7.6B - Tissue Fluid Flashcards
What is tissue fluid
A watery liquid that contains glucose, amino acids, fatty acids, ions in solution and oxygen
What is the function of tissue fluid
To supply tissues with the solution it contains
What does tissue fluid receive in return after supplying tissues with metabolic substances
Waste produces from respiration - co2 etc
What does tissue fluid essentially act as
The means by which materials are exchanged between blood and cells
Because it bathes all cells of the body, it is the immediate environment of cells.
What is tissue fluid formed from
Blood plasma, and the composition of such blood plasma is controlled by various homeostatic systems
Describe the process by which blood is pumped through blood vessels to create a hydrostatic pressure
Blood pumped by the heart passes along arteries, then even narrower arterioles and, finally, the even narrower capillaries
Pumping by the heart produces a hydrostatic pressure at the arterial end of the capillaries.
What does the hydrostatic pressure do
Causes tissue fluid to move out of the blood plasma
What is the outward pressure of tissue fluid opposed by (2 forces)
- Hydrostatic pressure of the tissue fluid outside the capillaries, which resists outward movement of liquid
- The lower water potential of the blood, due to plasma proteins that cause water to move back into the blood within capillaries.
What does the combined effect of all 3 forces do
Creates an overall pressure that pushes tissue fluid out of the capillaries at the arterial end.
What is this type of filtration called
ULTRAFILTRATION
How is tissue fluid returned back to the circulatory system
- The loss of the tissue fluid from the capillaries reduces the hydrostatic pressure inside them
- By the time the blood has reached the venous end of the capillary network its hydrostatic pressure is usually lower than that of the tissue fluid outside it
- Therefore tissue fluid is forced back into the capillaries by the higher hydrostatic pressure outside them
- In addition, the plasma has lost water and still contains proteins. It therefore has a lower water potential than the tissue fluid
- As a result, water leaves the tissue by osmosis down a water potential gradient.
What happens to some tissue fluid that doesnt return to capillaries
It is carried back via the lymphatic system.
They resemble capillaries however have dead ends, they gradually merge into larger vessels that form a body network. These larger vessels drain their contents back into the bloodstream via two ducts that join veins close to the heart
How are contents of the lymphatic system moved
- Hydrostatic pressure of the tissue fluid that has left the capillaries
- Contraction of body muscles that squeeze the lymph vessels. Lymph vessels have valves that prevent the backflow of tissue fluid
