Title: The Major Body Systems

Key words: circulatory, cardiovascular, urinary, reproductive, digestive, respiratory, skin, nervous, hormonal, motor, immune systems

Date: Aug 2000

Category: 6. The Body

Type: Table

Author: DJE Candlish

Functions and description of the major body systems

System and contents


Circulatory system:

Heart, blood, blood vessels, lymph vessels, spleen


  • Gases - oxygen from the lungs to the tissues and carbon dioxide from tissues to lungs
  • Nutrients - products of digestion from GI tract to all tissues in the body
  • Chemical messages - hormones from glands to tissues
  • Body defences - white blood cells to all tissues

Digestive system:

Mouth, teeth, oesophagus, stomach, small and large intestines, salivary glands, liver, gall bladder and pancreas

  • Ingesting (taking in), digesting and absorbing nutrients from food and absorbing water
  • Excreting unwanted foodstuffs and waste products.

Urinary system:

Right and left kidney and ureters, bladder and urethra

  • Eliminating water-soluble waste products from the bloodstream
  • Maintaining water and electrolyte (salts) balance of the body
  • Helping to maintain blood pressure within normal limits

Respiratory system:

The lungs, larynx, trachea and bronchi

  • Supplying the body with oxygen
  • Removing waste products, carbon dioxide and water vapour


The epidermis, dermis and adipose tissue, nerves, nerve endings, blood vessels, sweat glands, hair

  • Protecting the internal organs
  • Maintaining body temperature
  • Retaining water in the body
  • Detecting external conditions and dangers

Nervous system:

Brain, spinal cord, nerves, nerve receptors, eyes, ears, organs of smell and taste

  • Regulating and co-ordinating the activities of all organs
  • Detecting and interpreting stimuli from the body's internal and external environment
  • Producing responses to stimuli, such as movement or activation of specific organs or glands (e.g. sweat glands to reduce temperature)

Hormonal system:

Glands including pituitary, thymus, thyroid, parathyroid, adrenal glands (the pancreas, testes and ovaries also function as endocrine glands in addition to other functions)

  • Producing chemical messengers (hormones) to cause effects in target organs.
  • Regulating the body's growth and metabolism

Motor system:

The skeleton (bones, bone marrow, joints), muscles, ligaments and tendons

  • Supporting the body (to maintain shape and posture)
  • Protecting soft tissues
  • Producing blood cells
  • Producing movement

Reproductive system:

Female: ovaries, fallopian tubes, uterus, vagina

Male: testes, epididymis, penis, vas deferens, prostate

Reproducing the individual and the species:

  • Producing spermatozoa and ova for fertilisation
  • maintaining the embryo until it is capable of independent existence

Immune system:

leucocytes and cells of the reticulo-endothelial system found in lymph glands, spleen, liver and bone marrow

  • Protecting the body against external threats such as viruses, bacteria, fungi and parasites
  • Protecting the body by destroying abnormal cells, such as cells infected by viruses, chemically altered cells and cancer cells