tissue fluid formation

Tissue fluid formation:

1.Blood from the heart passes through arteries & arterioles &finally the capillaries.

2.Capillaries are much narrower & this creates pressure at the arterial end of the capillary  = hydrostatic pressure

3.This pressure forces tissue fluid out of the blood plasma.

4.This pressure is opposed by two other forces

a)Hydrostatic pressure of the tissue fluid outside the capillaries

b)The lower water potential of the blood, due to the plasma protein- pulls water back into the blood

The overall effect of all these forces results in tissue fluid leaving the capillaries. The pressure is only enough to force small molecules out of the capillaries- leaves cells & proteins.

Tissue fluid return:

Exchange of metabolic materials in the tissue fluid- tissue fluid needs to be returned to the circulatory system.

1.The loss of tissue fluid from the capillaries at the arterial end reduces the hydrostatic pressure inside them.

2.Therefore at the venous end the hydrostatic pressure is less than the tissue fluid surrounding the capillaries.

3.Plasma proteins in the capillaries generate an osmotic pressure that draws water back into the capillaries.

4.Tissue fluid is forced back into the capillaries.