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Physiology NBCE > Gastrointestinal > Flashcards

Gastrointestinal Flashcards

1
Q

4 main functions of the GI tract.

Note the GI tract has MANY MANY functions

A

digestion
absorption
excretion
endocrine

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2
Q

Function of the mouth (3).

A

mastication breaks down the food

salivary amylase (ptyalin) assists in chemical breakdown of carbs and starches into MALTOSE

lingual lipase secreted by lingual glands

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3
Q

What are the 3 types of cells located in the gastric glands of the stomach?

A

mucosal/neck cells
chief cells
parietal cells

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4
Q

What is the function of mucosal/neck cells?

A

secrete mucus and gastrin

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5
Q

What do G cells produce?

A

gastrin which stimulates gastric secretions

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6
Q

What is the function of chief cells?

A

produce pepsinogen

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7
Q

What happens to pepsinogen in the presence of hydrochloric acid?

A

pepsinogen is activated to form pepsin

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8
Q

What is pepsin necessary for?

A

protein digestion

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9
Q

What is the function of parietal cells?

A

secrete hydrochloric acid and intrinsic factor

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10
Q

What is needed for the activation of pepsinogen?

A

hydrochloric acid

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11
Q

What is the function of hydrochloric acid?

A

destroys many bacteria

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12
Q

What is intrinsic factor necessary for?

A

absorption of Vitamin B12 in the terminal ileum

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13
Q

What do mast cells release?

A

histamine

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14
Q

What is the mixture of food and gastric juices called?

A

chyme

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15
Q

How is chyme propelled through the small intestine?

A

peristaltic waves

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16
Q

What does the presence of chyme in the small intestine simulate?

A

the release of secretin from the S-cells found in the duodenum

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17
Q

Secretin simulates pancreatic acinar cells to release which two substances?

A

bicarbonate and water

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18
Q

What is bicarbonate secreted by in the duodenum and whats it’s function?

A

Brunner’s glands and it neutralizes the gastric acid and makes the pH alkaline

also protects the duodenal wall from digestion by the highly acidic gastric juice being emptied into the duodenum

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19
Q

What does secretin decrease?

A

gastric motility

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20
Q

What does the presence of fat in the duodenum stimulate?

A

the release of cholecystokinin (CCK)

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21
Q

What is CCK released by?

A

I-cells in the duodenum

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22
Q

What does CCK cause? (4)

A

the gallbladder to contract

sphincter of Oddi to relax

bile to be excreted into the duodenum

the pancreas to secrete enzymes which aid in the digestion of fat, starches, and protein

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23
Q

What pancreatic enzyme completes the breakdown of starch into maltose?

A

pancreatic amylase

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24
Q

What enzymes are located in the brush borders of enterocytes in the small intestine?

A

maltase
lactase
sucrase

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25
Q

What does maltase breakdown?

A

maltose into two molecules of glucose

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26
Q

What does lactase breakdown?

A

lactose into glucose and galactose

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27
Q

What does sucrase breakdown?

A

sucrose into glucose and fructose

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28
Q

What carrier actively transports glucose into the intestinal cells?

A

sodium-glucose carrier

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29
Q

Where is some digested fat absorbed into (in the small intestine)?

A

central lacteals which drain into the thoracic duct

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30
Q

What enzymes digest polypeptides that are released by the action of the proteolytic pancreatic enzymes?

What do they produce?

A

intestinal peptidases

produce amino acids which are actively transported from the lumen into the intestinal cells by a sodium-amino acid carrier

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31
Q

The final breakdown products of fat, starch, and protein digestion are produced in the small intestine. What are fat, starches and proteins broken down into?

A

fat to fatty acids and glycerol

starch, sucrose, and lactose to glucose, fructose, and galactose

proteins to amino acids

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32
Q

The final breakdown products of fat, starch and protein are _____________ by the small intestine and __________ to the liver EXCEPT some _____ which is absorbed by the _______ ________ which drain into the thoracic duct.

A

absorbed

transported

fat

central lacteals

33
Q

What two cell types are found in the pancreas?

A

exocrine cells

endocrine cells

34
Q

Functions of exocrine cells in the pancreas.

A 
secretes:
trypsinogen 
chymotrypsin, carboxypolypeptidase and proelastase 
pancreatic amylase 
lipase
35
Q

Function of trypsinogen.

A

activated to trypsin by enterokinase which is released by enterocytes in the small intestine

36
Q

Function of pancreatic amylase.

A

aids in digestion of starch to produce maltose

37
Q

Function of lipase.

A

breaks down fat into fatty acids and glycerol

38
Q

Where are endocrine cells located?

A

islets of Langerhans

39
Q

Function of endocrine cells.

A 
secrete glucagon (alpha cells which make up 20% of the islet cells) 
insulin (beta cells which make up 70% of the islet cells)  somatostatin (delta cells which make up 5-10% of the islet cells)
40
Q

What is absorbed in the large intestine?

A

most of the water in food

41
Q

What happens to undigested food in the large intestine?

A

it is propelled down the large intestine and out through the anal canal as feces

42
Q

What is the purpose of bacteria in the large intestine?

A

the bacteria produces some vitamin K

43
Q

What aids in the passage of feces?

A

the colon has numerous goblet cells that secrete mucus

44
Q

How are fat soluble vitamins processed and absorbed?

A

Vitamins A, D, E, and K are all absorbed in the same manner as other lipids in the diet

45
Q

How are water soluble vitamins absorbed?

A

Vitamins B, C, and folic acid (except vit B12) enter the enterocytes by secondary active transport mechanisms using Na+ amino acid co-transporters

46
Q

How do ALL water soluble vitamins exit the enterocytes?

A

by diffusion into the portal circulation

47
Q

Where are folic acid and iron absorbed?

A

in the jejunum

48
Q

What does iron form when it is combined with apotransferrin in the blood?

A

transferrin

49
Q

What is the function of transferrin?

A

carries the iron in the blood to cells in the liver, spleen, and bone marrow

50
Q

When iron gets carried to cells in the liver, spleen, and bone marrow, what does it bind to?

A

apoferritin to form ferritin

51
Q

What is Vitamin B12 (cobalamin) attached to?

A

intrinsic factor that is secreted by parietal cells

52
Q

Where is the vitamin B1- intrinsic factor complex delivered to?

A

the terminal ileum where it is bound to cubilin receptors on the enterocytes and transported into the enterocytes

53
Q

Where does vitamin B12 go after it diffuses out of the enterocyte?

A

the portal vein

54
Q

11 roles of the liver.

A
  1. carbohydrate metabolism: glycogenesis, glycogenolysis, and gluconeogenesis
  2. protein metabolism: builds proteins
  3. lipid metabolism: makes fat and cholesterol
  4. stores glycogen and vitamins A, D, and B12
  5. detoxifies toxic substances such as hormones, drugs, poisoning including alcohol
  6. conjugates bilirubin
  7. produces antibodies
  8. makes steroid hormones
  9. manufactures clotting factors
  10. makes red blood cells in the fetus
  11. involved in the immune system through the Kupffer cells
55
Q

What is bilirubin a byproduct of?

A

red blood cell breakdown in the spleen

56
Q

What are old red blood cells broken down into?

A

after about 120 days RBC’s are broken down to release heme and globin

57
Q

What is heme further broken down into?

A

biliverdin and iron

58
Q

What is biliverden converted to?

A

bilirubin which is carried in the blood attached to albumin

because this form of bilirubin is insoluble in water and soluble in lipids

59
Q

Where is bilirubin transported?

A

to the liver where it is conjugated

60
Q

What is bilirubin conjugated with in the liver?

A

a glucuronide by UDPG transferase

61
Q

What is the purpose of conjugation?

A

conjugation renders the previous water-insoluble (indirect) bilirubin into a water-soluble state

62
Q

Where is conjugated (direct) bilirubin secreted?

A

into the biliary tract and stored in the gallbladder

63
Q

What is bilirubin in the gut converted to in the gut?

A

converted by bacteria to urobilinogen

64
Q

How is urobilinogen absorbed?

A

90% in the blood stream
5% in the urine where it is converted to urobilin
10% in the gut converted to stercobilinogen

65
Q

What is responsible for turning the urine yellow?

66
Q

What is responsible for turning the feces brown?

A

stercobilinogen is oxidized to stercobilin which gives the characteristic brown color of stool

67
Q

What % of bile salts are reabsorbed and sent back to the liver via enterohepatic circulation?

68
Q

Roles of the gallbladder.

A
  1. stores and concentrates bile
  2. excretes bile in response to the presence of fat in the duodenum
  3. controlled by CCK by the small intestine when fat enters the duodenum
  4. CCK causes contraction of the gallbladder
69
Q

What is bile make up of?

A

water, bile salts, phospholipids, cholesterol, and bilirubin

70
Q

Name the 8 hormones that are responsible for endocrine secretion from the gut.

A 
gastrin 
somatostatin 
gastric inhibitory peptide 
cholecystokinin 
secretin 
glucagon-like peptide 
ghrelin 
motilin
71
Q

Where is gastrin from and what does it stimulate?

A

from G cells in the pyloric antrum of the stomach

stimulates hydrochloric acid secretion from parietal cells and stimulates gastric motility

72
Q

Where is somatostatin from and what is its function?

A

from D cells in the stomach and delta islet cells in the pancreas

inhibits gastric acid secretion and gallbladder contraction
decreases pancreatic secretion

73
Q

Where is gastric inhibitory peptide from and what is its function?

A

from K cells in the small intestine

inhibits the effect of gastrin on the parietal cells in the stomach
decreases gastric acid secretion

74
Q

Where is cholecystokinin secreted from and what is its functions?

A

from the I cells in the small intestine by the presence of fat in the duodenum

stimulates the release of bile from the gallbladder, pancreatic enzyme secretion, contraction of the gallbladder

relaxes the spinchter of Oddi and the lower esophegeal (cardiac) sphincter

inhibits gastric emptying

75
Q

Where is secretin secreted from and what is its functions?

A

from the S cells in the intestinal crypts of Lieberkuhn

stimulates the release of bicarbonate from the pancreas

decreases gastric acid secretion

76
Q

Where is glucagon-like peptide secreted from and what is its function?

A

secreted by the K cells in the duodenum and jejunum

inhibits gastric emptying

77
Q

Where is ghrelin secreted from and what is its function?

A

from the P cells in the stomach

increased before meals and decreased after eating

78
Q

Where is motilin secreted and what is its function?

A

secreted by M cells in the duodenum

controls cyclical movement in the gut

increased in the fasting state

Physiology NBCE (6 decks)

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