The study of the human body can be a very enlightening and, thereby, a very rewarding experience for a young child. Although all of us believe we are familiar with our individual bodies, we may also feel that they are mysterious(Tolman, 2001). As we look at ourselves in the mirror we see some of our body parts, but we know that there are other parts or organs that we cannot see, even as they function(Giddens, 2005).
This curiosity can motivate them to learn about the human body. Most of the human body is made up of water, H2O, with cells consisting of 65-90% water by weight(Tolman, 2001). Therefore, it isn't surprising that most of a human body's mass is oxygen. Carbon, the basic unit for organic molecules, comes in second. 99% of the mass of the human body is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus(Giddens, 2005).
The organ systems of the body include the musculoskeletal system, cardiovascular system, digestive system, endocrine system, integument system, urinary system, lymphatic system, immune system, respiratory system, nervous system and reproductive system(Tolman, 2001).
The cardiovascular system comprises the heart, veins, arteries and capillaries. The primary function of the heart is to circulate the blood, and through the blood, oxygen and vital minerals to the tissues and organs that comprise the body. The left side of the main organ (left ventricle and left atrium) is responsible for pumping blood to all parts of the body, while the right side (right ventricle and right atrium pumps only to the lungs(Giddens, 2005). The heart itself is divided into three layers called the endocardium, myocardium and epicardium, which vary in thickness and function(Tolman, 2001).
The digestive system provides the body's means of processing food and transforming nutrients into energy.
The integument system is the largest organ system in the human body, and is responsible for protecting the body from most physical and environmental factors(Tolman, 2001). The largest organ in the body, is the skin(Giddens, 2005). The integument also includes appendages, primarily the sweat and sebaceous glands, hair, nails and erectors pili (tiny muscles at the root of each hair that cause goosebumps).