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Kaplan: GI system > GI physiology: stomach, small/large intestine > Flashcards

GI physiology: stomach, small/large intestine Flashcards

1
Q

What are the 3 layers and function of stomach smooth muscle?

A

longitudinal=>outer, for peristalsis
circular=> for mixing
oblique=> inner

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2
Q

What structures can the stomach be divided into?

A

fundus, body, antrum

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3
Q

how and where does receptive relaxation occur?

A

mediated by VIP occurs in fundus

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4
Q

how is the receptive relaxation work as the stomach fills?

A

a vagovagal-mediated receptive relaxation occurs allowing storage

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5
Q

Before reaching the small intestine, what happens to the bolus of swallowed food?

A

it is macerated and mixed w/ HCl, mucus, and pepsin => chyme => discharged at controlled rate

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6
Q

How much chemical digestion occurs in the stomach?

A

very small amount

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7
Q

How and where does the pacemaker of the stomach work?

A

w/in greater curvature produces basal electric rhythm (BER) of 3-5 waves/min

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8
Q

What controls the magnitude of the gastric contractions?

A

increased by PANS;

decreased by SANS

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9
Q

define migrating motor complexes (MMC)

A

propulsive contractions initiated during fasting that begin in stomach and move undigested material from stomach and small intestine into colon

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10
Q

what mediates the migrating motor complexes?

A

motilin => repeat every 90-120min

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11
Q

why are migrating motor complexes important for general health?

A

this is a housekeeping function that lowers the bacterial count in the gut

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12
Q

what is the pylorus

A

continuous w/ circular muscle layer;

acts as “valve” to control gastric emptying

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13
Q

What limits the movement of chyme into duodenum and promotes retropulsion?

A

pyloric sphincter contraction at time of antral contraction

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14
Q

define retropulsion WRT gastric emptying

A

mixing by forceful regurgitation of antral contents back into fundus

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15
Q

What delays gastric emptying?

A
  • fat/protein in duodenum stimulating CCK release=> increases gastric distensibility
  • H+ in duodenum via neural reflexes
  • stomach contents that are hypertonic or hypotonic
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16
Q

what is the primary role of the small intestine?

A

digestion and absorption of nutrients via specialized villi on epithelial surface

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17
Q

What is the order of structures of the duodenum?

A

duodenum=> proximal pyloric end
jejunum
ileum

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18
Q

Mucus production occurs throughout the GI tract. What produces it in the small intestine?

A 
Brunner glands=> duodenum
Goblet cells => throughout intestine
19
Q

What are the functions of mucus?

A

lubrication of GI tract;
binding bacteria;
trapping Ig

20
Q

What may INCREASE rate of mucus secretion?

A

choinergic stimulation;
chemical irritation;
physical irritation

21
Q

How are gastritis, duodenitis and some peptic ulcer diseases related to small intestine?

A

any compromise of mucous protection can lead to damage and irritation

22
Q

regarding intestinal motility, how do small bowel slow waves move?

A

move caudally in circular smooth muscle => slows more distally

23
Q

what are the importance of segmentation contractions?

A

ring-like contractions that MIX INTESTINAL CONTENTS => occur at nodes along intestine

24
Q

define peristalsis

A

reflex response initiated by stretching of lumen of gut => propel contents caudally

25
Q

what modulates peristalsis?

A

autonomic input;

can occur in isolated loops of small bowel w/ no extrinsic innervation

26
Q

give the steps to peristalsis occurring

A

intrinsic control system senses stretch w/ CGRP;
contractile wave initiated by ACh and substance P;
relaxation caudal to stimulus initiated by NO & VIP

27
Q

what controls the contractions of the small intestine?

A

PANS increases;

SANS decreases

28
Q

How is small intestinal contents delivered to large intestine?

A

gastroileal reflex caused by food in stomach => stimulates peristalsis in ileum =>
relaxes ileocecal valve

29
Q

Why are small intestinal secretions alkaline?

A

neutralize acid nature of chyme from pylorus

30
Q

Since PANS activates peristalsis, what can be given for a dysfxn of PANS leading to constipation?

A

dopaminergic and cholinergic agents

31
Q

What muscles constitute the outer layer of the colon?

A

3 longitudinal bands of muscle => teniae coli

32
Q

How are haustra created?

A

colon is longer than teniae coli so haustra are created for them to fit

33
Q

How is mucus secreted in large intestine?

A

short, inward-projecting colonic glands => NO VILLI

34
Q

What are important immunological areas of the colon?

A

abundant lymphoid follicles => cecum and appendix

35
Q

Major fxns of colon

A

reabsorption of fluid and electrolytes;

temporary storage of feces

36
Q

What promotes movement of chyme in the colon?

A

peristaltic waves => increase speed distally

37
Q

What type of contractions are found only in the colon?

A

mass movement contractions

38
Q

What is the defecation reflex?

A

distention of rectum w/ feces

39
Q

What are important electrolytes that the large colon is responsible for absorbing?

A

Na+ actively transported w/ water following it;

K+ and HCO3 secreted into colon

40
Q

in normal feces, what % may be bacterial?

A

30%

41
Q

Why are bacteria a large portion of feces?

A

synthesize VITAMIN K, B-complex vitamins, folic acid;
split urea to NH3;
produce small organic acids from unabsorbed fat and carbohydrate

42
Q

How does PANS causes defecation feeling?

A

rectal distention w/ feces activates intrinsic and cord reflexes causing relaxation of internal anal sphincter

43
Q

What will lead to defecation actually occurring?

A 
pudendal nerve causes external anal sphincter to relax;
Valsalva maneuver (increased intra-abdominal pressure) leads to defecation
44
Q

What controls the gastrocolic reflex and what is its relation to defecation?

A

PANS=> distention of stomach by food INCREASES FREQUENCY OF MASS MOVEMENTS and produces urge to defecate

Kaplan: GI system (11 decks)

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