Cellular Adaptation PDF

CELLULAR ADAPTATION DR MUHAMMAD ALI SOOMRO INTRODUCTION: In cell biology and patho- physiology, 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). Six types of m...

CELLULAR ADAPTATION DR MUHAMMAD ALI SOOMRO INTRODUCTION: In cell biology and patho- physiology, 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). Six types of morphological adaptations: Atrophy, Aplasia, Hypertrophy, Hyperplasia, Dysplasia, and Metaplasia. Atrophy:  Decrease in size of an organ or tissue and occurs owing to decrease in pre-existing cells.  Causes: Disuse, Nutritional or Oxygen deprivation. Diminished Endocrine Stimulation. Aging. De-nervation.  Features:  Auto-phagic granules  Intra-cytoplasmic vacuoles containing debris from degraded organelles. Atrophy: Atrophy: Aplasia: Failure of Cellular Production. During foetal growth, aplasia causes agenesis, or due to failure of production. (Esp. Thymus). Later in life, it can be caused by permanent loss of precursor cells in proliferative tissues like bone marrow. Aplasia: Hypertrophy: Increase in size of an organ or tissue owing to rise in size of cells. Characterized by rise in protein synthesis and an increase in size or number of intracellular organelles. Often occurs in response to increased use of an organ or tissue e.g. impact of physical exercise on skeletal muscle; Left ventricular hypertrophy in hypertensive patients. Hypertrophy: Hypertrophy: Hyperplasia: Increase in size of an organ or tissue owing to rise in number of cells. Glandular proliferation in breast during pregnancy. Further during pregnancy, both hypertrophic and hyperplastic changes occur in uterine smooth muscle. During old age, males have an enlarged prostate owing to raised frequency of usage. Hyperplasia: Hyperplasia: Dysplasia:  Refers to abnormal changes in cellular shape, size, and/or organization.  Dysplasia is not considered a true adaptation and is thought to be related to hyperplasia and is sometimes called "atypical hyperplasia”.  Although dysplasia is reversible, if stress persists, then dysplasia progresses to irreversible carcinoma.  Tissues prone to dysplasia include cervical and respiratory epithelium, where it is strongly associated with the development of cancer; it may also be involved in the development of breast cancer. Dysplasia: Dysplasia: 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. Stem cells are found in epithelia and embryonic mesenchyme of connective tissue. Metaplasia: 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 carcinoma. Metaplasia: THE END! THANKS!