Veterinary Histology UFF
Department of Morphology - Biomedic Institute
LaBEc - Laboratory of Cellular and Extracellular Biomorphology 		 
Veterinary Histology Atlas
    Versão em Português
Introduction
Digestive System of Birds

Components

Salivary Glands
• In chickens, the salivary glands are all from the mucous type.
• They are located in the roof and floor of the oral cavity, in the tongue and in the pharynx.

Taste Buds
• They are present although diffused.
• They are associated to the salivary gland ducts at the base of the tongue and of the pharynx.

Esophagus

• It is lined by a thick and non-keratinized stratified squamous epithelium.
• The outer muscle layer is formed by smooth muscle along the entire esophagus.
• Mucous glands occur in the lamina propria.
Crop

• It is a caudal diverticulum located at approximately two thirds down the esophagus.
• The structure of the crop is identical to the rest of the esophagus, however it does not contain mucous glands.

Stomach

• The stomach in chickens consists of a glandular pro-ventricle and a muscular ventricle ( gizzard).

Pro-Ventricle

• The mucosa of the pro-ventricle has folds (plicae). The depressions between the plicae are called sulci.
• The epithelium is simple and columnar, except at the base of the sulci where it is cuboidal.
• The wall of the pro-ventricle consists of large compound tubular cells.
• The secreting cells, which are low cuboidal to columnar cells, produce pepsinogen as well as hydrochloric acid, and so combine the function of the main cells and the parietal cells of mammals.
• Each gland opens into the gastric lumen through a conic papilla.
Ventricle (Gizzard)

• The ventricle is a highly muscular grinding organ.
• It is lined by an epithelium that invaginates in the lamina propria, forming elongated holes of which each has terminal tubular gastric glands.
• The cells of these latter glands produce a thick corneous material equivalent to keratin.

Intestine
• The intestine of chickens is structurally similar throughout its length.
• It consists of a duodenum, a jejunum, an ileum and a large intestine.
• A pair of long and dead-ended ceca joins the intestine at the junction between the ileum and large intestine.
• The terminal-extremity of the large intestine joins the coprodeum of the cloaca.
• There are villi throughout the small and large intestine.
- They are longer in the duodenum, but gradually shorten and thicken towards the caudal end.
- In the coprodeum they are stubby and round.
- The villi are also present in the cecum, becoming flattened towards the dead-end.
• The crypts of Lieberkuhn are short and open between the villi, just as in mammals.
• Although the intestinal wall of chickens is similar to that of mammals, the absence of duodenal glands and an extremely thin submucosa in chickens constitute considerable differences.

Liver
• As in mammals, the liver is covered by a mesothelium
• There is a layer of connective tissue, the capsule of Glisson, underneath the mesothelium.
• The hepatic lobes are subdivided into numerous indistinctly separated lobules.


• In chickens, the radiating plates of hepatocytes in each lobule have the width of two cells, while the mammals’ plates have the width of one cell.

Gallbladder
• The gallbladder of chickens is similar to that of mammals.
• The mucosa is lined by a simple columnar epithelium and highly folded into villi-shaped projections when the vesicle contracts.

Pancreas
• The pancreas of chickens resembles that of mammals.
• The lobulation is indistinct, due to the lack of interlobular connective tissue.
• The exocrine portion is tubulacinar
• The islets of Langerhans are abundant. Two types of islets can easily be recognized: alpha and beta.
- The columnar alpha cells characterize the alpha islets. They produce glucagon.
- The polygonal beta cells are the main cells of the beta islets. They produce insulina.
Credits
Tissues
Epithelial
Connective
Cartilaginous
Osseous
Nervous
Muscle
Systems
Circulatory
Blood
Imune
Digestive
Accessory Gls.
Respiratory
Integumentary
Urinary
Endocrine
Male Reprod.
Female Reprod.
Birds Histology
Quiz
Videos
Bibliography