The following are the components of the transport system in human :

(a) Heart

(b) Blood

(c) Blood vessels

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(a) Work of heart : Heart is a muscular organ that is the size of our fist. It carries blood in the body, it receives deoxygenated blood from different parts of the body and on the other hand, oxygenated blood is pumped throughout the body.

(b) Blood : Blood is a fluid connective organ in which 1. Plasma 2. Red blood cells 3. white blood cells and platelets.

• Plasma transports food, carbon dioxide, and nitrogen-containing excretory substances.
• Red blood cells transport respiratory gases and hormones.
• White blood cells protect the body from infections.
• Platelets form a blood clot at the site of bleeding and block the passage in which the flow of blood stops.

(c) Blood vessels : Blood vessels carry blood from the heart to the different parts of the body, their walls are thick and flexible.