Digestive System in Aves/Birds

The process of breaking down of complex food into simpler forms with the help of various enzymes is known as digestion. The system that deals with with this process of digestion is known as digestive system.

Digestive system in Aves can be studied under  following  two headings:-

1. Alimentary Canal
2. Digestive Glands

Digestive System in Aves/Birds

1. Alimentary Canal
   1. Mouth and buccal cavity
      Mouth in birds is a small slit(pore) like opening surrounded by hard beaks. Mouth is immediately followed by a small buccal cavity. Buccal cavity in them lacks teeth. But consist of a narrow and keratinized tongue. Tongue in humming birds, woodpeckers, etc. is long and protrussible.
   2. Pharynx
      Pharynx in them is short tubular organ that leads towards the oesophagus.
   3. Oesophagus
      Oesophagus in them is a narrow, elongated and tubular organ. In grain eating birds(grainiativorous), oesophagus at its base consist of one or two swollen structures called crop. Crop internally consist of mucus glands which secrete mucus to soften and moisten the grains.
   4. Stomach
      It is a wide tubular organ differentiated into anterior proventriculus and posterior gizzard. Proventriculus consists of a no. of gastric glands which secrete gastric juice containing various enzymes to digest food , while gizzard simply helps in grinding of food.
   5. Small intestine
      Small intestine in them is a long, narrow and coiled organ differentiated into anterior duodenum and posterior ileum. It helps in digestion of food and absorption of digested food.
   6. Large Intestine
      It is a short, wide and tubular organ which mainly helps in absorption of water. In between the ileum of small intestine and rectum, their is a pair of lateral growth called intestinal caecum which is responsible for secretion of enzyme called cellulose to digest plant product.
   7. Cloaca and Cloacal Aperture
      Rectum in them is followed by a short cloaca which opens outside through the cloacal aperture through which the undigested food materials are finally passed outside.
2. Digestive Glands
   • Liver
     Liver in birds is a small, wide and flattened. It is usually bi-lobed and usually without gall bladder except in birds like pigeons and parrot. Liver secrete bile to emulsify the fat.

1. 1. Pancreas
      Pancreas in them is compact and relatively more developed. It is present in the coils of duodenum. It secrete pancreatic juice which contains various enzymes to digest the food.
   2. Salivary Glands
      Birds lack salivary glands in their buccal cavity but consist of sublingual glands which secrete mucus to make the food moist and soft.

If you want to learn about Digestive System in Reptiles, Click Here.