1. Composition of Blood and their Functions Blood is the body’s transport system, carrying materials from one part of the body to another. It also plays a part in fighting diseases and in controlling body temperature. (form antibodies) (engulfs micro- organisms) (55% of volume) (45% of volume)

2. Structure of the heart

3. Double Circulation In mammals the blood travels through the heart twice. From the heart to the lungs and back, then to the body and back. This is referred to as double circulation. A double circulation system maintains the high blood pressure required for efficient transport of materials around the body.

4. Double Circulation

5. Blood Vessels Blood leaves the heart through arteries and returns through veins. Capillaries connect the two. ArterySmall Arteries CapillariesSmall VeinsVein  Arteries, veins and capillaries are adapted to carry out their different functions.

6. Arteries, Veins and Capillaries

7. Blood Vessels Lumen

8. Capillary