3. Circulatory System - Tissue Fluid Flashcards
What is tissue fluid?
The fluid which surrounds cells in tissue.
What is tissue fluid made from?
Small molecules that leave the blood plasma.
eg oxygen, water, nutrients.
What does tissue fluid NOT contain?
Red blood cells or big proteins unlike blood.
What do the cells take in from the tissue fluid?
Oxygen and nutrients.
They then release metabolic waste into it.
What is a capillary bed?
A network of capillaries.
What happens in the capillary bed?
Substance move out of the capillaries into the tissue fluid by pressure filtration.
What is pressure filtration?
The net driving force which pushes fluid into tissue spaces and out of vascular sites - filtration under pressure.
At the start of the capillary bed, where is it nearest?
The arteries.
At the start of the capillary bed, nearest the arteries, what is the hydrostatic pressure like?
Hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid.
What happens because there is a higher hydrostatic pressure in the capillaries than in the tissue fluid?
The difference in hydrostatic pressure means an overall outwards pressure forces fluid out of the capillaries and into spaces around the cells, forming tissue fluid.
What happens as the fluid leaves the capillaries?
The hydrostatic pressure reduces in the capillaries - so the hydrostatic pressure is lower at the venule end of the capillary bed.
What is hydrostatic pressure?
The pressure exerted by a liquid.
Due to the fluid loss and increase in concentration of plasma proteins - which don’t leave capillaries, what does this cause?
The water potential at the venule end of the capillary bed is lower than the water potential in the tissue fluid.
Meaning water has re-entered the capillaries from the tissue fluid at the venule end by osmosis.
Where does excess fluid get drained into?
The lymphatic system.
Which transports excess fluid from the tissue and passes it back into the circulatory system.
What is a lymphatic system?
A network of tubes which transports excess tissue fluid back into circulatory system.
What is blood plasma?
The liquid which carries everything in the blood.
In tissue fluid what is pressure filtration talking about?
Small molecules being filtered out of the capillaries under hydrostatic pressure, forming tissue fluid.
Where is the pressure highest?
At the start of the capillary bed nearest the arterioles.
Why is the pressure highest at the start of the capillary bed nearest the arterioles?
Because the left ventricle contracts and sends blood out of the heart, through the arteries and arterioles at high pressure.
What does high blood pressure mean?
High hydrostatic pressure in the capillaries which can lead to an accumulation of tissue fluid in the tissues.
Where is there a net gain of fluid?
At the venous.
Where is there a net loss of fluid?
At the arterial.
Where is the main location where tissue fluid is formed?
Capillaries.
What allows the diffusion between blood and cells?
The liquid which surrounds the cells.
What things only move out of the tiny gaps in the capillary wall and what Doesn’t move?
Dissolved gases/nutrients move through.
Larger plasma proteins and cell do not.
The net loss of water from the capillaries gives the capillaries what?
More negative water potential.
