Cellular adaptation

Source: Wikipedia, the free encyclopedia.

In cell biology and pathophysiology, cellular adaptation refers to changes made by a cell in response to adverse or varying environmental changes. The adaptation may be physiologic (normal) or pathologic (abnormal).

Morphological adaptations observed at the cellular level include atrophy, hypertrophy, hyperplasia, and metaplasia.[1] In the medical context, outside of specialized branches of biomedicine, morphological adaptations are not always referenced to the fundamental cellular level, but are observed and assessed at the level of tissues and organs. Dysplasia is a process of cell change associated with cellular abnormality, which is not considered adaptive in the positive sense of adaptation.

Atrophy

Main article: Atrophy

Cellular atrophy is a decrease in cell size. If enough cells in an organ undergo atrophy the entire organ will decrease in size.

human development (childhood) is an example of physiologic atrophy. Skeletal muscle atrophy is a common pathologic adaptation to skeletal muscle disuse (commonly called "disuse atrophy"). Tissue and organs especially susceptible to atrophy include skeletal muscle, cardiac muscle, secondary sex organs, and the brain.[2][3]

Hypertrophy

Illustration of adipocytes of different sizes. In response to dietary excess energy intake, adipocytes adapt by increased storage of lipids, resulting in cellular hypertrophy.
Main article: Hypertrophy

Cellular hypertrophy is an increase in cell size and volume. If enough cells of an organ hypertrophy the whole organ will increase in size. Hypertrophy may involve an increase in intracellular

weight bearing exercise. An example of pathologic hypertrophy is in cardiac muscle as a result of hypertension.[5]

Hyperplasia

Main article: Hyperplasia

Hyperplasia is an increase in the number of cells.

fibroblasts. It occurs to a lesser extent in bone, cartilage, and smooth muscle cells. Hormonal hyperplasia occurs mainly in organs that depend on estrogen. For example, the estrogen-dependent uterine cells undergo hyperplasia and hypertrophy following pregnancy. Pathologic hyperplasia is an abnormal increase in cell division. A common pathologic hyperplasia in women occurs in the endometrium and is called endometriosis.[7]

Metaplasia

Main article: Metaplasia

Metaplasia occurs when a cell of a certain type is replaced by another cell type, which may be less differentiated. It is a reversible process thought to be caused by stem cell reprogramming.

squamous epithelium incapable of secreting mucus. These transformed cells may become dysplastic or cancerous if the stimulus (e.g., cigarette smoking) is not removed. The most common example of metaplasia is Barrett's esophagus, when the non-keratinizing squamous epithelium of the esophagus undergoes metaplasia to become mucinous columnar cells, ultimately protecting the esophagus from acid reflux originating in the stomach. If stress persists, metaplasia can progress to dysplasia and eventually carcinoma; Barrett's esophagus, for example, can eventually progress to adenocarcinoma.[8]

Dysplasia

Main article: Dysplasia

Dysplasia refers to abnormal changes in cellular shape, size, and/or organization. Dysplasia is not considered a true adaptation; rather, it is thought to be related to hyperplasia and is sometimes called "atypical hyperplasia". Tissues prone to dysplasia include

respiratory epithelium, where it is strongly associated with the development of cancer; it may also be involved in the development of breast cancer. Although dysplasia is reversible, if stress persists, then dysplasia progresses to irreversible carcinoma.[9]

See also

Notes and references

  1. ^ "Cellular Adaptation". The Lecturio Medical Concept Library. 26 October 2020. Retrieved 7 July 2021.
  2. ^ "Cellular Adaptation". The Lecturio Medical Concept Library. 26 October 2020. Retrieved 7 July 2021.
  3. PMC 7171462
    .
  4. doi:10.1038/news.2008.800. Archived from the original
    on 16 October 2019.
  5. PMC 7171462
    .
  6. ^ "Hyperplasia: MedlinePlus Medical Encyclopedia". medlineplus.gov.
  7. PMC 7171462
    .
  8. PMC 7171462
    .
  9. ISBN 0-7817-4988-3. Archived from the original
    (PDF) on 29 December 2016. Retrieved 28 December 2016.
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