Adaptaciones Celulares

CHAPTER 1

Cellular Adaptations, Cell Injury, and Cell Death
INTRODUCTION TO PATHOLOGY OVERVIEW: CELLULAR RESPONSES TO STRESS AND NOXIOUS STIMULI CELLULAR ADAPTATIONS OF GROWTH AND DIFFERENTIATION Hyperplasia Physiologic Hyperplasia Pathologic Hyperplasia Hypertrophy Atrophy Metaplasia OVERVIEW OF CELL INJURY AND CELL DEATH CAUSES OF CELL INJURY MECHANISMS OF CELL INJURY Depletion of ATPMitochondrial Damage Influx of Intracellular Calcium and Loss of Calcium Homeostasis Accumulation of Oxygen-Derived Free Radicals (Oxidative Stress) Defects in Membrane Permeability REVERSIBLE AND IRREVERSIBLE CELL INJURY MORPHOLOGY OF CELL INJURY AND NECROSIS Reversible Injury Necrosis EXAMPLES OF CELL INJURY AND NECROSIS Ischemic and Hypoxic Injury Ischemia–Reperfusion Injury Chemical Injury APOPTOSISCauses of Apoptosis Apoptosis in Physiologic Situations Apoptosis in Pathologic Conditions Biochemical Features of Apoptosis Mechanisms of Apoptosis Examples of Apoptosis SUBCELLULAR RESPONSES TO INJURY Lysosomal Catabolism Induction (Hypertrophy) of Smooth Endoplasmic Reticulum Mitochondrial Alterations Cytoskeletal Abnormalities INTRACELLULAR ACCUMULATIONS Lipids Steatosis (Fatty Change)Cholesterol and Cholesterol Esters Proteins Hyaline Change Glycogen Pigments PATHOLOGIC CALCIFICATION Dystrophic Calcification Metastatic Calcification CELLULAR AGING

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UNIT I

General Pathology

Introduction to Pathology
Pathology is literally the study (logos) of suffering (pathos). More specifically, it is a bridging discipline involving both basic science and clinical practice and isdevoted to the study of the structural and functional changes in cells, tissues, and organs that underlie disease. By the use of molecular, microbiologic, immunologic, and morphologic techniques, pathology attempts to explain the whys and wherefores of the signs and symptoms manifested by patients while providing a sound foundation for rational clinical care and therapy. Traditionally, the study ofpathology is divided into general pathology and special, or systemic, pathology. The former is concerned with the basic reactions of cells and tissues to abnormal stimuli that underlie all diseases. The latter examines the specific responses of specialized organs and tissues to more or less well-defined stimuli. In this book, we first cover the principles of general pathology and then proceed tospecific disease processes as they affect particular organs or systems. The four aspects of a disease process that form the core of pathology are its cause (etiology), the mechanisms of its development (pathogenesis), the structural alterations induced in the cells and organs of the body (morphologic changes), and the functional consequences of the morphologic changes (clinical significance). Etiologyor Cause. The concept that certain abnormal symptoms or diseases are “caused” is as ancient as recorded history. For the Arcadians (2500 BC), if someone became ill, it was the patient’s own fault (for having sinned) or the makings of outside agents, such as bad smells, cold, evil spirits, or gods.1 In modern terms, there are two major classes of etiologic factors: intrinsic or genetic, andacquired (e.g., infectious, nutritional, chemical, physical). The concept, however, of one etiologic agent to one disease — developed from the study of infections or single-gene disorders — is no longer sufficient. Genetic factors are clearly involved in some of the common environmentally induced maladies, such as atherosclerosis and cancer, and the environment may also have profound influences on certaingenetic diseases. Knowledge or discovery of the primary cause remains the backbone on which a diagnosis can be made, a disease understood, or a treatment developed. Pathogenesis. Pathogenesis refers to the sequence of events in the response of cells or tissues to the etiologic agent, from the initial stimulus to the ultimate expression of the disease. The study of pathogenesis remains one of the...