Digestive system of Pigeon - In pigeon the digestive system includes alimentary canal and digestive glands. In comparison to the size of the bird, the length of the alimentary canal is short and its different parts are modified in such a way that assimilation of simplified food occurs in a short time.
Digestive system of Pigeon
(i) Alimentary canal :
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| digestive system of pigeon |
The alimentary canal consists of the following parts:
Mouth:
Mouth is present at the tip of the heady .
Mouth leads into mouth cavity and pharynx.
These regions contain:
(a) Internal nostril-
It is a single opening on the roof of the pharynx through which both the nares open internally.
(b) Tongue:
Tongue is a prominent structure. .
(c) Glottis:
It is an aperture which leads into trachea and is placed near the base of the tongue.
(d) Gullet:
It is the last part of the pharynx .
Oesophagus:
Oesophagus begins from the gullet and runs through the ventral part of the neck . Near the junction of neck and trunk it comes between skin and muscle and enlarges to form a sac, called crop. The crop plays a dual role in the life of pigeon and other birds
Stomach:
It is divisible into two distinct parts:
(a) Proventriculus:
Proventriculus is the first part of the stomach to receive the oesophagus . It is tubular and internally lined by numerous gastric glands.
(b) Gizzard:
This is the second part of stomach and is semi-circular in outline. The walls of the gizzard are highly muscular. It contains very little inner space. Internally the wall contains numerous ridges and its epithelial lining becomes very thick and tough.
Intestine:
Intestine is divisible into following parts:
(a) Duodenum
(b) Ileum
(c) Rectum.
(a) Duodenum:
It is the first part of the intestine and is distinctly ‘U’-shaped in appearance.
(b) Ileum:
Ileum is the second part of the intestine having numerous villi inside it. The length of the ileum is shorter than that of other vertebrates.
(c) Rectum: Rectum is the last part of the intestine and is of same thickness as that of ileum. Near the junction of ileum and rectum, a pair of small lateral blind leaf-like caeca originates.
Cloaca:
The cloaca is spacious, muscular and is elaborated into three chambers: coprodaeum, urodaeum and proctodaeum . The coprodaeum receives the intestine. The urinogenital ducts open within the urodaeum and the proctodaeum opens externally by the vent.
Cloacal aperture:
The proctodaeum of cloaca opens to the exterior through the cloacal aperture or vent. It is present on the ventral side and near the base of the tail.
(ii) Digestive glands :
The following digestive glands are associated with the alimentary system:
Mucous glands: Mucous gland are present on the surface of the tongue and crop and are responsible for moistening of the food.
Salivary glands:
Paired angular and unpaired sublingual salivary glands are located in the pharyngeal region. The secretion called saliva moistens the food and also contains diastatic enzyme.
Crop glands:
These glands secreted “crop milk or pigeons milk” . The secretion is used for the nourishment of the youngs.
Gastric glands:
These are present on the internal lining of proventriculus and secrete gastric juice.
Tubular glands:
Tubular glands are present on the internal lining of gizzard.
Liver:
Liver produces the bile which passes through two bile ducts, one coming from each lobe of liver. The bile ducts open separately within the two limbs of the duodenum. The gall bladder is absent in pigeon. .
Pancreas:
Pancreas is a pinkish white gland located in between the two limbs of the duodenum. It is a combination of both exocrine and endocrine glands. The exocrine part producing pancreatic juice and the endocrine part produces insulin.
Glands in the ileum:
These glands produce digestive juices which contain various enzymes.
Caecal glands:
Produce certain digestive juices for the digestion of vegetable fibers. They are also concerned with the absorption of water.