Apoptosis is the process of
planned cell death, or cell removal. It may occur if a cell is
damaged beyond reclaim, or simply if it has outlived its usefulness.![](../images/apopt1.jpg)
Some cells with dense, darkly stained
chromatin in tissues with high rates of cell turnover are undergoing
programmed cell death (apoptosis) rather than mitosis.
- The two processes can be
difficult to distinguish in routinely stained slides.
- As shown in the adjacent figure, cells
undergoing apoptosis have their chromatin clumped into a uniform
dense mass (pyknotic nuclei) with no indication of chromosomes
as in mitosis.
- Apoptosis and mitosis generally
occur in different regions of tissues.
- Examine the small intestine
(slide 4), looking for pyknotic cells near the tips of the
projecting villi.
- The sequence of events leading
to apoptosis is also initiated when a cell’s nuclear DNA is
damaged beyond repair.
-
Slide 156 is skin from a
mouse treated with ultraviolet radiation and shows apoptotic
cells in the epidermis.
Pathology includes the study of cell
death both by apoptosis and by necrosis.
- What is the major
difference between these two processes with regard to the roles of
other cells involved?
Let's now take a look at
specific tissue types and their cellular
constituents. |