Human transport

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Left ventricle has a thicker wall to create a higher blood pressure to supply blood to the whole body

Right ventricle wall thinner as only needs to create pressure to supply blood to lungs

Arteries Veins

Always carry blood away from the heart Carry blood to the heart

Carry oxygenated blood, except for the pulmonary artery. Always carry deoxygenated blood, except for the pulmonary vein

Carry blood under high pressure Carry blood under low or negative pressure

Have thick muscular and elastic walls to pump and accommodate blood Have thinner walls - less muscular tissue than arteries

A type of supporting tissue called connective tissue provides strength Have less connective tissue than arteries

The channel in the blood vessel that carries blood - the lumen - is narrow Have a wide lumen

to maintain pressure

Arteries do not contain pocket valves Veins contain pocket valves to stop the backflow of blood

The walls of capillaries are just one cell thick. Capillaries therefore allow the exchange of molecules between the blood and the body's cells - molecules can diffuse across their walls. This exchange of molecules is not possible across the walls of other types of blood vessel. Capillaries form extensive networks so that every cell is near a capillary carrying blood.

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Blood

Component Function(s)

Plasma Transporting other components such as carbon dioxide, digested food molecules, urea and hormones. Distributing heat.

Red blood cells Transporting oxygen

White blood cells. Ingesting pathogens and producing antibodies

Platelets Involved in blood clotting

Features of an RBC

biconcave shape

large surface area

no nucleus

WBC

Phagocytes

About 70 per cent of white blood cells are phagocytes. Phagocytes engulf and digest unwanted microorganisms that enter the blood, by the process of phagocytosis. They are part of the body's immune system.

Lymphocytes

Lymphocytes make up about 25 per cent of white blood cells. They are also part of the body's immune system. Lymphocytes produce soluble proteins called antibodies and antitoxins when a foreign body such as a microorganism enters the body.

Platelets