Intestinal physiology 1: Fluid and electrolytes and digestion in the intestines

Question 1

GI function

Answer 1

• Take relatively large solids and digest them into smaller molecules that can be absorbed as nutrients, while still serving as a barrier to toxins, bacteria, parasites, etc.
• Objective – To understand biological mechanisms that facilitate GI function.

Question 2

Secretion and absorption

Answer 2

• Transport of fluid and electrolyte is a key function of the GI tract
• Epithelial Cells may:
– Secrete water and electrolytes
– Absorb water and electrolytes

Question 3

Movement of H2O and electrolytes

Answer 3

• Water moves down an osmotic gradient
• Electrolytes move down electrochemical gradients
• To move against concentration gradients requires energy
• Energy is supplied by sodium gradients (generated by the sodium pump) and by proton gradients

Question 4

The small intestine

Answer 4

• Absorbs 7.5L/day

* 3 segments: Duodenum, Jejunum, Ileum

Question 5

Na+ couples nutrient absorption

Answer 5

1st stage: membrane transport protein

2nd stage: Na+K+ATPase transporter

Question 6

Digestion and absorption

Answer 6

• Small intestine is primary site for digestion and absorption of food.
• Digestion occurs in the GI lumen by secreted enzymes and on surface of enterocytes by membrane-bound enzymes.
• Absorption occurs by simple diffusion, facilitated diffusion, active transport, endocytosis, and paracellular transport.
• Surface area of small intestine is greatly increased by extensive folding and the projection of fingerlike villi covered with microvilli.

Question 7

functions of saliva

Answer 7

1. Lubricates, cleans oral cavity
2. Dissolves chemicals
3. Suppresses bacterial growth
4. Digest starch by amylase

Question 8

pancreas

Answer 8

• Endocrine Function
secretes insulin and glucagon from islets of Langerhans
• Exocrine Functions
secretion of pancreatic juice

Question 9

relevant functions of the liver

Answer 9

1) Metabolic regulation
•	Store absorbed nutrients, vitamins
•	Release nutrients as needed
2) Haematological regulation
•	Plasma protein production
•	Remove old RBCs
 3) Production of bile
•	Required for fat digestion and absorption