Transportation system

Capillaries collect the waste products of metabolism (see page 188), such as carbon dioxide, and drain into venules and veins, which carry blood back to the heart and lungs. The portal system connects the small intestine to the liver. Nutrient-rich blood is carried by the portal vein from the digestive organs to the liver, where nutrients are absorbed for processing or stored until they are needed.

the heart There are two chambers, an atrium and a ventricle, on each side of the heart. The left side takes oxygenated blood from the lungs and pumps it around the body. The right side takes deoxygenated blood from around the body and pumps it to the lungs.

Superior vena cava carries deoxygenated blood from head and arms

Right atrium

Inferior vena cava carries deoxygenated blood from lower body

Superior vena cava

Pulmonary arteries

(see diagram,

Inferior vena blood supplies An average male adult has between 5 and 6 quarts (liters) of blood, which is circulated around the body by means of an extensive network of arteries (shown in red) and veins (shown in blue), both of which extend into all bodily tissue. Blood contains red blood cells that carry oxygen, white blood cells that fight infection, and blood platelets, which prevent leakage from blood vessels. Just over half the volume of blood is plasma, a straw-colored fluid consisting mainly of water, in which substances such as nutrients and hormones are carried.

Aorta carries oxygenated blood, and branches into major arteries

Pulmonary artery—the only artery to carry deoxygenated blood— branches into each lung

Aorta

Superior vena cava

Pulmonary arteries

(see diagram,

Inferior vena

Aorta carries oxygenated blood, and branches into major arteries

Septum is a thick muscle wall dividing heart in two vertically

Pulmonary artery—the only artery to carry deoxygenated blood— branches into each lung

Septum is a thick muscle wall dividing heart in two vertically

Right ventricle

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