Topic 21: Digestive system

Question 1

Give the primary function of digestive system

Answer 1

• Transfer nutrients + water + electrolytes from ingested food

Question 2

Give 4 functions of digestive system

Answer 2

1) Motility
2) Secretion
3) Digestion
4) Absorption

Question 3

Describe motility of digestive system

Answer 3

• Muscular contractions = mix + move forward contents of tract

Question 4

Give the 2 types of digestive motility

Answer 4

1) Propulsive movements:
- Push contents forward through tract
2) Mixing movements:
- Mixing food + digestive juices = promotes digestion
- Facilitate absorption by exposing all contents to absorbing surfaces of tract

Question 5

Describe digestive secretions

Answer 5

• H2O + electrolytes + specific organic constitutes
• Neural/hormonal stimulation
• Reabsorbed back to blood after used in digestion

Question 6

Describe absoption

Answer 6

• Small units resulting from digestion + water + vitamins + electrolytes = transferred from digestive tract lumen into blood/lymph

Question 7

Give the 4 major tissue layers of digestive tract

Answer 7

1) Mucosa
2) Submucosa
3) Muscularis externa
4) Serosa

Question 8

Describe mucosa

Answer 8

• Highly folded luminal surface = increase absorptive area
  1) Mucous membrane
  2) Lamina propria
  3) Muscularis mucosa

Question 9

Describe mucous membrane

Answer 9

• Protective surface
• Secretion + absorption
  1) Exocrine gland cells = digestive juices
  2) Endocrine gland cells = hormones
  3) Epithelial cells = absorbing

Question 10

Describe lamina propria

Answer 10

• GALT

Question 11

Describe muscularis mucosa

Answer 11

• Sparse layer of smooth muscle

Question 12

Describe submucosa

Answer 12

• Thick layer = CT
• Distentibility + elasticity
• Blood + lympth vessels
• Submucosal plexus

Question 13

Describe muscularis externa

Answer 13

• Smooth muscle coat
• Contractile activity = propulsive + mixing movement
• Contains = myenteric plexus between 2 layers
  1) Circular layer = inner
• Contraction decreases diameter
  2) Longitudinal layer = outer
• Contraction shortens tube

Question 14

Describe serosa

Answer 14

• Secretes fluids = lubricate + prevent friction between organs + surrounding viscera
• Continuous with mesentery

Question 15

Give the function of mesentery in tract

Answer 15

• Attachment = relative fixation
• Supports orgnas in place + allowing propulsive + mixing movement

Question 16

What are digestive motality + secretions regulated by?

Answer 16

• Autonomous smooth muscle function
  – Intrinsic nerve plexuses
  – Extrinsic nerves
  – Gastrointestinal hormones