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Digestion > 2A: Anatomy & Physiology of the Stomach > Flashcards

2A: Anatomy & Physiology of the Stomach Flashcards

1
Q

Where is the stomach located?

A

The stomach is a muscular organ located on the left side of the upper abdomen.

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2
Q

What are the main 4 regions of the stomach?

A

1) Cardia
2) Fundus
3) Body
4) Pylorus (pyloric antrum + pyloric canal)

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3
Q

What are the 2 sphincters of the stomach ?

A

1) LES

2) Pyloric

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4
Q

Describe the gross anatomy of the stomach

A
  • a lesser curvature located on inner portion
  • a greater curvature on outer portion
  • cardiac notch at the top
  • duodenum at the bottom of pyloric canal
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5
Q

What are the 3 layers to the muscularis externa?

A

1) Outermost longitudinal layer
2) Middle circular layer
3) innermost oblique layer

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6
Q

What property allows the stomach to contain acids and enzymes without having its wall digested ?

A

The stomach “lining” or mucosa usually is impermeable to the gastric juice it secretes

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7
Q

What is the most important factor that contributes to the protection of the gastric mucosa?

A

Layer of alkaline MUCUS—> GASTRIC MUCOSAL BARRIER

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8
Q

What role do prostaglandins play?

A

Role in protecting the stomach mucosa from injury by enhancing mucus production

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9
Q

What is the pH of gastric juice and cells at the surface?

A

pH of gastric juice = 2

pH of cells at surface=7

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10
Q

Describe the histology of the mucosal surface?

A

Simple columnar epithelium that is dotted w. millions of deep channels called GASTRIC PITS

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11
Q

what are GASTRIC GLANDS?

A

Gastric pits which are lined w/ columns of specialized cells called GASTRIC GLANDS (fundic)

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12
Q

What are Gastric folds also known as?

A

Rugae

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13
Q

What do Mucous neck cells do?

A

Secrete alkaline mucus

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14
Q

What do Parietal cells do?

A

secrete HCL & Intrinsic factor (IF)

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15
Q

What do Chief cells do?

A

secrete pepsinogen & gastric lipase

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16
Q

What do Endocrine cells do?

A

Some secrete GASTRIN (G cells); others secrete HISTAMINE (ECL cells)

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17
Q

Within a gastric gland describe the cells top to bottom

A

1) Surface lining cells
2) Regenerative cells
3) Mucus neck cells
4) Oxyntic (parietal) cells
5) Zymogenic (chief) cells
6) Enteroendocrine cells

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18
Q

What are the possible damaging forces of Normal gastric glands?

A
  • Gastric acidity

- Peptic enzymes

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19
Q

What are defensive forces against normal damaging forces?

A
  • Surface mucus secretion
  • Bicarb secretion into mucus
  • Mucosal blood flow
  • Apical surface memb. transport
  • Epithelial regenerative capacity
  • Elaboration of prostaglandins
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20
Q

What can cause injury?

A
  • H. pylori infections
  • NSAIDs
  • Aspirin
  • Alcohol
  • Cigarettes
  • Gastric hyperacidity
  • Duodenal-gastric reflux
21
Q

The cells of the ________ ___________ secrete about 2500ml of gastric juice daily

A

Gastric Glands

22
Q

What secretes HCL that kills many ingested bacteria, aids protein digestion, provides the necessary pH for pepsin to start protein digestion, and stimulates the flow of bile & pancreatic juice.

A

Parietal cells

***It is concentrated enough to cause tissue damage, but in normal individuals, the gastric mucosa does not become irritated or digested b.c it also contains mucus.

23
Q

What does the mucus form?

A

A flexible gel that coats the gastric mucosa

24
Q

What does the tight junctions between the cells which are also part of the mucosal barrier do?

A

Protects the gastric epithelium from damage

25
Q

What are some substances that tend to disrupt the barrier and cause gastric irruption/injury (gastritis) ?

A

1 )ethanol

2) bile salts
3) NSAIDS
4) H. pylori

26
Q

What specific gastric cell acts as an autoimmune effect released by the stomach?

A

The G cells releasing Gastrin

27
Q

What does the secretion of Gastrin do?

A

Stimulates parietal cells to secrete intrinsic factor (IF) and HCL

28
Q

What are the functions of the stomach?

A

1) Temporarily stores ingested liquids and solids until they are released into the small intestine

2) Mechanical digestion of the stomach
3) Secretes gastric juice that is involved w/ chemical digestion
4) Secretes the hormones gastrin and histamine

29
Q

What is chyme ?

A

The stomach vigorously churns food into a “creamy, soupy paste”

30
Q

What is an alkaline tide?

A

As bicab enters blood it will be more alkaline

31
Q

What is the cephalic phase?

A

Just the beginning of eating

32
Q

Vagus nerve weakly stimulates what?

A

Stimulates gastric juice serration when food is being chewed in the mouth or with the sight, smell, or thought of food

33
Q

What does the vagus nerve stimulate that is from the enteroendocrine cells of the gastric glands?

A

Gastrin secretion

34
Q

What does Gastrin further stimulate?

A

Stimulates secretion of gastric juice

35
Q

What phase beings when food reaches the stomach ?

A

Gastric phase

36
Q

Distention of the stomach and protein digestion products (amino acids) stimulate what?
What kind of loop is this?

A

Gastrin secretion and hence more gastric juice secretion this represents a positive feed back loop

37
Q

What does the Vagus nerve continue to stimulate?

A

Stimulates gastrin** release and gastric motility***

38
Q

Elevated levels of gastrin stimulate the release of what?

A

release of histamine, which in turn INCREASES HCL secretion from PARIETAL cells

39
Q

Does carbohydrate digestion occur in the stomach?

A

No, protein digestion occurs in the stomach

40
Q

Small amounts of acidic chyme enter the duodenum which stimulates the secretion of what 3 hormones ?

What is the effect of these hormones on gastric juice secretion?

What phase is this?

A

1) CCK
2) Secretin
3) Gastric Inhibitory peptide (GIP)

  • **These Inhibit gastric juice secretions
  • INTESTINAL PHASE
41
Q

GIP (Gastric inhibitory peptide) inhibits gastric juice secretion but also can inhibit what?

A

GIP also inhibits gastric MOBILITY

42
Q

What are 3 stimulators fro gastric secretion?

A

1) Histamine
2) Gastrin
3) Vagal stimulation (Acetylcholine)

43
Q

Why is the control of chyme leaving the stomach and entering the duodenum critical ?

A

1) So the duodenum DOESNT become TOO FULL (especially w/ acid)
2) So the small intestine can adequately process the incoming chyme

44
Q

Gastrin and vagus nerve activity can increase what?

A

Gastric motility– this pushes food towards the duodenum and causes the pyloric sphincter to relax (occurs during the gastric phase)

45
Q

What is Enterogastric reflex?
How does this affect vagus nerve activity?
What phase does this occur?

A

Products of protein digestion and H+ in the duodenum

***inhibits vagus nerve activity

**Occurs in the intestinal phase

46
Q

Fatty, acidic chyme can also stimulate and release what?

How does this affect gastric motility and emptying?

During what phase does this occur?

A

CCK, secretin, and GIP

***This inhibits gastric motility and emptying

**Occurs during the intestinal phase

47
Q

What kind of digestion does the stomach do most of?

A

Mechanical digestion of carbohydrates, proteins, and lipids

48
Q

Does the stomach do chemical digestion? explain

A

Yes, but it varies.

  • Proteins ( lots)
  • Lipids (a little bit)
  • Carbohydrates (not much at all)
49
Q

Is there absorption of nutrients in the stomach?

A

No

Digestion (15 decks)

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