruminants?

cylindrical, long, tubular, smooth

How many turns do ruminant spiral colon have?

2.5

How many turns/gyri do goat spiral colons have?

4

How many turns/gyri do sheep spiral colons have?

3

Where is the cecum located in pigs?

dorsal to the cone of ascending colon

What structures are seen on pig cecums?

taeniae and haustra

What are haustra?

sacculations

What are taeniae?

tendinous bands

What does the ascending colon of pigs look like?

conical spiral, with centripetal coils sacculated

Where is the apex of the ascending colon in pigs?

ventral

Where is the ascending colon in pigs?

left side of median plane