9.1 Blood . . . . . . . . . . . . . 88 9.2 Blood vessels . . . . . . . . . . 89 9.3 The heart . . . . . . . . . . . . 91 9.4 Blood circulation in the body . . 92 9.5 The circulatory system and health 94
Why it matters
The circulatory system is the body’s delivery and removal system. It transports essential nutrients and oxygen to every cell in the body and removes unwanted wastes. It spreads warmth around our body. It also protects our body from illness by destroying invading germs and from losing blood when we are cut. Blood is carried around the body by the circulatory system.
LO 4, 6 Biological World strand LO 4, 9 Nature of Science strand
The circulatory system consists of the blood, heart and the blood vessels: arteries, veins and capillaries. It has three main functions:
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1. Transport Transports gases to and from the respiratory system and the body. Transports nutrients and water from the digestive system around the body. Transports wastes from the body to the liver, kidneys, skin and lungs for removal.
Transports other chemical substances, such as hormones, around the body.
2. Temperature regulation As blood moves around the body, heat is transferred between different organs.
l Fig. 1 The human circulatory system
3. Protection Fights against disease-causing microbes or harmful substances introduced into the body. Protects against blood loss from injury.
