Applying an understanding of organelle specialisation

The pancreas is an organ that is made of tissues that have an endocrine function. That is releasing hormones such as insulin and glucagon. These will be studied in detail when we explore the control of blood sugar in topic 6. Some of these tissue also have an exocrine function. They release digestive enzymes into the pancreatic tubules and then the pancreatic duct that lead into the small intestine.

An acinar is an arrangement of cells around tiny duct tissue. The cell arrangement leads to a very high surface area supplying these ducts.

“Gray1105” by Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body (See “Book” section below)Bartleby.com: Gray’s Anatomy, Plate 1105. Licensed under Public Domain via Commons – https://commons.wikimedia.org/wiki/File:Gray1105.png#/media/File:Gray1105.png

This electronmicrograph shows a part of a single acinar cell in the exocrine pancreas.

The electron micrograph shows a huge surface area of endoplasmic reticulum and the dark secretory vesicles where the enzymes produced by the rEr are stored and then released into the vessels leading to the pancreatic duct.

Another example of where organelles are specialised is in the palisade mesophyll cells in a leaf.