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PHYSIOLOGY GIS > LEC 5 > Flashcards

LEC 5 Flashcards

1
Q

Gastric factors that promote emptying

A
  1. The amount of chyme in the stomach.
  2. The degree of fluidity of the chyme
  3. Type of food ingested (present in the stomach)
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2
Q

The amount of chyme in the stomach

A

1.↑food volume in the stomach→↑emptying
from the stomach
2.tension in stomach wall >stimulus for peristalsis

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3
Q

The degree of fluidity of the chyme in the stomach

A

increase fluidity influences gastric emptying.

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4
Q

Type of food ingested (present in the stomach)

A

a) Carbohydrate
b. Protein
c. Fat

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5
Q

Type of food causes rapid gastric emptying

A

Carbohydrate

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6
Q

Type of food ingested causes slow gastric emptying

A

Protein

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7
Q

Type of food ingested causes slowest gastric emptying

A

Fat

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8
Q

The rate of emptying of a high-fat meal is

A

six hours

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9
Q

The rate of emptying of a protein and carbohydrate meal is

A

three hours.

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10
Q

high protein food especially meat stimulate release of

A

gastrin

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11
Q

Duodenal factors that inhibits stomach emptying

A
  1. The presence of any degree of irritation of the duodenal mucosa
  2. The degree of distension of the duodenum
  3. The degree of acidity of the duodenal chyme.
  4. The degree of osmolality of the chyme
  5. Type of food.
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12
Q

The degree of distension of the duodenum

A

Slow or even stop stomach emptying if the volume of chyme in the duodenum
becomes too much

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13
Q

The degree of acidity of the duodenal chyme

A

Acid un-neutralized acid in the duodenum inhibits further empty
↑ acid → ↓ emptying of acidic
gastric contents

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14
Q

enterogastric means

A

from duodenum to stomach

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15
Q

enterogastric inhibitory reflexes

A

sensitive to the presence of irritants and acids in the duodenal chyme
2.activated within as little as 30 seconds

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16
Q

the reflexes when the chyme in the duodenum falls below about 3.5 to 4

A

block release of acidic stomach contents

2.pancreatic enzyme

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17
Q

The rate of gastric emptying is fastest when the stomach contents are

A

isotonic

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18
Q

The rate of gastric emptying is slowed when the stomach contents

A

hypertonic or hypotonic

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19
Q

The hypo-osmolar chyme in duodenum causes

A

distention of osmo-receptor, which causes mild inhibition of gastric emptying

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20
Q

hyperosmolar chyme in duodenum causes

A

shrinkage of osmo-receptor, which causes marked inhibition of gastric emptying.

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21
Q

Type of food.

A

When glucose, fat, or amino meet the duodenal mucosa inhibitory mechanisms decrease the fundic pressure and thereby slow the gastric emptying of nutrients.

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22
Q

Hyper-tonicity:

A

Large volumes of water entering the intestine from the plasma lead to intestinal distension,
more importantly, circulatory disturbances ensue كلب علبى يترتبbecause of the reduction in plasma
volume.
To prevent these effects, gastric emptying is reflexly inhibited when the osmolarity of the duodenal
content starts to rise.

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23
Q

The possible mechanism of duodenal factors that inhibits stomach emptying

A

↓entro-gastric reflex):

• Hormonal feedback from the duodenum inhibits gastric emptying

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24
Q

slow or even stop stomach emptying

A
  1. multiple nervous reflexes

2. the volume of chyme

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25
Q

entro-gastric reflexes have two effects on stomach emptying

A

First, they strongly inhibit the “pyloric pump” propulsive contractions, and
Second, they increase the tone of the pyloric sphincter

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26
Q

entro-gastric reflexs are mediated by three routes

A

1.directly from the enteric nervous system in the gut wall
2.extrinsic nerves→ the pre-vertebral sympathetic ganglia →back through
inhibitory sympathetic nerve fibers to the stomach
3.vagus nerves→ brain stem→ ↓ the normal excitatory signals transmitted to the stomach through the vagi.

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27
Q

normal excitatory signals transmitted to the stomach through

A

vagi

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28
Q

Hormonal feedback from the duodenum inhibits gastric emptying

A
  1. CCK
  2. GIP
  3. secretin
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29
Q

The degree of fluidity of the chyme leaving the stomach depends on

A

food,
 water, and
stomach secretions and on the
degree of digestion that has occurred

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30
Q

effect of CCK on gastric emptying

A

inhibition

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31
Q

CCK can inhibit gastric emptying when

A

a. excess quantities of chyme

b. acidic or fatty chyme,

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32
Q

Secretin released from the duodenum in response to

A

acid

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33
Q

Chyme

A

After food in the stomach has become thoroughly mixed with the stomach secretions, the resulting
mixture that passes down the gut

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34
Q

The appearance of chyme

A

murky semifluid or paste معجون.

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35
Q

Motility of Fasted Stomach

A
  1. Migrating Motor Complex (MMC)

2. Hunger Contractions

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36
Q

Periodic phasic contraction occurring at

A

regular and low frequency, once /6-20 min

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37
Q

Function of MMC

A

1) It clears stomach from indigestible residues.

2) It prevents duodeno-gastric reflux

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38
Q

Migrating Motor Complex (MMC) Mechanism

A

strength is increased by motilin hormone

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39
Q

Emotions can influence gastric motility:

A
  1. Sadness and fear
  2. Anger and aggression
  3. Intense pain
  4. Pregnancy
  5. Elderly
  6. Disease states e.g. diabetes mellitus (autonomic neuropathy), post -operative bowel surgery with resultant ileus
40
Q

Sadness and fear tend to

A

decrease motility

41
Q

Anger and aggression tend to

A

increase motility

42
Q

Intense pain from any part of the body tends to

A

tends to inhibit motility> response of increased sympathetic activity

43
Q

Progesterone effects on gastric emptying

A

a. relaxes smooth muscle
b. inhibits gastric smooth muscle
c. creating incompetence of the lower esophageal sphincter leading to gastroesophageal sphincter disease

44
Q

effect of gastrin produced by the placenta

A

increases gastric motility and secretion which may explain Gastric acid
production during the third trimester

45
Q

explain Gastric acid

production during the third trimester

A

gastrin is produced by the placenta

46
Q

Elderly

A

decrease gastric secretion and emptying

47
Q

the glands contains the following cells

A

Parietal (oxyntic) cells:

ii. Chief (peptic) cells:
iii. Neck mucous cells:
iv. Entrochromaffin (EC) cell:
v. G cell:
vi. D cell:

48
Q

Parietal (oxyntic) cells: secret

A

1.hydrochloric acid and intrinsic factor.

49
Q

Chief (peptic) cells secret

A

pepsinogen

50
Q

Neck mucous cells: secret

A

mucous

51
Q

Entrochromaffin (EC) cell

A

Histamine

52
Q

G cell:

A

Gastrin

53
Q

D cell

A

somatostatin

54
Q

Oxyntic gland

A

in the body region; contains Chief cell, D cell and Parietal cell, Entrochromaffin cell, mucous neck cell

55
Q

Pyloric gland

A

in the pyloric region; contains Entrochromaffin cell, D cell, and G cell
, mucous neck cell

56
Q

The mucus is also secreted along with

A

HCO3
− by mucus cells on the
surface of epithelium between glands

57
Q

The stomach absorbs

A

alcohol and aspirin but no food no water

58
Q

Alcohol

A

lipid soluble>diffuse through the lipid membranes of the epithelial cells that line the stomach >can enter the blood through the sub-mucosal capillaries

59
Q

Acetylsalicylic (aspirin).

A

In the highly acidic environment of the stomach lumen, weak acids are
lipid soluble, so they can be absorbed quickly by crossing the plasma membranes of the epithelial
cells that line the stomach

60
Q

Mucous cells secrete

A

thin, watery mucus

61
Q

Mucus serves as a

A

protective barrier against several forms of potential injury to the gastric mucosa

62
Q

how Mucus serves as a protective barrier

A

1.lubricating properties→ no mechanical
injury.
2.protect the stomach wall from self-digestion
3.alkaline →protect against acid injury

63
Q

how protect the stomach wall from self-digestion

A

pepsin is inhibited when it comes in
contact with the mucus layer coating the stomach lining. (However, mucus does not affect pepsin
activity in the lumen, where digestion of dietary protein proceeds without interference.

64
Q

The cells of the gastric glands secrete about

A

2500mL

65
Q

Gastric secretion includes

A

hydrochloric acid, pepsin, and intrinsic factor.

66
Q

The substance intrinsic factor is a

A

49-KDa glycoprotein

67
Q

The substance intrinsic factor is secreted by

A

the parietal cells

68
Q

When parietal cells of the stomach are destroyed

A
  1. achlorhydria

2. pernicious anemia

69
Q

achlorhydria

A

lack of stomach acid secretion

70
Q 
the Chief (peptic) cells of the oxyntic 
glands secreted
A

pepsinogen

71
Q

pepsinogen + hydrochloric acid,=

A

active pepsin

72
Q

pepsinogen molecular weight

A

42,500

73
Q

pepsin molecular weight

A

35,000

74
Q

Pepsin functions

A

proteolytic enzyme at pH 1.8 to
3.5)
2.Pepsinogen acts as a signal for release
gastrin and cholecystokinin.

75
Q

pH of about 5

A

no proteolytic activity

76
Q

Mucosal barrier

A 
The mucus gel layer (extrinsic barrier)
gastric mucosa (intrinsic barrier)
77
Q

mucosal barrier function

A

protects gastric and duodenal mucosa against the damaging effect (auto-digestion) of gastric juice

78
Q

The mucus gel layer visible layer

A

several millimeters thick over

the surface of the mucosa above gastric mucus membrane

79
Q

The mucus gel layer composed of

A

mucus

Bicarbonate

80
Q

Mucus is secreted by

A

neck cells of gastric gland and

surface mucosal cells

81
Q

Mucus is

A

slimy” لزجmaterial that coats epithelial surfaces of stomach

82
Q

Mucus is composed chiefly of

A

mucins and

inorganic salts

83
Q

Mucins are

A

large, heavily glycosylated proteins

84
Q

Mucins are located

A

on the surface of the stomach cavity

85
Q

main components of the gastric mucosa epithelial mucus layer.

A

Mucins

86
Q

Secretion of gastric mucin increases

A

i. by vagal stimulation
ii. by irritant foods.
iii. by some prostaglandins

87
Q

Mucins structure

A

trefoil peptides

88
Q

hh

A

Mucins form a barrier as apart of mucosal defense system that protects
gastric epithelial cells against chemical, enzymatic, microbial, and
mechanical damage.
The hydrochloric acid crosses this barrier in finger-like channels, leaving
the gel layer intact.

89
Q

Bicarbonate secreted by

A

surface mucosal cells

90
Q

Bicarbonate

A

is trapped in the mucus gel, so that a pH gradient is established that ranges
from pH 1.0 to 2.0 at luminal side to pH 6.0 to 7.0 at the surface of epithelial cells.
Prostaglandins stimulate mucus and bicarbonate secretion

91
Q

luminal membranes of the gastric mucosal cells are almost impermeable to

A

H+→acid cannot penetrate into the cells and damage them

92
Q

the gastric mucosal cells joined together near their luminal borders by

A

tight junctions →acid cannot diffuse between the cells from the lumen into the underlying submucosa.

93
Q

gastric mucosa entire stomach lining is replaced every

A

three days

94
Q

rapid mucosal turnover

A

cells are usually replaced before they are exposed to the wear and tear of harsh gastric conditions

95
Q

The daughter cells that result from cell division

A
  1. migrate out of the pit to become surface epithelial cells

2. migrate down deeper to the gastric glands, where they differentiate into chief or parietal cells

96
Q

When the barrier occasionally is broken

A

the gastric wall is injured by its acidic and
enzymatic contents
↓
an erosion, or peptic ulcer, of the stomach wall results.

PHYSIOLOGY GIS (17 decks)

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