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The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs. By the time the human reaches adulthood, the body consists of close to 10 trillion cells, the basic unit of life. Groups of cells combine and work in tandem to form tissue, which combines to form organs, which work together to form organ systems.
 Size, type and proportion
The average height (in developed countries) of an adult male human is about 1.7–1.8 m (5'7" to 5'11") tall and the adult female about 1.6–1.7 m (5'3" to 5'7") tall. This size is firstly determined by genes and secondly by diet. Body type and body composition are influenced by postnatal factors such as diet and exercise.
Systems
The organ systems of the body include;- Musculoskeletal system, cardiovascular system, digestive system, endocrine system, integumentary system, urinary system, lymphatic system, immune system, respiratory system, nervous system and reproductive system. |
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When the left ventricle of the heart contracts, the bicuspid valve closes, and the only way out is through a large artery called the "aorta." The branches of the aorta distribute blood to all parts of the body (See Arch of the Aorta). At the base of the aorta, there is an "aortic semilunar valve" that has three leaflets or cusps. It opens to allow blood to leave the left ventricle as it contracts. When the ventricular muscles relax, the valve closes to prevent blood from backing up into the ventricular chamber. |
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