Necrosis and Apoptosis
How it works
The two common types of cellular death are necrosis and apoptosis. Necrosis describes the changes of a cell that happen after a specified area of cell death and cellular self-digestion occur. Necrosis is an an accidental cell death which occurs because of the swelling and bursting of the cell. When a supply of oxygen is cut off from a cell, the needed amount of ATP is not being produced, leading to the cell not working effectively. Ion pumps no longer have ATP for fuel, leading to sodium and water leaking into the cell, causing it to swell.
As the process continues, calcium ions get into the cell, activating enzymes that damage the cells membrane. Cell proteins alter, organelles inside of the cell swell, and the cell bursts, spilling its contents. After rupture, inflammation occurs from the chemicals inside of the cell. This alerts neutrophils to come and pick up the debris which also contributes to inflammation as they release inflammatory cytokines. Once these processes start, they can not be undone. Necrosis includes karyolysis, which is when the cells nucleus is destroyed, and pyknosis, which is when the cell nucleus shrinks.
Necrosis differs due to the different tissues or organs it occurs in. Coagulative necrosis happens when not enough oxygen is supplied to the kidneys, heart and adrenal glands with protein alteration and thickening of tissues into a dense state. Liquefactive necrosis happens when the brain is infected or obstructed of blood supply, resulting in digestion of cells causing liquified brain material to build up. Caseous necrosis occurs when an infection of the lungs or other tissues results in a “cheesy” liquefied material to be left in the area. Fat necrosis happens in the breasts, pancreas and other abdominal areas of the body when lipase disgusts tissues and releases lipids and salts that form soaps. Gangrenous necrosis is when an area of oxygen deprived tissue cells start to die and leave liquid or thickened masses of tissues in the affected areas, especially in the most distal regions of the body.
Apoptosis differs from necrosis as it is a purposeful cell death, rather than an accidental one. The cell death is regulated and begins with a cellular program. Unlike necrosis, it can occur in single cells. Apoptosis causes shrinking, rather than swelling, and shattering of cellular components which are picked up by surrounding healthy cells to avoid inflammation. Apoptosis is a healthy form of cell death and removes old or dying cells from the body in an organized way. Necrosis is typically associated with unhealthy or nonfunctioning cells while apoptosis is associated with healthy cells which are no longer needed. Apoptosis occurs at the development of an embryo, the end of breast-feeding, rapid reproduction of cells that do not work properly, and after an inflammatory reaction to get rid of possibly harmful lymphocytes.
Apoptosis is also known as “cell suicide” as it is a purposeful process. Apoptosis can occur after a bacterial infection when an excess of neutrophils are no longer needed. Enzymes called caspases are activated when signals are sent to the cell telling it that it is no longer needed. Caspases take apart the internal components of the cell, causing it to shrink. The cell forms into multiple sections containing different portions of the cells cytoplasm and nuclei. The different sections of the neutrophil completely separate from each other but are not spilled into surrounding tissues since they are encapsulated by cell membrane, to avoid inflammation. The pieces are then ingested by macrophages or neighboring cells, ending the process.
Necrosis is important to understand in a pathophysiological sense because it gives healthcare workers an understanding of what needs to be done in order to prevent more cellular death from occurring. Since necrosis is a messy process, healthcare workers need to understand the causes of the death in order to treat them as well. Necrosis is often caused by external factors such as infection, toxins, or trauma which should set off an alarm for any healthcare worker. Apoptosis is important to understand because cells die everyday in our bodies in order to keep a balance between new cells and old cells no longer needed. Apoptosis is a healthy process which lets our bodies know when certain changes, such as breastfeeding, are no longer needed and help our bodies naturally adapt. The lymphocytes that surround an infection can be potentially harmful but with apoptosis, those cells are eliminated in order to prevent avoidable damage from happening.