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S + F 2 > 7. GIT - physiology 2 > Flashcards

7. GIT - physiology 2 Flashcards

1
Q

what are the 3 main functions of the stomach?

A
  1. Temporary food store
  2. some degradation of protein and starch
  3. hydrochloric acid kills bacteria in the food
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2
Q

what is kine?

A

food mix with gastric juices

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3
Q

what does the proximal stomach mainly refer to in terms of regions?

A

cardia and fundus

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4
Q

what is tonic contraction?

A

when stomach is empty, contraction is maintained

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5
Q

what is receptive relaxation and what does it allow?

A

when an animal eats the muscles relax allowing for an increase in stomach content without the increase in pressure

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6
Q

what regulates receptive relaxation in the proximal stomach?

A

vagal fibres

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7
Q

is the proximal stomach closer to the mouth or small intestine?

A

mouth

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8
Q

what does the distal stomach refer to mainly in terms of region?

A

pyloric

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9
Q

what happens in the distal stomach?

A

-food heads towards the pyloric sprinter
- more active digestion here due to stronger peristaltic contraction
- a large part of the pylorus wall contracts simultaneously, increasing luminal pressure and forcing chyme through the partially open sphincter
- large particles are held back in the stomach t be broken down further

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10
Q

what are the 4 main cells in the mucosa of the stomach wall pits?

A
  • mucin-producing cells
  • parietal cells
  • chief cells
  • endocrine cells
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11
Q

what epithelium lines the lumen?

A

simple columnar epithelium

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12
Q

what does mucin producing cells produce?

A

mucus

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13
Q

what is the function of mucin producing cells?

A

lubrication

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14
Q

what is the function of parietal cells?

A

secrete HCL and intrinsic factors

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15
Q

what are the intrinsic factors released by the parietal cell

A

glycoprotein cofactor required for absorption of vitamin B12

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16
Q

what is the function of chief cells?

A

produces a precursor enzyme called pepsinogen which will be broken down to pepsin in the stomach

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17
Q

what is the function of endocrine cells?

A

in the pyloric region there are g cells, which produce gastrin

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18
Q

what is the function of gastrin?

A

gastrin is secreted into the blood, it regulates:
- the secretion of HCL from parietal cells
- chief cells to produce pepsinogen
- influences gastric mobility and motility

19
Q

where is most gastric juice produced?

A

glands of fundus and corpus

20
Q

what does gastric juice mainly consist of?

A

HCL and pepsinogen

21
Q

what are the functions of HCL in the stomach?

A
  • transforms pepsinogen to pepsin
  • degrades connective tissue and muscle
  • kills microorganisms
22
Q

what 2 pumps are needed to produce HCL

A

H/K ATP-ase pump (hydrogen/potassium ATPase)
HCO3-/CL- pump (Bicarbonate/chloride pump)

23
Q

how is HCL produced?

A
  • CO2 taken up from blood, crosses interstitial fluid, goes into parietal cells
  • in the partial cells CO2 combines with water under action of carbonic anhydrase
  • causes production of carbonic acid
  • carbonic acid dissociates to form bicarbonate (which feeds bicarbonate chloride pump)
  • hydrogen pumped out into gland lumen
  • potassium exchanged and goes into parietal cell
  • similarly, bicarbonate pumped across interstitial fluid towards blood stream
  • chloride moves to gland lumen, interacts with Hydrogen to make HCL
24
Q

what is pepsinogen?

A

inactive form of pepsin

25
Q

what 3 substances regulate gastric secretion?

A
  • ACH - acetyl choline
  • gastrin
  • histamine
26
Q

what reflex is needed to regulate gastric secretion and what are they stimulated by?

A

vagal reflexes, stimulated by stomach expansion

27
Q

how does histamine stimulate HCL secretion?

A

acts as a paracrine hormone that stimulates HCL

28
Q

what are the main steps in the regulation of gastric secretion?

A
  • Sight/smell of food
  • Tells the brain to send a nervous impulse from the vagus nerve to the:
  • Chief cells to produce pepsinogen
  • Parietal cells to produce HCL
  • ECL cells to make histamine
  • G cells to make gastrin
  • Gastrin feeds back to the ECL cells to make more histamine
    Which in turn acts on parietal cells to make more HCL
29
Q

what inhibits secretion?

A
  • signals from the duodenum will slow down gastric secretion + inhibit stomach contents coming out
  • if pH falls to low
  • At the start of a meal proteins in the food buffers decrease the H+ in the stomach and block further acid secretion
30
Q

what does amylase degrade in the stomach?

A

starch

31
Q

what does pepsin degrade?

A

collagen in connective tissue

32
Q

what 2 factors affect the rate that the stomach empties?

A

1- expansion of stomach wall
2- gastrin

33
Q

what is optimal digestion?

A

rate of stomach emptying = capacity of intestine to digest food

34
Q

how does distension of the duodenum affect the rate of stomach emptying

A

As the duodenum fills, the pyloric sphincter will close, slowing and eventually stopping the transfer of chyme from the stomach to the intestine

35
Q

how do high fat and protein concentrations affect the rate of stomach emptying?

A

High fat content slows down gastric emptying. When high amounts of fat are released into the duodenum you get secretion of a peptide hormone called CCK from the duodenal cells. If fat is present only small quantities of the chyme are transferred from the stomach, it slows down release through the pyloric sphincter and CCK will stimulate the production and secretion of pancreatic enzymes like insulin and stimulate bile release from gall bladder

36
Q

how does a reduced pH affect the rate of the stomach emptying?

A

If more acid is transferred to the duodenum than can be neutralised then intestinal enzymes cannot function

37
Q

what hormones mediate the rate of the stomach emptying?

A
  • secretin
  • CCK
  • GIP
38
Q

what cells is the abomasum made up of?

A

columnar epithelium

39
Q

what do the epithelial glands produce in the abomasum?

A
  • pepsinogen
  • HCL
40
Q

What do young calves also produce in the abomasum?

A

Rennin

41
Q

where is rennin produced specifically and what does it do?

A

fundus
- allows for the coagulation and precipitation of casein

42
Q

what is casein?

A

milk protein

43
Q

is the abomasum a storage organ?

A

no, has continuous flow of rumen content

S + F 2 (30 decks)

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