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PHYSIOLOGY GIS > LEC 5 > Flashcards

LEC 5 Flashcards

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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
entro-gastric reflexes have two effects on stomach emptying
First, they strongly inhibit the “pyloric pump” propulsive contractions, and Second, they increase the tone of the pyloric sphincter
26
entro-gastric reflexs are mediated by three routes
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.
27
normal excitatory signals transmitted to the stomach through
vagi
28
Hormonal feedback from the duodenum inhibits gastric emptying
1. CCK 2. GIP 3. secretin
29
The degree of fluidity of the chyme leaving the stomach depends on
food,  water, and stomach secretions and on the degree of digestion that has occurred
30
effect of CCK on gastric emptying
inhibition
31
CCK can inhibit gastric emptying when
a. excess quantities of chyme | b. acidic or fatty chyme,
32
Secretin released from the duodenum in response to
acid
33
Chyme
After food in the stomach has become thoroughly mixed with the stomach secretions, the resulting mixture that passes down the gut
34
The appearance of chyme
murky semifluid or paste معجون.
35
Motility of Fasted Stomach
1. Migrating Motor Complex (MMC) | 2. Hunger Contractions
36
Periodic phasic contraction occurring at
regular and low frequency, once /6-20 min
37
Function of MMC
1) It clears stomach from indigestible residues. | 2) It prevents duodeno-gastric reflux
38
Migrating Motor Complex (MMC) Mechanism
strength is increased by motilin hormone
39
Emotions can influence gastric motility:
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
Sadness and fear tend to
decrease motility
41
Anger and aggression tend to
increase motility
42
Intense pain from any part of the body tends to
tends to inhibit motility> response of increased sympathetic activity
43
Progesterone effects on gastric emptying
a. relaxes smooth muscle b. inhibits gastric smooth muscle c. creating incompetence of the lower esophageal sphincter leading to gastroesophageal sphincter disease
44
effect of gastrin produced by the placenta
increases gastric motility and secretion which may explain Gastric acid production during the third trimester
45
explain Gastric acid | production during the third trimester
gastrin is produced by the placenta
46
Elderly
decrease gastric secretion and emptying
47
the glands contains the following cells
Parietal (oxyntic) cells: ii. Chief (peptic) cells: iii. Neck mucous cells: iv. Entrochromaffin (EC) cell: v. G cell: vi. D cell:
48
Parietal (oxyntic) cells: secret
1.hydrochloric acid and intrinsic factor.
49
Chief (peptic) cells secret
pepsinogen
50
Neck mucous cells: secret
mucous
51
Entrochromaffin (EC) cell
Histamine
52
G cell:
Gastrin
53
D cell
somatostatin
54
Oxyntic gland
in the body region; contains Chief cell, D cell and Parietal cell, Entrochromaffin cell, mucous neck cell
55
Pyloric gland
in the pyloric region; contains Entrochromaffin cell, D cell, and G cell , mucous neck cell
56
The mucus is also secreted along with
HCO3 − by mucus cells on the surface of epithelium between glands
57
The stomach absorbs
alcohol and aspirin but no food no water
58
Alcohol
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
Acetylsalicylic (aspirin).
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
Mucous cells secrete
thin, watery mucus
61
Mucus serves as a
protective barrier against several forms of potential injury to the gastric mucosa
62
how Mucus serves as a protective barrier
1.lubricating properties→ no mechanical injury. 2.protect the stomach wall from self-digestion 3.alkaline →protect against acid injury
63
how protect the stomach wall from self-digestion
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
The cells of the gastric glands secrete about
2500mL
65
Gastric secretion includes
hydrochloric acid, pepsin, and intrinsic factor.
66
The substance intrinsic factor is a
49-KDa glycoprotein
67
The substance intrinsic factor is secreted by
the parietal cells
68
When parietal cells of the stomach are destroyed
1. achlorhydria | 2. pernicious anemia
69
achlorhydria
lack of stomach acid secretion
70
``` the Chief (peptic) cells of the oxyntic glands secreted ```
pepsinogen
71
pepsinogen + hydrochloric acid,=
active pepsin
72
pepsinogen molecular weight
42,500
73
pepsin molecular weight
35,000
74
Pepsin functions
proteolytic enzyme at pH 1.8 to 3.5) 2.Pepsinogen acts as a signal for release gastrin and cholecystokinin.
75
pH of about 5
no proteolytic activity
76
Mucosal barrier
``` The mucus gel layer (extrinsic barrier) gastric mucosa (intrinsic barrier) ```
77
mucosal barrier function
protects gastric and duodenal mucosa against the damaging effect (auto-digestion) of gastric juice
78
The mucus gel layer visible layer
several millimeters thick over | the surface of the mucosa above gastric mucus membrane
79
The mucus gel layer composed of
mucus | Bicarbonate
80
Mucus is secreted by
neck cells of gastric gland and | surface mucosal cells
81
Mucus is
slimy" لزجmaterial that coats epithelial surfaces of stomach
82
Mucus is composed chiefly of
mucins and | inorganic salts
83
Mucins are
large, heavily glycosylated proteins
84
Mucins are located
on the surface of the stomach cavity
85
main components of the gastric mucosa epithelial mucus layer.
Mucins
86
Secretion of gastric mucin increases
i. by vagal stimulation ii. by irritant foods. iii. by some prostaglandins
87
Mucins structure
trefoil peptides
88
hh
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
Bicarbonate secreted by
surface mucosal cells
90
Bicarbonate
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
luminal membranes of the gastric mucosal cells are almost impermeable to
H+→acid cannot penetrate into the cells and damage them
92
the gastric mucosal cells joined together near their luminal borders by
tight junctions →acid cannot diffuse between the cells from the lumen into the underlying submucosa.
93
gastric mucosa entire stomach lining is replaced every
three days
94
rapid mucosal turnover
cells are usually replaced before they are exposed to the wear and tear of harsh gastric conditions
95
The daughter cells that result from cell division
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
When the barrier occasionally is broken
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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