1.3 Gut secretions and Reflexes

Question 1

What are the two digestive enzymes of saliva and where do they come from?

Answer 1

Lingual lipase from glands on tongue and salivary amylase from salivary glands

Question 2

What are the secreting cell types in the stomach, where are the located and what do they secrete

Answer 2

Parietal cells: fundus, H+ and intrinsic factor
Chief cells: fundus and antrum, pepsinogen
G cells: antrum and gastrin
D cells: antrum and somatostatin

Question 3

What is the role of intrinsic factor?

Answer 3

Helps absorb vitamin B12

Question 4

What are the 3 secretagogues?

Answer 4

Ach
Gastrin
Histamine

Question 5

What are the three phases of gastric acid secretion?

Answer 5

1. Cephalic
2. Gastic
3. Intestinal

Question 6

What are the four phases of the cephalic phase and what sets it off?

Answer 6

1. Direct stimulation of parietal cells (ACh mediated)
2. Release of histamine from ECL cells (ACh)
3. Release of gastrin from G cells (gastrin releasing peptide)
4. Decrease somatostatin release from D cells (ACh)

Initiated by sight, taste, smell and thought of food

Question 7

What is involved in the gastric phase of acid secretion and what are the 2 stimuli?

Answer 7

Entry of food into the stomach causes stimulation of H secretion

1. Distension of gastric wall in corpus and antrum
2. Partially digested proteins stimulate G cells in antrum to release more gastrin

Question 8

What are the three phases of the intestinal phase of gastric acid secretion?

Answer 8

1. Peptones stimulate G cells in duodenum - gastrin release
2. An entero-oxyntin stimulates parietal cells
3. Absorbed AAs stimulate acid secretion by unknown mechanism

Question 9

What is the role of Brunners glands

Answer 9

Secrete mucus rich in HCO3 to protect the duodenum from gastric acid

Question 10

What are the secretions in the small intestine and what cells?

Is there enzymes secreted?

Answer 10

Goblet cells - mucus
Enterocytes - water and electrolytes

No enzymes secreted but they are present in the brush border of the mucosal enterocytes

Question 11

What is the role of mucus in the large intestine?

Answer 11

Aqueous component is rich in K and HCO3 which protects the large intestine against abrasion, provides adherent medium for holding fecal matter together and with the alkalinity protects against bacterial activity in feces