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MCAT Biological Sciences > Chapter 9- The Digestive System > Flashcards

Chapter 9- The Digestive System Flashcards

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MCAT flashcards
1
Q

2 types of digestion

A
  1. intracellular- metabolism, oxidation of glucose and fatty acids for energy.
  2. extracelluar- process by which nutrients are obtained from food (occurs in lumen on alimentary canal- mouth to anus)
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2
Q

sphincters

A

circular smooth muscles around the canal that can contract to allow compartmentalization of function. sections off the alimentary canal (mouth to anus)

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3
Q

mechanical vs. chemical digestion

A

m- physical breakdown of large food particles into smaller ones.
c- enzymatic cleavage of chemical bonds

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4
Q

absorption

A

transport of products of digestion from digestive tract into the circulatory system for distribution to the body’s tissues and cells.

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5
Q

digestive tract order

A

oral cavity–> pharynx–> esophagus–> stomach–> small intestine–> large intestine–> rectum
other helper organs include: salivary glands, pancreas, liver, gallbladder

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6
Q

enteric nervous system

A

collection of 1hundredmillion neurons that governs the function of the GI system. neurons are present in walls of digestive tract and trigger peristalsis (rhythmic contractions of gut to move materials through system)

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7
Q

what hormone triggers the sensation of thirst?

A

ADH and aldosterone (encourage behavior of fluid consumption)

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8
Q

ghrelin

A

secreted by stomach and pancreas (stimulates feelings of hunger)

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9
Q

leptin and cholecystokinin

A

stimulate feelings of satiety (feeling full)

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10
Q

mastication

A

chewing

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11
Q

salivary amylase

A

aka: ptyalin. hydrolyzes starch into smaller sugars. (found in saliva)

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12
Q

lipase

A

catalyzes hydrolysis of lipids (found in saliva)

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13
Q

3 parts of pharynx

A
  1. nasopharynx- behind nasal cavity
  2. oropharynx- back of mouth
  3. laryngopharynx- above vocal cords
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14
Q

emesis

A

reversal of peristalsis, vomiting

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15
Q

upper esophageal sphincter

A

swallowing is initiated here (muscles of the oropharynx)

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16
Q

lower esophageal sphincter

A

cardiac sphincter. relaxes and opens to allow the passage of food into the stomach

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17
Q

4 main anatomical divisions of stomach

A

1/2. fundus/ body, which have mainly gastric glands

3/4. antrum/ pylorus, which contain mostly pyloric glands

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18
Q

gastric glands

A

respond to signals from the vagus nerve of the parasympathetic nervous system. 3 types of cells here: mucous, chief, and parietal

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19
Q

mucous cells of gastric glands

A

produce bicarbonate-rich mucus that protects the muscular wall from harsh stomach environment

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20
Q

chief cells and parietal cells of gastric glands

A

gastric juice is a combo of secretions from these two.
chief- secrete pepsinogen
parietal- secrete H+ions in form of HCl, intrinsic factor

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21
Q

pepsin

A

digests proteins by cleaning peptide bonds near aromatic amino acids resulting in short peptide fragments. activated by acidic environment

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22
Q

intrinsic factor

A

glycoprotein secreted by parietal cells. absorption of vitamin B12

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23
Q

stomach secretes 6 products

A

HCl (kill microbes, denatures proteins), Pepsinogen (cleaved to pepsin then digests proteins), mucus (protects mucosa), bicarbonate (protects mucosa), water (dissolves/dilutes ingested material), intrinsic factor (B12 absorption)

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24
Q

pyloric gland

A

contain G cells that secrete gastrin (peptide hormone that induces parietal cells in the stomach to secrete more HCl and signals stomach to contract to mix its contents)

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25
Q

chyme

A

digestion of solid food in stomach results in this acidic semifluid mixture

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26
Q

2 substances absorbed directly from stomach

A

alcohol and aspirin

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27
Q

3 segments of small intestine (in order)

A
  1. duodenum (major chemical digestion and minor absorption)
  2. jejunum (absorption)
  3. ileum (absorption)
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28
Q

pyloric sphincter

A

sphincter between stomach and duodenum

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29
Q

brush-border enzymes

A

present on luminal surface of cells lining duodenum and break down dimers and trimers of biomolecules into absorbable monomers

30
Q

what is secreted from the duodenum?

A
  1. enteropeptidase (involved in activation of other digestive enzymes from accessory organs of digestion)
  2. other hormones like secretin and cholecystokinin (CCK) into the bloodstream
31
Q

disaccharidases and what they digest

A
  1. maltase (maltose)
  2. isomaltase (isomaltose)
  3. sucrase (sucrose)- found on duodenal cells
  4. lactase (lactose)
32
Q

peptidases

A

break down proteins (peptides)

33
Q

aminopeptidase

A

peptidase secreted by duodenum that removes N-terminal amino acid from a peptide (aminopeptidase secretion)

34
Q

dipeptidases

A

cleave the peptide bonds of dipeptides to release free amino acids (unlike carbohydrates, larger peptides can be absorbed across the small intestine wall)

35
Q

enteropeptidase

A

enzyme critical for activation of trypsinogen (pancreatic protease) to trypsin (initiates activation cascade, also activates procarboxypeptidases A and B)– activates pancreatic juices!!!

36
Q

secretin

A

peptide hormone that causes pancreatic enzymes to be released into the duodenum/ regulates pH by reducing HCl secretion from parietal cells and increasing bicarbonate secretion from pancreas

37
Q

what type of hormone is secretin

A

slows motility through digestive tract which allows increased time for digestive enzymes to act on chyme (especially fats)

38
Q

cholecystokinin (CCK)

A

secreted in response to entry of amino acids and fat into duodenum. this stimulates the release of both bile and pancreatic juices while promoting satiety in the brain

39
Q

bile/ bile salts

A

complex fluid composed of bile salts, pigments, and cholesterol. bile salts mechanically digest fats and facilitate chemical digestion of lipids. bile salts emulsify fat and cholesterol into micelles to make them accessible to pancreatic lipase

40
Q

what two products does proper fat digestion depend on?

A

bile (mechanical) and lipase (chemical)

41
Q

pancreatic juices

A

complex mixture of several enzymes in a bicarbonate-rich alkaline solution (enzymes here are basic, about 8.5 pH)

42
Q

pancreas function

A

endocrine: release insulin, glucagon, and somatostatin for proper sugar levels
exocrine: acinar cells (pancreatic juice formation)

43
Q

pancreatic amylase

A

carbohydrate digestion

44
Q

pancreatic peptidases

A

trypsinogen, chymotrypsinogen, carboxypeptidases A and B are released in zymogen form then activated for protein digestion

45
Q

pancreatic lipase

A

capable of breaking down fats into free fatty acids and glycerol

46
Q

how are pancreatic juices released in the body?

A

transferred to duodenum via duct system with the major and minor duodenal papillae.

47
Q

2 structures of liver for communicating with digestive system

A
  1. bile ducts (connects liver-produces bile- with both gallbladder-stores bile- and small intestine-bile secreted here)
48
Q

liver

A

processing of nutrients, production of urea, detoxification of chemicals, production of bile, and synthesis of albumin and clotting factors.

49
Q

bilirubin

A

major pigment in bile. byproduct of the breakdown of hemoglobin. travels to liver where it is conjugated (attached to protein) and secreted into bile for excretion.

50
Q

jaundice

A

yellowing of skin that occurs when liver is damaged so it cannot process/excrete bilirubin

51
Q

albumin

A

a protein that maintains plasma oncotic pressure and also serves as a carrier for many drugs and hormones as well as clotting factors used during blood coagulation

52
Q

gall bladder

A

stores and concentrates bile. upon release of CCK the gallbladder releases bile into the biliary tree (bile duct system)

53
Q

segments of small intestine in order

A
  1. duodenum
  2. jejunum
  3. Ileum
    (2/3)- absorption of nutrients
54
Q

main purpose of large intestine

A

absorb water

55
Q

villi

A

small projections from epithelial lining with microvilli as well that line the small intestine to increase surface area for absorption

56
Q

whats inside of the villi of the small intestine?

A
  1. capillary bed- absorption of water-soluble nutrients

2. lacteal- a lymphatic channel that takes up fats for transport to lymphatic system

57
Q

everything requires facilitated secondary transport to go from small intestine to blood except for what and why?

A

fats b/c they are nonpolar, so they can pass through

58
Q

chylomicrons

A

insoluble packages of triglycerides and esterfied cholesterol molecules. these enter lymphatic circulation through lacteals which converge to form the thoracic duct

59
Q

4 fat-soluble vitamins

A

A, D, E, and K and the rest are water-soluble (B and C)

60
Q

where do fat-soluble vitamins go?

A

dissolve directly into chylomicrons to enter the body

61
Q

2 ways water is absorbed into the bloodstream?

A

transcellularly (across cell membrane) and paracellularly (squeezing between cells) to reach the blood

62
Q

large intestine sections

A
  1. cecum
  2. colon
  3. rectum
63
Q

cecum

A

accepts fluid exiting small intestine through ileocecal valve and is site of appendix.

64
Q

colon

A

absorb water and salts (NaCl). forms feces

65
Q

rectum

A

storage site for feces (indigestible material, water, bacteria)

66
Q

anus

A

opening with 2 sphincters (internal- autonomic involuntary control and external- somatic voluntary control)

67
Q

vitamin K production

A

bacteria in gut produces this. its necessary for clotting factors

68
Q

what absorbs the most water?

A

small intestine even tho the main purpose of the large intestine is water absorption

69
Q

hyperkalemia

A

buildup of K in the blood

70
Q

hyperammonemia

A

buildup of ammonia in the blood

MCAT Biological Sciences (12 decks)

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