Every part of the body is composed of various types of cells, the fundamental unit of life. At maturity, the estimated average number of cells in the body is given as 37.2 trillion.The study of the human body involves anatomy and physiology.
The human body consists of many interacting systems. Each system contributes to the maintenance of homeostasis, of itself, other systems, and the entire body. A system consists of two or more organs, which are functional collections of tissue. Systems do not work in isolation, and the well-being of the person depends upon the well-being of all the interacting body systems. Some combining systems are referred to by their joint names such as the nervous system and the endocrine system known together as the neuroendocrine system.
- Integumentary system
Skin, hair, nails, sweat and other exocrine glands.
- Skeletal system
Bones supporting the body and its organs.
- Nervous system
Collects and processes information from the senses via nerves and the brain and tells the muscles to contract to cause physical actions.
- Cardiovascular system
Circulates blood around the body via the heart, arteries and veins, delivering oxygen and nutrients to organs and cells and carrying their waste products away.
- Endocrine system
Provides chemical communications within the body using hormones.
- Muscular system
Enables the body to move using muscles.
- Respiratory system
The lungs and the trachea that bring air into the body.
- Urinary and Excretory system
Eliminates waste from the body.
- Reproductive system
The sex organs required for the production of offspring.
- Digestive system
Mechanical and chemical processes that provide nutrients via the mouth, esophagus, stomach and intestines.
- Immune system
Defends the body against disease-causing agents.
