{"id":7078,"date":"2021-09-26T12:52:07","date_gmt":"2021-09-26T10:52:07","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/pathology\/cell-injury-cell-death-and-adaptation\/adaptation\/hypertrophy-hyperplasia-and-metaplasia\/"},"modified":"2021-10-11T16:42:51","modified_gmt":"2021-10-11T14:42:51","slug":"hypertrophy-hyperplasia-and-metaplasia","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/pathology\/cell-injury-cell-death-and-adaptation\/adaptation\/hypertrophy-hyperplasia-and-metaplasia\/","title":{"rendered":"Hypertrophy, Hyperplasia, and Metaplasia"},"content":{"rendered":"\n

Remember the factors that influence cellular response:<\/strong><\/p>\n\n\n\n

  1. Glucose and glycogen levels.<\/li>
  2. Highly-metabolic cells are more sensitive to hypoxia.<\/li>
  3. Differentiating cells are more sensitive than fetal tissues.<\/li>
  4. Genomic DNA may help repair the damaged DNA.<\/li><\/ol>\n\n\n\n

    During adaptation, we see changes in cell number, size, phenotype, metabolic activity or function alterations:<\/h3>\n<\/span>\n\n\n
    • Hyperplasia<\/strong> — Increase<\/strong> in the number<\/strong> of cells<\/li>
    • Hypertrophy<\/strong> — Increase<\/strong> in size<\/strong> and function<\/li>
    • Atrophy<\/strong> — Decrease<\/strong> in size<\/strong> and function<\/li>
    • Metaplasia<\/strong> — Change from one cell type<\/strong> to another<\/li><\/ul>\n\n\n\n

      Adaptive responses can be both physiological and pathological, but excessive<\/strong> adaptation is of pathological origin.<\/p>\n\n\n<\/span>\n

      Hypertrophy:<\/h3>\n<\/span>\n\n\n
      • Means an increase in size and function<\/li>
      • Adaptation in non-dividing cells- cannot divide, thus respond by changing the size.<\/li>
      • Synthesis of structural cell components – cytoskeleton, myofilaments (in case of muscles), organelles size changes as well and so on.<\/li>
      • Hypertrophy can be activated due to changes in signal transduction
        • Mechanical trigger- <\/strong>Hemodynamic stress (increase pressure).<\/li>
        • Trophic trigger<\/strong>– IGF-1, angiotensin II, alpha-adrenergic agonists<\/li><\/ul><\/li>
        • Hypertrophy can either physiologic or pathologic:
          • Physiologic:<\/strong>
            • Workload: skeletal muscle<\/li>
            • Hormonal: lactation (together with hyperplasia)<\/li>
            • physiologic enlargement of the uterus- during pregnancy enlarge due to estrogen secretion.<\/li><\/ul><\/li>
            • Pathologic:<\/strong>
              • Myocardial enlargement due to chronic hypertension or aortic valve stenosis.<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n\n\n<\/span>\n

                Atrophy:<\/h3>\n<\/span>\n\n\n

                Cellular atrophy occurs due to decreased protein synthesis and increased protein degradation.<\/p>\n\n\n\n

                • Degradation of proteins, can be done by:<\/strong>
                  • Lysosomes (hydrolases)<\/li>
                  • Ubiquitin-proteasome pathway<\/li>
                  • Catabolic hormones, cytokines (TNFa)<\/li><\/ul><\/li>
                  • Autophagia:<\/strong>
                    • Autophagia is a natural, regulated mechanism of the cell that disassembles unnecessary or dysfunctional components<\/li>
                    • Elimination of intracellular substances<\/li>
                    • Membrane-bound vacuoles<\/li>
                    • Mitochondria, ER, complex protein fragments<\/li>
                    • Proteolysis<\/li>
                    • Undegradable – lipofuscin granules (brown atrophy)<\/li><\/ul><\/li><\/ul>\n\n\n\n
                      • Shrinkage in size \u2013 The cell loses its intracellular substances and contents.<\/li>
                      • Might occur due to developmental loss (involution; thymus, ductus thyroglossal).<\/li>
                      • Can be either physiological (uterus after labor or during menopause), or pathological;
                        • Decreased workload (inactivity)<\/li>
                        • Loss of innervation<\/li>
                        • Reduced blood supply<\/li>
                        • Nutritional defect (cachexia)<\/li>
                        • Loss of hormonal stimulation<\/li>
                        • Aging<\/li><\/ul><\/li>
                        • Atrophy is a common manifest in case of Alzheimer (cerebral atrophy).<\/li><\/ul>\n\n\n<\/span>\n

                          Metaplasia<\/h3>\n<\/span>\n\n\n
                          • Metaplasia is the change of one type of cell (epithelial or mesenchymal) to another adult cell type.<\/li>
                          • The ability to perform metaplasia increases the resistance to stress (adaptation).\u00a0<\/li>
                          • Characterized more by reprogramming of stem cells<\/strong> than transdifferentiation of already differentiated cells.<\/li>
                          • The adult, fully differentiated cells are unchanged, but rathert, the new growing cells<\/strong> will appear with the new phenotype, e.g. a different cell shape.<\/li><\/ul>\n\n\n\n

                            Examples for metaplasia:<\/p>\n\n\n\n

                            1. Columnar-to-squamous<\/strong>\u00a0\u2013 Cigarette smoking -> chronic irritation ->bronchial metaplasia (squamous epithelium is more resistant to irritation).<\/li>
                            2. Squamous-to-columnar <\/strong>\u2013 Barrett\u2019s esophagus (due to chronic exposure to acids- reflux (considered to be a\u00a0premalignant condition\u00a0because it is associated with a high incidence of further transition
                              to\u00a0esophageal\u00a0adenocarcinoma, an often deadly\u00a0cancer)).<\/li><\/ol>\n<\/span>

                              During adaptation, we see changes in cell number, size, phenotype, metabolic activity or function alterations:<\/h3>

                              Hypertrophy:<\/h3>

                              Atrophy:<\/h3>

                              Metaplasia<\/h3><\/div>","protected":false},"excerpt":{"rendered":"

                              Remember the factors that influence cellular response: Glucose and glycogen levels. Highly-metabolic cells are more sensitive to hypoxia. Differentiating cells are more sensitive than fetal tissues. Genomic DNA may help repair the damaged DNA. During adaptation, we see changes in cell number, size, phenotype, metabolic activity or function alterations: Hyperplasia — Increase in the number […]<\/p>\n","protected":false},"author":275,"featured_media":0,"parent":7074,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-7078","page","type-page","status-publish","hentry"],"yoast_head":"\nHypertrophy, Hyperplasia, and Metaplasia – Meddists<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/meddists.com\/learn\/pre-clinical\/pathology\/cell-injury-cell-death-and-adaptation\/adaptation\/hypertrophy-hyperplasia-and-metaplasia\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" 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