Biology B3 - The circulatory system

Blood is used to transport materials around the body, and to protect against disease. Blood contains plasma, a liquid that contains dissolved substances, cells and cell fragments. These include:

• Red blood cells, which transport oxygen
• White blood cells, which protect against disease
• Platelets, which help the blood to clot

FeatureReason Small size Lets red blood cells pass through narrow capillaries Flattened disc shape Provides a large surface area, allowing rapid diffusion of oxygen Contains haemoglobin Haemoglobin absorbs oxygen in the lungs…