Physiology Flashcards
(22 cards)
Time to move chyme from ileocecal valve to rectum?
8-15 hours
Poor motility of colon causes what?
greater absorption and hard feces causing constipation
Excess motility of colon causes what?
less absorption and diarrhea
longitudinal muscle of haustra?
tenia coli (3 aggregates)
Mass movement?
Cecum to sigmoid modified peristalsis that contract as a unit to propel fecal forward, lose haustra
Colon histology?
- crypts of lieberkuhn
- NO villi
- many goblet cells
- mucous with bicarbonate (pH 8) to protect colon and hold fecal together
What activates mucous secretion?
parasympathetics from pelvic nerves to increases peristalsis
Colon absorption? MoA?
- most of the water and ALL ions
- active absorption of Na (ATPase) into ISF causes gradient to pull in Cl- and water follows paracellular and transcellular
- tighter junctions than SI prevents back flow of ions
- aldosterone increases Na reabsorption
- bicarbonate secreted
Max absorption capacity of colon?
5-8L of fluid and electrolytes
what causes diarrhea?
Enteritis
- bacteria causes colon to secrete extra water and electrolytes and mucous
- rapidly moves toward anus to clear bug
Normal flora of colon?
bacilli digests cellulose and produce Vit K, B12, Thiamine, Riboflavin, gases
Gut microbiota functions?
- colon motility
- mucosal integrity
- immune function
- compete with pathogens
- digest food and make nutrients
- influence brain and behavior
Composition of feces?
3/4 water
1/4 solid matter
- bacteria
- fat
- inorganics
- protein
- undigested stuff
- bile and epithelial cells
Brown color of feces?
stercobilin and urobilin from heme metabolism metabolized by colonic bacteria (urobilinogen)
Odor of feces?
products of bacteria
-indole, skatole, mercaptole and hydrogen sulfide
Sphincters of colon?
- Internal anal sphincter
- thick SM inside anus
- involuntary - External anal
- striated voluntary surrounding internal
- Pudendal N.
Reflexes of defecation?
Local enteric NS
- Intrinsic reflex initiated by distention of rectum
- weak signal - afferent signal through myenteric plexus
- peristalsis in descending colon force feces toward anus
- Parasympathetic defecation reflex
- sacral spinal cord sends signals through Pelvic nerves
- internal sphincter relaxed by inhibition - Pudendal N. causes external sphincter to relax
Valsalva maneuver?
- deep breath to move diaphragm down
- contract abdominal muscles to increase pressure
- expire against closed glottis
Gastrocolic reflex?
- stretch signals from stomach to colon to increase colon motility and frequency of mass movements
- rapid parasympathetic caused by stomach stretch
- CCK and Gastrin
Peritoneointestinal reflex?
irritation to peritoneum inhibits excitatory enteric nerves causing intestinal paralysis
Renointestinal reflex?
kidney irritation inhibits intestinal activity
Vesicointestinal reflex?
bladder irritation inhibits intestinal activity
