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Physiology > The Gut > Flashcards

The Gut Flashcards

1
Q

Salivary Glands (3)

A

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

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2
Q

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

A
  1. 4% water

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

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3
Q

What controls Salivary secretion?

A

the autonomic nervous system

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4
Q

What can cause a change in salivary gland activity?

A

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

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5
Q

what causes watery saliva?

A

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

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6
Q

where does parasympathetic stimulation for the salivary glands originate?

A

the salivatory nuclei of the medulla oblongata

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7
Q

what three main things stimulate the salivary nuclei?

A
  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)
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8
Q

what are the three phases of swallowing?

A

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.

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9
Q

How does the stomach mix chyme?

A

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

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10
Q

four parts of the stomach

A

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

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11
Q

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

A

stomach. Parietal cells (in the fundus and body)

used for bit B12 absorption in the GI tract

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12
Q

where are gastric glands?

A

in the fundus

in the body

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13
Q

what do gastric glands contain?

A

parietal cell

chief cells

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14
Q

What do Parietal cells secrete?

A

intrinsic factor

HCL

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15
Q

Functions of gastric acid

A

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

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16
Q

What is pepsin?

A

a protein digesting enzyme secreted by chief cells

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17
Q

why do parietal cells not produce HCL in the cytoplasm?

A

destruction

18
Q

what happens to the ionic exchange in a parietal cell?

A

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.

19
Q

What is the alkaline tide?

A

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

20
Q

Where are chief cells located?

A

At the bottom of the gastric gland pit

21
Q

What do chief cells secrete?

A

pepsinogen (an inactive proenzyme)

22
Q

How is pepsinogen converted?

A

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

23
Q

what does the stomach produce in infants but not adults?

A

renin and gastric lipase for the digestion of milk

24
Q

Where is gastrin produced?

A

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

25
Q

What does gastrin do?

A

Stimulates the secretion of parietal and chief cells

stimulates contractions of the gastric wall

26
Q

what three overlapping gastric control phases are there?

A 
Cephalic phase (short - minutes)
Gastric phase (Long 3-4 hrs)
intestinal phase (long - hrs)
27
Q

ANS innervation of cephalic phase

A

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?

28
Q

Don’t forget mucous cells in the stomach that…

A

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

29
Q

When does the gastric phase start?

also name the three stimuli

A

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

30
Q

when does the intestinal phase start?

A

when there is a reduction in stomach distension.

31
Q

what is the enterogastric reflex?

A

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

32
Q

what must the duodenum do, to protect itself?

A

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

33
Q

what does the arrival of chyme in the intestine trigger?

A

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

34
Q

what type of meal leaves the stomach quickly?

A

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

35
Q

what drugs can be absorbed by the stomach?

what is the danger of these drugs?

A

alcohol and aspirin

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

36
Q

Where are most the enzymes manufactured?

A

in the pancreas

37
Q

Apart from enzymes, what else does the pancreas produce?

A

buffers - to neutralise the acidic chyme from the stomach

38
Q

what type of organ is the pancreas primarily?

A

an exocrine organ

makes digestive enzymes

39
Q

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

A

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

40
Q

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

A

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.

41
Q

Name four made enzyme classes in the pancreas

A

pancreatic lipase
carbohydrase
nucleases
proteolytic enyzmes (must abundant)

Physiology (13 decks)

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