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Block 1 > Small Intestine Anatomy and Physiology > Flashcards

Small Intestine Anatomy and Physiology Flashcards

1
Q

What 3 products does the small intestine secrete?

A

Mucus
Water
Hormones

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2
Q

What 2 hormones are stimulated by food entering the duodenum?

A

CCK

Secretin

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3
Q

What responses does secretin bring about on the GI tract?

A

Stimulates the pancreas to secrete HCO3-

Stimulates the liver to produce bile

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4
Q

What responses does CCK bring about on the GI tract?

A

Gallbladder contraction

Enzyme secretion from the exocrine pancreas

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5
Q

Which pancreatic cells secrete enzymes?

A

Acinar cells

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6
Q

Which pancreatic cells secrete alkali?

A

Duct cells

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7
Q

What makes up the pancreatic digestive enzymes?

A

Pancreatic amylase (breaks down starch)

Lipase (breaks down fat)

Trypsin (inactive)

Chymotrypsin (inactive)

Carboxypeptidase (inactive)

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8
Q

What makes up pancreatic alkali?

A

HCO3- (bicarbonate)

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9
Q

What enzyme activates trypsinogen to trypsin?

A

Membrane bound enterokinase (a brush border enzyme)

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10
Q

What does carbonic anhydrase do?

A

Catalyses the reaction of H20 + C02 = HC03- and H+ in the pancreas

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11
Q

In the PANCREAS, where is HCO3- secreted to?

A

The duct lumen

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12
Q

In the PANCREAS, where is H+ pumped to?

A

The blood

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13
Q

In the STOMACH, where is HCO3- secreted to?

A

The blood

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14
Q

In the STOMACH, where is H+ pumped to?

A

The stomach lumen

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15
Q

What stimulates pancreatic enzyme secretion?

A

CCK and acetylcholine (Ach from parasympathetic postganglionic neurones of vagus)

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16
Q

What stimulates pancreatic alkali secretion?

A

Secretin

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17
Q

What enzyme digests fats (triglycerides)?

A

Pancreatic lipase.

Digested into monoglyceride and fatty acid

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18
Q

What enzyme digests starch?

A

Pancreatic amylase

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19
Q

What enzyme breaks down proteins?

A

Trypsin and chymotrypsin (broken down into peptide fragments).

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20
Q

Which glands in the duodenal mucosa secrete mucus?

A

Brunner’s glands

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21
Q

How does water move out of the intestinal epithelium and into the lumen?

A

Down a concentration gradient (Na+, Cl- and HCO3-)

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22
Q

What hormones are secreted by the small intestine?

A

Secretin

CCK

Motilin

Vasoactive intestinal peptide (VIP)

Gastric inhibitory peptide (GIP)

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23
Q

What does vasoactive intestinal peptide do?

A

Increase blood flow to the GI tract

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24
Q

What does gastric inhibitory peptide do?

A

Inhibits gastric secretion

Stimulates insulin secretion

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25
Q

What does motilin do?

A

Stimulates migrating motor complexes (MMCs) via the enteric and autonomic nervous systems.
Sweeps the GI tract between meals.
Strong peristaltic movements

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26
Q

What are the four layers of the GI tract?

A

Mucosa, submucosa, muscularis, serosa

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27
Q

What is added to a fat globule to emulsify it?

A 
Bile salts (exocrine liver) and phospholipids. 
This holds the emulsion droplet in suspension.
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28
Q

What is an emulsion droplet broken down into?

A

Monoglyceride and fatty acids (micelles)

By pancreatic lipase.

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29
Q

Name some important disaccharides

A

Sucrose, lactose, maltose

30
Q

How does fructose move into a cell?

A

Facilitated diffusion down a concentration gradient - GLUT5 transporter.

31
Q

How does glucose or galactose move into a cell?

A

Secondary active transport - cotransport with Na+ at SGLT1. Uses the concentration gradient made by Na+ being actively pumped out of the cell by Na+/K+ATPase pump.

32
Q

How does glucose, galactose and fructose (monosaccharides) move out of the cell?

A

Facilitated diffusion via GLUT2 transporter.

33
Q

Which layer of the GI tract contains blood vessels, lymphatic vessels and nerves?

34
Q

What type of epithelial cells are found in the mouth, oesophagus and anus?

A

Stratified squamous

35
Q

What type of epithelial cells are found in the stomach, SI and LI?

A

Simple columnar - for secretion and absorption

36
Q

Where does the myenteric plexus sit?

A

Between the inner circular muscle layer and outer longitudinal muscle layer (muscularis)

37
Q

How are tri- and di-peptides formed from proteins absorbed into the cells of the GI tract?

A

Amino acid Na+ co-transporters.

38
Q

How are proteins broken down into polypeptides?

A

By pepsins and carboxypeptidase

39
Q

How are polypeptides broken down into tri- and dipeptides?

How is trypsinogen converted into trypsin? Why is this important?

A

Trypsin
Chymotrypsin
Carboxypeptidase
HCO3-

Enterokinases on the luminal epithelium convert trypsinogen into tripsin. Trypsin converts inactive pancreatic enzymes into the active forms (listed above)

40
Q

What stimulates the absorption of Ca2+?

41
Q

Name the two mechanisms by which Ca2+ is moved out of a cell.

A

ATPase pump

Na+ exchange channel

42
Q

Name the two types of dietary iron

A

Haem iron - in haemoglobin, myoglobin and cytochromes
Animal

‘Free’ iron - insoluble, inabsorbable Fe3+.
Plants

43
Q

Why is iron important in terms of enzymes?

A

Iron is a component of many active sites of enzymes

44
Q

How is Fe3+ (free iron) reduced to Fe2+ in the brush border?

A

By the brush border enzyme duodenal cytochrome B

45
Q

How is Fe2+ moved out of the cell?

A

Facilitated diffusion with ferroportin 1 channel

46
Q

What converts Fe2+ to Fe3+ on the basolateral side of the cell?

A

Hephaestin

47
Q

How does Fe2+ enter the enterocyte cell?

A

Divalent metal transporter 1 (DMT1)

48
Q

Name the four fat soluble vitamins

A

Vitamin A, D, E and K

49
Q

What does vitamin B12 bind to in the stomach?

50
Q

What does vitamin B12 bind to in the duodenum and jejunum?

A

Intrinsic factor

51
Q

Where is vitamin B12 absorbed and what is it bound to?

A

Terminal ileum

Intrinsic factor

52
Q

Where is intrinsic factor secreted from?

A

Parietal cell of the stomach

53
Q

What allows vitamin B12 to bind to intrinsic factor in the stomach?

A

An acidic pH

54
Q

What four things can malabsorption arise from?

A

Failure or deficiency in:
Pancreatic enzyme secretion

Absorption

Brush border enzymes

Bile secretion

55
Q

What is lactose intolerance?

A

Lack of or deficiency in the enzyme lactase

56
Q

What does lactose break down into in the SI?

A

Glucose and galactose

57
Q

Outline the 5 functions of the stomach

A

Store food

Minimise the ingestion of bacteria

Dissolve and partially digest macromolecules

Regulate the emptying of contents into the SI

Secrete intrinsic factor

58
Q

Name the three regions of the stomach

A

Fundus

Body

Antrum

59
Q

What does the enteric nervous system activate/work on?

A

Myenteric plexus

Submucosal plexus

60
Q

What inhibits pancreatic alkali production?

61
Q

Maltose is a disaccharide - what are the 2 monosaccharides it is made from?

62
Q

Lactose is a disaccharide - what are the 2 monosaccharides it is made from?

A

1 glucose

1 galactose

63
Q

Sucrose is a disaccharide - what are the 2 monosaccharides it is made from?

A

1 glucose

1 fructose

64
Q

What is the first enzyme to break down protein?

How is it activated?

What does this breakdown protein into?

A

Pepsin

Converted from pepsinogen by HCl in the stomach

Breaks protein down into polypeptides

65
Q

Where in the GI tract is the main place protein digestion and absorption takes place?

66
Q

How are amino acids (protein breakdown) moved into luminal epithelial cells?

A

Na+ co-transport

67
Q

Where are the main sites of Ca2+ absorption?

A

Duodenum

Jejunum

68
Q

How is calcium moved into a luminal epithelial cell?

A

Calcium channel

69
Q

What are the cells in the intestinal epithelium called?

A

Enterocytes

70
Q

How does heme iron enter the epithelial cell?

A

Heme transporter

71
Q

Where is R protein released from?

A

Salivary glands

72
Q

List some symptoms of malabsorption

A

Weight loss

Abdominal distension

Diarrhoea

Steatorrhoea

Pernicious anaemia

Hypochromic anaemia

Block 1 (13 decks)

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