key ideas key words
B4: Circulatory System
B4.1 - The Blood
❖ the blood is made up of liquid plasma (55%), red blood cells (45%) and carries
white blood cells and platelets (<1%)
➢ it also carries around waste substances substances
B4.2 - The Blood Vessels
❖ there are three types of blood vessels:
➢ arteries
■ carry the blood away from your heart and towards the organs
■ contains bright red, oxygenated blood
■ blood flow is fast (which means if you cut an artery, the blood
will spurt out)
■ a pulse can be felt from an artery
, key ideas key words
■ thick, muscley walls with elastic fibres to accommodate the blood
flow before returning to their original shapes
➢ veins
■ carry the blood away from the organs and back towards the heart
■ contains purpley-red coloured blood which is deoxygenated
■ blood pressure is low, so there are valves to prevent backflow
■ veins have no pulse
■ blood is squeezed back towards the heart by the action of the
skeletal muscles contracting and relaxing
➢ capillaries
■ huge network of tiny vessels that link arteries and veins
■ thin walls which enables easy and quick diffusion of oxygen and
glucose to cells and the same with waste products like CO2, but
vice versa
B4: Circulatory System
B4.1 - The Blood
❖ the blood is made up of liquid plasma (55%), red blood cells (45%) and carries
white blood cells and platelets (<1%)
➢ it also carries around waste substances substances
B4.2 - The Blood Vessels
❖ there are three types of blood vessels:
➢ arteries
■ carry the blood away from your heart and towards the organs
■ contains bright red, oxygenated blood
■ blood flow is fast (which means if you cut an artery, the blood
will spurt out)
■ a pulse can be felt from an artery
, key ideas key words
■ thick, muscley walls with elastic fibres to accommodate the blood
flow before returning to their original shapes
➢ veins
■ carry the blood away from the organs and back towards the heart
■ contains purpley-red coloured blood which is deoxygenated
■ blood pressure is low, so there are valves to prevent backflow
■ veins have no pulse
■ blood is squeezed back towards the heart by the action of the
skeletal muscles contracting and relaxing
➢ capillaries
■ huge network of tiny vessels that link arteries and veins
■ thin walls which enables easy and quick diffusion of oxygen and
glucose to cells and the same with waste products like CO2, but
vice versa
