Cell Injury and Adaptations PDF

Introduction  Important Concepts Pathology: Study of Disease “Pathos”: suffering, disease Disease: An abnormal variation of the structure and function of any organ or tissue of the body. Development of Disease: Host Environment Pathogen  Importan...

Introduction  Important Concepts Pathology: Study of Disease “Pathos”: suffering, disease Disease: An abnormal variation of the structure and function of any organ or tissue of the body. Development of Disease: Host Environment Pathogen  Important Concepts The core of pathology: The four aspects of a disease process that form the core of pathology : (1) Etiology: causes of the disease (2) Pathogenesis: the mechanisms of its development (3) Morphologic changes: the structural alteration induced in the cells and organs of the body. (4) Clinical significance: the functional consequences of the morphologic changes.  Important Concepts Classification: (1) Human pathology (Autopsy, Biopsy, Cytology) (2) Experimental pathology Position: It’s a bridging discipline involving both basic science and clinical practice Divisions of Pathology: (1) General pathology: Concerned with the basic reaction of cells and tissues to abnormal stimuli that underlie all diseases. (2) Systemic pathology : Describes the specific responses of specialized organs and tissues to defined stimuli. Cell injury and cellular adaptations  Cell Injury The basis of all diseases is injury to the smallest unit of the body (the cell). A normal cell is in a steady state, if able to handle physiologic demand according to its adaptive capacity.  Causes of Cell Injury Hypoxia: oxygen deprivation Biological agents: bacteria, viruses, fungi, and parasites. Chemical agents: strong alkalis and acids, insecticides, alcohol, narcotics and air pollutants. Physical agents: excessive heat and cold, radiation, mechanical trauma and electric injury.  Causes of Cell Injury Endogenous toxins: uremia, jaundice, & diabetic ketosis. Immunologic reactions and autoimmune diseases. Nutritional imbalances: protein calorie malnutrition, starvation, obesity, diabetes mellitus, and vitamin deficiencies. Genetic abnormalities.  Types of Cell Injury 1- Irreversible: 2- Reversible: Necrosis : cell death Hydropic swelling: excess Apoptosis : programmed water in the cell single cell death Fatty change: accumulation of fat in the cells of some organs. Reduce oxidative phosphorylation: decrease energy stores (ATP) CELLULAR RESPONSE TO STRESSOR NOXIOUS STIMULI  Cellular adaptation DEFINITION: Cellular adaptations are those in which new physiologic & morphologic changes occur in response to excessive physiologic or pathologic stimuli, but preserving the cell viability and modulating its functions. ETIOLOGY OF CELLULAR ADAPTATIONS : ↑ physiologic demands Minor stresses ↓ demand ↓ nutrition  TYPES OF CELLULAR ADAPTATIONS Hypertrophy Hyperplasia Atrophy Metaplasia  HYPERPLASIA ↑ in number of cells of an organ/ tissue Capability to divide: Physiologic Pathologic PHYSIOLOGIC HYPERPLASIA PATHOLOGIC HYPERPLASIA Excessive hormonal stimulation : Hormonal Excess of androgen → BPH Compensatory Viral infection Chronic injury → Corn / callus. Functional demand Fertile ground for cancer MULTINODULAR GOITRE  HYPERTROPHY ↑ in the size of cells resulting in ↑ size of tissue/ organ. Non- dividing cells. PHYSIOLOGIC HYPERTROPHY 1. Skeletal muscles of bodybuilders 2. Lactating breast. 3. Pregnant Uterus PATHOLOGIC HYPERTROPHY 1. Hypertension 2. Valvular stenosis HYPERTROPHY  ATROPHY Shrinkage in the size of the cell. Decrease function of cell. VIABLE Loss of cell substance PHYSIOLOGIC ATROPHY PATHOLOGIC ATROPHY 1. Atrophy of disuse 1. Aging (senile atrophy). 2. Denervation atrophy 2. Uterus in menopause. 3. ↓ blood supply 3. Thyroglossal duct. 4. Inadequate nutrition 4. Uterus after delivery. 5. ↓ endocrine stimulation 6. Pressure atrophy  ATROPHY GENERALISED Starvation atrophy ( ↓ Nutrition ) Senile atrophy Endocrine atrophy Osteoporosis ( osteopenia) LOCAL Ischemic atrophy ( Senility – local ) Pressure atrophy Disuse atrophy Neuropathic atrophy STARVATION ATROPHY PRESSURE ATROPHY DISUSE MUSCLE ATROPHY NEUROPATHIC ATROPHY ( POLIOMYELITIS )  METAPLASIA Conversion of one adult cell type to another adult cell type in response to adverse environmental conditions. Metaplasia is a “Two edged sword”. Pro: Cytoprotective. Con: Fertile ground for malignancy. ETIOLOGY Irritants Stones Deficiency of vitamin A  EPITHELIAL METAPLASIA Columnar to squamous Lungs: Cigarette, fumes. Cervix Ducts : Stones  EPITHELIAL METAPLASIA Squamous to columnar Barrett esophagus : gastric reflux.