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 100 trillion cells, the basic unit of life. These cells are organised biologically to eventually form the whole body. The average height of an adult male human (in developed countries) is about 1.7–1.8 m (5'7" to 5'11") tall and the adult female about 1.6–1.7 m (5'2" 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. The organ systems of the body include the musculoskeletal system, cardiovascular system, digestive system, endocrine system, integumentary system, urinary system, lymphatic system, immune system, respiratory system, nervous system and reproductive system. The cardiovascular system comprises the heart, veins, arteries and capillaries. The primary function of the...