Page 73 - Atlas of Histology with Functional Correlations

CHAPTER 2 Light and Transmission

Electron Microscopy

Histology, or microscopic anatomy, is a visual, colorful science. The light
source for the early microscopes was sunlight. In modern microscopes, electric
illumination is used as the main light source.

With the simplest light microscopes, examination of mammalian cells

showed a nucleus and a cytoplasm, surrounded by some sort of a border or cell
membrane. As microscopic techniques evolved, the use of various histochemical,
immunocytochemical, and staining techniques revealed that the cytoplasm of
different cells contained numerous subcellular elements called organelles.
Although much initial information in histology was gained by examining tissue

slides with a light microscope, its resolving power was too limited. To gain
additional information called for increased resolution.

With the advent of transmission electron microscopy, superior resolution,
and higher magnification of cells, the examination of the contents of the

cytoplasm became possible. Histologists are now able to describe the
ultrastructure of the cell, its membrane, and the numerous organelles that are
present in the cytoplasm of different cells.

CELL AND CYTOPLASM

Some living organisms are single celled, whereas others contain a multitude of

cells and cell types. The main function of these cells is to maintain a proper
homeostasis in the organism, which is to maintain the internal environment in a
relatively constant state. To perform this task, cells possess certain structural
features in their cytoplasm that are common to all. As a result, it is possible to

illustrate a cell in a more generalized, composite form with various cytoplasmic
organelles. It is essential to remember, however, that the quantity, appearance,
and distribution of the cytoplasmic organelles within a given cell depend on the
cell type and its function.

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