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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
What does motilin do?
Stimulates migrating motor complexes (MMCs) via the enteric and autonomic nervous systems. Sweeps the GI tract between meals. Strong peristaltic movements
26
What are the four layers of the GI tract?
Mucosa, submucosa, muscularis, serosa
27
What is added to a fat globule to emulsify it?
``` Bile salts (exocrine liver) and phospholipids. This holds the emulsion droplet in suspension. ```
28
What is an emulsion droplet broken down into?
Monoglyceride and fatty acids (micelles) | By pancreatic lipase.
29
Name some important disaccharides
Sucrose, lactose, maltose
30
How does fructose move into a cell?
Facilitated diffusion down a concentration gradient - GLUT5 transporter.
31
How does glucose or galactose move into a cell?
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
How does glucose, galactose and fructose (monosaccharides) move out of the cell?
Facilitated diffusion via GLUT2 transporter.
33
Which layer of the GI tract contains blood vessels, lymphatic vessels and nerves?
Submucosa
34
What type of epithelial cells are found in the mouth, oesophagus and anus?
Stratified squamous
35
What type of epithelial cells are found in the stomach, SI and LI?
Simple columnar - for secretion and absorption
36
Where does the myenteric plexus sit?
Between the inner circular muscle layer and outer longitudinal muscle layer (muscularis)
37
How are tri- and di-peptides formed from proteins absorbed into the cells of the GI tract?
Amino acid Na+ co-transporters.
38
How are proteins broken down into polypeptides?
By pepsins and carboxypeptidase
39
How are polypeptides broken down into tri- and dipeptides? How is trypsinogen converted into trypsin? Why is this important?
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
What stimulates the absorption of Ca2+?
Vitamin D
41
Name the two mechanisms by which Ca2+ is moved out of a cell.
ATPase pump Na+ exchange channel
42
Name the two types of dietary iron
Haem iron - in haemoglobin, myoglobin and cytochromes Animal 'Free' iron - insoluble, inabsorbable Fe3+. Plants
43
Why is iron important in terms of enzymes?
Iron is a component of many active sites of enzymes
44
How is Fe3+ (free iron) reduced to Fe2+ in the brush border?
By the brush border enzyme duodenal cytochrome B
45
How is Fe2+ moved out of the cell?
Facilitated diffusion with ferroportin 1 channel
46
What converts Fe2+ to Fe3+ on the basolateral side of the cell?
Hephaestin
47
How does Fe2+ enter the enterocyte cell?
Divalent metal transporter 1 (DMT1)
48
Name the four fat soluble vitamins
Vitamin A, D, E and K
49
What does vitamin B12 bind to in the stomach?
R protein
50
What does vitamin B12 bind to in the duodenum and jejunum?
Intrinsic factor
51
Where is vitamin B12 absorbed and what is it bound to?
Terminal ileum Intrinsic factor
52
Where is intrinsic factor secreted from?
Parietal cell of the stomach
53
What allows vitamin B12 to bind to intrinsic factor in the stomach?
An acidic pH
54
What four things can malabsorption arise from?
Failure or deficiency in: Pancreatic enzyme secretion Absorption Brush border enzymes Bile secretion
55
What is lactose intolerance?
Lack of or deficiency in the enzyme lactase
56
What does lactose break down into in the SI?
Glucose and galactose
57
Outline the 5 functions of the stomach
Store food Minimise the ingestion of bacteria Dissolve and partially digest macromolecules Regulate the emptying of contents into the SI Secrete intrinsic factor
58
Name the three regions of the stomach
Fundus Body Antrum
59
What does the enteric nervous system activate/work on?
Myenteric plexus Submucosal plexus
60
What inhibits pancreatic alkali production?
CCK ACh
61
Maltose is a disaccharide - what are the 2 monosaccharides it is made from?
2 glucose
62
Lactose is a disaccharide - what are the 2 monosaccharides it is made from?
1 glucose 1 galactose
63
Sucrose is a disaccharide - what are the 2 monosaccharides it is made from?
1 glucose 1 fructose
64
What is the first enzyme to break down protein? How is it activated? What does this breakdown protein into?
Pepsin Converted from pepsinogen by HCl in the stomach Breaks protein down into polypeptides
65
Where in the GI tract is the main place protein digestion and absorption takes place?
Duodenum
66
How are amino acids (protein breakdown) moved into luminal epithelial cells?
Na+ co-transport
67
Where are the main sites of Ca2+ absorption?
Duodenum Jejunum
68
How is calcium moved into a luminal epithelial cell?
Calcium channel
69
What are the cells in the intestinal epithelium called?
Enterocytes
70
How does heme iron enter the epithelial cell?
Heme transporter
71
Where is R protein released from?
Salivary glands
72
List some symptoms of malabsorption
Weight loss Abdominal distension Diarrhoea Steatorrhoea Pernicious anaemia Hypochromic anaemia

Block 1 (13 decks)

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