- * Water Absorption
Most relevant to the function of the large intestine but also occurs in the small intestine.
– Large intestine stores and concentrates fecal material before elimination.
– Mainly absorbs water and electrolytes to do so
– Also absorbs bacterial byproducts.
- Three General Steps of Water Absorption:
Step 1:
- Sodium-potassium pump on the basolateral surface
- Na+ passively enters via general sodium ion transporter on the apical surface (possible because of the active transport of sodium out of the cell)
- Net positive charge in the cell
Step 2:
- Chloride enters the cell through a general chloride ion transporter on the apical surfacen via facilitated diffusion down the electrical gradient.
- Higher solute concentration inside the cell relative to the lumen.
Step 3:
- Water crosses the apical surface via osmosis.
Intestinal Absorption: Transport of Water
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Water Absorption
- The main function of the large intestine is to store and concentrate fecal material before elimination.
- It mainly absorbs water and electrolytes to do so, but that it also absorbs bacterial byproducts.
- Basolateral surface
- Sodium-potassium pump (active)
- Apical surface
- Sodium ion transporter (passive)
- Chloride ion transporter (pasive)
- Water enters via osmosis