Pathophysiology

Pathophysiology Study Guide

Chapter 1: Cell Biology, Mechanisms of Cell Injury, and Neoplasia Objectives 1. Understand the basic biological characteristics of a cell when adapting to injury in the body. 2. Describe the consequences of adaption and injury in cells. 3. Identify genetic disorders and associated issues. 4. Explain Neoplasia and its mechanism and tumor markers. 1.1 Cellular Adaptation Cells actively participate in the environment by altering their structure as a response to the extracellular stresses and change in demands of the environment. Cells maintain the intracellular locale and range within a narrow range of physiological constraints known as homeostasis. When encountered by physiologic environmental stresses, the cells tend to undergo adaptation and gain a new steady state. Adaptation happens by way of changes in the number, size, metabolic activity, functionality, and phenotype of the cell. Adaptations can be due to physiologic or pathologic parameters. Physiological adaptation happens when endogenous hormones or chemical mediators are stimulated, while pathologic adaptation occurs by fostering change in the function or structure of a cell as a response to stress when escaping injury. Cells can undertake different adaptations as covered below. Atrophy Atrophy is the adaptation of the cell in which the substance of the cell is lost, and the cells shrink from their original size. When a large number of cells undergo atrophy, it causes the whole tissue or organ to reduce in size, known as an atrophic organ. Atrophy is caused by a decrease in the workload, loss of innervation, loss of endocrine stimulation, inadequate supply of blood, improper nutrition, and aging of cells. These factors impact metabolism, leading to the fall of protein synthesis, which encourages degradation of protein in the cells. When these factors are triggered, ubiquitin ligases are activated, which transfers small peptide ubiquitin in numbers to the proteins of the cells; that causes the protein cells to degrade. Hence, it can be said that Ubiquitin- proteasome pathway is involved in the degradation of proteins in cells. Hypertrophy Unlike atrophy, hypertrophy is cell adaptation in the form of an increase in the size of the cells. In this case, the cells enlarge due to increases in the structural proteins and organelles. Hypertrophy can be caused by either physiological or pathological parameters in cells. An example of physiologic hypertrophy is the development of rippled physique in an avid weightlifter due to extended workout. In contrast, when the heart of an individual enlarges due to hypertension or disease in the aortic value, it is due to pathologic hypertrophy.

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