Pathophysiology

Pathophysiology Study Guide

©2018 of 131 There are two common triggers of hypertrophy: mechanical and trophic. The signal transduction pathways are activated due to these triggers, which induce the genes to synthesize protein cells to alter its function and structure. The proteins and myofilaments of cells are increased due to the stimuli. Hyperplasia Hyperplasia is a type of cell adaptation in which the number of cells increases, by way of replicating, without causing any change in the size of the cell. Hyperplasia can be caused by physiological, as well as pathological, parameters. Physiological hyperplasia has two types: hormonal hyperplasia and compensatory hyperplasia. The former is due to the stimulation of a hormone, like at the time of pregnancy the glandular epithelium of the breast is proliferated. In contrast, compensatory hyperplasia occurs when a part of tissue is removed from the body. Pathologic hyperplasia occurs when the hormones stimulate excessively in the cells of the body. Hyperplasia is vital in the healing process, as the fibroblasts and blood vessels are proliferated due to hyperplasia, which helps in the repair of the wound. Metaplasia This adaptation is a kind of reversible alteration in which one type of cell (adult), which is sensitive, is replaced by another type of adult cell that has the ability to withstand the changes caused by the external environment. In the case of metaplasia, the stem cells in the body undergo genetic reprogramming. For example, among chain smokers, the respiratory epithelium undergoes a squamous change, which exemplifies the epithelial metaplasia. Another cause of respiratory epithelial metaplasia is the deficiency of Vitamin A. It should be noted that this adaptation may cause malignant transformation of the epithelium in cases where the irritation persists for a longer period. For instance, in the case of habitual smoking, squamous metaplasia is the first step, which later can cause cancer of the lungs in the changed foci of the cells. Dysplasia Dysplasia is not a true form of cellular adaptation as it is not responsible for any function. It is referred to as an appearance of cells that have undergone some atypical changes in response to chronic irritation. In dysplasia, the cells are reproduced in a controlled manner, but have the capacity to cause malignancy and can cause rapid and uncontrolled reproduction of cells. In that case, the architectural orientation of one cell with the adjoining next cell is completely lost regarding both shape and size. Epithelial cells are common sites for dysplastic changes and can cause Bronchial epithelium and cervical epithelium. 1.2 Cellular Injury When the cells are stressed to such an extent that they are no longer able to adapt themselves, they cause cellular injury. Other than over-stressing, cell damage is also possible when cells are Achieve Page 11

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