Gastrointestinal Tract - Stomach Flashcards

1
Q

Where is the stomach located?

2

A

Inferior to the diaphragm

Upper left quadrant of the abdominal cavity

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2
Q

List the four main functions of the stomach.

A

Stores ingested food

Mechanical breakdown

Secretes enzymes and acids

Secretes intrinsic factor (IF)

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3
Q

What does the stomach store?

A

Ingested food

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4
Q

What does the stomach secrete?

3

A

Enzymes

Acids

Intrinsic factor

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5
Q

Why does the stomach secrete enzymes and acid?

A

To break chemical bonds of ingested food

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6
Q

What happens if not enough intrinsic factor is secreted?

A

Not enough IF leads to pernicious anaemia

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7
Q

Describe the structure of the stomach. (5)

A

Greater curvature

Lesser curvature

Oblique angle

Folds -> rugae ->pits -> glands

Receptors

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8
Q

What are the names for the two types of curvature in the stomach?

A

Greater and lesser curvature

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9
Q

What angle is the stomach at?

A

An oblique angle

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10
Q

Why is the angle of the stomach important?

A

This means the stomach is always higher than the pyloric sphincter and the body of the stomach

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11
Q

What is the name given to the area where the oesophagus meets the stomach?

A

The pyloric sphincter

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12
Q

Why does the oesophagus need to be above the pyloric sphincter?

A

To prevent reflux

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13
Q

What puts you at risk of reflux?

A

Being obese -> large amounts of fat around the stomach leads to an increased pull of gravity on the stomach leading to a more horizontal stomach -> causing reflux

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14
Q

How much liquid can the stomach hold when not stretched?

A

One litre

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15
Q

How much liquid can the stomach hold when it is stretched?

A

Four litres

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16
Q

What do the folds of the stomach create?

A

Rugae

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17
Q

What are rugae?

A

Folds of the stomach

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18
Q

What do rugae form?

A

Pits

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19
Q

What forms pits in the stomach?

A

Rugae

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20
Q

What do pits in the stomach form?

A

Glands

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21
Q

What forms glands in the stomach?

A

Pits

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22
Q

How do the glands in the stomach work?

A

They secrete their products out between rugae

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23
Q

What receptors are found in the stomach?

3

A

Mechanoreceptors

Osmoreceptors

Chemoreceptors

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24
Q

Give an example of a mechanoreceptor.

A

Stretch receptors

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25
Q

How do osmoreceptors work?

A

They determine osmolarity of surrounding concentrations -> determine what response is needed to digest a substance with a high concentration of protein

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26
Q

How do chemoreceptors work in the stomach?

A

They determine how acidic a substance is and organise a suitable response to digest the substance

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27
Q

What is the overall function of the receptors in the stomach?

A

The detect what is in the stomach and what is happening in the stomach

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28
Q

Describe the epithelia of the mucosa of the stomach.

A

Simple columnar epithelium

29
Q

What is different about the muscularis externa in the stomach compared to anywhere else in the GIT?

A

There is a third type of muscle

30
Q

What are the three types of muscle fibres in the stomach?

A

Oblique fibres

Circular fibres

Longitudinal fibres

31
Q

What is the function of the oblique fibres in the stomach?

A

This allows the stomach to ring itself out like a cloth

32
Q

Name the five cell types found in the pits/glands of the stomach.

A

Neck cells

Parietal cells

Chief cells

P/D1 cells

G cells

33
Q

What is secreted by the neck cells?

A

Mucous

34
Q

How long does it take for the neck cells to turnover?

A

They have a high turnover rate of 5 days

35
Q

What will increase the turnover rate of neck cells?

A

Alcohol

36
Q

What will happen to the neck cells if one drinks too much alcohol?
(2)

A

Turnover rate is too high

Forms gastric ulcers as cells below the chief cells come in contact with the acid of the stomach and become damaged

37
Q

What do parietal cells secrete?

A

They secrete Hydrochloric acid (HCL)

38
Q

What is HCL used for?

5

A

Denature proteins

Break down cell walls

Break down connective tissues

Protection -kill microorganisms

Activate pepsin

39
Q

What does HCL do to proteins?

A

Denatures them

40
Q

What does HCL break down?

2

A

Connective tissue

Cell walls

41
Q

What does HCL protect us from?

A

Microorganisms

42
Q

What does HCL activate?

A

Pepsin

43
Q

What is found in chyme?

5

A
Intrinsic factor
Mucus 
Pepsinogen
HCL
Hormones
44
Q

What is the role of intrinsic factor in chyme?

A

Enters the Small intestine where it absorbs vitamin 12

45
Q

How does deficiency of intrinsic factor result in pernicious anaemia?

A

This is because intrinsic factor is needed to absorb vitamin 12 in the small intestine which is needed to form red blood cells

46
Q

What do the chief cells secrete?

A

Pepsinogen

47
Q

How are chief cells involved in the break down of proteins?

A

Chief cells secrete pepsinogen which is an inactive form of pepsin (an enzyme which breaks down proteins into smaller parts)

48
Q

What activates pepsin in the stomach?

A

HCL

49
Q

Where are P/D1 cells found?

A

The fundus of the stomach

50
Q

What is the fundus of the stomach?

A

The highest part of the stomach -> its higher than the pyloric sphincter

51
Q

What is secreted by the P/D1 cells?

A

A hormone called ghrelin

52
Q

What is ghrelin?

A

An enterogasterone ->hormone in the GIT

53
Q

What is the role of ghrelin?

A

It stimulates the hunger sensation

54
Q

How does ghrelin stimulate hunger?

3

A

P/D1 cells enter your bloodstream where they reach the hypothalamus and bind to it

They then secrete ghrelin

This tells you to eat

55
Q

What hormone is the opposite of ghrelin?

A

Lectin

56
Q

What does lectin do?

A

It tells you when your full

57
Q

What is secreted by G cells?

A

Gastrin

58
Q

What is gastrin?

A

An enterogasterone

59
Q

What do G cells do?

2

A

They detects undigested material such as proteins and secrete gastrin accordingly

If food is about to enter the small intestine but it has not been fully digested these G cells will increase their gastric secretions to ensure chyme is the right consistency

60
Q

What is the formation of gastric juice often called?

A

The Alkaline Tide

61
Q

What is the pH of gastric juice?

A

1.5

62
Q

What is the first step in the Alkaline Tide?

A

H+ produced in parietal cell by reduction of CO2 +H2O

63
Q

What cells produces H+?

A

Parietal cells

64
Q

How do parietal cells produce H+

A

By reducing CO2 and H2O

65
Q

What happens to the H+ produced by the parietal cells?

A

They are transported into the gastric glands

66
Q

What is the third step of the Alkaline Tide?

A

The HCO-3 diffuses into interstitial fluid via counter transport with Cl-

67
Q

How does the HCO-3 diffuse into the interstitial fluid?

A

Via counter transport with Cl-

68
Q

What is the fourth step in the Alkaline Tide?

A

HCO-3 diffuses into circulation which raises pH (alkaline tide)

69
Q

What is the fifth/final stage in Alkaline Tide?

A

Cl- diffuses into gastric gland via Cl- channels