What Is Necrosis? - Definition & Types

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  • 0:00 Definition of Necrosis
  • 1:42 Types of Necrosis
  • 5:01 Lesson Summary
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Lesson Transcript
Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Not everything gets to go through a full life cycle. This is true even in cells. Complete this lesson to learn about a form of cell death called necrosis. We'll outline the six different types, their possible causes, and the resulting tissue changes.

Definition of Necrosis

Everything that is born eventually dies. As humans, we hope to live a long, healthy life and die from old age, but sometimes things go wrong, and we don't make it that far. The same is true for each of our cells. A cell can live out its life, do its job, and die at the end of its natural life cycle (a process called apoptosis). But sometimes, something unexpected happens, and it dies early. An unnatural cell death is called necrosis, and just like anything that dies, there's no reversing the process.

Generally speaking, there are two steps that occur when a cell dies:

  1. Proteins inside the cell break down
  2. The body releases enzymes that digest these dead cells

The apoptosis process is a natural part of the cell's life cycle, and the body is ready to carry the dead cell materials away. In necrosis, however, the body isn't prepared to remove the dead cells, and as a result, causes an inflammatory response.

Cells need blood to live, and any interruption to blood flow results in necrosis. Injury, infection, disease, toxins, and many other factors can block blood from getting to a cell and cause unnatural death. Sometimes a dead cell releases chemicals that can affect the nearby cells, spreading necrosis to wide areas in a condition called gangrene, which is when tissue in certain areas, usually the hands and feet, dies. Again, a dead cell can't turn back into a living one, so the only cure for gangrene is to amputate the area.

Types Of Necrosis

There are six types of necrosis:

  • Coagulative necrosis
  • Liquefactive necrosis
  • Caseous necrosis
  • Fat necrosis
  • Fibroid necrosis
  • Gangrenous necrosis

The type of necrosis can often be categorized based on how the cells look after death. Sometimes the entire cell loses its structure, and sometimes the outer architecture remains the same and only the inside is affected. Let's take a closer look at the characteristics of each of them, and here is a good point to warn you that some of these images are a little graphic but hey, it's science! (Just put down the sandwich until you're done with this lesson...)

Coagulative necrosis:

What happens: Proteins in the cell break down when the cellular liquid becomes acidified due to the disrupted blood flow. The tissue stays firm, and the cells hold their structure, giving them a ghost-like appearance.

Causes: This is the most common type of necrosis that develops and is caused by inadequate blood supply to a region. Coagulative necrosis can affect any tissues in the body except the brain. In fact, it commonly occurs in major organs like the kidney, heart, or liver, particularly when oxygen is deprived for a certain amount of time.

Liquefactive necrosis:

What happens: The dead tissue softens and appears liquid-like, and a pus develops. Basically, the result is a 'goo' of cell material with no shape remaining. Bacterial or fungal infections can result in liquefactive necrosis.

Causes: This type of necrosis results from an enzyme imbalance that causes the cell to digest itself. It can be caused by bacterial or fungal infections and can occur in the brain (for example, after a stroke).

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