The heart is a muscular organ which is as big as our fist. Heart is a pumping organ to push blood around the body.
It receives deoxygenated blood from the body parts and pump it to lungs for enriching with oxygen. It receives purified blood from lungs and pumps it around the body.
Blood is fluid connective tissue; it consists of a fluid medium known as plasma in which the cells are suspended, such as white blood cells and red blood cells.
Plasma transports food, carbon dioxide and nitrogenous wastes (urea and uric acid) in dissolved form. Red blood cells transport oxygen. Blood also transport many other substances like hormones, salt etc. Platelets present in the blood stop bleed from injuries by forming blood clots.
(iii) Blood vessels:
Blood vessels form a closed network of tubes to reach all the tissues. Thus, the blood pushed by the heart flows in the blood vessels (arteries) and also comes back to the heart in the blood vessels (veins).