Page 113 - Atlas of Histology with Functional Correlations

CHAPTER 3 Cells and the Cell Cycle

During embryonic development, the cells divide and multiply to form new cells,
tissues, and organs. In an adult organism, however, not all cells retain the ability
to further divide and reproduce. As a result, different populations of cells are
recognized based on their ability or inability to divide and reproduce.

PERMANENT CELL POPULATION IN

ADULT ORGANISMS

Nerve cells in the nervous system and muscle cells (skeletal and cardiac)
continue to divide during embryonic development. Once these cells establish the

organs in postnatal life, however, their ability to further divide ceases, and they
cannot be replaced if they are damaged or destroyed.

Stable Cell Population

In such organs as the liver, cells remain relatively stable in postnatal life and
exhibit a slow rate of replacement under normal conditions. However, when part
of the liver is surgically removed or is damaged by toxic substances, the liver

cells exhibit regenerative capabilities. They regenerate, proliferate, and replace
lost cells in order to maintain the normal functions of the organ. The life span of
normal and healthy liver cells is about 5 months, in contrast to the life spans of
cells in organs where cell renewal is continuous.

Renewing Cell Population

These cells are continuously dividing to replace lost or worn-out cells in
different tissues and organs of the body. Skin cells and gastrointestinal

epithelium (oral cavity, esophagus, stomach, small and large intestine) cells
continually divide. Similarly, numerous blood cells have short life spans and are
continually reproduced in red bone marrow of different bones to replace the

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