Page 31 - ASOP ROT Study Guide

7. THE CARDIOVASCULAR SYSTEM

The cardiovascular system consists of the heart, blood vessels and the blood. The heart
pumps the blood in the blood vessels round the body. The function of this system is
transport: moving important substances such as oxygen, nutrients and hormones to the
tissues and taking waste substances such as carbon dioxide away.

7 . 1 The Heart

The heart is a four chambered organ with a wall of cardiac muscle. When the muscular
wall contracts, the heart "beats" and blood in the chambers of the heart is pumped out
into the blood vessels and round the body.

7 . 2 Blood vessels

There are three types of blood vessel:

Capillaries are microscopic blood vessels 5 - 2 0 um (micrometers, thousandths of a
millimetre) in diameter which form networks in the tissues of the body. The wall of a
capillary is only one cell thick so substances can move rapidly in and out of the tissues.

Arteries transport blood away from the heart. The major arteries branch into smaller and
smaller arteries which then branch into smaller and smaller vessels called arterioles which
connect with the capillary network.

Veins transport blood towards the heart. Capillaries connect with very small veins called
venules which connect with larger and larger veins which connect with the major veins.