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Flashcards in Small Intestine Function Deck (13)
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1
Q

BER

A

Rate decreases as you move distally

It is a property of the smooth muscle in that region

2
Q

How are stomach and SI rhythm linked?

A

By distention reflexes and continuity of the longitduinal layer of muscle across pyloric sphincter

Segmentation due to circular smooth muscle contraction - piramry mixing mvmnt

Chyme moves in both directions but net movement is aboral bc pressure graident established by higher intrinsic rate int he duodenum

Mvmt via short peristaltic waves

3
Q

How are propulsion and mixing related

A

Feeding inc molity but can dec propulsive action

Morphine inc tonic tone of gut which dec average size of lumen and dec flow…this results in inc water reabsroptiin and pot constipation

4
Q

Interdigestive complex

A

Stimulated by motilin

Causes intermittent periods of contraction

5
Q

Neural and hormonal regulation

A

Vagal and celiac/superior mesenteric ganglia - changes of rate of BER

Local reflexes - distention act mechanos which result in ENS reflex to - proximally contract circular layer of smooth muscle (Ach and sub P) and relax distally (VIP and NO) (while contracting long)…mostly through myenteric plexus

Regional reflexes - if sensory upstream then move aborally…if sensor downstream, then dec upstream fxn

6
Q
Intestinointestinal reflex
Gastroenteric reflex
Ileogastric
Gastroilial 
Gastrocolic
A

Extrinsic innervation…overdistension of one part causes relaxation of the raminader

Gastric distension inc intestinal peristaltic activity

Distension of ileum dec gastric motility and gastric emptying

Inc in stomach motility cause inc ileal motility and inc emtytihng of intestine

Inc stomach fxn leads to inc colonic activity…resulting in MMC contraction which triggers urge to defacate

7
Q

Hormonal

A

Gastrin - positive effect ot inc motility

CCK - weak gastrin-like action…also competes with gastrin receptors

Secretin - dec stomach secretions except pepsinogen

8
Q

Villi movements

A

Musc mucosa contracts irregularly about 3 times/min

Individual villi also contract

Both stmulated by local reflexes from tactile and distension…villikinin from mucsoal cells

Countercurrent exchange - hypoxia at tip leads to inc cell turnoved…ischemic bowel dz

9
Q

Ileocecal valve

A

Normally closed

Short wave into small intestine immediately orad to vavle causes relaxation

As chyme flow into cecum, distension causes contraction

Tone and opening of the ICV are controlled by intramural plexus supplemented by gastroileal reflex

This regulates absorption

10
Q

INtestinal secretions

A

Most of serous from proximal intestine due to rapidly inc osmolarity bc of carb digestion by pancreatic amylase

Mucus - released by golbet cells by processes of exfoliation and exocytosis…inc by PNS, secretin, tactile reflexes…low level by SNS

Electrolytes - plasma ultrafiltrate with neutral pH…serves as vehile for reabsorption….inc during digestive phase

Hormones - GEP cells in the intertinal mucosa release secretin (inc electrolyic) and CCK (inc enzymatic and bile salt release)

11
Q

Enzymatic secretion of small intestine

A

Enteropeptidases
Intestinal amylase

Brush border - peptidases (exopeptidase and endopeptidase)
Diasaccharidases
Lipases

12
Q

Regulation of intestinal fxn

A

Dysfunction - cholera toxin leads to excessive secretion due to Cl mediated secretion

Osmotic - pulls water into lumen due to particales and osmolairyt in the lumen

Hypermotile - not enough time to absorb

Hypomotile - not enough mixing to dec sitance for diffusion

Secretory - pumps osmotic particles into the lumen which then draws water

13
Q

GI digestion and absorption

A

IC - phagocytosis and lysosome
EC - exocytotic release
BB enzymes

Typical strucutre of absorptive enterocyte - short life span…part of villus structure contains goblet cells…dense array of microvilli on apical membrane….covered by a glycocalyx…unstirred layer of fluid overtop of glycocalyx