Red blood cell Carry oxygen. Contain haemoglobin (rich in iron) to carry oxygen. Biconcave shape to provide a large surface area for the diffusion of oxygen. No nucleus to provide more space for ...

Your heart's will to beat ... This short film offers a look at respiration and a tour around the circulatory system and digestive system in the human body, through blood vessels and into mitochondria.

Veins between two capillary networks are portal systems. Closed circulatory system, but fluid constituents of blood leak out of capillaries and return to the heart by the second component of the ...