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Cell injury, death and adaptation Yemen University Lectures 1 and 2. Dr H eyam Awad FRCPath. Coordinator : Dr Heyam Awad Email: h_awad@ju.edu.jo Lectures will be available on my university website www.ju.edu.jo Office hours: Monday and Wednesday 10-12 .. Office in hospital 3 rd floor.
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Cell injury, death and adaptationYemen UniversityLectures 1 and 2 Dr HeyamAwad FRCPath
Coordinator : Dr HeyamAwad • Email: h_awad@ju.edu.jo • Lectures will be available on my university website www.ju.edu.jo • Office hours: Monday and Wednesday 10-12 .. Office in hospital 3rd floor.
Lecture distribution • Cell injury 4+lab • Inflammation 6 +2labs • Repair 3 +lab • Haemodynamic diseases 5+lab • Neoplasia 8 +2 labs • Genetic diseases 8 + 2 labs
EVALUATION • 1 EXAM • THEORY AND PRACTICAL. • mock
What is pathology? • Patho… disease • Logy… study • Pathology = study of disease involves: causes of disease.. Etiology : mechanisms.. pathogenesis :morphological changes.
Etiology: Origin of disease , underlying causes. • Pathogenesis: steps in the development of disease…… cellular and molecular changes . • Morphology: macroscopic and microscopic changes.
Cellular adaptations and cell injury • Cells maintain a steady state.. Homeostasis. • Stresses .. Adaptation….. New homeostatic state with preservation of function. • Stress beyond capability of adaptation.. Cell injury. • Cell injury… reversible within certain limits • Then .. Irreversible…. Ends in cell death. • Two types of cell death: necrosis and apoptosis.
Adaptation • Hyertrophy • Hyperplasia • Atrophy • metaplasia
Adaptation • Adaptive changes are reversible. • Can be physiologic or pathologic.
Hypertrophy: Increased cell size. • Hyperplasia: increased number of cells.. Cell division. • Metaplasia: change from one adult cell type to another • Atrophy: decreased size.
Hypertrophy • Increased cell size. • Due to increased organelles and proteins. • Increased intracellular synthesis.. Caused by: increased demands, hormones or growth factors.
Physiologic hypertrophy • Uterus during pregnancy… due to estrogen • Skeletal muscle… due to increased demand
Pathologic hypertrophy • Cardiac.. Hypertensive heart disease • Pathogenesis.. Two types of signals: mechanical: stretch and trophic: growth factors and androgenic hormones
hyperplasia • Only in tissues that can replicate. • Can be physiologic or pathologic.
Physiologic hyperplasia • Hormonal: uterus, breast. • Compensatory: after removal or loss of part of tissue.
Pathologic hyperplasia • Due to excess in hormones or growth factors. • E:g endometrial hyperplasia. • Controlled.. Responds to decreased stimulation. This differentiates it from cancer
atrophy • Shrinkage in cell size due to loss of cell substance. Causes • decreased work load. • Loss of innervation • Loss of endocrine stimulation. • Aging
Atrophy • Physiologic: endometrial atrophy during menopause • Pathologic: loss of innervation.
atrophy Mechanisms: • Decreased protein synthesis. • Degradation of cellular proteins. • Autophagy…. Literally means self eating.
metaplasia • Adult cell type replaced by another adult cell type. • Arise in reprogrammed stem cells to differentiate along a new pathway.
Epithelial metaplasia • Respiratory epithelium to squamous. • Barrett's mucosa.. Esophegeal squamous to columnar
Metaplasia in mesenchymal tissue • Usually pathologic • Ossification of soft tissue due to injury.
Causes of cell injury/ 1 • Chemical agents • Infections. • Immunologic • Genetic factors • Nutritional imbalances • Physical agents • Aging.
Causes of cell injury/ 2 Oxygen deprivation.. Hypoxia and ischemia. Hypoxia= oxygen deficiency Ischemia = loss of blood supply due to impaired arterial flow or reduced venous return. -Ischemia is the most common cause of hypoxia. -Other causes of hypoxia: *reduced oxygen carrying capacity in anemia or carbon monoxide deficiency. *inadequate oxygenation of the blood as in pnumonia.
Rules and principles/ 1 • Cell response to injurious stimuli depend on type, duration and severity of the injury. • Example: low dose of a toxin can cause reversible injury whereas larger dosed can cause cell death. • Short-lived ischemia.. Reversible • Ischemia of long duration… death
Rules and principles/ 2 • Response to injury also depends on type, status, adaptability and genetic makeup of the injured cell. • Example: skeletal muscle cells can stand 2-3 hours of ischemia without irreversible injury but cardiac muscles die in 20-30 minutes . • Glycogen content in hepatocytes can determine their response to injury.. How? • Genetic polymorphism in cytochrome P-450 influences response to toxins.
Rules and principles/ 3 Cell injury results from functional and biochemical changes in essential cellular components, mainly: • Mitochondrial function • Calcium homeostasis • Cell and organelle membranes • DNA • Protein synthesis and folding.
Rules and principles/ 4 All injurious stimuli first affect the molecular or biochemical level. Cellular functions lost before cell death occurs. The morphologic changes of cell injury (or cell death) occur very late.
Rules/4 example • Ischemia of the heart… coronary artery occlusion. • Myocardial cells loose function ( become non-contractile) after 1-2 minutes of ischemia. • They die 20-30 minutes after ischemia. • It takes 2-3 hours to recognise ultrastructural changes of death (EM) • 6-12 hours by light microscope to appear dead.
Morphology of reversible cell injury • Cellular swelling : due to failure of energy-dependent ion pumps in the plasma membranecausing inability to maintain ion and fluid homeostasis. • Fatty change : small or large lipid vacuoles (hepatocytes and myocardial cells)
Cell swelling • The first manifestation of almost all forms of cell injury. • Reversible. • Grossly: organ affected becomes pale and gains weight. • Micro: small clear cytoplasmic vacuoles … which are distended endoplasmic reticulum.