Introduction
Apoptosis vs Necrosis:
Necrosis is the death of cells and tissues by autolysis caused by disease or injury. When cells are injured, they rupture and release their contents. This triggers a local inflammatory response, with the immigration of leukocytes to the site of injury.
Apoptosis is the process of "cell suicide" by which redundant or defective cells are eliminated without provoking a local inflammatory response in the tissue. Apoptosis is a normal, healthy process that is important for shaping organs and tissues during embryonic development. For example, apoptosis is responsible for the removal of the webbing between the fingers and toes during development. Apoptosis is also important for removing cells that are damaged, infected, or no longer needed.
Key features of apoptosis:
Apoptosis, also known as programmed cell death, is a quick process where a cell self-destructs without causing inflammation. This is in contrast to necrosis, which is a messy process where a cell is killed by injury and releases its contents, causing inflammation.
It starts with Bcl-2 proteins, which are found in the cytoplasm. When activated, Bcl-2 proteins cause mitochondria to release cytochrome c.
Cytochrome c then activates enzymes called caspases. Caspases break down proteins all over the cell.
Other enzymes called endonucleases are also activated. Endonucleases chop up the cell's DNA.
Without a cytoskeleton or properly functioning DNA, the cell quickly shrinks. The nucleus becomes a dense, dark blob called a pyknotic nucleus.
The cell membrane starts to bulge and bubble as its proteins break down.
Finally, the cell breaks apart into little membrane-bound packages called apoptotic bodies. These are then engulfed and digested by nearby cells or white blood cells.
Because apoptosis happens so quickly and cleanly, it doesn't trigger the body's inflammatory response. This makes it a very efficient way to get rid of unwanted or damaged cells.
During apoptosis, cells undergo a series of orderly changes, including:
Cell Shrinkage: The cell becomes smaller and more compact.
Chromatin Condensation: The DNA condenses and the nuclear envelope breaks down.
Formation of Apoptotic Bodies: The cell eventually breaks apart into smaller, membrane-bound vesicles called apoptotic bodies, which can be phagocytosed by surrounding cells or macrophages without causing inflammation.
Necrosis, on the other hand, is a form of uncontrolled cell death that typically occurs in response to acute cellular injury, such as lack of blood flow, toxins, or infection. Key features of necrosis include: