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Human physiology > digestion structures and function > Flashcards

digestion structures and function Flashcards

1
Q

what are parietal cells stimulated by

A

gastrin

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2
Q

what are D cells inhibited by

A

cephalic stage

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3
Q

three regions of the small intestine

A

deudenum
jujunum
ileum

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4
Q

what is segmentation

A

slow contractions of circular muscles
drives contents back and from mixing the chyme with digestive enzymes
strength of contraction regulated by food content

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5
Q

what is peristalsis

A

rhymic propulsive movements to move chyme along small intestine
mixes chyme with digestive enzymes

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6
Q

where are peristalsis contractions stronger?

A

duodenum to keep food going in right direction

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7
Q

Key histological features of the small intestine

A

folds called pilicae circulares adding surface area

villi and brush boarder

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8
Q

where does most of the absorption occur

A

jejunum

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9
Q

were are there the most plicase circulares

A

jejunum

lowest amount in duedenum

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10
Q

what are columar epitheial cells used for?

A

nutrient and electrolyte absorption

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11
Q

what is the crypt of lieberkuhn

A

bit at the bottom of the vili
no enzymes here but used for secretion
goblet cells
stem cells at base

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12
Q

what is a paneth cell?

A

synthesis and secretion of antimicrobial peptides and proteins

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13
Q

what is a goblet cell

A

secretion of mucin, major part of mucus

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14
Q

what is an undifferentiated crypt cell used for

A

proliferates to replace lost enterocytes

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15
Q

what is the fuction of enteric endocrine cells

A

secretion of CCK, gastrin, secretin and glucose-dependent insulinotrophic

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16
Q

what can be secreted by the small intestine?

A

mucus
water
bicarbonate
immune functions

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17
Q

why is mucus needed in the small intestine

A

protection from acids and proteases

most needed in the duodenum as lots of digestion is here and chyme is acidic

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18
Q

why is water secreted from the crypt/ small intestine

A

made in th cryt
makes mucus runny for movemnt
functional envronmnt for enzymes

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19
Q

where does bicarbonate get secreted from

A

brunners glands

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20
Q

role of bicarbonate

A

protects from acids

optimal conditions for enzymes to work in

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21
Q

what immune function secretions are made in the small intestine

A

chym is ner sterile due to acid
lots of bacteria are found in large intestin howver
antibacterial enzymes are secreted to help

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22
Q

where ar antimicrobials secreted?

A

peyers patch

paneth cells

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23
Q

what is the peyers patch

A

only found in the ileum
small masses of lymphatic tissue
boarder control for intestin and microbes

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24
Q

what is a brunner gland

A

found in the duedenum
releases bicarbonate rich alkaline fluid containing mucus
they protrude the lining of the duodenum

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25
Q

how is the peyers patch seen in the small intestine

A

small circul pumps of tissues in the cell lining

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26
Q

diffrnce between parts of the small intetine

A

duedenum: plicase and brunners glands
jejunum: plicae, more folds
ilum: vili, peyers patch

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27
Q

where does CCK come from

A

I cells of the duodenum and jejunum

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28
Q

where does secretin come from

A

S cells of small intestine

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29
Q

where does somatostatin come from

A

D cells of the stomach and duodenum

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30
Q

where does GIP come from

gastric inhibitory peptide

A

K cells in duodenum and jejunum

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31
Q

what does secretin do>

A

inhibits HCL/gastric juice
stimulates bicarbonate
neutralises the acid

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32
Q

what is the function of CCK

A

stops G cells making gastrin and stops chief and parietal cells
stimulates the pancreas to release digetive enzymes and makes the gall blader contract to digest food

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33
Q

what is the function of scretin

A

stops gastrin

neutralises acid making optimal conditions for enzymes

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34
Q

what stimulates secretin

A

pH drop

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35
Q

where is stomatastin made?

A

D cells

36
Q

what does stomatastin do/

A

stops gastrin firther
inhibits enzymes by the pancreas
stops everything at the end

37
Q

what is the gall bladers function

A

bile storage and concentration

38
Q

what controls the release of bile and pancreatic juice

A

sphincters

39
Q

what type of organ is the pancreas

A

exocrine gland

acessory digestive organ

40
Q

what does the pancreas do

A

rich in bicarbonate
neutralises the gastric contents that enter the small intestine
digests the carbohydrates, proteins and fats

41
Q

where does glucagon and insulin come from

A

glucagon comes from alpha cells

insulin beta cell

42
Q

what is an acinar

A

The pancreatic acinar cell is the functional unit of the exocrine pancreas. It synthesizes, stores, and secretes digestive enzymes.

43
Q

what are found in acinar cells

A

lots of RER and ribosomes

lots of proteins that are made and packages for ecretion

44
Q

what prevents autodigestion in the acinar cells

A

granules are acidic so not yet activated and require alkali for this
they are transported in acidic capsule then released and they can work

45
Q

what is a zymogen

A

digestive enzyme in the inactive form

prevents autodigetion

46
Q

what is trypsinogen

A

the inactive form of trypsin

cleaves peptide bonds

47
Q

what is elastase

A

also cleaves internal peptide bonds

48
Q

how do zymogens get activatd

A

for trypsin it gets activated by something in the brush boarder
once this is activated it can then go on and activate all the other zymogens of proteases

49
Q

what inceases the secretion of the pancreas

A

CCK and secretin
vagal nerve
contraction

50
Q

describe the process of activating the pancreas

A 
food arives
contains polypeptides to stimulate CCK
pH drops
stimulates secretin
secretin released into blood
CCK acts on pancreas to make zymogens
moves to intestines and are ativated
CCk causes gall blader to contract releasing bile
secretin acts on liver making more bile
more bicarbonate made too
51
Q

what action do CCK, gastrin and acetylcholine have on the pancreas

A

increassed secretion of pancreatic enzymes and chloride right fluid by acinar cells

52
Q

what action do secretin, histodine and vasoactive intestinal polypeptide have on the pancreas

A

increased secretion of bicarbonate rich fluid from the duct cells

53
Q

what action do insulin and insulin like growth factors have on the pancreas

A

increased enzyme synthesis and secretion

54
Q

what action does stomatastatin have on the pancreas

A

inhibited secretion from acinar and duct cells

55
Q

where is the most digestion

A

duodenum

brush boarder specifically

56
Q

most absorption

A

jejunum and ileum

57
Q

what role does the borush boarder have on digesion

A

enzymes are localise here and they digest the macromolecules

58
Q

what is sodium key for in digestion

A

osmolarity and transport of molecules from lumen to the blood

59
Q

where does Na need to be

A

less Na in lumen
follows a concentration gradient of diffusion
but polar so needs some help to move

60
Q

what allows Na to move

A

facillitatied diffusion

then active transport

61
Q

describe the process of sodium absorption

A

sodium channels allows facillitative diffusion of Na acros from the lumen of intestine into epithelial cell
from here, activate transport is used to pump it from the epithelial cell to the blood where it can enter the vessel

62
Q

whats the balance of amino acids like?

A

more in cells that in the lumen

63
Q

how are amino acids transported

A

active transport along with na
allos them to get in, glucose too
secondary active transport
once in epithelia cells can diffuse into the blood

64
Q

what does exopeptidase do

A

cut ends of proteins into oligopeptides

65
Q

what does endopeptidase so

A

cut middles of proteins into oligopeptides

66
Q

describe the process of protein digestion

A

enzymes break them down into oligopeptides then into dipeptides or tripeptides or single amino acids
they are transported across the membrane along with Na in co- transport
Na is moved back out again to maintain a gradient
cytosolic peptidases then complete the digestion

67
Q

what completes protein digestion

A

cytosolic peptidases

68
Q

where do proteins go once in the cells

A

hydrophobic amino acids move into the blood by diffusion

hydrophilic amino acids need co-transport with Na+

69
Q

how do amino acids get to the liver

A

portal vein

70
Q

describe the proecss of breaking down carbohydrates

A

saliva in mouth, amylase breaking down to maltose

then brush boarder

71
Q

what happens at the brush boarder to carbohydrtes

A

enzymes at the boarder are needed to separate the parts down further
competes the digestion of it

72
Q

how are carohydrates transported after being broken down

A

Na gradient i key
activive transport moves glucose/galactose into cell, the go with Na
now diffuse into blood
Na pumped back out for gradient maintene

73
Q

what is the GLUT2 transporter

A

carrier to move glucose into the cell
works when there is more glucose in the lumen than then cell after eating
rising glucose in lumn activates the GLUT2 into apical membrane

74
Q

where is fructose moving

A

higher conc in lumen than cell
diffuses through a carrier
independent of Na
diffuses into blood

75
Q

what carrier out lipid hydroloysis

A

lipase

76
Q

describe the proces of lipid digestion

A

bile salts from liver coat fat droplets
pancreatic lipase and colipase breaks down fats inot monoglycerides and fatty acids
stored in micelles
monoglycerides and fatty acids move into cels by diffusion
at same time cholesterol transported into cells
cholesterol combined with aborbed fats and protens in intestinal cells forming chylomicrons
these are then removed by the lymphatic system

77
Q

what is a chylomicron

A

fats combining with cholesterol and proteins in the intestinal cells form these structures

78
Q

what substances are found in the lumen?

A 
glucose
 proteins
oligopeptides
sucrose
fructose
peptides
tryglycerols
79
Q

what is found in the interstitial space

A

glucose
amino acids
fructose
triglcerols

80
Q

main function of the large intestine

A

absorbing left over water

sorts and concntrates faecal matter

81
Q

name the parts of the large intesine

A 
caecum
appendix
colon: ascending, transverse, desending, sigmoid
rectum
anal canal
82
Q

what are taeniae coli

A

longitudinal muscles thickened to form bands

83
Q

what are haustra

A

circular mucles contracting at intervals to make sacks

84
Q

where are the least numbers of bacteria found

A

duodenum

85
Q

why are bacteria needed in the large intesine

A

ferment indigestiable carbohydrates and proteins

make vitamins B and K

86
Q

describe the process of defecation

A

gastroileal refex increases ileal contractions after a meal
chyme enters caecum through the sphincter
slow mixing and propulsive movements
defecating refex initiated by distension of rectal wall
relaxation of external anal sphincter
explusion of faeces

Human physiology (21 decks)

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