6- Transfer of materials between the circulatory system and cells

What is tissue fluid formed as the result of?

The interplay between hydrostatic pressure and oncotic pressure in capillaries.

What is hydrostatic pressure?

Residual pressure from the heartbeat. This is higher at the arterial end of the capillary than the venous end.

What is oncotic pressure?

The movement of fluid out of capillaries due to hydrostatic pressure, water potential of the capillaries becomes more negative (although oncotic pressure is relatively constant).

Where is the hydrostatic pressure greater?

At the arterial end, so fluid moves out.

Where is the oncotic pressure greater?

At the venous end, but the overall movement is still net out of the capillaries.

What forms tissue fluid?

The movement of fluid out of the capillaries.

Where and why does excess tissue fluid drain?

It drains into the lymphatic system (where it is then called lymph) to prevent tissues from swelling.

What does the lymph pass through and then drain back in through?

It passes through the lymphatic system and then drains back into the blood at the subclavian vein.

What does lymph contain and what does it do?

Lymphocytes that produce antibodies which are emptied into the blood along with the lymph.

Lymph glands also remove bacteria and other pathogens. This is the reason why lymph nodes swell when there is an infection in the body.