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• Excretory or Urinary System ↳ pertaining to the organs of excretion and osmoregulation, such as the gills of fishes and the kidneys of fishes and other animals.
• Reproductive System ↳ pertaining to the generative organs (ovaries and testes/gonads, and their ducts) which ensure the perpetuation of the species.
• Circulatory System ↳ Referring to the organs of circulation such as the heart and blood vessels, and the lymphatic system.
• Nervous System and Sense Organs ↳ pertaining to the brain and spinal cord, cranial and spinal nerves, the sympathetic system, and the sensory organs.
• Endocrine System ↳ referring to the glands of internal secretion (endocrine glands), that secrete substances called hormones which are responsible for the control of metabolism, growth, and reproduction.
• The typical vertebrate body consists of three principal regions: head, trunk, and tail.
• Head - are the special sense organs, for monitoring the environment.
• Trunk ↳ the part containing the body cavity, which houses the internal organs or viscera. ↳ The body wall, consisting of skin, muscles, and bones, must first be opened to expose the viscera.
• Tail ↳ the part that extends beyond the anus, or more commonly the vent, hence it is termed post anal.