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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
What does maltase breakdown?
maltose into two molecules of glucose
26
What does lactase breakdown?
lactose into glucose and galactose
27
What does sucrase breakdown?
sucrose into glucose and fructose
28
What carrier actively transports glucose into the intestinal cells?
sodium-glucose carrier
29
Where is some digested fat absorbed into (in the small intestine)?
central lacteals which drain into the thoracic duct
30
What enzymes digest polypeptides that are released by the action of the proteolytic pancreatic enzymes? What do they produce?
intestinal peptidases produce amino acids which are actively transported from the lumen into the intestinal cells by a sodium-amino acid carrier
31
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?
fat to fatty acids and glycerol starch, sucrose, and lactose to glucose, fructose, and galactose proteins to amino acids
32
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.
absorbed transported fat central lacteals
33
What two cell types are found in the pancreas?
exocrine cells | endocrine cells
34
Functions of exocrine cells in the pancreas.
``` secretes: trypsinogen chymotrypsin, carboxypolypeptidase and proelastase pancreatic amylase lipase ```
35
Function of trypsinogen.
activated to trypsin by enterokinase which is released by enterocytes in the small intestine
36
Function of pancreatic amylase.
aids in digestion of starch to produce maltose
37
Function of lipase.
breaks down fat into fatty acids and glycerol
38
Where are endocrine cells located?
islets of Langerhans
39
Function of endocrine cells.
``` 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
What is absorbed in the large intestine?
most of the water in food
41
What happens to undigested food in the large intestine?
it is propelled down the large intestine and out through the anal canal as feces
42
What is the purpose of bacteria in the large intestine?
the bacteria produces some vitamin K
43
What aids in the passage of feces?
the colon has numerous goblet cells that secrete mucus
44
How are fat soluble vitamins processed and absorbed?
Vitamins A, D, E, and K are all absorbed in the same manner as other lipids in the diet
45
How are water soluble vitamins absorbed?
Vitamins B, C, and folic acid (except vit B12) enter the enterocytes by secondary active transport mechanisms using Na+ amino acid co-transporters
46
How do ALL water soluble vitamins exit the enterocytes?
by diffusion into the portal circulation
47
Where are folic acid and iron absorbed?
in the jejunum
48
What does iron form when it is combined with apotransferrin in the blood?
transferrin
49
What is the function of transferrin?
carries the iron in the blood to cells in the liver, spleen, and bone marrow
50
When iron gets carried to cells in the liver, spleen, and bone marrow, what does it bind to?
apoferritin to form ferritin
51
What is Vitamin B12 (cobalamin) attached to?
intrinsic factor that is secreted by parietal cells
52
Where is the vitamin B1- intrinsic factor complex delivered to?
the terminal ileum where it is bound to cubilin receptors on the enterocytes and transported into the enterocytes
53
Where does vitamin B12 go after it diffuses out of the enterocyte?
the portal vein
54
11 roles of the liver.
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
What is bilirubin a byproduct of?
red blood cell breakdown in the spleen
56
What are old red blood cells broken down into?
after about 120 days RBC's are broken down to release heme and globin
57
What is heme further broken down into?
biliverdin and iron
58
What is biliverden converted to?
bilirubin which is carried in the blood attached to albumin | because this form of bilirubin is insoluble in water and soluble in lipids
59
Where is bilirubin transported?
to the liver where it is conjugated
60
What is bilirubin conjugated with in the liver?
a glucuronide by UDPG transferase
61
What is the purpose of conjugation?
conjugation renders the previous water-insoluble (indirect) bilirubin into a water-soluble state
62
Where is conjugated (direct) bilirubin secreted?
into the biliary tract and stored in the gallbladder
63
What is bilirubin in the gut converted to in the gut?
converted by bacteria to urobilinogen
64
How is urobilinogen absorbed?
90% in the blood stream 5% in the urine where it is converted to urobilin 10% in the gut converted to stercobilinogen
65
What is responsible for turning the urine yellow?
urobilin
66
What is responsible for turning the feces brown?
stercobilinogen is oxidized to stercobilin which gives the characteristic brown color of stool
67
What % of bile salts are reabsorbed and sent back to the liver via enterohepatic circulation?
95%
68
Roles of the gallbladder.
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
What is bile make up of?
water, bile salts, phospholipids, cholesterol, and bilirubin
70
Name the 8 hormones that are responsible for endocrine secretion from the gut.
``` gastrin somatostatin gastric inhibitory peptide cholecystokinin secretin glucagon-like peptide ghrelin motilin ```
71
Where is gastrin from and what does it stimulate?
from G cells in the pyloric antrum of the stomach stimulates hydrochloric acid secretion from parietal cells and stimulates gastric motility
72
Where is somatostatin from and what is its function?
from D cells in the stomach and delta islet cells in the pancreas inhibits gastric acid secretion and gallbladder contraction decreases pancreatic secretion
73
Where is gastric inhibitory peptide from and what is its function?
from K cells in the small intestine inhibits the effect of gastrin on the parietal cells in the stomach decreases gastric acid secretion
74
Where is cholecystokinin secreted from and what is its functions?
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
Where is secretin secreted from and what is its functions?
from the S cells in the intestinal crypts of Lieberkuhn stimulates the release of bicarbonate from the pancreas decreases gastric acid secretion
76
Where is glucagon-like peptide secreted from and what is its function?
secreted by the K cells in the duodenum and jejunum inhibits gastric emptying
77
Where is ghrelin secreted from and what is its function?
from the P cells in the stomach increased before meals and decreased after eating
78
Where is motilin secreted and what is its function?
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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