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human physiology > GI tract > Flashcards

GI tract Flashcards

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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
gastric pits - what are the secretory products
pepsinogen, H+, intrinsic factor, gastrin
26
gastric pits - what secretes pepsinogen
chief cells
27
gastric pits - what secretes H+
parietal cells
28
gastric pits - what secretes intrinsic factor
parietal cells
29
gastric pits - why is intrinsic factor important
so that B12 can be absorbed
30
gastric pits - what secretes gastrin
G cells
31
what are the 3 divisions of the small intestine
duodenum, jejunum, ileum
32
what is secreted into the duodenum
pancreatic juice and bile
33
what are crypts of lieberkuhn
epithelial cells that secrete bicarbonate-rich fluid in small intestine
34
what happens in the hepatic portal system
delivers fresh blood to liver, nutrients travel from liver to heart
35
what are the 3 divisions of the large intestine
cecum, colon and rectum
36
function of colon
concentrate wastes to faeces, absorption of water
37
what are the 4 sections of the colon
ascending, transverse, descending, sigmoid
38
what type of muscle is the internal anal sphincter
smooth
39
what type of muscle is the external anal sphincter
skeletal
40
GI gland types
surface glands, mucosal/submucosal glands, deep tubular glands, specialised glands
41
characteristics of salivary glands
rich in bicarbonate, contain mucous, salivary amylase, lysozyme
42
saliva - what does a serous secretion contain
salivary amylase
43
saliva - what does a mucous secretion contain
mucins
44
3 types of glands in the stomach
cardiac, oxyntic/gastric, pyloric
45
gastric juice: what do the cardiac glands secrete
mucous
46
gastric juice: what do the oxyntic glands secrete
HCl, pepsinogen, mucous
47
gastric juice: what do the pyloric glands secrete
pepsinogen, mucous
48
what causes peptic ulcers
too much acid and too much pepsin. Too much mucous or irritation/ infection vof the mucosa
49
how do helicobacter pylori make ulcers
activate the immune response which destroys the tissue of the stomach
50
what is in the pancreatic juice
bicarbonate, amylase and lipase, proteases, nucleases
51
how does the pancreas not digest itself
the enzymes it secretes are zymogens (inactivated enzymes)
52
where are zymogens stored
in zymogen granules in acinar cells
53
key liver functions
secrete bile, processes nutrients
54
what is the ampulla of vater
where the liver and pancreatic duct join
55
what enzymes are found in the brush boarder
dextrinase, glucoamylase, sucrase, lactase, maltase
56
what does dextrinase do
break down limit dextrins into glucose
57
how are zymogens activated
they are cleaved, once one is cleaved a cascade begins
58
how is pepsinogen (zymogen) FULLY activated
HCl partially activates it and then it acts on other molecules of pepsinogen to activate them
59
what are the brush border proteases
aminopeptidase and enterokinase
60
what are the pancreatic proteases
trypsin, chymotrypsin, carboxypeptidase
61
which vitamins are fat soluble
A,D,E,K
62
How is vit B12 absorbed
by being bound to intrinsic factor
63
when is K+ secreted
when lumenal concentrations are low
64
how is Ca2+ absorbed
binds to calcium-binding protein on brush border
65
how does Vitamin D effect Ca2+ absorbtion
increases it as it increases the conc of calcium-binding protein
66
what is the feeding centre called
lateral hypothalamus
67
what is the satiety centre (fullness) called
ventromedial hypothalamus
68
what are the chemical satiety signals
glucostatic and lipostatic (release of leptin)
69
what is the nervous satiety signal
reflexes initiated by distension
70
what is the hormonal satiety signal
feedback by cholecystokinin
71
how are endocrine pathways effected by neural pathways in relation to the GI tract
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
GI hormones: Gastrin
in stomach and stimulated by proteins and protein products as well as stretch
72
GI hormones: Cholecystokinin (CCK)
in duodenum and jejunum and stimulated by fat or protein digestion
73
GI hormones: secretin
in duodenum or jejunum and stimulated by acid in duodenum
74
GI hormones: glucose-dependent insulinotropic peptide (GIP)
in duodenum and jejunum and stimulated by glucose, fats or acids in duodenum
75
what does CCK do
inhibits gastric secretion and motility
76
what does secretin do
potentiates actions of CCK, inhibits gastric secretion
77
phases of GI control: cephalic phase
thoughts, taste and smell of food. Requires CNS input
78
phases of GI control: gastric phase
stimuli in stomach, long and short reflex, GI hormones
79
Phases of GI control: intestinal phase
stimuli originate in small intestine, long and short reflex, GI hormones
80
how is saliva secretion stimulated?
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
what type of saliva is produced by PNS
watery
82
what type of saliva is produced by SNS
more mucus, thick saliva
83
what causes gastric secretion
PNS, gastrin, histamine
84
what inhibits gastric secretion
food leaving stomach, drop of pH, increased osmolarity and distention of small intestine
85
what does secretin do
stimulates bile secretion in the liver
86
how does the electrical activity in the GI smooth muscle work
spontaneous slow waves of depolarisation, PNS leads to excitation and SNS leads to inhibition
87
what are the interstitial cells of cajal
cells that trigger the slow waves of depolarisation in GI tissue
88
how does peristalsis occur
circular and longitudinal muscles contract and relax at different times
89
what is being stimulated when vomiting
stretch receptors and chemoreceptors
90
vomiting reflex summary
afferent nervous impulses from GI lining through sympathetic and vagal nerves to brain, mediated through vomiting center in medulla
91
what happens when you trigger the vomiting centre
reverse peristalsis in duodenum and relaxation of pyloric sphincter, respiration is suppressed
92
what is the migrating motility complex
intense contractions in small intestine that cleans it between meals
93
what is the colonocolonic reflex
distention of colon in one area causes relaxation in other areas
94
what is the gastrocolic reflex
food in stomach increases colonic motility

human physiology (15 decks)

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