Lecture 26: Secretion

Question 1

What is the function of salivary secretions?

Answer 1

Lubrication: chewing and swallowing
Hygiene: irrigation
Digestion: dissolved food allows tasting

Question 2

How are salivary secretions regulated?

Answer 2

Nervous stimuli = thought, smell & sight of food; and through presence of food in mouth - chewing
Autonomic nervous system
Parasympathetic = acetylcholine
Sympathetic = adrenaline

Question 3

What are the sources of saliva?

• describe the two-way model

Answer 3

Parotid: a-amylase = serous only
Submandibular = mixed
Sublingual = mucous only
Saliva is secreted as a primary secretion = isotonic serous solution from acing cells it is secrete into ducts which modify it —-> becomes hypotonic

Question 4

What are the functions of gastric secretions?

Answer 4

• Mucus = protection
• Intrinsic factor = absorption of vitamin B12 in small intestine
• Pepsin = secreted as pepsinogen(inactive) then converted to pepsin - starts digestion of proteins
• Gastric acid = denatures proteins, activates pepsinogen to pepsin, protection

Question 5

How are gastric secretions regulated?

Answer 5

• Coordinated with eating and arrival of food
• Divided into 3 phases
  1. Cephalic phase = head controls secretion
  2. Gastric phase = stomach controls secretion
  3. Intestinal phase = intestine regulates secretion

Question 6

What are the functions of pancreatic secretions?

Answer 6

• Secretes enzymes which: chemically digest food material

Question 7

How are pancreatic secretions regulated?

Answer 7

• Slow basal rate during fasting
• Hormonal regulation during meal
  CCK = is produced by duodenal endocrine cell in reopen to digestive products in lumen - it stimulates enzyme secretion by acinar cells
  Secretin = is produced by endocrine cells in response to increased H+ in lumen - it stimulates HCO3 secretion by duct cells

Question 8

What are the function of bile secretions?

Answer 8

• Bile salts and lecithin = fat digestion and absorption
• HCO3 rich fluid = neutralises acid chyme
• Bile pigments = excretions

Question 9

How are bile secretions regulated?

Answer 9

Delivery of bile is under hormonal control

- bile is secreted constantly and stored in gall bladder and is delivered to small intestine when food is present

Question 10

Describe intestinal secretion
- what does the small intestine secrete?

• what does the large intestine secrete?

Answer 10

Small intestine secretes
- mucus = lubrication
- sodium bicarbonate solution = neutralises acid and dilutes food
Large intestine secretes
- mucus = lubrication