3F - Reabsorption and Secretion

Reabsorption

• efferent arterial branches to the peritubular capillary

• after materials have moved out of the blood and become the filtrate, what is left goes through the peritubular capillary

• tubular fluid —> blood

Secretion

• blood —> tubular fluid

Secretion barriers

cross

• blood

• interstitial space

• cells of the tubule

• lumen

Reabsorption barriers

cross

• cells of renal tubule

• interstitial space

• blood

Movement of materials are

passive or active

Passive movement

simple/faciliated diffusion

Active movement

Primary and secondary transport

Paracellular transport

• can cross in between the epithelial cells on the wall of the renal tubule

• H2O

• rare

Transcellular transport

• common mode

• cross the membrane of the epithelial membrane cells that form the lining of the renal tubule

• need transport proteins

• cross luminal membrane

• cross basolateral membrane

• moving into interstitial fluid

• into the blood through endothelium cells that form the wall of the peritubular capillaries

Transcellular transport reabsorption

1. luminlal membrane

2. basolaterial membrane

3. endothelium cell

4. enter blood

Transcellular transport secretion

1. out of blood

2. basolateral membrane

3. luminal membrane

4. enter interstitial fluid

Transport proteins

controls what moves and direction of movement

Glucose

only reabsorbed in the proximal convoluted tubules bc that’s where the transporters are

Transport Maximum

• all of the transport proteins are being used