The human body consists of close to 100 trillion cells and each one of them is part of an organ system designed to perform essential life functions such as respiration, growth and development, movement, reproduction, control and cordination. Heart which beats over 60 – 100 times a minute, over 2.5 billion times during the life time, recirculates about 10,000 litres of blood around the body in 24 hours time, supplies all the muscles and tissues with food and oxygen.

Blood containing fresh oxygen travels from the lungs to the heart through pulmonary veins, which is pumped to the rest of the body. Blood with very little oxgen left, returned to the heart from the muscles and tissues is pumped to the Lungs where it is enriched with oxygen before sending it back to the heart. We take about 23000 breaths every day to draw fresh air and lungs obsorb vital oxygen from it into the blood and then passes stale air out. Pumped by the heart, blood collects oxygen from the lungs and dissolved food from liver and delivers it to all parts of the body.

Blood is made up of miilions of cells foating in a fluid called plasma, with red cells carrying oxygen and white cells fighting infection and platelets making the blood clot when a vessel is damaged.

electricity that travels ver fast at 100 metres per second, pass through this vast network, representing our thoughts and memories. The spinal cord carries nerve signals to and fro between the brain and all parts of the body. Nervous system and hormonal or endocrine system help the body‘s organs work togeher.

The adult body is made up of 206 bones, 600 muscles and 22 internal organs. The 206 bones of the skeleton form a strong inner framework for the rest of the body, which is soft. The skull is a domed protective case for the brain, backbone is a strong and yet flexible central suppport and bones of limbs work like levers. Muscles are attached to the bones of the skeleton and pull on them to make the body move.

Pancreas makes stong digestive juices and liver makes bile to aid the process of digestion. Digestion takes place in small intestines by causing chemical break down of food with digestive juices. The resulting nutrients are carried through blood to the liver where it stores the nutrients and send the blood with impurities and substances the body doesnot need to kidneys. The kidneys receive more than one litre of blood and pass the blood through nearly one million flltering units called nephrons to remove excess water and waste substances from blood.