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human physiology > GI tract > Flashcards

GI tract Flashcards

1
Q

how is intake regulated

A

neural and endocrine pathway

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2
Q

2 major parts of the GI system

A

GI tract and accessory glands

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3
Q

what does the GI system supply the body w

A

water, electrolytes and nutrients

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4
Q

what are the 8 essential amino acids in humans

A

tryptophan, methionine, valine, threonine, phenylalanine, leucine, isoleucine, lysine

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5
Q

how long is the gut

A

15ft

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6
Q

what are the 4 layers of the GI tract (inside to out)

A

mucosa, submucosa, muscularis externa, serosa

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7
Q

What makes up the mucosa

A

mucous membrane, lamina propria, muscularis mucosae

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8
Q

what makes up the mucous membrane

A

enterocytes- epithelial cell layer, absorptive cells, exocrine cells, goblet cells, endocrine cells

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9
Q

what do goblet cells do

A

secrete mucous

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10
Q

what is the lamina propria

A

layer of connective tissue with blood vessels, nerves and lymphatic system

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11
Q

what is the muscularis mucosae

A

thin layer of smooth muscle

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12
Q

what is the submucosa made of

A

connective tissues so that vol of stomach can stretch, enteric nervous system

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13
Q

what is the enteric nervous system made of

A

submucosal plexus and myenteric plexus

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14
Q

what is a plexus

A

where nerves meet

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15
Q

what is the muscularis externa

A

2 separate layers of smooth muscle which contract to narrow lumen or lengthen. inner later generates spontaneous depolarisations

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16
Q

what is the inner layer of the serosa made of

A

fibrous connective tissue, structural support

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17
Q

what is the outer layer of the serosa made of

A

epithelial tissue - the mesothelium, mesenteries - sheets of connective tissues

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18
Q

what does the mesothelium do

A

protects GI tract from friction by lubricating organs so they can slide past eachother

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19
Q

what are the muscles in the esophagus like

A

upper 1/3 is skeletal, lower 2/3 are smooth

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20
Q

what happens in the swallowing reflec

A

tongue pushes the bolus to the back of the mouth, upper esophageal sphincter relaxes, epiglottis closes, food moves down

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21
Q

what does the stomach do

A

secretes gastric juice, releases food to intestine slowly

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22
Q

what are the 3 regions of the stomach and their characteristics

A

fundus, body- storage and mixing, antrum- release of food to intestine

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23
Q

what are rugae

A

folds in stomach that flatten on expansion

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24
Q

why is the stomach acidic

A

pepsinogen can only be activated in acidic environments, denature proteins, kill bacteria

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25
Q

gastric pits - what are the secretory products

A

pepsinogen, H+, intrinsic factor, gastrin

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26
Q

gastric pits - what secretes pepsinogen

A

chief cells

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27
Q

gastric pits - what secretes H+

A

parietal cells

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28
Q

gastric pits - what secretes intrinsic factor

A

parietal cells

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29
Q

gastric pits - why is intrinsic factor important

A

so that B12 can be absorbed

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30
Q

gastric pits - what secretes gastrin

A

G cells

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31
Q

what are the 3 divisions of the small intestine

A

duodenum, jejunum, ileum

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32
Q

what is secreted into the duodenum

A

pancreatic juice and bile

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33
Q

what are crypts of lieberkuhn

A

epithelial cells that secrete bicarbonate-rich fluid in small intestine

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34
Q

what happens in the hepatic portal system

A

delivers fresh blood to liver, nutrients travel from liver to heart

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35
Q

what are the 3 divisions of the large intestine

A

cecum, colon and rectum

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36
Q

function of colon

A

concentrate wastes to faeces, absorption of water

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37
Q

what are the 4 sections of the colon

A

ascending, transverse, descending, sigmoid

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38
Q

what type of muscle is the internal anal sphincter

A

smooth

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39
Q

what type of muscle is the external anal sphincter

A

skeletal

40
Q

GI gland types

A

surface glands, mucosal/submucosal glands, deep tubular glands, specialised glands

41
Q

characteristics of salivary glands

A

rich in bicarbonate, contain mucous, salivary amylase, lysozyme

42
Q

saliva - what does a serous secretion contain

A

salivary amylase

43
Q

saliva - what does a mucous secretion contain

A

mucins

44
Q

3 types of glands in the stomach

A

cardiac, oxyntic/gastric, pyloric

45
Q

gastric juice: what do the cardiac glands secrete

A

mucous

46
Q

gastric juice: what do the oxyntic glands secrete

A

HCl, pepsinogen, mucous

47
Q

gastric juice: what do the pyloric glands secrete

A

pepsinogen, mucous

48
Q

what causes peptic ulcers

A

too much acid and too much pepsin. Too much mucous or irritation/ infection vof the mucosa

49
Q

how do helicobacter pylori make ulcers

A

activate the immune response which destroys the tissue of the stomach

50
Q

what is in the pancreatic juice

A

bicarbonate, amylase and lipase, proteases, nucleases

51
Q

how does the pancreas not digest itself

A

the enzymes it secretes are zymogens (inactivated enzymes)

52
Q

where are zymogens stored

A

in zymogen granules in acinar cells

53
Q

key liver functions

A

secrete bile, processes nutrients

54
Q

what is the ampulla of vater

A

where the liver and pancreatic duct join

55
Q

what enzymes are found in the brush boarder

A

dextrinase, glucoamylase, sucrase, lactase, maltase

56
Q

what does dextrinase do

A

break down limit dextrins into glucose

57
Q

how are zymogens activated

A

they are cleaved, once one is cleaved a cascade begins

58
Q

how is pepsinogen (zymogen) FULLY activated

A

HCl partially activates it and then it acts on other molecules of pepsinogen to activate them

59
Q

what are the brush border proteases

A

aminopeptidase and enterokinase

60
Q

what are the pancreatic proteases

A

trypsin, chymotrypsin, carboxypeptidase

61
Q

which vitamins are fat soluble

A

A,D,E,K

62
Q

How is vit B12 absorbed

A

by being bound to intrinsic factor

63
Q

when is K+ secreted

A

when lumenal concentrations are low

64
Q

how is Ca2+ absorbed

A

binds to calcium-binding protein on brush border

65
Q

how does Vitamin D effect Ca2+ absorbtion

A

increases it as it increases the conc of calcium-binding protein

66
Q

what is the feeding centre called

A

lateral hypothalamus

67
Q

what is the satiety centre (fullness) called

A

ventromedial hypothalamus

68
Q

what are the chemical satiety signals

A

glucostatic and lipostatic (release of leptin)

69
Q

what is the nervous satiety signal

A

reflexes initiated by distension

70
Q

what is the hormonal satiety signal

A

feedback by cholecystokinin

71
Q

how are endocrine pathways effected by neural pathways in relation to the GI tract

A

breakdown products trigger receptors which in turn trigger enteric nervous system leading to a change in secretory activity in the endocrine cells. The receptors can also trigger CNS and then ANS which then does the same as the short pathway

71
Q

GI hormones: Gastrin

A

in stomach and stimulated by proteins and protein products as well as stretch

72
Q

GI hormones: Cholecystokinin (CCK)

A

in duodenum and jejunum and stimulated by fat or protein digestion

73
Q

GI hormones: secretin

A

in duodenum or jejunum and stimulated by acid in duodenum

74
Q

GI hormones: glucose-dependent insulinotropic peptide (GIP)

A

in duodenum and jejunum and stimulated by glucose, fats or acids in duodenum

75
Q

what does CCK do

A

inhibits gastric secretion and motility

76
Q

what does secretin do

A

potentiates actions of CCK, inhibits gastric secretion

77
Q

phases of GI control: cephalic phase

A

thoughts, taste and smell of food. Requires CNS input

78
Q

phases of GI control: gastric phase

A

stimuli in stomach, long and short reflex, GI hormones

79
Q

Phases of GI control: intestinal phase

A

stimuli originate in small intestine, long and short reflex, GI hormones

80
Q

how is saliva secretion stimulated?

A

taste and texture of food stimulates mechanoreceptors and taste receptors in the mouth, salivary center in medulla is stimulated which triggers ANS which leads to saliva secretion

81
Q

what type of saliva is produced by PNS

A

watery

82
Q

what type of saliva is produced by SNS

A

more mucus, thick saliva

83
Q

what causes gastric secretion

A

PNS, gastrin, histamine

84
Q

what inhibits gastric secretion

A

food leaving stomach, drop of pH, increased osmolarity and distention of small intestine

85
Q

what does secretin do

A

stimulates bile secretion in the liver

86
Q

how does the electrical activity in the GI smooth muscle work

A

spontaneous slow waves of depolarisation, PNS leads to excitation and SNS leads to inhibition

87
Q

what are the interstitial cells of cajal

A

cells that trigger the slow waves of depolarisation in GI tissue

88
Q

how does peristalsis occur

A

circular and longitudinal muscles contract and relax at different times

89
Q

what is being stimulated when vomiting

A

stretch receptors and chemoreceptors

90
Q

vomiting reflex summary

A

afferent nervous impulses from GI lining through sympathetic and vagal nerves to brain, mediated through vomiting center in medulla

91
Q

what happens when you trigger the vomiting centre

A

reverse peristalsis in duodenum and relaxation of pyloric sphincter, respiration is suppressed

92
Q

what is the migrating motility complex

A

intense contractions in small intestine that cleans it between meals

93
Q

what is the colonocolonic reflex

A

distention of colon in one area causes relaxation in other areas

94
Q

what is the gastrocolic reflex

A

food in stomach increases colonic motility

human physiology (15 decks)

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