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Physiology > 27-29 - The Gut > Flashcards

27-29 - The Gut Flashcards

1
Q

Processing of food involves 5 general processes…

A

1. Motility

2. Secretion

3. Digestion

4. Absorption

5. Excretion

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2
Q

In the stomach, mucus is produced by which type of cell?

A

Surface epitheleal cells

(not goblet cells)

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3
Q

Why must ions, minerals and vitamins be absorbed by active transport in the small intestine?

A

They are charged molecules (therefore cannot cross cell membranes passively)

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4
Q

In the small and large intestines mucus is secreted by which cell type?

A

Goblet cells

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5
Q

Gut function is regulated in three ways…

A
  1. Neurocrine (neural)
  2. Endocrine (hormonal)
  3. Paracrine (local)
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6
Q

Saliva provides 5 properties…

A
  1. Lubrication
  2. Digestion
  3. Solution
  4. Moistness
  5. Protection
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7
Q

Salivary glands are divided into 3 main groups…

A
  1. Parotid
  2. Sublingual and submandibular
  3. Minor glands
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8
Q

Structure of the salivary glands

The acinus is the site of _________

The fluid here is _________

A

Primary secretion

Isotonic (plasma-like)

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9
Q

Structure of the salivary glands

The duct is the site of ________

Sodium and Chloride ions are __________

Potassium and Bicarbonate ions are _________

A

Secondary modification

Reabsorbed

Secreted

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10
Q

After secondary modification in the duct of the salivary glands, the resulting fluid is…

A

Bicarbonate rich and hypotonic

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11
Q

The low H2O permeability of the salivary gland duct makes the fluid more…

A

Concentrated

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12
Q

Control of salivation

Salivation occurs during the _______ phase of digestion

A

Cephalic

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13
Q

Control of salivation

Salivation is increased by activity through parasympathetic nervous system via cranial nerves ___ and ___

Transmission involves the neurotransmitter _________

A

Cranial nerves VII and IX (not the vagus)

Acetylcholine (cholinergic)

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14
Q

Control of salivation

Salivation is reduced through activity of the sympathetic nervous system. The neurotransmitter involved is _________

A

Noradrenaline (noradrenergic)

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15
Q

Name 5 gastric (stomach) functions…

A
  1. Reservior
  2. Mixing food with gastric secretions
  3. Digestion
  4. Controlled gastric emptying
  5. Protection
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16
Q

The main region of the stomach is known as the _____ (or _____ )

At the entrance is the _______ sphinctre

At the exit is the ______ sphinctre

The folds on the lining of the stomach are called _____

A

Body (or corpus)

Esophageal

Pyloric

Rugae

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17
Q

The top part of the stomach is known as the ______

The bottom part of the stomach is known as the _____

A

Fundus

Antrum

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18
Q

The cells found in the gastric glands are (6)…

A

(In order from opening to bottom of the gland)

1. Mucus neck cells

2. Parietal cells

3. ECL (Enterochromaffin-like) cells

4. Chief cells

5. D cells

6. G cells

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19
Q

What do mucous neck cells secrete and what stimulates this secretion?

A

Mucus and bicarbonate

Secretion is tonic (constant at a low level) but increases in response to irritation of the mucosa

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20
Q

Parietal cells secrete gastric acid (HCl) and intrinsic factor.

This is stimulated by both neurocrine (nervous) and paracrine (local) factors, which are…

A
  • Acetylcholine (nervous)
  • Gastrin and histamine (local)
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21
Q

Enterochromaffin-like cells in the gastric mucosa secrete ______ in response to ________ or _______ . This stimulates gastric acid secretion by the parietal cells.

A

Histamine, in response to Acetylecholine or Gastrin

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22
Q

Chief cells secrete ______ and gastric ______.

A

Pepsinogen and Gastric Lipase

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23
Q

When stimulated by stomach acid, D cells secrete _______.

This (inhibits / increases) gastric acid secretion.

A

Somatostatin

Inhibits gastric acid secretion

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24
Q

Intrinsic factors secreted by the parietal cells complex with vitamin ____ to allow its absorption

A

B12

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25
Q

The key enzyme in parietal cells responsible for providing the H+ ions needed to make HCl is ____________

A

Carbonic Anhydrase

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26
Q

How does the stomach stop autodigestion?

A

Mucus acts as a mixing barrier

(some H+ will diffuse through the mucus, but it is neutralised by bicarbonate secreted from the cells)

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27
Q

How does omeprazole reduce stomach acidity?

A
  • Omeprazole is a proton-pump inhibitor (PPI)
  • By inhibiting the proton pump on the apical membrane of the parietal cells, H+ ions can no longer move into the lumen of the stomach.
  • Less H+ = lower acidity
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28
Q

Parietal cell function is regulated by both _______ and _______ chemical regulators.

A

Direct and indirect

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29
Q

How does cimetidine reduce stomach acidity?

A
  • Cimetidine competively inhibits histamine binding to H2 receptor
  • reduces cAMP, reducing HCl production
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30
Q

Vagus nerve activity (increases / decreases) stomach acid production

A

Increases

  • G cell gastrin increased
  • D cell somatostatin, G cell inhibition reduced
  • ECL cell histamine increased
  • Direct effect on parietal cells
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31
Q

In the small intestine the chyme is comes into contact with (3)…

A
  • Membrane-bound enzymes
  • Bile from the liver
  • Pancreatic enzymes
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32
Q

The primary secretion from the pancreas comes from which cell type?

A

Acinar cells

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33
Q

Duct cells in the pancreas modify the primary secretion by adding ______ , increasing the pH

A

Duct cells in the pancreas modify the primary secretion by adding HCO3- , increasing the pH

34
Q

The pancreatic secretion is ( acidic / neutral / alkaline ) …

A

The pancreatic secretion is alkaline to neutralise gastric acid and provide optimal pH for lipase and other intestinal enzymes

35
Q

Most enzymes are secreted in the form of inactive _________ in order to protect against __________ ___________.

A

Most enzymes are secreted in the form of inactive zymogens in order to protect against pancreatic autodigestion.

36
Q

Name 4 classes of enzmes present in the pancreatic secretion (and subtypes)…

A
  • Amylolytic
  • Proteolytic (trypsin, chymotripsin, elastase)
  • Lipolytic (lipase, phospholipase)
  • Nucleolytic (DNA & RNA -ases)
37
Q

Trypsinogen (an inactive zymogen) is converted into the active form trypsin by the enzyme…

A

Enterokinase

38
Q

Outline the difference between an endo versus exo protease…

A

Endoproteases chop proteins in the middle (‘inside’), exoproteases chop the ends (‘outside’)

39
Q

Intestinal peptidases ( begin / continue / finish ) protein breakdown

A

Intestinal peptidases finish protein breakdown

40
Q

Intestinal peptidases are involved in protein digestion in the small intestine. They are present both in the cytosol (cytosolic) and…

A

In the brush-border membrane (membrane-bound)

41
Q

Which two hormones regulate pancreatic secretion?

A
  • Secretin
  • CCK
42
Q

S cells release secretin when stimulated by…

A

Acids, lipids, bile acids and hyperosmolarity

43
Q

Secretin increases pH via…

A

HCO3- rich secretion from the ductal cells of the pancreas

44
Q

Secretin regulates pH and CCK regulates…

A

Enzyme secretion

45
Q

CCK is released by I cells in response to stimulation by…

A

Lipids, peptides and amino acids

46
Q

CCK causes gall bladder ( relaxation / contraction ) to release bile to ( aid / prevent ) digestion

A

CCK causes gall bladder contraction to release bile to aid digestion

47
Q

CCK stimulates the release of what from the pancreas?

A

Digestive enzymes

48
Q

The effect of CCK on enzyme secretion in humans is…

a) direct
b) mediated via NA
c) mediated via Ach
d) mediated via secretin

A

The effect of CCK on enzyme secretion in humans is…

a) direct
b) mediated via NA

c) mediated via Ach

d) mediated via secretin
* The effect is direct in rats*

49
Q

Bile has 2 main functions…

A
  1. Elimation of waste (such as lipophilic drugs)
  2. Promotion of digestion and absorption
50
Q

Like the pancreas, bile ducts secrete fluid rich in…

A

HCO3-

51
Q

Hepatocytes (in the liver) secrete bile into ____________

A

Hepatocytes (in the liver) secrete bile into canaliculi (bile capillaries)

52
Q

Bile enters the duodenum via the _____________

A

Bile enters the duodenum via the common bile duct

53
Q

When not eating what happens to bile secreted by the liver?

A

50% is collected in the gall bladder

54
Q

Bile salts coat lipids to make…

A

Emulsions

55
Q

What is the main change that bile undergoes in the gall bladder?

A

Concentration

(Gall bladder bile is 20x more concentrated than the isotonic hepatic bile)

56
Q

Describe the 3 steps of bile acid synthesis…

A
  1. Primary bile acid is derived from cholesterol
  2. Secondary bile acid is dehydroxylated by intestinal bacteria
  3. Bile acids are conjugated with amino acids to improve solubility -> conjugate bile acids
57
Q

Control of bile acid secretion occurs through 3 mechanisms…

A
  • Bile-acid dependent (based on bile acid plasma conc)
  • Ductal
    • Secretin
  • Gall bladder contraction (integrated w/ pancreatic enzyme secretion)
    • CCK
    • Vagal nerves (ACh)
58
Q

Intestinal surface area is enhanced by…

A

Villi (and microvilli)

59
Q

Dietary polysaccharides must be…

A

Broken down into monosaccharides in order to be absorbed

60
Q

Amylase is an endoenzyme, which means it can’t produce…

A

Monosaccharides (monomers)

61
Q

Glucose (or galactose) is co-transported out of the lumen with…

A

Sodium (Na+)

62
Q

Name the transporter responsible for the co-transport of sodium and glucose…

A

SGLT-1

63
Q

SGLT-1 works by

a) diffusion
b) active transport
c) secondary active transport
d) facilitated diffusion

A

SGLT-1 works by

a) diffusion
b) active transport

c) secondary active transport

d) facilitated diffusion

64
Q

Fructose is absorbed from the intestinal lumen via which transporters?

A

GLUT5 and GLUT2

65
Q

GLUT5 transports fructose from the intestinal lumen via…

A

Facilitated diffusion

66
Q

Gastric pepsin includes

a) endopeptidases
b) exopeptidases
c) endo and exopeptidases
d) pancreatic pepsides

A

Gastric pepsin includes

a) endopeptidases

b) exopeptidases
c) endo and exopeptidases
d) pancreatic pepsides

(endo - cuts in the middle, not the ends)

67
Q

Pancreatic peptidases include both…

A

Endo and exo peptidases

68
Q

How is the pH gradient between the intestinal lumen and the epithelial cells used in the absorption of peptides?

A

Peptides are transported coupled with H+

(the H+ gradient is maintained by NHE3 a sodium/H+ exchanger)

69
Q

Amino acids are absorbed in the intestine by ( a single / many different types of) transporter.

A

Amino acids are absorbed in the intestine by many different types of transporter.

70
Q

Transport of amino acids across the apical membrane occurs via…

A

secondary active transport by carrier proteins (coupled with ion transport, much like glucose)

71
Q

Amino acids pass across the basolateral membrane by:

a) diffusion
b) facilitated diffusion
c) active transport
d) secondary active transport

A

Amino acids pass across the basolateral membrane by:

a) diffusion
b) facilitated diffusion
c) active transport
d) secondary active transport

72
Q

The main barrier to lipid digestion is their low ____________.

A

The main barrier to lipid digestion is their low solubility.

73
Q

Which process is the function of bile salts?

A

Solubilisation of lipids

74
Q

After solubilisation by bile salts, lipids are digested via…

A

Pancreatic lipase

75
Q

After digestion, lipids are absorbed…

a) passively
b) via active transport
c) via secondary active transport
d) via facilitated diffusion

A

After digestion, lipids are absorbed…

a) passively

b) via active transport
c) via secondary active transport
d) via facilitated diffusion

76
Q

Name 3 types of dietary lipid…

A

Phospholipid, triglycerides and short chain fatty acids

77
Q

After passive absorption, lipids undergo ________________ and exit the cell to maintain the concentration gradient.

A

After passive absorption, lipids undergo reesterification and exit the cell to maintain the concentration gradient.

78
Q

Pancreatic lipase and colipase break down fats into ____________ and ______ _________ .

A

Pancreatic lipase and colipase break down fats into monoglycerides and fatty acids.

79
Q

Lipids are solubilised by bile salts in a process called…

A

Emulsification

(large droplets (1microM) from stomach are broken into smaller micelles (5nM))

80
Q

Describe the microanatomy of the small intestine (3)…

A

Finger-like villi (which are covered with microvilli) and crypts between them, which extend down into the mucosa.

81
Q
A

Physiology (17 decks)

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