Circulatory System Year 8 Science – Chapter 3.3

Circulatory System The circulatory system is the transport system that makes sure everything gets to where it is needed in your body. This system carries nutrients and oxygen to the cells, carries wastes to where they can be disposed of, and distributes heat (a by-product of respiration) throughout your body. It consists of the heart, blood vessels and blood

Blood Vessels Arteries carry blood away from the heart Capillaries are the narrowest blood vessel that reaches nearly every cell of the body. The walls are only one cell thick. This allows dissolved materials to pass through them Veins carry blood back to the heart

The Heart Your heart is about the size of your fist and is situated in the middle of your chest The heart is made of a special type of muscle called cardiac muscle. The heart has four chambers. Two of the chambers collect blood from the lungs and pump it round the body (red). The other two chambers collect blood from the body and pump it to the lungs (blue)

Double circulatory system Your blood follows two separate pathways in your body. One pathway from the heart to the body and back to the heart (first circulation). The other pathway if from the heart to the lungs and back to the heart again (second circulation)

Blood flow around the heart

Path of a red blood cell The blood enters the heart via the pulmonary vein and into the left atrium. The blood then pumps down to the left ventricle and out via the aorta. This blood is rich in oxygen and nutrients (coloured red). The blood cells are carried to the cells around our body. At the cells, the oxygen and nutrients are unloaded and wastes such as carbon dioxide are collected via a process called diffusion. The deoxygenated blood (coloured blue) is transported back to the heart and enters through the vena cava and into the right atrium. The blood is then pumped down into the right ventricle and out of the heart via the pulmonary artery and into the lungs. In the lungs, carbon dioxide passes out of the blood and oxygen passes into the blood (via the capillaries). The blood rich in oxygen then returns to the heart to be pumped around the body.

Heart Beat There are three main phases of a heartbeat: The two atria (plural of atrium) contract, pushing blood down into the ventricles. The ventricles contract, forcing blood out of the heart to the body and lungs. The heart muscle relaxes and the atria fill with blood.

Blood The function of blood in the body is to: carry food and oxygen fight infection clot wounds distribute heat and hormones.

Red Blood Cells Red Blood Cells – They live for 120 days Iron is required to make haemoglobin (is a protein) which attaches the oxygen to the red blood cells Red blood cells transport oxygen around the body

Blood Platelets – are broken up bits of cells produced in the bone marrow. They help blood to clot White Blood Cells - are part of the immune system that helps fight disease Plasma – Liquid part of the blood. Transports nutrients, wastes and chemicals needed by the cell http://www.youtube.com/watch?v=R-sKZWqsUpw

eBook – Drag and Drop Activity

Disease and Disorders Haemophiliac – A condition whereby a person can not clot their blood Anaemia – lack of iron in the blood leading to weakness and fatigue. A hole in the heart – is a birth defect which babies are born with a hole in their septum. Deoxygenated blood leaks in and mixes with oxygenated blood therefore less oxygen is reaching the cells around the body resulting in a decrease of energy and growth Heart disease – caused by lack of exercise, poor diet and smoking