Cellular Adaptation PDF 2020

Сellular Adaptation Dr. WALID THEIB AL HUSSEIN BIN TALAL UNIVERSITY PRINCESS AYSHEH BINT AL-HUSSEIN COLLEGE OF NURSING AND HEALTH SCIENCES 2020  Introduction Cellular adaptation refers to changes made by a cell in response to adverse o...

Сellular Adaptation Dr. WALID THEIB AL HUSSEIN BIN TALAL UNIVERSITY PRINCESS AYSHEH BINT AL-HUSSEIN COLLEGE OF NURSING AND HEALTH SCIENCES 2020  Introduction Cellular adaptation refers to changes made by a cell in response to adverse or varying environmental changes  CELLULAR ADAPTATION: The ability of cells to respond to various types of stimuli and adverse environmental changes. The cell changes chat occur are: Atrophy(reduction in size and cell number) Hypertrophy (enlargement of individual cells) Hyperplasia, (increase in cell number) Metaplasia(transformation from one type of epithelium to another) Dysplasia(disordered growth of cells) Anaplasia,,,, Neoplasia.  HYPERPLASIA Basic description: Increase in the number of cells. Types of hyperplasia Physiologic hyperplasia: Occurs due to a normal stressor. For example, increase in the size of the breasts during pregnancy, increase in thickness of endometrium during menstrual cycle, and liver growth after partial resection  Pathologic hyperplasia: Occurs due to an abnormal stressor. proliferation of endometrium due to prolonged estrogen stimulus  HYPERTROPHY Increase in the size of the cell. Types of hypertrophy Physiologic hypertrophy: Occurs due to a normal stressor. For example, enlargement of skeletal muscle with exercise. Pathologic hypertrophy: Occurs due to an abnormal stressor. For example, increase in the size of the heart due to aortic stenosis  ATROPHY is the shrinkage in cell size by loss of cellular substance With the involvement of a sufficient number of cells, an entire organ can become atrophic Causes of atrophy include decreased workload, pressure, diminished blood supply or nutrition, loss of endocrine stimulation, and aging  METAPLASIA REVERSIBLE change in which one mature/adult cell type (epithelial or mesenchymal) is replaced by another mature cell type A protective mechanism rather than a premalignant change Physiological metaplasia: cervical ectopy Pathological metaplasia Occurs as a response to chronic chemical or physical stimuli May completely regress or lead to malignant transformation (considered precancerous)  Four types of morphological adaptations include atrophy, hypertrophy, hyperplasia, and metaplasia.  Causes of injury /Types of stress Oxygen deprivation “Hypoxia & ischemia” Free radicals Chemical agents –glucose, hypertonic saline, increased oxygen & poisons Physical agents –trauma, extreme heat / cold , increased atmosphere pressure, radiation, electric shock Infections  Immune reactions Genetic defects –gene mutations & chromosomal abnormality, enzyme defects, damaged DNA ,, increased cell susceptibility to injury Nutritional defects –decreased proteins, decreased enzymes, increased cholesterol Aging  Cell damage (also known as cell injury) is a variety of changes of stress that a cell suffers due to external as well as internal environmental changes  Repair When a cell is damaged the body will try to repair or replace the cell to continue normal functions. If a cell dies the body will remove it and replace it with another functioning cell, or fill the gap with connective tissue to provide structural support for the remaining cells  Regeneration Regeneration of Parenchema cells, or the functional cells, of an organism. The body can make more cells to replace the damaged cells keeping the organ or tissue intact and fully functional.  Replacement When a cell cannot be regenerated the body will replace it with stromal connective tissue to maintain tissue/organ function. Stromal Cells are the cells that support the parenchymal cells in any organ.