GIT Secretion

Question 1

What are the regulatory 3 phases of the GI system?

Answer 1

Cephalic, Gastric and Intestinal

Question 2

What causes increased salivary secretion in cephalic phase?

Answer 2

Parasympathetic and sympathetic stimulation.

Question 3

What initiates the cephalic phase?

Answer 3

Taste, smell of food etc.

Question 4

What changes occur to stomach in the cephalic phase? And what causes them?

Answer 4

Increased secretion of HCl, mucus, pepsin, and gastrin occurs.

Caused by either parasympathetic stimulation, increased blood flow to stomach, and blood factors e.g. insulin and glucagon.

Question 5

What causes stimulation of bile ducts, hepatocytes and pancreatic acinar cells?

Answer 5

Parasympathetic stimulation.

Question 6

What initiates gastric phase?

Answer 6

Food entering the stomach causing distension and release of gastrin especially caffeine, alcohol and calcium.

Question 7

What type pf cells produce gastrin?

Answer 7

G Cells

Question 8

What inhibits gastrin release?

Answer 8

Low pH/increased HCl

Question 9

What stimulates gastrin release?

Answer 9

Parasympathetic stimulation, decreased acidity in due to buffering of food, distension of antrum and proteins, peptides and amino acids.

Question 10

What does gastrin stimulate?

Answer 10

Gastric motility, parietal cells to produce HCl and trophic maintenance of GI epithelium.

Question 11

What initiates intestinal phase?

Answer 11

Presence of food in the duodenum.

Question 12

In the intestinal phase, what occurs if the pH is a) >3, or b) <2

Answer 12

A) duodenal peptides/amino acids cause release of gastrin.
B) gastric inhibition and intestinal stimulation.

Duodenal fats and breakdown pr products cause release of gastric inhibitory peptide and cholecystokinin.

Acid enters intestine intestine causes secretin release.

Question 13

What is a secretagogue? Give an example.

Answer 13

Substance that promotes the secretion of another substance.

Examples include hormones, neurotransmitters, enzymes etc.

Can be exo- or endogenous compounds. The selectivity or specifity is determined by the structure of the secretagogue and its receptor.

Question 14

Salivary secretion: Functions? Made by?

Answer 14

Fumctions include initil digestion of starches and lipids, dilution and buffering of ingested food, protection of teeth and gums, and lubrication of ingested foods with mucous (mucin).

Made by sublingual, submandibular and parotid glands.

Question 15

Where can you find the sublingual gland?

Answer 15

Deep in floor of mouth, underneath the tongue, mostly mucus cells.

Question 16

Where does the submandibular gland reside?

Answer 16

The submandibular gland lies under the lower edge of mandible, mixed glands containing serous and mucus cells.

Question 17

Where does the parotid gland lie?

Answer 17

The parotid gland lies below the ear and over at the masseter, serous cells secreting and aqueous fluid is composed of water, ions, and enzymes.

Question 18

What are the three stages of salivation?

Answer 18

• Acini cells secrete primary secretion (isotonic); sodium, chlorine, potassium, bicarbonate as well as amylase and mucin production.
• Myoepithelial cells stimulated by neural input to eject saliva to ductal portion.
• Duct cells are the secondary modification. The reabsorb sodium and chlorine and add potassium. HCO3 concentration is altered depending on flow rate. High flow rate, saliva has increased HCO3. Low flow rate, more HCO3 is extracted.

Question 19

What is the difference between saliva that has been stimulated by parasympathetic nerves compared to sympathetic saliva?

Answer 19

Parasympathetic saliva is watery, enzyme rich, and there is a large volume. Sympathetic saliva has a small volume, is thick, and mucousy.