Basic Concepts in Pathology: Cell Adaptation (PDF)

Basic Concepts in Pathology Cell Adaptation Karen Gil M.D. PATHOLOGY •Literal translation: “Study (logos) of suffering (pathos)” •Field of medicine which studies disease processes •Pathologists identify: – changes in the gross or microscopic appearance (morphology) of cells and tissues – biochemic...

Basic Concepts in Pathology Cell Adaptation Karen Gil M.D. PATHOLOGY •Literal translation: “Study (logos) of suffering (pathos)” •Field of medicine which studies disease processes •Pathologists identify: – changes in the gross or microscopic appearance (morphology) of cells and tissues – biochemical alterations in body fluids (such as blood and urine) Pathology Pathology involves: • Etiology – Genetic – Acquired • Pathogenesis – Sequence and patterns of cellular injury that lead to disease – Underlying mechanisms that result in the presenting signs and symptoms of the patient. Pathology • Morphologic changes of the disease process – Gross changes – Microscopic changes • Clinical significance – Know the sign and symptoms of each disease – Disease course – Prognosis Adaptation and Cell Injury • Cells are constantly adjusting their structure and function to accommodate changing demands and extracellular stress • Cells tend to maintain normal homeostasis • Homeostasis ability to maintain a constant internal environment in response to environmental changes Cellular Adaptive Responses to Injury • • • • • Atrophy Hypertrophy Hyperplasia Metaplasia Dysplasia (irreversible) • Cellular Adaptation is the result of a persistent stress or injury • If the adaptive capability is exceeded, cell injury develops Adaptive Responses • Adaptive responses are potentially reversible once the stress has been removed • Severe or persistent stress results in irreversible injury and the affected cell die • Two patterns of cell death: – Necrosis – Apoptosis Atrophy • Definition: decrease in cell size and functional ability • Causes of atrophy: —Decreased workload (e.g., immobilization of a limb to permit healing of a fracture) —Loss of innervation —Diminished blood supply - ischemia —Inadequate nutrition —Loss of endocrine stimulation (hormonal or neuronal stimulation) —Aging (senile atrophy) Atrophy Hypertrophy • Definition: an increase in cell size and functional ability due to increased synthesis of intracellular components •Cause of hypertrophy 1. Increased mechanical demand – – 2. Physiologic (striad muscle of weight lifters) Pathologic (cardiac muscle in hypertension) Increased endocrine stimulation – – – Puberty (growth hormone, androgens/estrogens) Gravid uterus (estrogen) Lactating breast (prolactin and estrogen) Retinal pigment epithelium (RPE) Hypertrophy •pigmented layer of the retina which can be thicker than normal at birth (congenital) or may thicken later in life •do not cause symptoms •typically found during routine eye examinations Hypertrophy and Hyperplasia Hyperplasia • Definition: an increase in the number of cells in a tissue or organ • Some cell types are unable to exhibit hyperplasia (e.g., nerve, cardiac, skeletal muscle cells) • Physiologic causes of Hyperplasia – Compensatory ( e.g. after partial hepatectomy) – Hormonal stimulation (e.g. breast development at puberty) – Antigenic stimulation (e.g.lymphoid hyperplasia) • Pathologic causes of hyperplasia – Endometrial hyperplasia – Prostatic hyperplasia of aging Hyperplasia Conjunctival Lymphoid Hyperplasia Metaplasia •Definition: – is a reversible change in which one adult cell type is replaced by another adult cell type •The replacement cell is better able to tolerate the environmental stresses •Proposed mechanism: –the reverse cells (or stem cells) of the irritated tissue differentiate into a more protective cell type due to the influence of growth factors Metaplasia Conjunctival Metaplasia Endometrial Metaplasia Dysplasia • Irreversible process • Definition: an abnormal proliferation of cells that is characterized by changes in cell size, shape, and loss of cellular organization • Dysplasia is not cancer but may progress to cancer (preneoplastic lesion) • E.g., cervical dysplasia, actinic (solar) keratosis Dysplasia Squamous dysplasias of the conjunctival epithelium Actinic Keratosis