Module 3 Blood plasma and tissue fluid Flashcards
What is blood plasma made up of? What is the difference between blood plasma and tissue fluid?
Blood plasma consists of red blood cells (erythrocytes), white blood cells and platelets, along with the materials the plasma carries such as oxygen, C02, minerals, glucose and proteins. Tissue fluid is similar however it does not contain most of the cells found in blood nor does it contain plasma proteins.
What does tissue fluid do? What type of movement is this?
Tissue fluid carries oxygen and nutrients. As they surround the cells in tissues they supply them with the oxygen and nutrients they require for metabolic activity. They do this by mass flow, rather than diffusion. As the waste products from cell metabolism leaves the cells, they will be carried back into the capillary as some of the tissue fluid returns to the capillary.
How is tissue fluid formed?:
At the arterial end of a capillary, the blood is at a relatively high hydrostatic pressure. This pressure causes some of the blood fluid to leak from the capillaries through the capillary wall in tiny gaps. Oxygen and nutrients, however cells such as erythrocytes are too big and and are not taken out of the capillary. This tissue fluid then surrounds cells and the oxygen and nutrients can exchange across the plasma membranes of cells.
How does tissue fluid return back into the capillary with the waste products?
As the blood at the venous end of the capillary is much lower, the oncotic pressure means some of the tissue fluid can then return to the capillary carrying the waste products such as CO2. Oncotic pressure does not change but hydrostatic pressure does.
What is the difference between hydrostatic and oncotic pressure?
Hydrostatic pressure: The pressure that a fluid exerts when pushing against a vessel.
Oncotic pressure: The pressure caused by the osmotic effects of the solutes.
