The Pancreas under the Microscope (OCR A Level Biology): Revision Note

The Pancreas Under the Microscope

• The pancreas is an organ found in the abdomen of mammals

• It functions as both an endocrine gland and an exocrine gland

  • Endocrine glands secrete hormones directly into the blood, whereas exocrine glands secrete substance via a duct

• The exocrine function of the pancreas is to produce pancreatic juice (containing digestive enzymes) to be delivered to the small intestine where it helps in the digestion of food

• The endocrine function of the pancreas is to produce the hormones glucagon and insulin

• Within the pancreas, these two functions are performed by different tissues, which can be clearly seen and distinguished from each other when observed under a microscope

  • Most of the cells of the pancreas secrete digestive enzymes (exocrine function) but throughout the organ, there are small sections of cells known as the islets of Langerhans that produce hormones (endocrine function)

  • The islets of Langerhans contain two cell types: alpha cells, which secrete glucagon, and beta cells, which secrete insulin

The location and microscopic structure of the pancreas

The histology of the pancreas

• Histology (also known as microscopic anatomy or microanatomy) is the branch of biology that studies the microscopic anatomy of biological tissues

• The histology of the pancreas can be studied by staining sections of pancreatic tissue and viewing them under a microscope

• These stained samples can then be examined for drawing and labelling to identify the exocrine and endocrine tissues of the pancreas

  • Sections of pancreatic tissue can be differentially stained to show the exocrine tissue and the endocrine tissue (the islets of Langerhans) in different colours

• An example of a labelled diagram of stained pancreatic tissue is shown below

A photomicrograph of stained pancreatic tissue (×200) showing the histology of the pancreas. This is an artistic interpretation.