Tissue Fluid
Capillaries:
Connect the smallest branches of arteries and veins
Walls are 1 cell thick to allow the exchange of molecules between the blood and the body’s cells
Molecules can diffuse across their walls
Out of the Capillaries:
Oxygen - diffuses through the capillary wall, into the tissue fluid and the cells
Glucose diffuses from the blood plasma, across the capillary walls to the tissue fluid and then into the cells
Into the capillaries:
Urea (waste product) diffuses from the cells of the liver, to the tissue fluid and across the capillary walls into the blood plasma
Carbon Dioxide diffuses from the cells into the tissue fluid, then across the capillary walls into the blood plasma
Tissue Fluid:
Watery substance that bathes the cells of tissues
Formed from blood plasma
Fluid by which substances are exchanged between the blood and cells
Function - to supply tissues with essential solutes in exchange for waste products
Made up of substances that are small enough to escape through the gaps in capillary walls
Movement through the capillary walls:
Hydrostatic Pressure
Residential pressure from the heart beating created when blood is forced through the capillaries
Onocotic pressure
A specific type of osmotic pressure generated by large molecule (like proteins) in a solution that prevents water from moving out of the capillaries
When there is movement of fluid out of capillaries the water potential of the capillaries become more negative
Becoming negative causes water to move down the water potential gradient
Lymphatic Sytem:
Carries back remaining tissue fluid pushed back in the capillaries
Now known as lymphatic fluid
This process helps to prevent swelling by water retention
Excess molecules may return to the circulatory sytem supraclavicular lymph nodes
Lymph Capillaries
Have closed ends and large pores that allow large molecules to pass through
Lymphatic fluid moves along the larger vessels by compression caused by body movement
Back flow is prevented by small valves
Lymph nodes produce antibodies
Lymph glands removes bacteria and other pathogens
Conditions affecting exchange in the capillaries:
Cardiovascular disease - increases Hydrostatic pressure, reducong reabsorption and damaging capilllaries
High blood pressure
Diabetes - Disrupts the balance of hydrostatic and osmotic pressure
High glucose - reduced fluid formation
Low glucose - reduced reabsorption