Answer:
The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart. The circulatory system carries oxygen, nutrients, and hormones to cells, and removes waste products, like carbon dioxide.
•Blood
Blood consists of:
Red blood cells – to carry oxygen
White blood cells – that make up part of the immune system
Platelets – needed for clotting
Plasma – blood cells, nutrients and wastes float in this liquid.
•The heart
The heart pumps blood around the body. It sits inside the chest, in front of the lungs and slightly to the left side. The heart is actually a double pump made up of four chambers, with the flow of blood going in one direction due to the presence of the heart valves. The contractions of the chambers make the sound of heartbeats.
•The right side of the heart
The right upper chamber (atrium) takes in deoxygenated blood that is loaded with carbon dioxide. The blood is squeezed down into the right lower chamber (ventricle) and taken by an artery to the lungs where the carbon dioxide is replaced with oxygen.
•The left side of the heart
The oxygenated blood travels back to the heart, this time entering the left upper chamber (atrium). It is pumped into the left lower chamber (ventricle) and then into the aorta (an artery). The blood starts its journey around the body once more.
•Blood vessels
Blood vessels have a range of different sizes and structures, depending on their role in the body.
•Arteries
Oxygenated blood is pumped from the heart along arteries, which are muscular. Arteries divide like tree branches until they are slender. The largest artery is the aorta, which connects to the heart and picks up oxygenated blood from the left ventricle. The only artery that picks up deoxygenated blood is the pulmonary artery, which runs between the heart and lungs.
•Capillaries
The arteries eventually divide down into the smallest blood vessel, the capillary. Capillaries are so small that blood cells can only move through them one at a time. Oxygen and food nutrients pass from these capillaries to the cells. Capillaries are also connected to veins, so wastes from the cells can be transferred to the blood.
•Veins
Veins have one-way valves instead of muscles, to stop blood from running back the wrong way. Generally, veins carry deoxygenated blood from the body to the heart, where it can be sent to the lungs. The exception is the network of pulmonary veins, which take oxygenated blood from the lungs to the heart.
•Blood pressure
Blood pressure refers to the amount of pressure inside the circulatory system as the blood is pumped around.
