Prof Chetana Kanekar

M.Sc (SET life sciences)

Histological structure of Pancreas

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.

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 Langerhans.

Islets of langerhans secrete two hoprmones ,

insulin and glucagon.

Insulin plays important role in carbohydrate

metabolism while glucagon causes elevation of

blood sugar.

Microscopic structure.

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.

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.

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

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.

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

Intralobular ducts have a classical cuboidal

epithelium and, as the name implies, are seen

within lobules. They receive secretions from

intercalated ducts.

Intralobular duct

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.

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

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.

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

Thank you………