4 Chapter 4 The Tissue Level of Organization
By Joseph D’Silva
Motivation
Diabetes is a disorder of the endocrine system. It is caused by a more-than-normal level of glucose sugar in the blood. The normal level is 70-100 mg/dL. Above 100 mg/dL, the person has an impaired blood-glucose level. There is a high incidence of diabetes among Afro-Americans. 34.2 million people of all ages—or 10.5% of the US population—has diabetes. Among African Americans, 10.9 % are affected. About 7.3 million adults aged 18 years or older are not aware of diabetes.
The amount of blood sugar in the body is regulated by insulin. This is a hormone and is secreted by cells known as the Islets of Langerhans that are located in the tissues of the pancreas. When the islets release insulin, blood sugar is controlled in the blood. When it fails to, a person develops diabetes.
To know about the pancreas is to study its histology. The histological examination of a pancreas requires that it be sectioned by using a microtome. (A microtome is an instrument. You can slice tissues as thin as 05-06 microns. The slices of tissues can be processed through a procedure and stained with dyes. After staining and more processing they can be put on a glass slide with a cover slip on top and sealed with a sealant (Canada balsam or Permount). Once dried, the section is then examined under a compound microscope using 10 x 4, 10 x 10, or 10 x 40 magnification.
This laboratory exercise studies a section of the pancreas to identify structures in it. The structures are:
- Lobules
- Pancreatic acini
- Islets of Langerhans
See figures below and locate the (a) pancreas; (b) Islets of Langerhans; (c) Interlobular ducts, acinar cells.
Learning Objectives
Upon completion of work in this chapter, students should be able to:
- Define histology and histological tissues in general.
- Define and recognize four types of tissues on stained tissues on microscope slides.
- Describe tissues of organs.
- Explain a histologically impaired tissue.
Background
There are more than 200 different tissue types in the human body. All the organs in the body are made of tissues that are made of cells. The tissues in a body characterize organs. It would be impossible to try and remember all the tissues that are characteristic of all the organs. Therefore, histologists (cell-study specialists) have classified the 200 tissues into four categories: Epithelial, Connective, Muscle and Neural. Each category of tissues has its own distinct characteristics. For example, epithelial cells are flat, cuboidal or tall. Connective tissue can be tough or fluid. Muscle tissue is made of muscle fibers (cells). Nerve tissues is made up of neurons.
Consider your skin or integument. If you cut yourself or if a surgeon makes an incision on your skin you will see tissues that are epithelial, connective, muscular and neuronal. The first layer is the epithelial tissue made up of epithelial cells. The second layer is connective. There are blood vessel