Physiology Flashcards

1
Q

what does the small intestine receive from the stomach?

A

chyme - via the pyloric sphincter

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2
Q

what does the small intestine receive from the pancreas?

A

pancreatic juice

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3
Q

what does the small intestine receive from the gallbladder?

A

bile

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4
Q

what does the small intestine secrete?

A

intestinal juices and moves remaining residue to the large intestine

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5
Q

name the adaptations of the small intestine which increases surface area

A

arranged in circular folds
contains villi
villi contain microvilli

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6
Q

Name the peptide hormones that the small intestine secretes (7)

A
gastrin
Cholecystokinin (CCK)
Secretin
Motilin
Glucagon like insulinotropic peptide (GIP)
Glucagon like peptide-1 (GLP 1)
Ghrelin
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7
Q

which cells are the peptide hormones secreted from in the small intestine?

A

endocrine cells within the mucosa into the blood

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8
Q

where does gastrin come from?

A

G cells of the gastric antrum and duoenum

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9
Q

where does CCK come from?

A

cells of the duodenum and jejunum

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10
Q

where does secretin come from?

A

s cells of the duodenum

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11
Q

where does motilin come form?

A

m cells of the duodenum and jejunum

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12
Q

where does GIP come from?

A

K cells of the duodenum and jejunum

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13
Q

Where does GLP-1 come from?

A

incretin from L cells of the gut

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14
Q

Where does ghrelin come from?

A

Gr cells of the gastric antrumm, small intestine and pancreas

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15
Q

which receptors do peptide hormones from the small intestine act on?

A

g-protein coupled receptors

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16
Q

what does incretin do?

A

acts on b-cells of the pancreas to stimulate the release of insulin

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17
Q

Control mechanisms of the succus entericus

A

arrival of chyme
gastrin
CCK
secretin
parasympathetic nerve activity - enhances activity
sympathetic nerve activity - decreases activity

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18
Q

what does secretion of the small intestine contain?

A

mucous and aqueous salt

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19
Q

steps of mixing of chyme

A
  1. moved back and forth
  2. contraction and relaxation initiate by pacemaker cells
  3. segmentation of duodenum
  4. segmentation in the ileum (empty) triggered by gastrin
  5. overall net movement
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20
Q

what controls the segmentation of the small intestine during the mixing of chyme?

A

parasympathetic and sympathetic stimulation

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21
Q

what inhibits the migrating motor complex of peristalsis

A

feeding and vagal activity

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22
Q

what does peristalsis clear from the small intestine?

A

debris, mucus and endotheliac cells between meals

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23
Q

what are the components of the endocrine secretion of the pancreas?

A

insulin and glucagon onto the blood

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24
Q

what are the components of the exocrine secretion of the pancreas?

A

digestive enzymes and sodium bicarbonate

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25
Q

what do acinar cells secrete in the pancreas?

A
trypsinogen
chymotrypsinogen
procarboxypeptidase A and B
pancreatic amylase
pancreatic lipase
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26
Q

what does trypsinogen become in the duodenum?

A

trypsin (enterokinase is added)

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27
Q

what is autocatalysis

A

the process by which a substance catalyses its own production e.g. trypsin

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28
Q

what does chymotrypsinogen become in the duodenum?

A

chymotrypsin (trypsin is added)

29
Q

what does procarboxypeptidase A and B become?

A

carboxypeptidase A and B (acted on by trypsin)

30
Q

why do duct cells secrete alkaline fluid into the duodenum?

A

neutralises chyme to make optimum pH for pancreatic function and protects mucosa from acid erosion

31
Q

What are the three phases of pancreatic secretion?

A

cephalic
gastric
intestinal

32
Q

what mediates the cephalic stage of pancreatic secretion?

A

vagal stimulation of the acinar cells

33
Q

what does the large intestine recieve from the ileum?

A

indigestible residue
unabsorbed biliary compounds
unabsorbed fluid

34
Q

what is the function of the ilieocaecal sphincter?

A
  1. maintains positive resting pressure
  2. relaxes in response to distension of duodenum
  3. contracts in response to ascending colon
  4. prevents bacteria getting from the colon
35
Q

What are the functions of the Large intestine?

A
  1. absorbs water, Na and Cl
  2. secrets K, bicarbonate and mucus
  3. absorbs short chain fatty acids
  4. storage for colonic content
  5. elimination of faeces
36
Q

what is haustration?

A

caused by contraction of the circular muscle which occurs in the proximal colon and mixes its content

37
Q

what are peristaltic propulsive movements?

A

joint contraction of large sections of the circular muscle of the ascending and transverse colon

38
Q

what are peristaltic propulsive movements triggered by?

A

after a meal via gastrocolic responses (gastrin and extrinsic nerve plexuses)

39
Q

Where does most of the water in the body come from?

A

Secreted within the body itself

40
Q

what is the absorption of water driven by?

A

The transport of Na from the lumen of the intestine to the blood stream

41
Q

define diarrhoea in terms of fluid loss?

A

Loss of fluid and solutes from the GI tract in excess of 500ml per day

42
Q

What are the 5 main ways that is Na reabsorbed?

A
  1. Na+/glucose co-transport
  2. Na+/amino acid co-transport
  3. Na+/H+ exchange
  4. Parallel Na+/H+ and Cl-/HCO3- exchange
  5. Epithelial Na+ channels
43
Q

where does Na+/glucose and Na+/amino acid co-transport take place?

A

small intestine

44
Q

where does Na+/H+ exchange take place and what is it facilitated by?

A

duodenum and jejunum - facilitated by luminal HCO3-)

45
Q

where does Parallel Na+/H+ and Cl-/HCO3- exchange take place?

A

ileum and colon

46
Q

where are Epithelial Na+ channels and what facilitates reabsorption here?

A

colon - facilitated by aldosterone

47
Q

Na+/H+ exchange in the jejunum occurs where?

A

both the apical and basolateral membranes

48
Q

what is exchange of Na+/H+ stimulated by in the apical membrane of the jejunum?

A

the alkaline environment of the lumen due to the presence of bicarbonate from the pancreas

49
Q

Does the lumen have a lower or higher concentration of protons compared to the cytoplasm?

A

Lower

50
Q

what is the primary mechanism of absorption of Na in the interdigestive period?

A

Na+/H+ and CI-/HCO3- exchange

51
Q

How is the absorption through Na+/H+ and CI-/HCO3- exchange described?

A

Electroneutral

52
Q

what is Na+/H+ and CI-/HCO3- exchange regulated by?

A

intracellular cAMP, cGMP and Ca2+, all of which reduce NaCl absorption

53
Q

What can a reduction in NaCl cause?

A

diarrhoea

54
Q

what does Epithelial Na+ channels mediate?

A

electrogenic Na absorption in the distal colon

55
Q

what increases Epithelial Na+ channels?

A

Aldosterone

56
Q

What are the three actions of Aldosterone?

A
  1. opens ENaC
  2. inserts more ENaC into membrane from intracellular vesicle pool
  3. increases synthesis of ENaC and Na+/K+-ATPase
57
Q

what is the driving force of Cl absorption in the small intestine?

A

electrogenic transport of Na+ - Na+/glucose and Na+/amino acid

58
Q

what is the driving force of Cl absorption in the late intestine?

A

electrogenic movement of Na+ through ENaC

59
Q

What are the two other ways Cl is absorbed?

A

Cl–HCO3- exchange

Na+-H+ and Cl–HCO3- exchange

60
Q

where does Na+-H+ and Cl–HCO3- exchange take place?

A

ileum and proximal colon

61
Q

where does Cl–HCO3- exchange take place?

A

ileum and proximal and distal colon

62
Q

What are the benefits of colonic flora?

A

increase intestinal immunity
promote motility
synthesise vitamin K2 and free fatty acids
activate certain drufs

63
Q

How is intestinal immunity increased by colonic flora?

A

by competition with pathogenic microbes

64
Q

where do gases released from the anus arise from?

A

swallowed air
bacteria in the colon attacking carbohydrate
gas which is not absorbed in the large intestine

65
Q

Define constipation?

A

Presence of hard dried faeces within the colon from a delay in deification and enhanced absorption of water

66
Q

what is constipation caused by?

A

ignoring the urge to defecate
decreased colonic motility
obstruction of faecal movement
impairment of defecation reflex

67
Q

What symptoms can constipation cause?

A

abdominal discomfort
headaches
loss of apetite
malaise

68
Q

what can hardened faecal matter cause?

A

appendicitis