THE CIRCULATORY SYSTEM IN MAN
1 - The HEARTThe heart is the major organ of the circulatory system (cardiovascular system) in humans. It is a muscular, self-powered pump that transports blood around the body.
The heart is just about the size of a human fist. It beats about 60 - 70 times in a minute when at rest. |
2 - Blood VesselsThere are 3 major blood vessels connecting the heart with the entire body.
1. The arteries - takes blood away 2. Capillaries - fine branches connecting and touching nearly every cell 3. Veins - returns blood to the heart Sometimes arterioles and venules are the names given to smaller arteries and larger veins respectively. Arteries, veins and capillaries have different structures and thus different functions. |
3 - BloodBlood is thicker than water, literally!
Blood is the transporting medium that moves around the body and is able to reach every single cell. Apart from blood cells - red and white, blood has liquid known as plasma which transports many dissolved substances. Platelets are little cell fragments important for blood clotting when you get a cut. The main functions of blood are: 1. Transport of substances like oxygen, carbon dioxide, urea, hormones, glucose, etc. 2. Protection of the body - white blood cells are mainly responsible for this! |