Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 4 Injury, Inflammation, and Repair Review of Structure and Function • The body is capable of undergoing dynamic changes to carry out body functions. • Each component of a cell carries out a specific, necessary function. Major Cell Types • Epithelial cells • Connective tissue cells • Nerve cells • Muscle cells Events Following Injury • Necrosis or sublethal cell injury – Death or damage of cells due to injury • Inflammation – The vascular and cellular response attempting to limit damage and remove necrotic tissue Events Following Injury • Repair – The body’s attempt to replace dead cells Necrosis vs. Sublethal • Necrosis is the irreversible death of the cell • Sublethal injury indicates the cell is capable of at least some recovery. Acute Injury and Necrosis • The most common cause of acute injury is a reduced level of oxygen. • Cells that are very active require more oxygen, and will suffer ill effects first. • Localized hypoxia due to poor blood flow (not decreased oxygen levels) is called ischemia. If this becomes more severe, ischemia progresses to infarct. Causes of ischemia or necrosis • Thrombus • Embolus • Trauma • Infections Causes of ischemia or necrosis • Immunologic Reactions • Coagulation, liquefaction, caseous, gangrenous, and enzymatic fat necrosis Chronic Injury • Chronic injury may cause atrophy or accumulation of material within cells. • Atrophy – Senile – Disuse – Pressure – Denervation – Endocrine Chronic Injury • Accumulation – Fatty Change – Adiposity – Glycogen Storage – Hyaline – Metastatic Calcification – Hemosiderosis – Hemochromatosis Acute Inflammation • Vascular response: Increased blood flow to the injured area, and the vasculature becomes more permeable. • Cellular response: Movement of leukocytes, predominantly neutrophils and monocytes from the blood into the tissue. Chemical Mediators • The inflammatory reaction is initiated by local factors in the injured tissue • Histamine • Vasoactive amines Chemical Systems • There are three chemical systems at work together during the inflammatory reaction – Kinin system – Complement system – Coagulation system Chronic Inflammation • Chronic inflammation causes histologic changes different from acute inflammation. Granulomatous Inflammation • Characterized by focal collections of closely packed, plump macrophages, it is in response to indigestible organisms. • The object is too large to be broken down, so macrophages engulf the offender to keep it from moving elsewhere. • Examples include: TB, fungal infections, and sarcoidosis Transudates and Exudates • Transudate – Caused by increased hydrostatic pressure or decreased osmotic pressure – These have a low protein count • Exudate – Caused by increased oncotic pressure – These have a high protein count Repair • Regeneration – This is the desired repair, as replacement of destroyed tissue is with similar tissue, and normal function is restored. Repair • Fibrous connective tissue repair – This is less desired, as the damaged area is replaced with fibrous tissue, and normal function is not restored. – The goal of this repair is to provide a bridge across the damaged area.