PBL 4- Large Intestine Flashcards
where does the large intestine extend from
Extends from the caecum to the anal canal
what is the function of large intestine
receives digested food from the small intestine, from which it absorbs water +electrolytes to form faeces
what is large intestine’s total length
150 cm
what are the parts of the large intestine
Ascending colon
Transverse colon- intraperitoneal, enclosed by transverse mesocolon
Descending colon
Sigmoid colon- attached to thepelvic wall by the sigmoid mesocolon
what is the hepatic flexure
the start of transverse mesocolon
what is the splenic flexure
attached to spleen and start of descending colon
colon attaches here to the diaphragm by the phrenicolic ligament
what are the paracolic gutters
two spaces between ascending and descending colon. allows passage for infectious fluids from different compartments of the abdomen
what are the omental/epiploic appendices
small pouches of peritoneum, filled with fat
what are the teniae coli
3 strips of muscle that run longitudinally along the surface of the large intestine
what are haustra
Teniae coli contract to shorten the wall of large intestine, producing sacculations known as haustra
what is the blood supply of the large intestine
- (midgut) ascending colon + proximal 2/3 of the transverse colon- superior mesenteric artery
- (hindgut) distal 1/3 of transverse colon + descending colon + sigmoid colon- inferior mesenteric artery
what is the caecum
1st part of the LI, connects to ileum through the ileocaecal valve
what is the vermiform appendix/ appendix
worm like tube which opens into the caecum and position is variable
what is the rectum
Downward continuation of the sigmoid canal, continues to anal canal
what is the anal canal and what muscles does it have
Downward continuation of the rectum that ends in the anus. has external and internal sphincters.
External- skeletal muscle and under voluntary control
Internal- smooth muscle and under involuntary control
what type of cells are found in the large intestine
- absorptive cells (enterocytes)- responsible for absorption of mainly water and electrolytes
- goblet cells- synthesise alkaline mucous that lines mucosal wall and protects it from acidic enzymes
what are the walls of the LI lined with
lined with simple columnar epithelium with invaginations. The invaginations are called the intestinal glands or colonic crypts.
does LI have villi
no villi
Large intestine has ___ typical pacemaker activity
no
how does the LI mix material
since it functions to absorb water, it mixes material without propulsion
what is the purpose of haustrations
segmentation movements that mix the contents of the adjacent haustra. The purpose of haustration seems to be to squeeze and roll the faecal material around so that every portion of it is exposed to the absorptive surfaces of the colonic mucosa, thus aiding the absorption of water and electrolytes
Since LI does not have a typical pacemaker activity, what does it have then and what controls it?
mixture of short + long duration contractions controlled by parasympathetic activity
what are the other roles of colon (other than water absorption)
Act as a storage site
Cause aboral movement of content.
Expel faeces