digestive gland

Digestive glands
The major glands are located outside the wall of the alimentary canal but are connected to the lumen of the digestive tract via ducts . These glands include the major salivary glands, liver, pancreas and gallbladder.

1- Major salivary glands
The three major salivary glands , parotide, submandibular , and sublingual, deliver their secretion ,saliva, into the oral cavity

2- Liver
Is the largest mass of glandular tissue in the body and also is the largest internal organ consists of lobules , the parenchymal cells of the liver , known as hepatocytes which organized as plates separated by sinusoids .A liver lobule schematically diagramed as a six sided polyhedral prism with portal canals containing inside interlobular branches of:- (hepatic artery , portal vein , and bile duct) at each of the corners , and in the center of each lobule a central vein .The hepatic sinusoids are lined with two types of cells:
1-Endothelial cells , they are small in size and only the nucleus is visible.
2-Kupffer cells , that are derived from monocytes can seen just in section that stains with india ink.



3- Pancreas
Is a mixed gland , in that it has exocrine and endocrine functions .The endocrine part is composed of scattered spherical aggregates of richly vascularized cords of endocrine cells, known as islet of Langerhans, five cell types are present in these structures : a (A) cells , producing glycogan ; b (B) cells , manufacturing insulin ; G cells ; producing gastrin ; d(D)cells , manufacturing somatostatin; and PP cells , secreting pancreatic polypeptide.
The exocrine pancreatic portion is a compound acinar gland , composed of several pyramidal serous cells surrounding a lumen , they have a spherical nucleus , and the apex of the cell stains with acidic dyes while the base stains with basic dyes.





4-Gallbladder
Is a small pear-shaped hollow organ attached to the posterio-inferior surface of the liver , consists of mucosa , a simple columnar epithelium exhibit deep mucosal folds, the lamina propria rich in capillaries and small venules , resemble that in colon , there is no well defined submucosa and muscularis externa , but a bundles of smooth muscle cells randomly oriented , then a thick layer of dense connective tissue ,the adventitia.