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Bad Girl's MCAT Club > Biology 9: The Digestive System > Flashcards

Biology 9: The Digestive System Flashcards

1
Q

what are the two types of digestion?

A

intracellular digestion: oxidation glucose and fatty acids for energy

extracellular digestion: obtainment of nutrients from food in the alimentary canal (from mouth to anus)

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2
Q

what is the difference between absorption and digestion?

A

digestion: the breakdown of food into its constituent organic molecules

absorption: the transport of product for digestion from the digestive tract into the circulatory system for distribution to the body’s tissues and cells

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3
Q

what are the two types of digestion?

A

mechanical digestion: the physical breakdown of large food particles

chemical digestion: the enzymatic cleavage of chemical bonds

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4
Q

pathway of the digestive tract

A

oral cavity -> pharnyx -> esophagus -> stomach -> small intestine -> large intestine -> rectum

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5
Q

enteric nervous system

A

a collection of one hundred million neurons that govern the function of the the gastrointestinal system

present in the walls

trigger peristalsis

can function independent of the brain and spinal cord, but is also regulated by parasympathetic inputs rest and digest

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6
Q

which hormones stimulate feelings of hunger

A

glucagon and ghrelin

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7
Q

which hormones stimulate feelings of satiety?

A

leptin and cholecystokinin

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8
Q

which hormones trigger the sensation of thirst?

A

ADH and aldosterone

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9
Q

salivary amylase

A

enzyme present in saliva

capable of hydrolyzing starch into smaller sugars

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10
Q

lipase

A

enzyme present in saliva

catalyzes the hydrolysis of lipids

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11
Q

pharynx

A

cavity which leads from the mouth and posterior cavity to the esophagus and larynx

the epiglottis covers the larynx during swallowing

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12
Q

what are the three divisions of the pharynx

A

nasopharynx (behind nasal cavity)

oropharynx (back of mouth)

laryngopharynx (above vocal cords)

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13
Q

esophagus

A

a muscular tube that connects the pharynx to the stomach

top third skeletal muscle - somatic control

middle third is a mix of skeletal and smooth

bottom third smooth muscle - automatic control

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14
Q

emesis

A

fancy word for vomiting

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15
Q

upper esophageal sphincter

A

present in the oropharynx at the back of the mouth

initiates the process of swallowing

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16
Q

lower esophageal sphincter / cardiac sphincter

A

present at the top of the stomach

relaxes to allow the passage of food into the stomach

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17
Q

stomach

A

highly muscular organ in upper left quadrant of the abdominal cavity under the diaphragm

uses HCl acid and enzymes to digest food

has thick mucosa to prevent autodigestion

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18
Q

what are the four main divisions of the stomach?

A

fundus

body

antrum

pylorus

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19
Q

rugae

A

folds of the internal lining of the stomach

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20
Q

gastric glands

A

glands in the mucosa of the fundus and body of the stomach

respond to signals from the vagus nerve of parasympathetic (activated by sight, smell, taste of food)

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21
Q

what are the three different cell types of gastric glands?

A

mucous cells

chief cells

parietal cells

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22
Q

mucous cells

A

gastric glands which produce the bicarbonate-rich mucous that protects the muscular wall from the acidic and proteolytic environment of the stomach

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23
Q

chief cells

A

gastric glands which secrete pepsinogen (inactive zymogen form of pepsin)

24
Q

parietal cells

A

secrete HCl, producing hydrogen ions which cleave pepsinogen -> pepsin

secrete intrinsic factor - glycoprotein involved in absorption of b12

25
Q

pepsin

A

proteolytic enzyme

cleaves peptide bonds near aromatic amino acids

most active at a low pH

26
Q

pyloric glands

A

glands in the antrum and pylorus of the stomach

contain G-cells that secrete gastrin

27
Q

gastrin

A

secreted by G cells

induces parietal cells to secrete more HCl, signals stomach to contract and mix contents

28
Q

chyme

A

acidic, semifluid mixture resulting from the digestion of solid food in the stomach

has a very high surface area for optimal absorption in the small intestine

29
Q

what are the three segments of the small intestine?

A

duodenum (chemical digestion)

jejunum (absorption)

ileum (absorption)

30
Q

how does food leave the stomach to enter the small intestine

A

through the pyloric sphincter into the duodenum

31
Q

brush-border enzymes

A

enzymes present on the luminal surface of cells lining the duodenum

triggered to release by the presence of chyme in the duodenum

ex. disaccharidases, peptidases

breaks down dimers and trimers into absorbable monomers

32
Q

duodenum

A

first segment of the small intestine

secretes brush-border enzymes, enteropeptidase (activates other digestive enzymes from accessory organs)

secretes hormones secretin and cholecystokinin into bloodstream

33
Q

aminopeptidase

A

peptidase secreted by glands in the duodenum that removes the N-terminal amino acid from a peptide

34
Q

enteropeptidase

A

enzyme critical for the activation of trypsinogen (pancreatic protease) to trypsin, which activates a cascade

also activates procarboxypeptidases A and B to their active forms, which removed the C-terminal amino acid from a peptide

35
Q

cholecystokinin (CCK)

A

secreted into the duodenum as a response to the presence of chyme

stimulates the release of bile, pancreatic juices

promotes satiety in the brain

36
Q

bile

A

complex fluid of bile salts, pigments, and cholesterol

involved in the mechanical digestion of fats and lipids

are amphipathic, can bridge aqueous and lipid enviornments

emulsify fats and cholesterol into micelles to make them accessible to pancreatic lipase (chemical digestion)

37
Q

pancreatic juices

A

complex mixtures of enzymes in a bicarbonate-rich alkaline solution

helps to neutralize acidic chyme

provides an ideal working environment for each digestive enzyme (about 8.5)

enzymes can digest carbs, fats, and proteins

38
Q

secretin

A

hormone that signals the release of pancreatic enzymes into duodenum

regulates pH by reducing HCl secretion from pancreatic cells and increasing bicarbonate secretion from pancreas

enterogastrone - functions to slow motility through the digestive tract

39
Q

acinar cells

A

exocrine cells in the pancreas that produce pancreatic juices

40
Q

what are three enzymes present in pancreatic juice?

A

pancreatic amylase - breaks down polysaccharides (carb digestion)

pancreatic peptidases (trypsinogen, chymotrypsinogen, procarboxypeptidases A and B activated by enteropeptidase made in duodenum)

pancreatic lipase breaks down fat into free fatty acids and glycerol

41
Q

liver

A

organ in the upper right quadrant of the abdomen

makes bile, which can be stored in gallbladder or secreted into duodenum directly

detoxifies endogenous and exogenous compounds

detoxifies and metabolizes substances

converts ammonia into urea

synthesizes albumin and clotting factors

42
Q

what are the two unique structures in the liver for communication with the digestive system?

A

bile ducts: connect liver with gallbladder and duodenum

hepatic portal vein: allows liver to receives all blood draining from the abdominal portion of the abdominal tract for processing before reaching the IVC

43
Q

bilirubin

A

a major pigment in bile

byproduct of the breakdown of hemoglobin

conjugates (attached to a protein) in the liver and secreted into bile for secretion

44
Q

gallbladder

A

organ located beneath the liver

stores and concentrates bile

contracts and pushes bile out into the biliary tree in response to CCK release

45
Q

lacteal

A

located in the middle of each villus in the small intestinal jejunum and ileum

lymphatic channel that takes up fats for transport into the lymphatic system

form the beginning of the lymphatic system

converge and enter the venous circulation directly through thoracic duct, drains into subclavian vein

46
Q

how are water-soluble compounds absorbed into the small intestines?

A

water-soluble compounds such as monosaccharides, amino acids, some vitamins, small fatty acids, enter the capillary bed

unlike the others, small fatty acids are nonpolar and thus do not require transporters to cross the membrane

capillaries come together to form portal vein, which drains to the liver

47
Q

chylomicrons

A

packages of triglycerides and esterified cholesterol molecules formed from larger fats

don’t enter the bloodstream following absorption but instead enter the lymphatic circulation through lacteals

48
Q

what are the major sections of the large intestine?

A

cecum

colon

rectum

49
Q

cecum

A

outpocketing in the large intestine that accepts fluid exiting the small intestine through the ileocecal valve

the site of attachment of the appendix

50
Q

ileocecal valve

A

valve between the ileum and the cecum connecting the small and large intestines

51
Q

colon

A

part of the large intestine which absorbs remaining water and salts from undigested material from the small intestine

concentrates remaining material to form feces

52
Q

rectum

A

part of the large intestine that stores feces

53
Q

what two sphincters control the anus?

A

external sphincter under voluntary control (somatic)

internal sphincter under autonomic control

54
Q

what are the two circulatory vessels in a villus?

A

capillaries, which absorb water-soluble nutrients

lacteals, which absorb fat-soluble nutrients

55
Q

what are the fat-soluble vitamins?

A

vitamins A, D, E, and K

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