Histological structure of pancreas

1. Prof Chetana Kanekar M.Sc (SET life sciences) Histological structure of Pancreas

2. Introduction The pancreas is a compound tubuloacinar , lying behind the stomach and extending transversely from the spleen to the loop of duodenum.The head is joined to the body of the gland by slightly constricted part neck.The body becomes narrow,tapering into tail. Pancreas is a duplex gland .i.e. it has both exocrine and endocrine parts. Exocrine portion consists of twp ducts, the longer main pancreatic duct or duct of wirsung and shorter duct or duct of santorini . These ducts carry the pancreatic juice in duodenum which contains several digestive enzymes like trypsin,amylase and lipase.

3. Introduction continued… Inside the substance of pancreas there are groups of specialized cells surrounded by connective tissue, which form the endocrine part of the gland. These cells are called islets of La ngerhans . Islets of langerhans secrete two hoprmones , insulin and glucagon. Insulin plays important role in carbohydrate metabolism while glucagon causes elevation of blood sugar.

4. Microscopic structure .

5. Microscopic structure continued…. The pancreas has a thin cover of loose connective tissue from which septa pass into the gland, subdividing it into many small lobules. Each lobule is again composed of several rounded or tubular groups of pancreatic cells called acini . Among the acini are the scattered the islets of langerhans . The acini cells form the parenchyma of the gland which secrete the pancreatic juice.

6. Exocrine Pancreas It consist of acini,which are of serous type. The acini are pear-shaped or short tubular groups of pancreatic cells at the tip of inter-lobular ducts. The connective tissue is very little between two acini . Each acinus consists of a group of pyramidal cells with their apical tips towards the lumen. The cells rest upon the basal lamina. Each cell has a big basal spherical nucleus and one or two nucloeli . Half of the cell towards the lumen contains numerous zymogen granules in the cytoplasm. The basal zone contains endoplasmic reticulum and elongated mitochondria. The apical region of the cells shows irregular microvilli .

7. In the lumen of many acini one or more epithelial cells, lying in contact The exocrine pancreas is classified as a compound tubuloacinous gland. The cells that synthesize and secrete digestive enzymes are arranged in grape-like clusters called acini , very similar to what is seen in salivary glands. Acini cells

8. Pancreatic Ducts:- Digestive enzymes from acinar cells ultimately are delivered into the duodenum. Secretions from acini flow out of the pancreas through a tree-like series of ducts. Duct cells secrete a watery, bicarbonate-rich fluid which flush the enzymes through the ducts and play a pivotal role in neutralizing acid within the small intestine. Pancreatic ducts are classified into four types which are discussed here beginning with the terminal branches which extend into acini .

9. Intercalated ducts receive secretions from acini . They have flattened cuboidal epithelium that extends up into the lumen of the acinus to form what are called centroacinar cells . Intercalatted ducts

10. Intralobular ducts have a classical cuboidal epithelium and, as the name implies, are seen within lobules. They receive secretions from intercalated ducts. Intralobular duct

11. Interlobular ducts are found between lobules, within the connective tissue septae . They vary considerably in size. The smaller forms have a cuboidal epithelium, while a columnar epithelium lines the larger ducts. Intralobular ducts transmit secretions from intralobular ducts to the major pancreatic duct.

12. The main pancreatic duct received secretion from interlobular ducts and penetrates through the wall of the duodenum. In some species, including man, the pancreatic duct joins the bile duct prior to entering the intestine

13. The endocrine portion of the pancreas takes the form of many small clusters of cells called islets of Langerhans or, more simply, islets. Humans have roughly one million islets In standard histological sections of the pancreas, islets are seen as relatively pale-staining groups of cells embedded in a sea of darker-staining exocrine tissue. The image to the right shows three islets in the pancreas of a horse.

14. Pancreatic islets house three major cell types, each of which produces a different endocrine product: Alpha cells (A cells) secrete the hormone glucagon . Beta cells (B cells) produce insulin and are the most abundant of the islet cells. Delta cells (D cells) secrete the hormone somatostatin , which is also produced by a number of other endocrine cells in the body

15. Thank you………