Chapter 1 - The Cell
The goal of this chapter is to learn how to look for items of interest in histological specimens using light microscopy. A variety of cells, tissues, and organs are provided as samples.
Characteristics to notice and observe:
- Size of the cell
- Shape of the cell
- Nuclear/cytoplasmic ratio
- Chromatin condensation: heterochromatin or euchromatin
- Cytoplasmic staining: basophilic or acidophilic
- Secretion granules
- Special staining properties
A microscope is an instrument used to see objects that are too small to be seen by the naked eye.
Biological material is inherently of low contrast and provides little to see in a standard bright field microscope unless treated with a histological stain.
Hematoxylin and eosin are the most widely used dyes in histology and pathology. The following slides demonstrate the staining characteristics of these dyes alone, and more importantly, in combination.
Cells and Tissues
The cell is the basic structural and functional unit of all living organisms. Cells vary widely in size and shape depending on their function. Microscopes are used to study cells because most cannot be seen with an unaided eye.
It is not necessary to learn the names of specific cells and tissues for this chapter, but rather learn to recognize variations in the size, shape, and staining properties of cells.
Besides hematoxylin & eosin H&E, other histological stains can be used to demonstrate different features of cells.
Different stains and techniques can be used to identify cells and structures. These tissue sections demonstrate different methods that can be used to visualize Purkinje cells in the cerebellum.
Mitosis is the process during which one cell gives rise to two daughter cells. The chromosomes of the parent cell are duplicated and separated into the two nuclei of the daughter cells. Cytokinesis takes place differently in animal and plant cells.
Although widely used as an example of mitosis in histology, the onion root tip is not a good example because plant cells undergo cytokinesis differently than mammalian cells.