2.59 Describe the composition of the blood: red blood cells, white blood cells, platelets and plasma

red blood cells

carry O2 from lungs to rest of body and carry CO2 from rest of body to lungs

adaptations of red blood cells

• biconcave shape —> increase SA for gas exchange

• no nucleus —> maximise space for haemoglobin (protein that binds to O2)

• flexible —> can squeeze through narrow capillaries to transport oxygen

white blood cells

attack foreign cells e.g. pathogens (bacteria and virus)

what does plasma transport

• CO2 —> from body cells to lungs

• digested food —> from small intestine to body cells'

• urea → liver to kidneys

• hormones —> endocrine glands to target organs e.g. muscle

• heat energy —> from muscles to whole body (maintain stable temp)

platelets' role in blood clotting

• platelets = activated by exposure of collagen in vessel wall

• activated platelets stick to the damaged area and each other to form a platelet plug to reduce blood loss

• platelets release chemicals that trigger a complex chain reaction AKA clotting cascade

• cc leads to conversion of soluble fibrinogen to insoluble fibrin

• fibrin forms a mesh-like network that traps RBCs, WBCs, and more platelets —> stable clot

• the clot seals the wound and provides a framework for tissue repair