8.3 Blood, tissue fluid and lymph Flashcards
What components does plasma transport?
Dissolved glucose Amino acids Mineral ions Hormones Large plasma proteins
Plasma proteins
Albumin - maintains osmotic potential of the blood
Fibrinogen - important in blood clotting
Globulins - involved in transport and immune system
What are platelets?
Fragments of large cells called megakaryocytes found in red bone marrow
Involved in clotting mechanism of the blood
Functions of the blood
Transport:
O2 to and CO2 from respiring cells
Digested food from the small intestine
Nitrogenous waste products from cells to excretory organs
Hormones
Food molecules from storage compounds to the cells that need them
Platelets to damaged areas
Cells and antibodies involved in the immune response
Maintain body temperature, acts as a buffer to reduce pH changes
What is oncotic pressure?
The tendency of water to move into the blood by osmosis
What causes oncotic pressure?
Plasma proteins give the blood a high solute potential and low WP, so water moves into the blood in capillaries by osmosis
What causes hydrostatic pressure?
When blood flows through the arterioles into the capillaries, it is still under pressure from the surge of blood that occurs every time the heart contracts.
Hydrostatic and oncotic pressure at arterial end of the capillary
Higher hydrostatic pressure than oncotic pressure
Fluid is squeezed out of capillaries
This fluid fills spaces between cells - tissue fluid
Hydrostatic and oncotic pressure at venous end of the capillary
Hydrostatic pressure falls, as pulse is completely lost, oncotic pressure is still 3.3 kPa and is stronger, so water moves back into capillaries by osmosis
How is lymph different to plasma and tissue fluid?
Has less O2 and fewer nutrients and contains fatty acids which are absorbed from the villi of the small intestine
Transport in lymph system
Lymph capillaries join up to form larger vessels
Fluid is transported through these vessels by squeezing of body muscles
One way valves prevent backflow
Eventually returns to the blood flowing into the R & L subclavian veins
Lymph nodes
Found along lymph vessels
Lymphocytes build up in the lymph node and produce antibodies when required
Intercept bacteria and other debris from the lymph - ingested by phagocytes
Sites of major lymph nodes
Neck, armpits, stomach, groin
