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GI physiology > physiology > Flashcards

physiology Flashcards

1
Q

what are the main 5 functions of the liver?

A

storage - glycogen and fatty acids, vitamins and minerals
detoxification - metabolise toxins into their inactive metabolites
digestion - old red blood cells destroyed by kupffer cells and contents passed on to hepatocytes.
synthesis - plasma proteins. e.g. fibrinogen, prothrombin, albumin
excretion - of bilirubin, and bile salts to digest.
de-amination - of amino acids. conversion to urea - excreted as waste

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2
Q

what is MALT?

A

musoca associated lymphoid tissue. closely related to the epithelia. they act as an immunological defence system to intercept pathogens as they attempt to enter the body.

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3
Q

what is GALT?

A

gut associated lymphoid tissue. Peyer’s patches. an example of MALT.

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4
Q

what is the structure of a sinusoid?

A

fenestrated capillary-like structure. separated from hepatocytes by the space of Disse. sit on a reticulin meshwork. endothelial cells interspersed with ITO cells and Kupffer cells.

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5
Q

What are Kupffer cells and what is their function?

A

resident macrophages of the liver. capture old red blood cells and other unwanted components of the blood and phagocytose.

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6
Q

What are ITO cells and what is their function?

A

vitamin A storage in fat droplets. secrete collagen scar tissue during liver damage, can lead to cirrhosis.

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7
Q

What are Kupffer cells and what is their function?

A

resident macrophages of the liver. capture old red blood cells and blood bourne pathogens.

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8
Q

what do the fibroblasts in the walls of the alveoli produce?

A

reticulin and elastic tissue.

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9
Q

what are the functions of the gallbladder?

A

storage and concentration of bile. they have a poor brush border to reabsorb water from the bile.

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10
Q

how does the gall bladder contract?

A

in response to cholecytokinin released from the duodenum in response to fat in the stomach.

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11
Q

what does CCK do?

A

produces in the I-cells of the small intestine. stimulates release of bile from bile duct and digestive enzymes from the pancreas.

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12
Q

what is the macula densa and how does it work?

A

area of specialised cells located in the distal convoluted tubule. It senses Na/Cl conc in the filtrate. If it is low, it (1) can uses vasodilation of the afferent arteriole, to increase GFR and (2) causes the juxtaglomerular cells to release renin.

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13
Q

what are podocytes and how do they function?

A

cells in the bowman’s capsule that wrap around capillaries and leave slits between their foot like projections (pedicles). these slits are called slit diaphragms, and allow blood to filter through without letting serum albumin and gamma globulin through. slits are composed of nephron etc.

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14
Q

what substances are allowed to pass though podocytes?

A

glucose, water, ionic salts.

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15
Q

what substances are not allowed to pass though podocytes?

A

gamma globulin, serum albumin

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16
Q

what comprises the filtration barrier?

A

podocyte epithelium and basement membrane and fenestrated capillary epithelium

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17
Q

how long is the duodenum?

A

12cm.

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18
Q

how much of the filtered glucose is reabsorbed in the PCT?

A

100%

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19
Q

how much of the filtered water and sodium is reabsorbed in the PCT?

A

60%

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20
Q

what is the average salivary production per minute?

A

0.3-7 mls

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21
Q

what are the functions of salivary glands?

A

defence against microorganisms, digestion of starch - a-amylase, help you taste, maintenance of pH 7.2, washes mouth

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22
Q

name 3 defence mechanisms of the mouth

A

palatine tonsils - lymphoid tissue and dendritic cells. mucosa - physical barrier. salivary glands - wash away food particles etc.

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23
Q

which glands are active constantly?

A

sunmandibular, sublingual and minor glands. parotid becomes active on stimulation.

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24
Q

what do serous glands secrete?

A

water and digestive enzymes

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25
Q

what do mucous glands secrete?

A

water and glycoproteins

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26
Q

which structures pass through the parotid gland?

A

facial nerve, external carotid, retromandibular vein.

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27
Q

which duct does the salivary ducts drain into?

A

P = Stensons, SM = whartons, SL = whartons

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28
Q

why is the parasympathetic innervation of the salivary glands?

A

P = IX, SM = VII, SL = VII

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29
Q

describe the structure of a salivary duct.

A

The acini produce a very NaCl rich secretion. this then enters the intercalated duct that connects the acini to the larger ducts. it the becomes the striated duct where the secretions are modified to reabsorb NaCl and secrete HCO3- and K+ by active transport. there is no movement of water due to the epithelium so final saliva is hypotonic.

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30
Q

How do the salivary ducts facilitate active transport?

A

The microvilli present on the striated ducts have many mitochondria within them.

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31
Q

How is the final saliva hypotonic?

A

there is no transport of H20 in the striated ducts.

32
Q

what are interlobular ducts?

A

the second largest type of duct after the excretory duct.

33
Q

where does the submandibular gland empty into the mouth?

A

sublingual papillae

34
Q

where are the minor glands located? what type of secretions do they produce?

A

Weber’s glands on tonsils, von Eber’s glands underlying circumvallate papillae. mucous apart from von Eber’s which are serous.

35
Q

describe the 3 phases of swallowing.

A

stage 1 - voluntary. elevation of tongue to squish food against hard palate and pushed towards oropharynx. stage 2 - elevation of hyoid bone by the supra hyoid muscles. and therefore pharynx, nasopharynx closed off by soft palate muscles which are tensor palatine (CN 5-2) and legator palatine (CN X). stage 3 - sequential contraction of constrictor muscles to propel the food down the pharynx into the oesophagus and depression of hyoid bone by the infra hyoid muscles (ansa cervicalis 123)

36
Q

what is trituration?

A

grinding of food

37
Q

name the 3 types of tonsil.

A

palatine, lingual, pharyngeal.

38
Q

what is the innervation of the pharyngeal constrictor muscles?

A

X, XI

39
Q

how is the hyoid bone elevated and depressed during swallowing?

A

elevation = supreahyoid muscles and buccinator. depression = infrahyoid muscles

40
Q

which muscles elevate the soft palate and how are they innervated?

A

tensor palitini (V) and levator palitini (X)

41
Q

what are the muscles of the lower mouth?

A

diagstric, mylohyoid, geniohyoid

42
Q

where are the attachments of the diagstric?

A

mastoid process and hyoid bone.

43
Q

what are the infra hyoid bones?

A

sternocleidomastoid (ext), thyrohyoid (int), sternohyoid (int), sternothyroid (ext), omohyoid (ext).

44
Q

which muscles act to shorten and widen the pharynx during swallowing?

A

stylopharyngeus, salpingopharyngeus, palatopharyngeus

45
Q

which muscles act to propel food down the pharynx during swallowing?

A

3 constrictor muscles

46
Q

how is pressure equalised during swallowing?

A

auditory tube stays open

47
Q

what is the upper oesophageal sphincter composed of?

A

the cricopharyngeus portion of the inferior constrictor muscle.

48
Q

what are the oropharynx, nasopharynx and laryngopharynx inntervated by during closure?

A

IX, V, X

49
Q

what happens to the rims glottidis during swallowing?

A

the vocal and false folds close it.

50
Q

what is the gag reflex formed by?

A

irritation of the oropharynx. reflex arc between IX and X.

51
Q

what are the 3 indentations of the barium swallow?

A

aortic arch, left main bronchus, left atrium.

52
Q

what are the functions of the stomach?

A

kill microbes, store and mix food, dissolve and continue digestion, lubrication, secrete intrinsic factor, activate proteases.

53
Q

what are the cells found in gastric pits, in order of most superficial.

A

mucous cells, parietal cells, chief cells and enteroendocrine cells.

54
Q

how much HCl do we secrete in a day?

A

2L

55
Q

describe the stimulation of parietal cell secretion.

A

chewing and smell stimulates the realise of Ach, parasympathetic. this binds to the cell and stimulates the release of gastrin and histamine. gastrin further stimulates the release of histamine. Ach, histamine and gastrin increase the number of H+/K+ active transport puns on the luminal membrane, so secrete H+ into the lumen which then combines with Cl to form HCl. This acid lowers the pH. however, proteins mop up any extra H+ and act as a luminal buffer, so that the relase of somatostatin is not yet stimulated.

56
Q

what types of molecule are Gastrin, Histamine Somatostatin, CCK and ACh.

A

ACh = neurotransmitter. Gastrin = hormone. Histamine and somatostatin are paracrine molecules and CCK and secretin are enterogastrones.

57
Q

what is an endogastrone?

A

a hormone released by the mucosa of the duodenum in response to fat being present in the stomach. it then travels through the blood to the stomach to inhibit the actions of gastrin and lower the HCl production.

58
Q

what causes ulcers?

A

helicobastor pylori

59
Q

how are the parietal cell turned off?

A

the pH inside the gastric lumen lowers. this directly stops the production of gastrin and histamine. The intestinal lumen pH also lowers which stimulates the enterogastrones to be released. secretin stimulates the release of somatostatin and the I cells in the duodenal wall stimulate the release of CCK which contracts the gall bladder to produce alkaline bile to neutralise the acid.

60
Q

what are the phases of parietal cell stimulation?

A

cephalic phase, gastric phase, turning off phase.

61
Q

how does our body prevent duodenal overfilling?

A

increasing the release of enterogasterones, which decrease gastric emptying.

62
Q

what is another name for ‘inactive form’. give an example.

A

zygomen. pepsinogen.

63
Q

How is pepsinogen converted to pepsin?

A

in the presence of HCl as a catalyst. pepsin goes on to break down proteins into polypeptides. it is also in a positive feedback loop to catalyse the formation of pepsin.

64
Q

is pepsin essential? what is its percentage breakdown of protein?

A

no. 20%. speeds up and breaks down large chunks for a larger surface area for digestion in the intestines.

65
Q

what are the stomach volumes when full and when eating?

A

50ml, 1.5L

66
Q

what is receptive relaxation? and how is it stimulated? how is relaxation mediated?

A

relaxation of the stomach when full. smooth muscle in the body and fundus. parasympathetic nervous system acting on enteric nerve plexus. afferent input is from the vagus. NO and serotonin are released by the enteric nerve plexus.

67
Q

describe the steps behind peristalsis.

A

waves begin in the gastric body and are weak. they are stronger in the gastric antrum. the pylorus closes as the wave reaches it and only a small amount of chyme gets into the duodenum. the rest is forced backwards for mixing.

68
Q

how is the basal electrical rhythm waves determined?

A

pacemaker cells in the muscular propria. 3 per minute. slow depolarisation of cells. there is only weak contraction when the stomach is empty.

69
Q

what factors increase the strength of peristalsis?

A

gastrin and gastric distension.

70
Q

what factors decrease the strength of peristalsis?

A

sympathetic activity, duodenal osmolarity, duodenal luminal fat, low duodenal pH, low parasympathetic action, duodenal distension.

71
Q

where are secretin and CCK released from?

A

S cells and I cells in the walls of the duodenum.

72
Q

where are long chain carbohydrates broken down?

A

in the colon by bacteria.

73
Q

what are the uses of Vit A, Vit C, B Vits and Vit D?

A

Vit A = cell growth and differentiation. Vit C = synthesis of collagen and neurotransmitters, absorption of non-harm iron. Vit D = blood and bone calcium homeostasis. B vitamins = important in metabolism and energy production.

74
Q

what is the diagstric muscle innervated by?

A

facial

75
Q

what is the piriform fossa?

A

food can get suck here. lateral to the aryepiglottic folds. also sight for cancer.

76
Q

what are the defence mechanisms of the GI tract?

A

alkaline mucosa, tight junctions between cells, feedback loops, replacement of damaged cells.

77
Q

what can lack of B12 lead to?

A

anaemia.

GI physiology (4 decks)

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