Damaged cells are primarily destroyed through a process of cellular self-destruction, mediated by lysosomes. These organelles, often called the "suicide bags" of the cell, contain enzymes that break down cellular components. When a cell is severely damaged, its lysosomes release these enzymes, resulting in the cell's destruction.
However, the destruction of damaged cells isn't solely dependent on lysosomes. Other mechanisms also contribute, including:
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Immune System Response: Phagocytes, a type of white blood cell, engulf and digest dead or damaged cells. This is a critical part of the body's immune response to injury and infection. https://medlineplus.gov/ency/article/000821.htm
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Apoptosis (Programmed Cell Death): The body employs a controlled process, apoptosis, to eliminate damaged cells that cannot be repaired. This prevents further harm and maintains tissue integrity.
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Necrosis (Uncontrolled Cell Death): In cases of severe injury or infection, cells may undergo necrosis, a form of uncontrolled cell death that can lead to inflammation. This is different from the controlled dismantling of cells by lysosomes or the immune system.
Several factors can lead to cellular damage, including:
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Viral Infections: Viruses, such as SARS-CoV-2 (the virus causing COVID-19), can damage cells, particularly mitochondria (the cell's energy producers). This can lead to lasting damage to various organs. https://www.nih.gov/news-events/nih-research-matters/sars-cov-2-can-cause-lasting-damage-cells-energy-production https://covid19.nih.gov/news-and-stories/long-term-effects-sars-cov-2-organs-and-energy
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Exposure to Radiation: High doses of radiation, such as from CT scans, can cause DNA damage within cells. http://med.stanford.edu/news/all-news/2015/07/dna-damage-seen-in-patients-undergoing-ct-scanning-study-finds.html
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Genetic Mutations: Cells with mutations in DNA repair genes are more prone to accumulating further mutations, which can lead to cellular dysfunction and potentially cancer. https://www.cancer.gov/about-cancer/understanding/what-is-cancer
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Mechanical Stress: Continual mechanical stress, as seen in sensory hair cells of the inner ear, can cause damage and eventual cell death. https://pmc.ncbi.nlm.nih.gov/articles/PMC6556399/
The specific mechanism of damaged cell removal depends on the cause and extent of the damage.
