Page 89 - Atlas of Histology with Functional Correlations

layers as in the basal layers of the skin. Here, hemidesmosomes anchor the

epithelial cells to the basement membrane and the adjacent extracellular
connective tissue. Basement membrane consists of a basal lamina and
reticular fibers of the connective tissue.

Gap junctions are also spotlike in structure. The plasma membranes at
gap junctions are closely apposed, and tiny fluid channels called connexons

connect the adjacent cells. Molecules, ions, and low-resistance electrical
communication occurs through these connexons between adjacent cells.
These fluid channels are vital in cardiac muscle cells and nerve cells, where
fast impulse transmission through the adjacent cells or axons is essential for

synchronization and coordination of normal functions.

FIGURE 2.5 | Basal Regions of Epithelial Cells

A medium-magnification electron micrograph illustrates the appearance of the
basal region or the base of epithelial cells. Note that the basal regions of the cells
are attached to a thin, moderately electron-dense layer called the basal lamina
(3). Deep to the basal lamina (3) is a connective tissue (2) layer of fine reticular
fibers. The basal lamina (3) is seen only with the electron microscope. Basal

lamina (3) and the reticular fibers of connective tissue (2) are recognized under
the light microscope as a basement membrane.

Inferior to the epithelial cells is an elongated, spindle-shaped fibroblast (4)
with its nucleus (4) and dispersed chromatin (5), surrounded by numerous

connective tissue fibers (2) produced by the fibroblasts. In the cytoplasm of one
of the epithelial cells is also seen a nucleus (8), dispersed chromatin (9), and a
dense, round nucleolus (7). Cisternae of rough endoplasmic reticulum (11),
elongated mitochondria (14), and various types of dense bodies (6) are visible

in different cells. Between the individual epithelial cells is a distinct cell
membrane (1, 10). Hemidesmosomes are not illustrated but attach the basal
membrane of the cells to the basal lamina (3).

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