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GI physiology > Physiology > Flashcards

Physiology Flashcards

1
Q

what types of cells do you find in gastric glands and what are their function?

A

Mucous neck cells- produce mucus
chief cells- produce pepsinogens
parietal cells- produce HCl and intrinsic factor

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2
Q

How does Gastrin increase HCl output?

A

receptor- excretes more Ca, creates more protein kinases and increases K H pump this increase HCl

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3
Q

How does histamine increase HCl content?

A

G protein coupled receptor, Gs coupled to AC, AC converts ATP to cAMP, increase protein kinases, increase HCl

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4
Q

how does Acetylcholine increase HCl production?

A 
receptor 
increase Ca
increase protein kinases 
increase pump 
increase HCl
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5
Q

what does prostaglandins do to HCl production and how?

A 
decreases HCl production
by Gi turns off AC
no cAMP produced
decreases protein kinases  
decreases HCl
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6
Q

hat are the 3 mechanisms used to control gastric acid secretion?

A

neurocrine (vagus/local reflexes)
endocrine (gastrin)
paracrine (histamine)

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7
Q

describe mechanisms of the cephalic phase of gastric secretion

A

you see/ smell/ taste food this stimulates the vagus nerve increasing ACh which stimulates parietal cells to release more HCl, vagus nerve also stimulates G cells to release gastrin which stimulates parietal cells.

Gastrin and ACh also stimulate ECL cells which release Histamine which stimulates parietal cells to release more HCl

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8
Q

in the gastric phase of gastric acid secretion what stimulates more HCl production?

A

distension of stomach stimulates vagal/ enteric reflexes which releases ACh and stimulates parietal cells.
peptides in lumen stimulates G cells which release gastrin stimulating parietal cells

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9
Q

describe the cephalic and gastric phase of gastric acid inhibition

A

cephalic phase: stop eating, decreases vagal activity

gastric phase: decreasing pH due to increased HCl causes decreasing gastrin production

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10
Q

describe the intestinal phase of gastric acid inhibition

A

acid in duodenum causes a enterogastric reflex and secretin release this causes a decrease in gastrin secretion and gastrin stimulation of parieta cells

fat and carbohydrates in the duodenum causes GIP to be released which causes gastrin secretion and parietal HCl to decrease

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11
Q

what are enterogastrones?

A

hormones released from gland cells in duodenal mucosa

eg. secretin, cholecystokinin, GIP

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12
Q

what does zymogen means and give an example?

A

zymogen is a inactive precursor and pepsinogen is an example

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13
Q

what increases contraction of the stomach?

A

gastrin and distension it stomah wall (long and short reflexes)

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14
Q

what decreases contraction of the stomach?

A

fat/aa/hypertonicity in duodenum

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15
Q

where is bicarbonate secreted from in the duodenum?

A

brunner’s gland duct cells

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16
Q

what triggers secretion of HCO3 in duodenum?

A

acid in duodenum which triggers long (vagal) and short )ENS) reflexes which secrete HCO3
and release of secretin from S cells cause HCO3 secretion in duodenum, pancreas and liver

inhibited by acid neutralisation

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17
Q

where would you find islets of Langerhans? and what are they for?

A

in the pancreas and they are made up of islet cells which produce insulin, glucagon and somatostatin

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18
Q

what is the function of th exocrine pancreas

A

digestion:
secrets bicarbonate by duct cells
secret digestive enzymes by acinar cells

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19
Q

what does enterokinase do in the duodenum?

A

converts trypsinogen to trypsin

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20
Q

what tiggers the release of cholecystokinin (CCK) in the duodenum and what does this trigger the release of?

A

CcK is released in response to fat/amino acids in duodenum and this stimulates the secretion of zymogen in the pancreas

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21
Q

what are the 2 minor lobes of the liver called

A

caudate and quadrate

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22
Q

what is found in the portal triad located at each corner of hexagonal lobule in the liver?

A

hepatic portal vein, hepatic artery and hepatic duct

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23
Q

What is a peyer’s patch?

A

a majpr organised lymphoid structure in the gut that samples cells in lumen and decides if harmful or not

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24
Q

what do dendritic cells mature into?

A

Potent antigen presenting cells

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25
Q

what does dysbiosis mean?

A

There is ca change in composition in microbiol communities eg in IBD

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26
Q

What is the crypt of Lieberkuhn?

A

Develops from epithelium of villus burrowing down, they secrete water

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27
Q

Why is H2O secretion important for digestive process?

A

Maintains lumenal contents in liquid state, promotes mixing of nutrients with digestive enzymes, aids nutrient presentation to absorbing surface, dilutes and washes aaway potentially injurious substances

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28
Q

what is the enzyme adenylate cyclase’s function in the basolateral membrane of small intestine?

A

Turns ATP into cAMP, which secretes PKA which then regulates the CFTR

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29
Q

WHat does CFTR stand for

A

Cystic fibrosis Transmembrane Conductance regulator

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30
Q

Describe segmentation

A

there is complemetary contraction and relaxation of short intestinal segments, when there is contraction the chyme moves up and down into adjacent areas of relaxation, the relaxed areas then contract and push the chyme back.

31
Q

where are pacemaker cells found in the small intestine?

A

The longitudinal muscle layer

32
Q

What is the pattern of peristaltic activity called?

A

migrating motility complex

33
Q

What does migrating motility complex act on?

A

Moves undigested material into large intestine, limits bacteria colonisation of small intestine

34
Q

what triggers the defaecation reflex?

A

Mechanoreceptors which notice distension of the rectal wall which is produced by mass movement of faecal material into rectum

35
Q

why does enterotoxigenic bacteria (eg vibrio cholerae, escherichia coli)cause diarrhoea?

A

they produce protein enterotoxins which turn on intestinal chloride secretion from crypt cells by elevating intracellular secind messengers (cAMP, cGMP, Ca), this increases H2O secretion , and the H2O secretion swamps the absorptive capacity of villus cells

36
Q

Normal Gi tract bacteriology?

A

bacteroides, colifroms, lactobacilli, streptococci

37
Q

Rectal bleeding and associated symptoms high risk features?

A

persistent change in bowel habit (>6 weeks), persistent rectal bleeding with no anal symptoms, right sided abdominal mass, palpable rectal mass, unexplained iron deficiency anaemia, clinical doubt

38
Q

Ways to visualise the bowel

A

colonoscopy, flexible/rigid sigmoidoscopy +/- barium enema, CT colongraphy

39
Q

What do you do if someone presents with dyspesia features, no alarm features and is under 55?

A

test for helicobacter pylori, and if positive eradication therpay and symptomatic treatmetn with PPIs or H2R antagonists

40
Q

Name the 3 pairs of salivary glands

A

Parotid, sublingual, sybmandibular

41
Q

What type of epithelium is found in the mucosa layer of the mouth, oesophagus and anal canal?

A

stratified squamous

42
Q

What type of epithelium is found in the mucosa layer of the stomach, small and large intestines?

A

simple columnar

43
Q

What different layers are there in the mucosa layer of the alimentary canal?

A

epithelium, lamina propria and muscularis mucosae

44
Q

What does the epithelium produce in the mucosa layer of the alimentary canal?

A

digestive enzymes, hormones and mucus

45
Q

what typeof tissue is the submucosa layer of the alimentary canal?

A

thick, irregular connective tissue

46
Q

Where can you find submucosal glands in the alimentary canal

A

in oesophagus and duodenum

47
Q

What are the 2 layers of the muscularis external called?

A

circular muscle and longitudinal muscle

48
Q

What is the nerve plexus called between the circular and longitudinal muscle?

A

myenteric (Auerbach’s) plexus

49
Q

What is the enteric nervous system made of?

A

submucosal and myenteric plexuses

50
Q

WHat is parasympathetic salivation controlled by?

A

facial and glossopharyngeal nerve

51
Q

What arterial supply supplies the stomach, small intestine, pancreas and liver?

A

celiac trunk

52
Q

What arterial supply supplies the small intestine, caecum, ascending and transverse colon?

A

superior mesenteric artery

53
Q

What does the inferioir mesenteric artery supply?

A

descending colon, sigmoid colon and rectum

54
Q

What is the stomach drained by

A

gastric vein

55
Q

What is the pancreas drained by?

A

splenic vein

56
Q

What drains into the superior mesenteric vein?

A

small intestine, caecum, ascending colon and transverse colon

57
Q

What drains the descending colon, sigmoid colon and rectum?

A

inferioir mesenteric vein

58
Q

what drains into the hepatic portal vein and what does that drains into that and what does that drain into?

A

the superioir and inferioir mesenteric veins drain into the hepatic portal vein which drains into the hepatic vein which drains into the IVC

59
Q

What hydrolyses glucose monomers that are linked by alpha-1,4 glycosidic bonds?

A

hydrolysed by amylases (saliva and pancreas)

60
Q

What are the 2 membranes found in the villi

A

apical membrane on the outside (Bart simpson hair) and basolateral membrane

61
Q

name the different types of transport across a villi cell membrane

A

transcellular (through cell)

paracellular (between the cells)

vectorial transport (between with transport channels)

62
Q

What is the transport channel that pumps glucose into the small intestine cells?

A

SGLT1

63
Q

Via which transporter does glucose leave the cell and fructose enter

A

GLUT2

GLUT5

64
Q

What do we hydrolyse peptide bonds with?

A

proteases and peptidases

65
Q

What is a micelle formed from?

A

bile salt + monoglyceride + FA + phospholipids

66
Q

What are chylomicrons

A

extracellular fat droplets which contain phospholipids, cholesterol and fat soluble vitamins

67
Q

What do chylomicrons from the smooth endoplasmic reticulum pass into?

A

lacteals

68
Q

What does iron bind to in the blood

A

transferrin

69
Q

How is voluntary chewing controlled?

A

via somatic nerves controlling skeletal muscles of mouth and jaw

70
Q

What is saliva made of?

A

water, electrolytes, mucins, alpha-amylase, lysozyme

71
Q

What nerve stimulates the production of saliva in the parasympathetic system?

A

cranial nerves VII(facial) and IX (glossopharyngeal)

stimulates profuse watery salivary secretion

72
Q

What nerves stimulate the production of saliva in the sympathetic nervous system?

A 
alpha1 adrenoreceptors (high mucus content)
beta2 adrenoreceptors (high amylase content)
73
Q

What is the peristaltic wave sweep?

A

when the bolus is in the oesophagus and behind the wall contracts and in front of it relaxes

GI physiology (1 decks)

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