Digestion Diagrams

The Small Intestine and Peristalsis

1. From outside to inside:

• serosa.

• lonitudinal muscle.

• circular muscle.

• sub-mucosa.

• mucosa.

• (villi).

• (microvilli).

2. Movement via peristalsis:

• circular muscle contracts in front of bolus

• longitudinal muscle contract around bolus

Villus Structure

Absorption in Small Intestine

Process of absorption in the small intestine:

• Sodium-glucose co-transporter proteins in microvilli transfer Na+ and glucose from lumen to cells (- facilitated diffusion).

• Na⁺/K⁺ pumps transfer Na⁺ from epithelial cells to interstitial spaces inside villus, and K⁺ in opposite direction, creating a low concⁿ of Na⁺ inside cells (- active transport).

• Glucose channels allow glucose to move from cells to interstitial spaces and on to blood capillaries (- facilitated diffusion).

• Fatty acids and monoglycerides pass into epithelial cells by simple diffusion.