Frog: Anatomy

Digestive System

  • The digestive system in frogs is complete, with a mouth and an anus.
  • It consists of an alimentary canal and associated digestive glands.
  • Salivary glands are absent in frogs.
  • Adult frogs are carnivorous, while the tadpoles are herbivorous.
  • Since frogs are carnivores, the length of intestine is reduced and therefore the alimentary canal is short.
  • The structure of the alimentary canal is as follows:

  • Stomach
      • Walls of the stomach secrete HCl and gastricjuices.
      • Digestion of food takes place by the action of these secretions.
  • Intestine
    • Chyme (artially digested food) is passed from stomach to the first part of the small intestine called the duodenum.
    • The bile produced by liver is stored in gall bladder. Duodenum receives this bile from gall bladder and pancreatic juices(containing digestive enzymes) from the pancreas through a common bile duct.
    • Bile – Emulsifies fat.
    • Pancreatic juices – Digest carbohydrates and proteins.
    • Final digestion takes place in the intestine.
    • There are numerous finger-like folds in the inner wall of intestine called villi and microvilli. They increase the surface area for the absorption of digested food.
  • Cloaca
    • It is the common external opening of both digestive and reproductive system.
    • The undigested solid waste from intestines moves into the rectum and finally passes out through cloaca.

Respiratory system

  • Adult frogs respire on land and in the water by two different methods.
  • On land, they respire through lungs, skin and buccal cavity.
  • Respiration through lungs is called pulmonary respiration.


  • Lungs are sac- like and pink colored. A pair of lungs is present in the thorax region of the trunk. Air enters into the buccal cavity through nostrils, and then into the lungs.
  • During aestivation and hibernation, frog shows cutaneous respiration (through skin).

  • In water also, frogs respire through skin (cutaneous respiration). Dissolved oxygen in the water is exchanged through the skin by diffusion.


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