7. GIT - physiology 2

Question 1

what are the 3 main functions of the stomach?

Answer 1

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

Question 2

what is kine?

Answer 2

food mix with gastric juices

Question 3

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

Answer 3

cardia and fundus

Question 4

what is tonic contraction?

Answer 4

when stomach is empty, contraction is maintained

Question 5

what is receptive relaxation and what does it allow?

Answer 5

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

Question 6

what regulates receptive relaxation in the proximal stomach?

Answer 6

vagal fibres

Question 7

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

Answer 7

mouth

Question 8

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

Answer 8

pyloric

Question 9

what happens in the distal stomach?

Answer 9

-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

Question 10

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

Answer 10

• mucin-producing cells
• parietal cells
• chief cells
• endocrine cells

Question 11

what epithelium lines the lumen?

Answer 11

simple columnar epithelium

Question 12

what does mucin producing cells produce?

Answer 12

mucus

Question 13

what is the function of mucin producing cells?

Answer 13

lubrication

Question 14

what is the function of parietal cells?

Answer 14

secrete HCL and intrinsic factors

Question 15

what are the intrinsic factors released by the parietal cell

Answer 15

glycoprotein cofactor required for absorption of vitamin B12

Question 16

what is the function of chief cells?

Answer 16

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

Question 17

what is the function of endocrine cells?

Answer 17

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

Question 18

what is the function of gastrin?

Answer 18

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

Question 19

where is most gastric juice produced?

Answer 19

glands of fundus and corpus

Question 20

what does gastric juice mainly consist of?

Answer 20

HCL and pepsinogen

Question 21

what are the functions of HCL in the stomach?

Answer 21

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

Question 22

what 2 pumps are needed to produce HCL

Answer 22

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

Question 23

how is HCL produced?

Answer 23

• 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

Question 24

what is pepsinogen?

Answer 24

inactive form of pepsin

Question 25

what 3 substances regulate gastric secretion?

Answer 25

- ACH - acetyl choline - gastrin - histamine

Question 26

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

Answer 26

vagal reflexes, stimulated by stomach expansion

Question 27

how does histamine stimulate HCL secretion?

Answer 27

acts as a paracrine hormone that stimulates HCL

Question 28

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

Answer 28

- 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

Question 29

what inhibits secretion?

Answer 29

- 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

Question 30

what does amylase degrade in the stomach?

Answer 30

starch

Question 31

what does pepsin degrade?

Answer 31

collagen in connective tissue

Question 32

what 2 factors affect the rate that the stomach empties?

Answer 32

1- expansion of stomach wall 2- gastrin

Question 33

what is optimal digestion?

Answer 33

rate of stomach emptying = capacity of intestine to digest food

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

what hormones mediate the rate of the stomach emptying?

Answer 37

- secretin - CCK - GIP

Question 38

what cells is the abomasum made up of?

Answer 38

columnar epithelium

Question 39

what do the epithelial glands produce in the abomasum?

Answer 39

- pepsinogen - HCL

Question 40

What do young calves also produce in the abomasum?

Answer 40

Rennin

Question 41

where is rennin produced specifically and what does it do?

Answer 41

fundus - allows for the coagulation and precipitation of casein

Question 42

what is casein?

Answer 42

milk protein

Question 43

is the abomasum a storage organ?

Answer 43

no, has continuous flow of rumen content