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Medicine LibreTexts

4.07: Body Systems

Organs do not work in isolation but function in cooperation with other organs and body structures to bring about the MRS GREN functions necessary to keep an animal alive. For example the stomach can only work in conjunction with the mouth and oesophagus (gullet). These provide it with the food it breaks down and digests. It then needs to pass the food on to the intestines etc. for further digestion and absorption. The organs involved with the taking of food into the body, the digestion and absorption of the food and elimination of waste products are collectively known as the digestive system.

The 11 body systems

  1. Skin
    The skin covering the body consists of two layers, the epidermis and dermis. Associated with these layers are hairs, feathers, claws, hoofs, glands and sense organs of the skin.
  2. Skeletal System
    This can be divided into the bones of the skeleton and the joints where the bones move over each other.
  3. Muscular System
    The muscles, in conjunction with the skeleton and joints, give the body the ability to move.
  4. Cardiovascular System
    This is also known as the circulatory system. It consists of the heart, the blood vessels and the blood. It transports substances around the body.
  5. Lymphatic System
    This system is responsible for collecting and “cleaning” the fluid that leaks out of the blood vessels. This fluid is then returned to the blood system. The lymphatic system also makes antibodies that protect the body from invasion by bacteria etc. It consists of lymphatic vessels, lymph nodes, the spleen and thymus glands.
  6. Respiratory System
    This is the system involved with bringing oxygen in the air into the body and getting rid of carbon dioxide, which is a waste product of processes that occur in the cell. It is made up of the trachea, bronchi, bronchioles, lungs, diaphragm, ribs and muscles that move the ribs in breathing.
  7. Digestive System
    This is also known as the gastrointestinal systemalimentary system or gut. It consists of the digestive tube and glands like the liver and pancreas that produce digestive secretions. It is concerned with breaking down the large molecules in foods into smaller ones that can be absorbed into the blood and lymph. Waste material is also eliminated by the digestive system.
  8. Urinary System
    This is also known as the renal system. It removes waste products from the blood and is made up of the kidneys, ureters and bladder.
  9. Reproductive System
    This is the system that keeps the species going by making new individuals. It is made up of the ovaries, uterus, vagina and fallopian tubes in the female and the testes with associated glands and ducts in the male.
  10. Nervous System
    This system coordinates the activities of the body and responses to the environment. It consists of the sense organs (eye, ear, semicircular canals, and organs of taste and smell), the nerves, brain and spinal cord.
  11. Endocrine System
    This is the system that produces chemical messengers or hormones. It consists of various endocrine glands(ductless glands) that include the pituitary, adrenal, thyroid and pineal glands as well as the testes and ovary.

    Contributors

Ruth Lawson (Otago Polytechnic; Dunedin, New Zealand)