The Gut

Question 1

Salivary Glands (3)

Answer 1

Submandibular salivary glands (70%)
Parotid (25%)
Sublingual (5%)

Question 2

Saliva 1.5-2 litres daily - a reduction can cause a bacterial explosion in the oral cavity.

Answer 2

99. 4% water

0. 6% electrolytes Na+, Cl-, HCO3, buffers, antibodies, enzymes

Question 3

What controls Salivary secretion?

Answer 3

the autonomic nervous system

Question 4

What can cause a change in salivary gland activity?

Answer 4

radiotherapy, emotional distress, certain drugs. Can cause bacterial imbalances in the oral cavity

Question 5

what causes watery saliva?

Answer 5

parasympathetic nervous system stimulation. All salivary glands have both sympathetic and parasympathetic supply.

Question 6

where does parasympathetic stimulation for the salivary glands originate?

Answer 6

the salivatory nuclei of the medulla oblongata

Question 7

what three main things stimulate the salivary nuclei?

Answer 7

1. chewing (even with an empty mouth)
2. the presence of irritating stimuli in the oesophagus, stomach or intestines.
3. the presence of unpleasant stimuli
   (this helps water the potentially noxious substance)

Question 8

what are the three phases of swallowing?

Answer 8

buccal - voluntary
pharyngeal phase - involuntary. As the bolus hits the posterior pharyngeal wall, information goes to the swallowing centre of the medulla oblongata via the trigeminal and glossopharyngeal nerves.
oesophageal phase - opening of oesophageal sphincter.

Question 9

How does the stomach mix chyme?

Answer 9

via the three layers of smooth muscle running in different directions.

Question 10

four parts of the stomach

Answer 10

cardia - the entrance
fundus (top bit)
body
pylorus (bottom bit)

Question 11

where is intrinsic factor made? which cells? what type of molecule is it? and use?

Answer 11

stomach. Parietal cells (in the fundus and body)

used for bit B12 absorption in the GI tract

Question 12

where are gastric glands?

Answer 12

in the fundus

in the body

Question 13

what do gastric glands contain?

Answer 13

parietal cell

chief cells

Question 14

What do Parietal cells secrete?

Answer 14

intrinsic factor

HCL

Question 15

Functions of gastric acid

Answer 15

Kills microorganisms.
Denatures proteins and inactivates most of enzymes in food.
Acidity helps break down plant walls and connective tissue in meat.
ESSENTIAL FOR THE ACTIVATION AND FUNCTION OF PEPSIN

Question 16

What is pepsin?

Answer 16

a protein digesting enzyme secreted by chief cells

Question 17

why do parietal cells not produce HCL in the cytoplasm?

Answer 17

destruction

Question 18

what happens to the ionic exchange in a parietal cell?

Answer 18

H20 + C02 forms H2CO3. Using carbonic anhydrase this dissociates to form H+ and HCO3-. The H+ enters the lumen of the gastric pit (active transport). The HCO3- enters the interstitial fluid and at the same time Cl- ions enter the parietal cell (counter transport). Cl- ions then leave the parietal cell and go into the gastric pit. The HCO3- ions then go into the blood stream.

Question 19

What is the alkaline tide?

Answer 19

The influx of alkaline HCO3- ions due to the production of HCL in the stomach. This will decrease the pH of the blood.

Question 20

Where are chief cells located?

Answer 20

At the bottom of the gastric gland pit

Question 21

What do chief cells secrete?

Answer 21

pepsinogen (an inactive proenzyme)

Question 22

How is pepsinogen converted?

Answer 22

by gastric acid in the gut it is converted into pepsin (proteolytic enzyme)

Question 23

what does the stomach produce in infants but not adults?

Answer 23

renin and gastric lipase for the digestion of milk

Question 24

Where is gastrin produced?

Answer 24

in the G cells (endocrine cells) in the pylorus of the stomach

Question 25

What does gastrin do?

Answer 25

Stimulates the secretion of parietal and chief cells | stimulates contractions of the gastric wall

Question 26

what three overlapping gastric control phases are there?

Answer 26

``` Cephalic phase (short - minutes) Gastric phase (Long 3-4 hrs) intestinal phase (long - hrs) ```

Question 27

ANS innervation of cephalic phase

Answer 27

smell/taste of good - parasympathetic division of ANS stimulated (vagus nerve) - postganglionic fibres activate secretory cells of stomach. (vagus nerves stimulate submucosal plexus of stomach) NB * in the cephalic phase, the vagus nerve also stimulates the pancreas. Why?

Question 28

Don't forget mucous cells in the stomach that...

Answer 28

protect the stomach lining (found in top of gastric pits)

Question 29

When does the gastric phase start? | also name the three stimuli

Answer 29

when food arrives in the stomach (builds on stimulation of cephalic phase) - stomach distension - increase in stomach pH levels - presence of indigested proteins/ peptides in the stomach

Question 30

when does the intestinal phase start?

Answer 30

when there is a reduction in stomach distension.

Question 31

what is the enterogastric reflex?

Answer 31

a reflex due to distension in the duodenum that inhibits stomach activity, thus preventing further emptying of contents into the duodenum.

Question 32

what must the duodenum do, to protect itself?

Answer 32

produce alkaline mucus ( stimulated by gastric contractions) to protect the intestinal lining.

Question 33

what does the arrival of chyme in the intestine trigger?

Answer 33

neural and hormonal events that coordinate the intestinal tract, pancreas, liver, and gall bladder

Question 34

what type of meal leaves the stomach quickly?

Answer 34

one that has less protein, more carbohydrates, and stimulants such as coffee and alcohol that stimulate gastric secretion and activity.

Question 35

what drugs can be absorbed by the stomach? | what is the danger of these drugs?

Answer 35

alcohol and aspirin | they alter the mucosal layer and can cause damage to the the endothelium by stomach acid and enzymes.

Question 36

Where are most the enzymes manufactured?

Answer 36

in the pancreas

Question 37

Apart from enzymes, what else does the pancreas produce?

Answer 37

buffers - to neutralise the acidic chyme from the stomach

Question 38

what type of organ is the pancreas primarily?

Answer 38

an exocrine organ | makes digestive enzymes

Question 39

what controls exocrine enzyme secretions from the pancreas and the release of bile?

Answer 39

cholecystokinin (stimuli is fats in the intestine) from the duodenum

Question 40

when chyme arrives in the duodenum, secretin is released. What does it do?

Answer 40

triggers the pancreatic secretion of a watery bicarbonate and phosphate buffer solution with a pH of 7.5–8.8 that help elevate the pH of the chyme Secretin stimuli is acid.

Question 41

Name four made enzyme classes in the pancreas

Answer 41

pancreatic lipase carbohydrase nucleases proteolytic enyzmes (must abundant)