Cellular Adaptations & Injury Mastery Guide: Hypertrophy, Hyperplasia, Atrophy, Metaplasia, Reversible vs Irreversible Cell Injury, Apoptosis vs Necrosis, Hormonal & Compensatory Growth, Myocardial Hypertrophy, Endometrial Hyperplasia, Cachexia, Barrett E

Cellular Adaptations & Injury Mastery Guide: Hypertrophy, Hyperplasia, Atrophy, Metaplasia, Reversible vs Irreversible Cell Injury, Apoptosis vs Necrosis, Hormonal & Compensatory Growth, Myocardial Hypertrophy, Endometrial Hyperplasia, Cachexia, Barrett Esophagus, Squamous Metaplasia, Chronic Inflammation, Protein Synthesis & Degradation Mechanisms Exam Questions Verified and Complete with A+ Graded Rationales Latest Updated 2026 Objective: major types of cellular adaptations of cellular growth and differentiation •↑ cellular size (hypertrophy) •↑ cell number (hyperplasia) •Change in phenotype (metaplasia) •↓ in cell size and metabolic activity (atrophy) Objective: major types of cellular adaptations of cellular growth and differentiation Hypertrophy •↑in size of cells, ↑ in the size of the affected organ (no new cells) May be due to increased workload Heart tissues (myocardial fibers) INCREASE in size not in number Hypertrophy Examples •Hormone-induced enlargement of an organ results from hypertrophy of smooth muscle fibers. Normal (Physiologic) •Growth of the uterus during pregnancy. Pathologic: Increased workload in the heart •Body builders • Chronic hemodynamic overload. •Hypertension or faulty valves (HBP) Hyperplasia Only takes place in cells that can divide •↑ in cell numbers in response to hormones and other growth factors. •Could be precancerous •Hypertrophy and hyperplasia can occur in the same tissue (if the cell population is capable of dividing). Hyperplasia 4 Examples Hormonal: •Endometrial hyperplasia during pregnancy. •Breast hyperplasia during puberty pregnancy. Compensatory: •Regeneration of liver after a portion is removed. •Enlargement of remaining kidney after unilateral nephrectomy. Atrophy •↓in cell size due to ↓in demand. •Cells are not dead. •↓ in protein synthesis ↑ in protein degradation. •↓ mitochondria & myofilaments •↓ rough endoplasmic reticulum Atrophy Examples •Physiologic atrophy: •Embryonic structures: notochord & thyroglossal duct. •Loss of endocrine stimulation: endometrial atrophy following menopause. •Pathologic atrophy: 1. Decreased workload: skeletal muscle atrophy following a broken bone. 2. Loss of innervation: damage to nerves can lead to muscle atrophy. 3. Diminished blood supply. 4. Inadequate nutrition: cachexia (muscle wasting) seen in cancer patients. 5. Pressure: tumor exerting pressure on surrounding tissue Metaplasia •Change in phenotype of differentiated cells. Reversible change in which one differentiated cell type is replaced by another cell type •Caused by chronic irritation. Adaptive substitution of cells that are sensitive to stress to withstand adverse environment •Change is stimulated by signals generated by cytokines, growth factors, and ECM components in cell’s environment. Metaplasia Examples •Respiratory epithelium of habitual smokers. •Epithelial metaplasia: columnar to squamous type •Normal columnar epithelium cells of trachea and bronchi are often replaced by stratified squamous epithelium cells. •Squamous cells are more rugged, can handle the stress of noxious chemicals. Metaplasia Examples •Can develop due to acid reflux. •Barrett esophagus: squamous to columnar type. •Columnar cells are less sensitive to the increased acidity than squamous cells. •Glandular epithelium with tall columnar cells punctuated by round to oval goblet cells. •Chronic inflammation. Objective: Recognize and differentiate the types of cellular injury and mechanisms. Reversible vs Irreversible •Reversible