Historia

Human body

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,[1] the basic unit of life. These cells are organised biSize, type and proportion
Main article: Body proportion
Constituents of the human body
In a normal man weighing 60kg
Constituent Weight [2] Percent of atoms[2]
Oxygen 38.8 kg 25.5 %
Carbon 10.9 kg 9.5 %
Hydrogen 6.0 kg 63 %
Nitrogen 1.9 kg 1.4 %
Calcium 1.2 kg 0.2%
Phosphorus 0.6 kg 0.2 %
Potassium 0.2 kg 0.07 %

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.[3] Thissize is firstly determined by genes and secondly by diet. Body type and body composition are influenced by postnatal factors such as diet and exercise[citation needed].
Systems
Main article: Organ systems

The organ systems of the body include the musculoskeletal system, cardiovascular system, digestive system, endocrine system, integumentary system, urinary system, lymphatic system, immunesystem, respiratory system, nervous system and reproductive system.
Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow.
Cardiovascular system
Main articles: Cardiovascular system and Human heart

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 are transferred 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 for re-oxygenation of the blood.[4][5] The heart itself is divided into three layers called the endocardium,myocardium and epicardium,(liquidation) which vary in thickness and function.[6]
Digestive system
Main articles: Digestive system and Human gastrointestinal tract

The digestive system provides the body's means of processing food and transforming nutrients into energy. The digestive system consists of the - buccal cavity, esophagus, stomach, small intestine, large intestine ending in therectum and anus. These parts together are called the alimentary canal (digestive tract).
Integumentary system
Main article: Integumentary system

The integumentary system is the largest organ system in the human body, and is responsible for protecting the body from most physical and environmental factors. The largest organ in the body, is the skin. The integument also includes appendages,primarily the sweat and sebaceous glands, hair, nails and arrectores pili (tiny muscles at the root of each hair that cause goose bumps).
Lymphatic system
Main articles: Lymphatic system and Immune system

The main function of the lymphatic system is to extract, transport and metabolise lymph, the fluid found in between cells. The lymphatic system is very similar to the circulatory system in terms ofboth its structure and its most basic function (to carry a body fluid).
Musculoskeletal system
Main article: Musculoskeletal system

The human musculoskeletal system consists of the human skeleton, made by bones attached to other bones with joints, and skeletal muscle attached to the skeleton by tendons.
Bones
Main articles: Human skeleton and List of bones of the human skeleton

An adulthuman has approximately 206 distinct bones:

Spine and vertebral column (26)
Cranium (8)
Face (14)
Hyoid bone, sternum and ribs (26)
Upper extremities (70)
Lower extremities (62)

Nervous system
Main articles: Nervous system and Human brain

The nervous system consists of cells that communicate information about an organism's surroundings and itself. The...