Gastrointestinal Physiology: Secretion

Question 1

What do the salivary glands secrete? What is the composition of its secretions? (3)

Answer 1

Mucus, dilute solution of NaHCO3 and NaCl, digestive enzymes (salivary amylase and lingual lipase)

Question 2

What regulates the secretion of the salivary glands?

Answer 2

Nervous stimuli, autonomic nervous system

Question 3

This stimulates the secretion of copious amounts of fluid in the salivary glands.

Answer 3

Parasympathetic nervous system

Question 4

This stimulates the secretion of small volumes of viscous fluid in the salivary glands.

Answer 4

Sympathetic nervous system

• this augments the parasympathetic response

Question 5

What is the composition of gastric secretions? (4)

Answer 5

Mucus, intrinsic factor, digestive enzymes and acid + bicarbonate

Question 6

What secretes mucus and bicarbonate in the stomach?

Answer 6

Epithelial cells

Question 7

What secretes intrinsic factor in the stomach?

Answer 7

Parietal cells

Question 8

What secretes digestive enzymes like pepsinogen in the stomach?

Answer 8

Chief cells

Question 9

This contains bicarbonate which buffers acid at the epithelial surface. It also protects from abrasion at the stomach.

Answer 9

Mucus

Question 10

This stabilises vitamin B12 and facilitates its absorption in the small intestine. It is secreted by the stomach.

Answer 10

Intrinsic factor/acid

Question 11

This is an inactive for of pepsin, and is responsible for the digestion of proteins in the stomach.

Additional question:
What activates this protein in the stomach?

Answer 11

Pepsinogen

Pepsinogen activated by acid

Question 12

This creates the optimum pH for pepsin action, dilutes food and denatures protein in the stomach.

Answer 12

Gastric acid

Question 13

What are the 3 phases of gastric secretion? What stimulates each of the secretions?

Answer 13

The different regions of the body control secretion.

Cephalic phase (head) - CNS and ENS (local reflex and then the long reflex) - extrinsic
Gastric phase (stomach) - nervous (parasympathetic nervous system) and hormones
Intestinal phase (intestine) - nervous (enterogastric reflex) and hormonal (CCK and secretin)

Question 14

What stimulates the cephalic phase? (2)

Answer 14

CNS and extrinsic parasympathetic nervous response via ENS

Question 15

This is responsible for stimulating the secretion of parietal cells, chief cells and goblet cells during the cephalic phase. It also stimulates the secretion of the hormone gastrin.

Answer 15

Extrinsic parasympathetic response.

Question 16

What stimulates the gastric phase? (3)

Answer 16

Stimuli in stomach, nervous and hormonal regulation

Question 17

This is responsible for stimulating the secretion from gastric glands, motility and gastrin secretion during the gastric phase. (2)

Answer 17

Local nervous reflex (ENS) and external (long) nervous reflex (CNS)

Remember ENS: local nervous system (short range)
CNS: long reflexes (far range)

Question 18

What stimulates the intestinal phase? (2)

Answer 18

Hormones and nerves

Question 19

This describes the long reflex from duodenum to brain to stomach as a part of what stimulates secretion in the intestinal phase.

Answer 19

Enterogastric reflex

Question 20

True or false. Both hormones and nerves inhibit secretion and motility in the intestinal phase.

Answer 20

True

Question 21

What is the composition of pancreatic secretion? (2) What cells secrete them?

Answer 21

Enzymes (acinar cells) and alkaline fluid (duct cells)

Question 22

True or false. Pancreas is the most important source of enzymes.

Answer 22

True

Question 23

What stimulates the pancreatic secretion of enzymes?

Answer 23

Hormone - CCK

Question 24

What stimulates arrival of CCK?

Answer 24

Arrival of lipids and carbohydrates in duodenum

Question 25

This is the proteolytic enzyme that converts trypsinogen to trypsin. Trypsin then converts other enzymes to their active form.

Answer 25

Enterokinase

Question 26

What stimulates the pancreatic secretion of HCO3/alkaline fluid?

Answer 26

Hormone - secretin

Question 27

What stimulates arrival of secretin?

Answer 27

Secretion of acidic chyme in duodenum

Question 28

This neutralises the avid chyme delivered from the stomach and creates optimum pH for pancreatic and intestinal digestive enzyme.

Answer 28

Alkaline fluid (HCO3)

Question 29

What is the composition of billiary secretions?

Answer 29

Bile salts, HCO3- rich fluid, bile pigments (excretory wastes)

Question 30

True or false. Cholesterol is an excretory product secreted by the pancreas.

Answer 30

False. Cholesterol is an excretory product secreted by the liver.

Question 31

What stimulates initial delivery of billiary secretions?

Answer 31

Hormonal control - CCK and secretin

Question 32

What stimulates the secretion of bile from the liver?

Answer 32

Bile via enterohepatic circulation

Question 33

This is metabolically expensive to produce, and is reabsorbed and secreted which is what stimulates its reproduction.

Answer 33

Bile

Question 34

What is the composition of intestinal secretion? (3)

Answer 34

Mucus, isosmotic fluid (mixture of NaCl and NaHCO3), digestive enzymes (brush border enzymes)