Necrosis:

….sis is the name given to the accidental death of cells and living tissue. Necrosis is ….quential than apoptosis.

….s of necrosis:

…. Are many causes of necrosis including injury, infection, cancer, infarction, …. And inflammation. Necrosis is accompanied by the release of special ….s from the lysosomes. The lysosomal enzymes break cellular components and…. Also released outside the cell to break other surrounding cells. Cells …. Necrosis may also release harmful chemicals that damage other cells.

Distinctive patterns of necrosis:

There are many distinctive patterns of necrosis e.g.

1. Necrosis may occur when a cell is given hypoxic (with less oxygen) environments.
2. Necrosis may be usually associated with cellular destruction and pus formation (e.g. pneumonia).
3. Necrosis may be due to blockage of the venous drainage of an organ or tissue.

Apoptosis and necrosis:

Apoptosis and necrosis are two phenomena of cell death.

Apoptosis:

Apoptosis is one of the main types of programmed cell death and involves a series of biochemical events. This process is controlled by extracellular signals (e.g. hormones) or intracellular signals (e.g. food deprivation, viral infection).

Series of events in apoptosis:

Following is the series of events in apoptosis.

1. Cell shrinks and becomes rounded due to the breakdown of the cytoskeleton by enzymes.
2. The cytoplasm appears dense, and the organelles appear tightly packed
3. Chromatin undergoes condensation into compact patches against the nuclear envelope
4. The nuclear envelope breaks and the DNA is fragmented. Thus, the nucleus breaks into several discrete chromatin bodies.
5. The cell membrane shows irregular buds known as blebs, through which the cellular components are discharged.
6. The blebs break off from the cell and are now called apoptotic bodies, which are then phagocytosed by other cells.

Significance of apoptosis:

1. Apoptosis can occur when a cell is damaged, infected with a virus, or undergoing stress conditions such as starvation. DNA damage from ionizing radiation or toxic chemicals can also induce apoptosis. The decision for apoptosis can come from the cell itself or the surrounding tissue.
2. Apoptosis removes the damaged cell, preventing it from getting further nutrients from the organism, or preventing the spread of viral infection.
3. Apoptosis generally gives advantages during an organism's life cycle. For example, the differentiation of fingers and toes in a developing human embryo requires cells between the fingers to initiate apoptosis so that the digits can separate.
4. In the adult organism, the number of cells is kept relatively constant through cell death and division. Cells must be replaced when they become diseased or malfunctioning.