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Structure of the heart

The heart is a double pump consisting mainly of muscle called myocardium. On each side, blood flows through veins into an upper chamber (atrium), then passes into a lower chamber (ventricle), which pumps the blood into the arteries. Blood flow through the chambers is controlled by one-way valves. The right side of the heart pumps blood into the pulmonary arteries and so to the lungs, and the left side pumps blood into the aorta and around the body.

Cardiovascular system

The cardiovascular system transports blood around the body, taking oxygen and nutrients to body tissues and removing waste products. The heart is a hollow, muscular organ that pumps all the body's blood - roughly 5 litres (9 pints) -around the body about once a minute and faster during exercise. Blood flows through ■ / Common a network of vessels that reaches all parts of the body. \ / , Superior vena cava

Arteries carrying blood from the heart branch into smaller vessels and then r . artery into capillaries, which in turn join a network of veins that return blood to the heart.

Pulmonary vein

Jugular vein

Brachial

Heart

Radial artery

Inferior vena cava

Brachial artery

Renal vein

Common iliac vein

Common iliac artery

Femoral vein

Great saphenous vein

Popliteal vein

Anterior tibial artery

Anterior tibial vein

Peroneal artery Posterior tibial artery

Dorsal artery of the foot

Posterior tibial vein

Small saphenous vein

Dorsal vein of the foot

Hepatic artery

Renal artery

Femoral artery

Popliteal artery

Arteries and veins

Arteries have thick, muscular, elastic walls to withstand the high pressure of blood pumped out of the heart. Veins return blood to the heart. They have thinner walls that stretch easily, allowing them to expand and hold large volumes of blood when the body is at rest. The linings of many large veins have folds that act as one-way valves to stop blood from flowing the wrong way.

Blood circulation

The heart pumps blood into two linked circuits: the pulmonary and the systemic. The pulmonary circuit takes deoxygenated blood to the lungs, where it absorbs oxygen and releases carbon dioxide (a waste gas) through a network of capillaries; the oxygenated blood is then returned to the heart. The systemic circuit takes oxygenated blood to body tissues, where it releases oxygen and nutrients through capillary walls; carbon dioxide and other wastes pass from the tissues into the blood, and the deoxygenated blood is returned to the heart.

Deoxygenated blood coming from the upper body

Deoxygenated blood going to the lungs

Oxygenated blood going to the upper body

Capillary network

Deoxygenated blood coming from the upper body

Deoxygenated blood going to the lungs

Oxygenated blood going to the upper body

Capillary network

Deoxygenated blood coming from the lower body

Oxygenated blood going to the lower body

Deoxygenated blood coming from the lower body

Oxygenated blood going to the lower body

Thick, muscular layer

Elastic layer

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