What is an organ system? A complete insight

Organ Systems 
The organ systems of the body have been divided into the five categories that follow.
Integumentary System 
The integumentary system, in­cludes the skin and accessory organs, such as the hair, nails, sweat glands, and sebaceous glands. The skin protects un­derlying tissues, helps regulate body temperature, contains sense organs, and even synthesizes certain chemicals that affect the rest of the body.
The integumentary system, vvhich includes the skin, not only protects the body, but also has other functions.
Support and Movement 
The skeletal system and the muscular system give the body support and are involved in the ability of the body and its parts to move.
The skeletal system, consists of bones of the skeleton and associated cartilage, as well as the ligaments that bind these structures together. The skele­ton protects body parts. For example, the skull forms a pro­tective encasement for the brain, as does the rib cage for the heart and lungs. Some bones produce blood cells, and all bones are a storage area for calcium and phosphorus salts. The skeleton, as a whole, serves as a place of attachment for the muscles.
Contraction of skeletal muscles accounts for our ability to move voluntarily and to respond to outside stimuli. These muscles also maintain posture and are responsible for the production of body heat. Car­diac muscle and smooth muscle are called involuntary mus­cles because they contract automatically. Cardiac muscle makes up the heart, and smooth muscle is found within the walls of internal organs.
The skeletal system contains the bones, and the muscular system contains the three types of muscles. The primary function of these systems is support and movement, but they have other functions as well.
Integration and Coordination 
The nervous system, consists of the brain, spinal cord, and associated nerves. The nerves conduct nerve impulses from the sense organs to the brain and spinal cord. They also conduct nerve impulses from the brain and spinal cord to the muscles and glands.
The sense organs provide us with information about the outside environment. This in­formation is then processed by the brain and spinal cord, and the individual responds to environmental stimuli through the muscular system.
The endocrine system con­sists of the hormonal glands that secrete chemicals that serve as messengers between body parts. Both the ner­vous and endocrine systems help maintain a relatively constant internal environment by coordinating and regu­lating the functions of the body's other systems. The ner­vous system acts quickly but has a short-lived effect; the endocrine system acts more slowly but has a more sus­tained effect on body parts. The endocrine system also helps maintain the proper functioning of male and female reproductive organs.
The nervous system contains the brain, spinal cord, and nerves. Because the nervous system is in communication vvith both the sense organs and muscles, it allows us to respond to outside stimuli. The endocrine system contains the hormonal glands. The nervous and endocrine systems coordinate and regulate the activities of the body's other systems.
Maintenance of the Body 
The internal environment of the body is the blood within the blood vessels and the tissue fluid that surrounds the cells. Five systems add substances to and/or remove sub­stances from the blood: the circulatory, lymphatic, respira­tory, digestive, and urinary systems.
The circulatory system con­sists of the heart and the blood vessels that carry blood through the body. Blood transports nutrients and oxygen to the cells, and removes waste molecules to be excreted from the body. Blood also contains cells produced by the lymphatic system, discussed in chapter 13. The lymphatic system protects the body from disease.
The respiratory system con­sists of the lungs and the tubes that take air to and from the lungs. The respiratory system brings oxygen into the lungs and takes carbon dioxide out of the lungs.
The digestive system consists of the mouth, esophagus, stomach, small intestine, and large intestine (colon), along with the ac­cessory organs: teeth, tongue, salivary glands, liver, gall bladder, and pancreas. This system receives food and di­gests it into nutrient molecules, which can enter the cells of the body.

The urinary system contains the kidneys and the urinary bladder. This system rids the body of nitrogenous wastes and helps regulate the fluid level and chemical content of the blood.
The circulatory system (heart and vessels), lymphatic system. respiratory system (lungs and conducting tubes), digestive system (mouth. esophagus, stomach, small and large intestines. and associated organs), and the urinary system (kidneys and bladder) all perform specific processing and transporting functions to maintain the normal conditions of the body.

Reproduction and Development 
The reproductive system in­volves different organs in the male and female. The male reproductive system consists of the testes, other glands, and various ducts that conduct semen to and through the penis. The female reproductive system consists of the ovaries, oviducts, uterus, vagina, and external genitalia. Both systems produce sex cells, but in addition, the fe­male system receives the sex cells of the male and also nourishes and protects the fetus until the time of birth.
The reproductive system in males (testes. other glands, ducts. and penis) and in females (ovaries, oviducts, uterus, vagina. and external genitalia) carries out those functions that give humans the ability to reproduce.