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Blood and Circulation (Blood composition (White blood cells (All different…
Blood and Circulation
Blood composition
White blood cells
All different shapes
Protect the body from invasion by disease-causing microorganisms, such as bacteria and viruses.
Red blood cells
bioncave
transport oxygen-contain mainly haemoglobin, which loads oxygen into the lungs and unloads it into the rest of the body
Plasma
Liquid part of blood
carries the blood cells around the body; carries dissolved nutrients, hormones, carbon dioxide and urea
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Circulation Systems
Double Circulation
The heart pumps blood around the body twice, so higher pressures are achieved. This means blood travels quicker to organs.
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Human Circulation
Parts
Blood vessels - these carry the blood around the body; arteries away from the heart and veins back to the heart. Capillaries carry blood through organs
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Blood Vessels
Veins
Carry blood back towards the heart. The pressure of blood here is much lower than in the arteries. It puts little pressure on the walls of the veins.
Cappilaries
Carry blood through organs, bringing blood close to every cell in the organ.Substances are transferred between the blood in the capillary and the cells. To do this, capillaries must be small enough to fit between cells, and allow materials to pass through their walls easily.
Arteries
Carry blood from the heart to organs of the body. The blood has been pumped out by the ventricles and puts a lot of pressure on the walls of the arteries. They must be able to stretch under pressure.
The Heart
Cardiac Cycle
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The walls of the atria contract. This raises the pressure of the blood in the atria which forces open the bicuspid and tricuspid valves. Blood passes through these valves into the ventricle
When the ventricles are full, they contract. This increases the pressure of blood in the ventricles which closes the bicuspid and tricuspid valves again. Blood cannot return to the atria
As the ventricles empty, higher pressure in aorta and pulmonary artery closes the valves in these blood vessels. The cycle then begins again as the atria starts to fill with blood.
The ventricles continue to contract and the pressure continue to increase. This forces open the semi-lunar valves at the base of the aorta and the pulmonary artery. Blood is ejected into these two arteries.The pulmonary artery carries the blood to the lungs. The aorta has branches that carry blood to all other parts of the body