Heart

• Double circulation means that the blood passes through the heart twice in one cycle
• Artery carries oxygenated blood at high pressure away from the heart. It has thick muscular walls containing elastic fibres and fibrous tissue, and a narrow lumen.
• Blood in arteries flow very fast, the structure withstands blood pressure and prevent it from bursting.
• Vein carries deoxygenated blood in low pressure to the heart. The wall is thin because pressure has been lost. Veins have valves to stop backflow of blood when the muscle relaxes. Muscle contracts so the valves open
• Capillaries are tiny vessels where exchange between cells takes place. They’re only one cell thick and have large surface area to maximise diffusion. The lumen is the size of a RBC so it goes in a single file line.
• Coronary arteries supply the heart muscles with oxygen and nutrients
• Treatment to CHD are angioplasty surgery and taking in Aspirins
• Plaque made of WBC and cholesterol builds up in coronary arteries and reduces blood flow.
• Platelets release chemicals that changes soluble fibrinogen into insoluble fibrin, it forms a mesh that traps platelets and blood cells, forming a scab.