Blood and Blood Vessels

The following are found inside the blood:

Red blood cells

• These contain haemoglobin which transport the oxygen to cells around the body.
• They have a large surface area so they can transport more oxygen.
• They also have a dent in them which makes them more flexible to fit through small blood vessels.

White blood cells

• These cells fight infection.
• They make antibodies to surround and overcome bacteria.
• Some white blood cells change shape to engulf bacteria.

Platelets

Plasma

• This is the yellow part of the blood.
• It contains many substances dissolved in it such as the products of digestion.

BLOOD VESSELS:

Artery

• Thick and muscular with only a small hole through the middle so that it can withstand high pressure.
• The arteries carry blood with high levels of oxygen from the heart around the body.

Vein

• Thinner wall than the artery and it has lower pressure but a larger space inside.
• The veins also contain valves to prevent the blood from flowing the wrong way

Capillary

• Very thin wall which is only one cell thick.
• They pass close to cells and allow the blood to leak in and out of them.