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physiology test 3 > GI Physiology > Flashcards

GI Physiology Flashcards

1
Q

The GI tract is one long _____ digestive tube that extends from the ___ to the ____

A

muscular

mouth to the anus

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2
Q

along the GI tract, there are major sections such as the esophagus, stomach, small intestines that are all separated by ____

A

sphincters

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3
Q

what are the four layers of the GI tract wall ranging from the esophagus to the anus

A

muscosa, submucosa, muscularis, and serosa

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4
Q

describe the mucosa

A

the innermost layer which functions in the production of mucus, digestive enzymes, hormones, absorption of nutrients, and protection against infectious diseases

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5
Q

what type of cells are present in the intestinal lumen of the mucosa that contains cappilaries

A

simple columnar epithelial cells

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6
Q

what function do the capillaries have in the mucosa

A

nourish the cells and allow for efficient absorption of digested nutrients into the blood

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7
Q

where is the submucosa located

A

the second innermost layer

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8
Q

what is the function of the submucosa

A

contains elastic fibers that enable the GI tract to regain its shape after food moves through it.

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9
Q

in the submucosa, what intrinsic neuronal system is housed here

A

enteric nervous system

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10
Q

what is the function of the enteric nervous system

A

regulated digestive activities such as motility, secretion and blood flow

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11
Q

where is the muscularis layer located

A

the muscular portion, the third layer

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12
Q

what types of muscles are present in the muscularis layer

A

longitudinally and circular layered smooth muscules

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13
Q

what layer in the GI tract forms sphincters

A

muscularis layer (located throughout the GI tract)

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14
Q

the coordinated contractions of the muscularis layer are responsible for what function

A

peristalsis and other contractions which propels food forward so that it goes towards the distal end of the GI tract

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15
Q

when does peristalsis occur in the GI tract

A

as soon as food enters into an area of the GI tract

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16
Q

what is the function of the smooth muscle in the front muscularis layer

A

it relaxes

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17
Q

what is the function of the smooth muscle in the behind muscularis layer

A

contracts and essentially squeezes food forward

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18
Q

where is the serosa located

A

the protective outermost layer

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19
Q

what is the function of the serosa

A

adheres to the GI tract to support structures and secretes serous fluid that lubricates the organs reducing friction during movement

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20
Q

the intestines receive _______ innervation from the autonomic nervous system

A

extrinsic

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21
Q

what is the function of the parasympathetic neurons in the GI tract

A

rest and digest, which occurs by the release of ACETYLCNOLINE which increase the secretions and contractions of the smooth muscles

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22
Q

what is the function of the sympathetic neurons in the GI tract

A

Epinephrine and norepinephrine which will decrease the activity of the smooth muscles, reduce secretions, and cause the sphincters to contract, blocking progression of intestinal contents

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23
Q

_____ receives food and mixes it with saliva from the mouth

A

esophagus

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24
Q

relaxation of the upper esophageal sphincter allows for what to occur

A

food to enter the upper portion of the esophagus

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25
Q

once food is in the esophagus, what action takes place

A

an esophageal contraction propels food to the lower esophageal sphincter (LES)

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26
Q

the lower esophageal sphincter takes part in _____ activity resulting in what action to occur

A

TONIC (a contracted state), however it relaxes reflexively to allow for food to enter into the stomach

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27
Q

the lower esophageal sphincter remains _____ between swallowing which aids in ______

A
  • closed

- prevents regurgitation of gastric contents into the esophagus

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28
Q

what are the three different types of muscles present in the lower esophageal sphincter

A
  1. smooth muscle and muscularis layer of the esophagus
  2. skeletal muscles from the diaphragm
  3. smooth muscles from the stomach
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29
Q

when the LES opens following a meal, to expel swallow air what occurs

A

a burp

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30
Q

what is the function of the stomach

A

a temporary storage unit where chemical digestion of food begins

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31
Q

ingested contents and digestive secretions are mixed by coordinated muscular contractions forming ____ in the stomach

A

chyme

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32
Q

what are the three regions of the stomach

A

cardia
fundus of the body (aka corpus)
antrum

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33
Q

the lining of the stomach is covered in _____ cells

A

columnar epithelial cells folded into gastric pits

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34
Q

in the stomach, each gastric pit which allows for____

A

an opening of a duct into which one or more gastric glands empty

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35
Q

list the 4 types of secretory gastric cell types

A
  1. mucous cells
  2. parietal cells
  3. chief cells
  4. endocrine cells (G cells)
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36
Q

where are mucous cells located and what is their primary function

A

cardia and antrum

-Fx: mucus secretion

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37
Q

where are parietal cells located and what is their primary function

A

fundus and body

-Fx: gastric acid secretion

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38
Q

where are chief cells located and what is their primary function

A

fundus and body

-Fx: pepsinogen and lipase secretion

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39
Q

where are endocrine cells located and what is their primary function

A

antrum

-Fx: gastrin secretion

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40
Q

____ and ____ is where most chemical digestion occurs

A

body and fundus

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41
Q

typically, how much volume is released from gastric muscosa throughout the day

A

3L

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42
Q

gastric juice consists of what types of enzymes

A

electrolytes
hydrochloric acid (the enzyme pepsinogen)
mucus
intrinsic factor

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43
Q

the primary secretion of the stomach is ________ ions produced by _____

A

hydrogen ions

parietal cells

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44
Q

what are the two types of mechanisms that control gastric secretions

A

neural and hormonal

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45
Q

what are the three enzymes regulating gastric secretion

A

acetylcholine, gastrin, histamine

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46
Q

Gastrin can directly stimulate _____ and ______

A

proton potassium APTase pump and parietal cells

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47
Q

gastrin can additionally stimulate enterochromaffin like cells (ECL) causing______

A

histamine

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48
Q

what are the two specific PGE 2 and their function

A

somatostatin and prostaglandins— inhibit acid secretion

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49
Q

the gastric juices that the stomach is exposed to, has a pH of ____

A

1.5-3.5 and contains digestive enzymes

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50
Q

the acidic environment in the stomach produced by the digestive enzymes aid in

A

digestion and absorption of ingested contents as well as destroys ingested bacteria and microorganisms

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51
Q

due to the extreme pH that the stomach is exposed to, a protective mucosal barrier is composed of

A

bicarbonate rich mucus

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52
Q

the mucosal barrier protects the stomach lining and protects the epithelial cells in the mucosa by

A

maintaining a thin layer of pH which is 6-7

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53
Q

in addition to the mucosal barrier, the stomach contains ________ ______ preventing gastric juice from leaking into underlying tissue between epithelial cells and the mucosa

A

thin junction

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54
Q

____ and ____ increase the frequency and magnitude of stomach contractions augmenting gastric mixing

A

gastrin and acetylcholine

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55
Q

gastric contents are mixed and formed into a semi solid state known as _____ typically within ___ hrs after the meal is injested

A

chyme

4 hours

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56
Q

in order for chyme to enter into the small intestine, ____ acts as a filter only allowing ___ cc in at a time

A

pyloric sphincter

3 cc or less

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57
Q

the rate of emptying is dependent on what two factors

A

chemical and physical contents

58
Q

Carbohydrate rich meals empty ____ while fats empty ____

A

carbs-rapidly

fats- slows

59
Q

fats empty slower due to

A

fat forming an oily layer at the top of the chyme and move through the stomach slower

60
Q

what are the three sections of the small intestines

A

duodenum
jejunum
ileum

61
Q

____ is made of food and digestive enzymes, passing from the stomach through the pyloric sphincter and enters the duodenum in small parts containing tiny suspended particles

A

chyme

62
Q

______ is the primary site for the mixing of chyme with additional secretions from the common bile duct and the pancreatic ducts which aid in ____

A

small intestines

digestion and absorption

63
Q

the small intestines provide _____ which digestion and absorption occur

A

substantial surface area

64
Q

what are the 4 factors contributing to the large surface area of the small intestines

A
  1. length of small intestines (5 Meters)
  2. mini folds of mucosa and submucosa layer
  3. villi (finger like projections that increase absorptive surface area)
  4. microvillin on apical surface increase surface area (600 fold, allow for rapid mvnt of nutrients into BLOOD)
65
Q

there is ___ layers of epithelial cells between the intestinal lumen and systemic blood

A

1

66
Q

cells that are located at the base of the villi _______ as they migrate toward the tip of the villi which causes shedding every _____

A

differentiate

2-6 days

67
Q

what is the primary physiological function of the small intestine

A

digestion and absorption of ingested nutrients such as (carbs, proteins, lipids)

68
Q

humans shed ____ cells per day

A

17 billion

69
Q

what are dietary carbohydrates primarily comprised of

A

polysaccharides (starch) and disaccharides (sucrose and lactose)

70
Q

enterocytes are only capable of absorbing

A

monosaccharides

71
Q

for enterocytes, carbohydrates must be digested as what two things

A

monosaccharides or simple sugars (glucose, galactose, and fructose)

72
Q

describe stage 1 that occurs for carbohydrate digestion

A
  1. amylase cleaves the internal bonds of polysaccharides to form fragments such as disaccharides, trisaccharides, and oligosaccharides. If hydrolase is present at the brush border, then digest disaccharides and oligosaccharides into monosaccharides. Monosaccharides are water soluble they have to be assisted across the plasma membrane of the enterocytes by action of transport protients
73
Q

_____ are water soluble, needing transport proteins to aid across plasma membrane

A

water soluble

74
Q

describe stage 2 that occurs for carbohydrate digestion

A
  1. lipid digestion/absorption are ENTIRELY soluble in water, making lipids aggregate together. First, emulsification must occur producing a suspension of fine lipid droplets. Bile sats are then triggered to be released from the liver aiding in emulsification of lipids. Next lipids are chemically digested by LIPASE, which occurs by the brush border on the intestines.
75
Q

what is another lipase

A

phospholipase (which hydrolyzes phospholipids and cholesterol esterase which break down esters in cholesterol… ex soap and water in an oiled pan (soap is the emulsifier and washes away the oil)

76
Q

proteins must be able to digests to _____, _____, and ____ for transport into enterocytes

A

tripeptides
dipeptides
amino acids

77
Q

where do digestion of proteins being

A

in the stomach, where the acidic environmentw can hydrolyze peptide bonds

78
Q

what do the chief cells in the stomach release and

A

pepsinogen

79
Q

Pepsinogen causes a cascade of events which is activated by

A

the low pH to an ACTIVE form called pepsin

80
Q

premature activation of digestive enzymes can lead to

A

damage of the intestinal lining or stomach lining

81
Q

when does pepsin function the best

A

in an acidic environment

82
Q

pepsin is preferentially hydrolyzes the peptide bond following the aromatic amino acids such as

A

phenylalanine, tryptophan, and tyrosine

83
Q

since pepsin only constitutes a few of the amino acids, a more complete digestion of proteins require additional _____

A

proteases released by the pancrease

84
Q

in the stomach, the pancreatic proteases are released as _______ precursors which are converted into ___ enzymes

A

inactive and active

EX: trypsinogen inactive is converted into trypsin active

85
Q

when trypsin is converted to the active form, it activates

A

all other pancreatic proteases

86
Q

digestion of oligopeptides occurs ______ which produced what three peptides

A

brush boader proteases

tripeptides, dipeptides, or individual amino acids

87
Q

the converted oligopeptides are transported into the cells via _________ containing ____ or coupled with ____ symporters

A

secondary active transport

sodium or coupled with proton symporters

88
Q

____ and _____ and further digested by systolic peptidase to individual amino acids

A

dipeptides and tripeptides

89
Q

The small intestines is the major site for what type of absorption.

A

water and electrolyte

90
Q

water absorption is _______ and most occurs by what type of route

A

passive

transcellular route via water channels (aka aquaporins)

91
Q

small amounts of water can still move through a _______route, even though epithelial cells are interconnected by tight junctions

A

paracellular route

92
Q

in the duodenum and jejunum tight junctions are ____ and become _______ in the ileum or colon

A

leaky

progressively tighter

93
Q

how does water move in the small intestines

A

both directions across the mucosa depending on the osmotic gradient

94
Q

depending upon the intestinal contents, osmolarity of the duodenal contents may be ____ or ______ to that of the plasma

A

hypertonic or hypotonic

95
Q

once contents enter the jejunum, the osmolarity is _________

A

similar to plasma and maintained throughout the rest of the small intestine

96
Q

sodium absorption in the small intestines is mainly _______traveling through the cells passing through both ____ and _____ membranes

A

transcellular

apical and basolateral membranes

97
Q

the Sodium potassium ATPase, maintains what in the small intestines

A

low intracellular concentrations of sodium allowing for the luminal sodium to enter the enterocyte

98
Q

sodium transport is primarily coupled with ______

A

glucose and some amino acids

99
Q

glucose is also important in driving what

A

sodium reabsorption

100
Q

since ______ can drive sodium reabsorption, what is important to remember for individuals with HTN

A

GLUCOSE—we need this patient population to avoid glucose

101
Q

______ are reabsorbed through a antiporter exchanger

A

quadions (which bicarb ions are secreted into the lumen)

102
Q

______ acts on the protected epithelial cells in the most proximal section of the duodenum, where acid and pepsin are in high levels

A

bicarbonate

103
Q

the movement of electrolytes and nutrients form the intestinal lumen into the blood creates the _____ driving what process to occur

A

osmotic gradient

drive water absorption

104
Q

the net movement of water and electrolytes int eh small intestines is primary

A

absorptive, allowing electrolytes secretion to occur

105
Q

what ions are secretes through channels in the small intestines

A

potassium

chloride

106
Q

where is potassium secreted in the SI

A

through K channels into the intestinal lumen

107
Q

where are chloride ions secreted in the SI

A

the intestinal lumen via chloride channels located in apical membrane

108
Q

the movement of negatively charged ions, create a

A

electrical gradient

109
Q

the result of increased ions in the intestinal lumen causes an increase in the

A

osmotic concentration

110
Q

water will move from _____ into the _____ to maintain equal solid concentrations

A

plasma into the lumen

111
Q

what is the target drug therapy for patients struggling with constipation

A

by increasing the amount of ions in the intestinal lumen, this results in higher water contents in the intestines allowing for more intestinal contents to pass freely

112
Q

how do fluid and electrolyte secretions act to protect the mucosal layer

A

they flush bacterial products and toxins away from epithelial cells

113
Q

what two signaling molecules stimulate fluid and electrolyte secretions in healthy and sick individuals

A

neural and paracrine signaling

114
Q

what are the two ways that smooth muscle contractions can occur in the small intestines

A

segmentation contractions and peristaltic waves

115
Q

what occurs during segmentation contractions

A

nonadjacent segments of the intestines, rhythmically contract and relax moving food in both directions, mixing intestinal contents with cell secretions

116
Q

what occurs during peristaltic waves

A

these waves propel the chyme forward through SI towards the large intestines, allowing for adjacent segments to alternatively contract and relax propelling food forward.

117
Q

when does peristalsis occur in the digestive process

A

late, after most nutrients have been absorbed

118
Q

segmentation contractions aid in _____ transit, and increase contact time which ultimately _______

A

slowing transit

this increases contact btw chyme and epithelial cells (increasing absorption)

119
Q

what three segments compose the large intestines

A

ascending, transverse, descending

120
Q

what are the 4 functions of the colon (large intestines)

A
  1. complete digestion
  2. absorb remaining water/electrolytes
  3. secrete mucus
  4. store unabsorbed material until eliminated by the body
121
Q

the wall of the large intestine differs from the small intestines because

A
  • few folds
  • no villi
  • no cells secreting digestive enzymes
  • large number of goblet cells (increasing mucus production)
122
Q

once the unabsorbed material reaches the LI, ____ nutrients remain

A

very few

123
Q

how much digestion occurs in the LI

A

very little except for the small amounts of digestion by the intestinal microbial flora

124
Q

similar to the SM, in the LI water absorption is coupled to _____ and _____ electrolyte movement

A

sodium and chloride

125
Q

_____ nervous system is composed of nerve fibers from the elementary track from esophagus to the anus

A

enteric

126
Q

how many nerve fibers are present in the enteric nervous system

A

100 million (which rivals the number found in the entire spinal cord)

127
Q

majority of the enteric nerve fibers are found along the _____ and are within the walls of _____

A

alimentary track

gastrointestinal tissues

128
Q

the other nerve fibers that enter and leave the ENS (enteric) maintain communication with high control centers found in what two systems

A

autonomic nervous system and central nervous system

129
Q

the enteric nervous system is primarily localized to two

A

extensive plexuses (web like collection of nerves)

130
Q

the enteric NS runs along the ____ tissue layer in the GI tract

A

inner

131
Q

where is the myenteric plexus located and what is the primary function

A
  • located btw longitudinal and circular muscle layers

- fx: responsible for control of muscular contraction and mechanical aspects of digestion

132
Q

what are the two plexuses from the enteric nervous sytem

A

myenteric and submucosal

133
Q

where is the submucosal plexus and what is its function

A
  • lies in the submucosa
  • fx: controlled digestive secretions, absorption, and local contration of submucosal muscle leading to enfolding of the mucosa
134
Q

the enteric nervous system must be able to respond to control signals from the ____ & _____ nervous sytem

A

sympathetic and parasympathetic

135
Q

why does the gut need to know how to respond to the autonomic nervous system

A

to permit or inhibit blood flow to our GI tract

  • fight/flight: blood and nutrients shunted to skeletal muscles and brain
  • rest/digest: blood/nutrients increases activity of the gut to replenish nutrients, minerals, water
136
Q

the enteric nervous system must additionally respond to what two nerve fibers

A

efferent (carry signals to the ENS)

afferent (originate in the wall of gut/carrying signals alimentary canal into ENS plexuses allowing GI tract to respond)

137
Q

some of the afferent nerve fibers lead the GI tract all together causing the relay of signals from the ___ to the _______

A

gut to the prevertebral sympathetic ganglion

138
Q

when the afferent nerve fibers transfer signals to prevertebral sympathetic ganglion, this evokes a

A

reflex whereby distant portion of the GI tract can be controlled by effects else where
(EX: signals can be sent to the stomach to initiate colon motility as room is needed for the newly digested foods_

139
Q

an additional afferent nerve fiber that runs into the ____ nerve allows higher level control for all aspects of digestion

A

vagus

140
Q

over-activation or under-activation fo the enteric nervous system can lead to

A

excessive or diminished secretions, absorption, motility, prolonged food residents and chyme

141
Q

abnormal enteric nervous system functions can also manifest as

A

pain and other sensations

142
Q

when adding a medication to a patients stomach, it is important to remember the potential impact on the ENS as well as the

A

microbiome located in their system

physiology test 3 (11 decks)

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