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Physiology II > digestive > Flashcards

digestive Flashcards

1
Q

digestive system includes

A

gastrointestinal (GI or alimentary) tract (mouth, pharynx, esophagus, stomach, small intestine, large intestine), plus accessory organs that secrete via ducts into the GI tract (salivary glands, liver, gallblader, exocrine pancrease).

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2
Q

digestion

A

breaking down of food into smaller particles and of macromolecules in food into smaller, absorbable molecules (accomplished mechanically and by the actios of digestive enzymes, acid, and bile)

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3
Q

secretion

A

release of substances into the lumen of the GI tract

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4
Q

absorption

A

movement of the molecules resulting from digestion from the GI tract lumen across a layer of epithelial cells and into the blood or lymph

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5
Q

motility

A

contractions of the smooth muscles in the GI tract wall that mix the luminal contents and propel them from mouth to anus

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6
Q

salivary glands (3 pair) secete saliva, which

A

is antibacterial

contains muscus for lubricating food particles before swallowing

contains anylase - enzyme that begins polysaccharide digestion

dissolves molecules that can then interact with chemoreceptors to give rise to taste sensations

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7
Q

pharynx and esophagus

A

provide pathway from oral cavity to stomach

are muscular walls that control swallowing

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8
Q

stomach stores food, produces the hormone gastrin, and produces exocrine secretions including:

A
  • HCl which kills bacteria, dissolves the particulate matter in food and activates pepsinognes into pepsins
  • pepsins - which begin the digestion of proteins
  • mucus - for lubrication and protection
  • intrinsic factor for vitamin B12 absoprtion in the small intestine
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9
Q

chyme

A

the solution of partially digested protein and polysaccharide fragments, fat droplets, salt, water, and other small molecules in the stomach, small intestine, and large intestine

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10
Q

no absorption of carbs, fats, or proteins in the _______

A

stomach

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11
Q

stomach regulates the rate at which its contents empty into the

A

small intestine

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12
Q

small intestine is divided into

A

a duodenum, jejunum, and ileum

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13
Q

small intestine performs

A

most digestion (via hydrolytic enzymes) and absorption of food molecules

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14
Q

small intestine enzymes for carbs, fats, and proteins are located where

A

embedded in the luminal surfaces of cells lining the small intestine or are secreted into the small intestine lumen by the pancreas

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15
Q

small intestine secretes:

liver/gallbladder secrete:

A

salts, water, and mucus (from goblet cells) into its own lumen

bile into its lumen

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16
Q

in addition to absorbing monosaccharides (from carbs), fatty acids (from fats), and amino acids (from proteins), the small intestine also absorbs

A

vitamins, mineals, and water

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17
Q

small intestine mixes

A

its luminal contents with the various secretions, brings the contents into contact with the epithelial surface of its wall where things can be absorbed, and slowly propels its contents toward the large intestine

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18
Q

the pancreas has an exocrine and endocrine portion; the exocrine portion secretes

A

pancreatic juice into the small intestine

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19
Q

pancreatic juice contains bicarbonate (HCO3-) for:

pancreatic juice also contains enzymes specific for:

A

neutralizing stomach acid (necessary to prevent inactivation of pancreatic enzymes)

digesting carbs, proteins, fats, and nucleic acids

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20
Q

the liver secretes

A

bile salts (via the bile) into the small intestine - not enyzmes but break fats into smaller fat droplets

bicarbonate into to small intestine for acid neutralization

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21
Q

the liver puts some organic waste products and trace metals into

A

the feces (via the bile) for elmination from the body

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22
Q

the liver performs many metabolic activities that help

A

the body handle carbohydrates (especilly glucose and glycogen), amino acids/proteins, and fatty acids/lipids (including cholesterol)

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23
Q

the gallbladder

A

stores and concentrates bile between meals and contracts to secrete it into the duodenum when needed

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24
Q

large intestine functions

A

secretes mucus, concentrates and temporarily stores undigested matter, absorbs water and salts from it, and mixes and propels its contents

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25
Q

functions of the final segment of the large intestine (the rectum)

A

performs defecation in which feces are expelled by muscular contractions and sphincter relaxation

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26
Q

the luminal (inside) surface of the wall of the GI tract is

A

convoluted to increase surface area

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27
Q

from stomach on, the luminal surface of the GI tract is lined by

A

a single layer of epithelial cells across which absorption occurs

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28
Q

in the single layer of epithelial cells that line the GI tract from the stomach on, there exist

A

exocrine cells that secrete (e.g. mucus) into the lumen and endocrine cells that secrete homrones into the blood

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29
Q

the single layer of epithelial cells that line the luminal surface of the GI tract from the stomach on sometimes invaginates

A

into the underlying tissue to form small exocrine glands that secrete water, acid, enzymes, mucus, and ions into the lumen

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30
Q

4 tunics (layers) of the GI wall

A

mucosa

submucosa

muscularis externa

serosa

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31
Q

mucosa

A

the mucosal epithelial (thin layer of epithelial cells lining the luminal surface of the GI tract from stomach on), plus a layer of connective tissue containing blood and lymphatic vessels and nerve fibers (the lamina propria), plus a thin layer of smooth muscle (th muscularis mucosa)

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32
Q

submucosa

A

connective tissue layer just beneath the mucosa that contains a network of neurons (the submucosal plexus, some neurons of which project to the mucosa) plus blood and lymphatic vessels

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33
Q

muscularis externa

A

2 layers of smooth muscle (plus a network of neurons between them, the myenteric plexus) that contract to provide mixing and propulsion of the GI contents

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34
Q

2 layers of the muscularis externa:

A

circular muscle: the fibers of which encircle the tube and thus narorw its lumen when they contract

longitudinal muscle: the fibers of which run along the tube and thus shorten the tube when they contract

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35
Q

the neurons of the myenteric plexus are innervated by:

and are connected with neurons of the:

A

neurons from the autonomic nervous system

submucosal plexus

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36
Q

the muscularis externa of the stomach contains

A

an additional layer of muscle

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37
Q

serosa

A

thin layer of connective tissue forming outer surface of the GI tube

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38
Q

the outer tunic in the esophagus is called the _______ rather than the serosa

A

adventitia

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39
Q

in the abdominal cavity, sheets of connective tissue connect to serosa to

A

the abdominal wall

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40
Q

projections, villi, extend from the lumial surface of the small intestine into

A

its lumen

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41
Q

the surface of each villus is lined by a layer of musosal epithelial cells, the plasma membranes of which form much smaller projections _________ , that are collectively called the ________

A

microvilli

brush border

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42
Q

villi and microvilli increase

A

the small intestine surface area

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43
Q

in the center of each villus are

A

capillaries and a single blind-ended lymphatic vessel called a lacteal

44
Q

most absorbed fat enters the lymph in the:

most other absorbed materials enters:

A

lacteal (lymph is eventually emptied into the blood)

the blood capillaries

45
Q

veins draining the small intestine (and LI, pancrease, and part of the stomach) do not empty directly into the inferior vena cava. instead, these veins merge to form the

A

heptatic portal vein which travels to and gives rise to a second capillary netowrk within the liver

46
Q

products of digestion are absorbed into the SI blood ( but not the lacteal) are processed (metabolized, detoxified, stored, etc) by

A

liver enzymes before entering the general circulation

47
Q

peritoneum

A

a serous membrane similar to the pleural and pericardial membranes that covers the external surfaces of many digestive organs and also lines the inner surface of the abdominopelvic cavity wall

48
Q

the peritoneum encloses a cavity, the

A

peritoneal cavity, that is filled with a thin layer of lubricating serous fluid

49
Q

a fused, double layer of the peritoneal membrane called _________ extends from the body wall to:

A

mesentery

some digestive organs

50
Q

functions of the mesentery

A

holds organs in place and provides routes for blood vessels, lymphatics, and nerves to reach the organs

51
Q

carbs are ingested mostly as

A

starch (a plant polysaccharide), sucrose (table sugar, a disaccharide), and lactose (milk sugar, a disaccharide)

52
Q

only small amounts of monosacchardies such as ______ and _______ are normally ingested

A

glucose and fructose

53
Q

cellulose (fiber), a plant polysaccharide, is not metabolized by _______ enzymes and thus travels to the _______ , where it is partly borken down by ______ enzymes

A

human-produced

Large intestine

bacterial

54
Q

amylase in saliva

A

provides a small amount of starch digestion in the oral cavity, but it is inactivated by acid in the stomach

55
Q

amylase in pancreatic juice secreted into the SI performs the vast majority of

A

carb digestion in the SI, resulting in a mix of maltose (a disaccharide) and short chains of glucose molecules

56
Q

several enzymes ( ______ , _______ , _______ , and _______ ) are embedded in the luminal membranes (that is the brush border) of:

these enzymes protrude into the:

A

lactase, sucrase, maltase, and alpha-dextrinase

SI mucosal epithelial cells

SI lumen wehre they can be contacted by chyme

57
Q

the actions of the brush border enzymes and of pancreatic amylase result in water-soluble monosaccharides - ______ , _______ , and especially _______ - that are absorbed across the

A

fructose, galactose, and especially glucose

SI mucosal epithelium into blood capillaries, and the moved to the liver via the hepatic portal vein

58
Q

fructose is absorbed into SI mucosal epithelial cells via

A

facilitated diffusion (non ATP using carrier) and thus requires a membrane-bound carrier protein (GLUT) and a fructose concentration gradient, but does not require ATP expenditure

59
Q

glucose and galactose enter SI mucosal epithelial cells via

A

secondary active transport that uses a sodium-glucose cotransport protein called SGLT

60
Q

fructose, glucose, and galactose move from teh epithelial cells into the interstitial fluid via

A

facilitated diffusion (using a GLUT carrier in the basolateral membranes of the cells) and then into the blood via simple diffusion through pores in capillary walls

61
Q

the majority of absorptiono occurs in

A

the duodenum and first part of jejunum

62
Q

cause of lactose intolerance

A

absence of brush border lactase

63
Q

fructose:

transport into enterocyte:

transport out of enterocyte:

A

GLUT (facilitated diffusion)

GLUT (facilitated diffusion)

64
Q

glucose and galactose:

transport into enterocyte:

transport out of enterocyte:

A

SGLT (secondary active transport)

GLUT (facilitated diffusion)

65
Q

protein digestion and absorption is required in the diet to provide

A

essential amino acids and to replace the nitrogen contained in protein/amino acids that are converted to urea

66
Q

in addition to dietary protein, much protein is

A

secreted into the GI tract lumen as enzymes and mucus; these are also digested and absorbed

67
Q

pepsin (secreted as pepsinogen)

A

enzyme created by stomach and secreted into the stomach lumen, breaks proteins into peptide fragments

68
Q

trypsin and chymotrypsin

A

pancreatic enzymes that act in the SI and assist with digesting proteins into peptide fragments

69
Q

peptide fragments are borken into free amino acids in the SI by the pacreatic enzyme ________ and by ________ (and several othe peptidases, such asdipeptidase) embedded in:

A

carboxypeptidase and by aminopeptidase

SI mucosal epithelial cell membranes

70
Q

absorption of amino acids

free amino acids enter epithelial cells by

A

sodium cotransport. this involves many transporters with different amino acid specificities

71
Q

some chains of 2 or 3 amino acids move into the cells by

A

secondary active transport coupled to H+ (rather than Na+) ; these chains are hydrolyzed into free amino acids within the cells

72
Q

amino acids move from the cells to the interstitial fluid by

A

facilitated diffusion involving many carrier molecules and then enter the blood by diffusin through capillary pores

73
Q

occasionally very small amounts of intact proteins can be absorbed without being _______ . these proteins are engulfed by the SI mucosal epithelial cells via _______

A

digested

endocytosis

74
Q

the ability to absorb proteins without being digested is especially great in _______ and allows them to get ______ from teh mother’s milk

A

infants

antibodies

75
Q

most lipids are ingested as

A

triglycerides

76
Q

most digestion of fats/lipids occurs in

A

the SI by the pancreatic enzyme lipase

77
Q

a triglyceride molecule is

A

3 fatty acids bound to a single glycerol

78
Q

digestion of a triglyceride molecule results in

A

2 free fatty acids and one monoglyceride molecule (2-monoglyceride)

79
Q

most ingested lips are not _______ and thus form _______

A

water soluble

large lipid droplets

80
Q

because lipase is water soluble, its digestive action can only occur

A

at the surface of the large lipid droplets

81
Q

emulsification

A

process of breaking large lipid droplets into many smaller droplets which serves to speed up digestion of fats/lipids by increasing the surface area accessible to lipase

82
Q

emulsification is achieved by

A

by mechanical disruption of the droplets due to churning activity in the stomach and SI, and by emulsifyin agents contained in bile (bile salts and the phospholipid lecithin)

83
Q

a bile salt or lecithin molecule has a nonpolar part which is:

a bile salt or lecithin molecule also has a polar part which is:

A

soluble in fat and thus dissolves in the surface layer of a fat droplet

water soluble and is left exposed at the water surface of the small fat droplet where it repels other lipid droplets

84
Q

fatty acids and monoglycerides are also not _______ so absorbing them would be slow, except that bile salts form ______

A

water soluble

micelles

85
Q

micelles

A

are similar to emulsifed small fat droplets but MUCH smaller, and consist of fatty acids, monoglycerides, bile salts, and phospholipids with the polar ends of each moelcule facing the surface of the micelle

86
Q

a fatty acid or monoglyceride up against a SI mucosal epithelial cell can diffuse across

A

the lipid bilayer portion of the cell’s plasma membrane

87
Q

micelles (by breaking down and reforming) slowly release

A

fatty acids and monoglycerides where they can undergo diffusion across the lipid bilayer portion of a SI mucosal epithelial cell’s plasma membrane

88
Q

in the smooth ER of epithelial cells, enzymes reassemble the fatty acids and monoglycerides into ______ which

A

triglycerides

aggregate into small fat droplets (coated by amphiphatic proteins)

89
Q

vesicles containing small fat droplets pinch off from the ER, move to the _______ and fuse with the cell’s _______ . this releases fat droplets into

A

Glogi

plasma membrane

the ECF where they are called chylomicrons

90
Q

basement membranes associated with blood capillaries prevent

A

chylomicrons from entering capillaries, instead, chylomicrons pass into lacteals

91
Q

the lymph from the lacteal (as with all lymph) eventually empties

A

into the blood contained within systemic veins

92
Q

the fat-soluble vitamins are

A

A, D, E, and K

93
Q

fat-soluble vitamins undergo the same absorption pathway as

A

fats

94
Q

some water soluble vitamins are absrobed by _______ and some by _______

A

diffusion and some by carrier-mediated transport

95
Q

B12 , is water soluble, is large and charged and cannot be absorbed unless it is first combined with

A

intrinsic factor (protein) that is secreted by the stomach

96
Q

intrinsic factor bound B12 binds to

A

epithelial cells in the ileum, where B12 is absorbed by endocytosis into mucosal epithelial cells

97
Q

B12 is required for

A

red blood cell production

98
Q

a deficiency in B12 can result if

A

pernicious anemia

99
Q

small amounts of water are absorbed in

A

the stomach

100
Q

about 80 percent of the ingested and secreted water entering the SI is absorbed

A

there in the SI

101
Q

SI epithelial membranes are very water permeable, and water absorption occurs whenever

A

a water concentration gradient exists

102
Q

water concentration gradient are established by the

A

absorption of solutes, especially sodium

103
Q

Na+ is moved via the sodium-potassium pump _______ the intestinal epithelial cells and into the ______. This ______ the Na+ concentration within the cell to below the value typically found in the chyme

A

out of

ECF

lowers

104
Q

once out of the intestinal epithelial cells and into the ECF, Na+ then moves down its electrochemical gradient from

A

the chyme into the epithelial cells by moving through ion channels or by co-transport mechanisms that also bring amino acids, glucose, galactose, or chloride ions into the cells

105
Q

potassium, magnesium, calcium, zinc, iodide, iron, and other minerals are absorbed via various mechanims, some that are ______ and others that are ______

A

active and others that are passive

106
Q

when the entire lenghts of the SI and LI are considered, some ions such as bicarbonate, are ________ from the lumen in some locations and are _______ into it in other locations

A

absorbed

excreted

Physiology II (16 decks)

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