The heart requires its own constant blood supply in order to keep beating and this is delivered through the coronary arteries. Genetic and lifestyle factors can lead to the coronary arteries becoming blocked, and an increased risk of heart disease.

The blood in veins is under lower pressure than the blood in arteries.

The veins have:

.thin walls thin layers of muscle and elastic fibres

Unlike arteries, veins have one-way valves in them to keep the blood moving in the correct direction.

Inside of the blood inside of our bodies are cells. Blood is made up of 44% red blood cells. The red blood cells carry oxygen around our body and give the red colour of our blood. 1% is white blood cells. White blood cells are like the police in our blood as they attack any infections that may cause any harm. 55% of our blood is plasma. Plasma carries nutrients and protein around the body.

Our blood has antigens inside of it. That means are blood can be A type antigens B type antigens AB type antigens or 0 type with no antigens.