Introduction to Pathology and Adaptation PDF

Introduction to Pathology Assistant Professor Dr. Rafal Abdulrazaq M. B. Ch. B. F.I.C.M.PATH. INTRODUCTION TO  Lecture outline Introduction to pathology Diagnostic pathology Cellular adaptation  Pathology “The branch of medical science that studies th...

Introduction to Pathology Assistant Professor Dr. Rafal Abdulrazaq M. B. Ch. B. F.I.C.M.PATH. INTRODUCTION TO  Lecture outline Introduction to pathology Diagnostic pathology Cellular adaptation  Pathology “The branch of medical science that studies the causes, nature and effects of diseases " Pathology : the science behind the cure. The word pathology comes from the Greek words Pathos meaning disease (suffering) – logos meaning study – study of disease –  Histopathology From the Greek histos (tissue) and pathos (suffering). It is the microscopic study of tissues affected by disease.  Pathophysiology Is the functional changes associated with or resulting from disease or injury.  Disease Is an abnormal alteration of structure or function in any part of the body.  Classification of Diseases Congenital Acquired - inflammatory - vascular - growth disorder - metabolic - degenerative - drug induced - infective  PATHOLOGY It is abridging discipline involving both basic science and clinical practice. Traditionally, the study of pathology is divided into general pathology and 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.  The pathologist typically identifies: MORPHOLOGY: - The morphologic changes refer to the structural alterations in cells or tissues that are either characteristic of the disease or diagnostic of the etiologic process. -Identify changes in gross or macroscopic( by naked eye inspection) and microscopic appearance. ETIOLOGY: Means the cause of the disease (either Congenital or Acquired causes ) PATHOGENESIS: Means the mechanism and the pathways by which morphological changes occur. Correlate the findings with clinical features so the goal of pathology : 1- Diagnosis of disease 2- Disease prevention 3- Successful therapy  Introduction to Pathology A sign is an indication of some fact or quality; and – a medical sign is an objective indication of some medical fact or quality that is detected by a physician during a physical examination of a patient A symptom is a departure from normal function – or feeling which is noticed by a patient, indicating the presence of disease or abnormality. A symptom is subjective, observed by the patient, and not measured A lesion is any abnormal tissue found on or in an – organism, usually damaged by disease or trauma. Lesion is derived from the Latin word laesio which means injury. Prognosis is the expected outcome of the disease, – It is the clinician's estimate of the severity and possible result of a disease. The Father of Modern Pathology Rudolph Virchow 1821-1902 recognized the change in diseased tissue at Cellular level  Diagnostic Pathology Biopsy : Removal and examination of tissue obtained from the living body. - Needle biopsy - Endoscopic biopsy - Incisional biopsy (only a portion of the lesion is sampled (diagnostic nature). - Excisional biopsy ( the entire lesion is removed usually with a rim of normal tissue (diagnostic and therapeutic nature). Cytology: is the study of normal & abnormal morphologic characteristics of human cells. e.g. sputum ,urine. Autopsy :Is the examination of a dead body to determine the cause and manner of death. Clinical features of acute appendicitis Surgical procedure Normal & Inflamed Appendix 871 jh Acute Appendicitis  Cellular Responses to Stress The normal cell is confined to a fairly narrow range of function and structure by its genetic programs of metabolism and differentiation. It is nevertheless able to handle normal physiologic demands, maintaining a steady state called homeostasis The cells can adjust their structure and function to accommodate the changes caused by physiological or pathological stimuli and this is called adaptation achieving a new steady state and preserving viability , If the limits of adaptive response to a stimulus are exceeded, or in certain instances when the cell is exposed to an injurious agent or stress, a sequence of events follows that is loosely termed cell injury. Cell injury is reversible up to a certain point, but if the stimulus persists or is severe enough from the beginning, the cell reaches a "point of no return" and suffers irreversible cell injury and ultimately cell death. Figure : Stages in the cellular response to stress and injurious stimuli Figure: The relationships between normal, adapted, reversibly injured (fatty change), and dead myocardial cells  Cellular adaptations These reactions are induced by physiological or pathological stimuli. The aim is to escape cell injury. The adaptive responses include: 1- Atrophy 2- Hypertrophy 3- Hyperplasia 4- Metaplasia The –trophy brothers  Atrophy This refers to a decrease in the size of the cell by loss of cell substance. When sufficient numbers of cells are involved, the entire organ or tissue decreases in size i.e. become atrophic Causes of atrophy include 1-Decrease workload e.g. muscular atrophy due to immobilization as in fractured limb. 2-Denervation (loss of nerve supply) e.g. paralysis of a limb due to nerve injury. 3-Ischemia e.g. brain atrophy as an ageing phenomenon due to atherosclerosis. 4-Undernutrition, as in starvation. 5-Loss of endocrine stimulation e.g. endometrial atrophy (decrease estrogen secretion from the ovary in old age female).  Brain atrophy A. Brain atrophy in an elderly man. B. Normal brain of a young man. The aim of this adaptation is to bring into balance cell survival in the face of reduced blood supply, nutrition etc. The cells become smaller with diminished function and thus reduced metabolic needs ( decrease protein synthesis and increase catabolism ) and by doing so they escape injury. Cytokines, such as tumor necrosis factor (TNF), are capable of increasing muscle proteolysis. Because of the above cell debris accumulate, some resist digestion by intracellular enzymes and become enclosed by a membrane (residual bodies) e.g. lipofuscin granules.  Hypertrophy Refers to increase in the size of cells and as a consequence increase in the size of the organ or tissue containing them (opposite to atrophy) It is due to synthesis of more structural components within the cell {synthesis of more proteins and myofilaments per cell } The aim is to achieve equilibrium between the demand and the cell’s functional capacity. It can be physiological or pathological ,examples: 1-Uterus in pregnancy (physiological: hormonal) 2. Skeletal muscles in athletes (physiological: increased workload) Athletes as an example of muscular hypertrophy Muscular hypertrophy 3. Left ventricle hypertrophy in systemic hypertension (pathological: increased workload; the ventricle has to contract against increased pressure in the aorta) If the burden persists the hypertrophy reaches a limit beyond which the enlarged muscle is no longer able to compensate for the increased work and cardiac failure ensues. At this point there is lysis and loss of myofibril’s contractile elements.  HYPERTROPHY IN-CREASE IN SIZE OF CELLS  Hyperplasia Refers to an increase in the number of cells in an organ or tissue leading to an increase in its size. Hyperplasia and hypertrophy can also occur together ,thus the enlargement of uterus during pregnancy occurs as a consequence of estrogen stimulated smooth muscle hyperplasia and hypertrophy. Not all adult cell types have the same capacity for hyperplasia. Those capable of cell division (labile cells) can undergo profound hyperplastic growth.  Enlargement of uterus in pregnancy On the left is a normal uterus showing the normal mass of smooth muscle in its wall. On the right is a uterus from a recently pregnant women, in which the striking increase in mass of smooth muscle is evident. At cellular level this is due to both hyperplasia and hypertrophy of uterine smooth muscle. Hyperplasia is divided into : Physiological hyperplasia is either 1. Hormonal (e.g. proliferation of the breast glandular epithelium in females at puberty or during pregnancy) 2. Compensatory (e.g. after partial hepatectomy). Pathological hyperplasia is either 1-Excessive hormonal stimulation (e.g. endometrial hyperplasia ) 2- Stimulation by growth factors is also involved in the hyperplasia that is associated with certain viral infections, such as papillomaviruses, which cause skin warts. skin wart  Metaplasia Refers to replacements of one mature adult cell type by another mature cell type & this is a reversible change. It may represent an adaptation of cells more sensitive to stress by other cells that are more resistant to the adverse environment. Metaplasia is thought to arise by genetic ‘reprogramming’ of stem cells rather than transdifferentiation of already differentiated cells, brought about by signals generated by cytokines, growth factors, and extracellular matrix components in the cell's environment. Moreover, the influences that predispose to metaplasia, if persistent, may induce malignant transformation in metaplastic epithelium  Examples of Metaplasia : Squamous metaplasia of the laryngeal and bronchial respiratory epithelium due to smoking. Squamous metaplasia of the urothelium in the urinary bladder due to Bilharzia or stone. Columnar metaplasia of esophageal squamous epithelium as a result of prolonged reflux of acidic gastric juice into the esophagus.  Columnar metaplasia esophagus Metaplastic transformation (arrow) of the normal esophageal stratified squamous epithelium (Lt) to mature columnar epithelium (Barrett’s esophagus)