Inflammation Self Note PDF

INFLAMATION Major Components of Acute Inflammation Acute inflammation is characterized by three major components: dilation of small blood vessels, increased vascular permeability, and emigration of leukocytes. These components work together to respond to injurious agents effectively. Vasodilation:...

INFLAMATION Major Components of Acute Inflammation Acute inflammation is characterized by three major components: dilation of small blood vessels, increased vascular permeability, and emigration of leukocytes. These components work together to respond to injurious agents effectively. Vasodilation: Following injury, small blood vessels dilate due to the action of mediators like histamine, leading to increased blood flow. This is responsible for the classic signs of inflammation, including heat and redness at the affected site 2. Increased Vascular Permeability: This process allows plasma proteins and leukocytes to exit the circulation and enter the tissue. Vascular permeability is enhanced by mediators such as histamine and bradykinin, leading to the exudation of fluid rich in proteins into extravascular spaces. This results in edema, which is an accumulation of fluid in tissues 23. Emigration of Leukocytes: After the initial vascular changes, leukocytes adhere to the endothelium and migrate through the vascular wall into the interstitial tissue. This migration is a multi-step process involving rolling, adhesion, and transmigration, facilitated by various adhesion molecules and chemokines 45. Blood Vessel Reactions in Acute Inflammation The reaction of blood vessels during acute inflammation includes significant changes in blood flow and permeability designed to enhance the movement of immune cells to the site of injury. Vasodilation Initiation: Immediately after an injury, vasodilation occurs, primarily involving arterioles which results in an increased capacity and flow of blood to the inflamed area, leading to redness and warmth 3. Changes in Blood Flow: Due to vasodilation, blood flow becomes slower (stasis), allowing leukocytes like neutrophils to accumulate along the endothelial lining, preparing them to exit into the tissue 36. Increased Permeability Mechanisms: There are several mechanisms that cause increased permeability, including the contraction of endothelial cells, direct endothelial injury, and increased transport of fluids and proteins. These lead to fluid leakage and ultimately edema 34. Leukocyte Involvement in Acute Inflammation Leukocytes play a crucial role in the inflammatory response by mobilizing to eliminate pathogens and assist in tissue repair. Types of Leukocytes: Initially, neutrophils are the predominant leukocytes, arriving at the injury site within the first 6 to 24 hours. They are eventually replaced by monocytes, which can survive longer and aid in tissue healing 45. Recruitment and Migration: The recruitment of leukocytes from the bloodstream to the site of inflammation involves chemotactic signals. This process includes stages of rolling on the endothelium, firm adhesion, and finally transmigration, allowing leukocytes to reach the inflamed tissue 56. Functional Role of Leukocytes: Once they arrive, leukocytes perform crucial functions such as phagocytosis of microbes and debris and releasing growth factors that promote tissue repair. However, an overly aggressive leukocyte response can also lead to tissue damage and prolonged inflammation 34. In summary, acute inflammation involves a coordinated response characterized by vascular changes, increased permeability, and the recruitment of leukocytes, all aimed at protecting the host and facilitating repair of damaged tissue 2. PEMULIHAN The process of tissue repair consists of different types of reactions and mechanisms, which can be broadly categorized into two main types: regeneration and scar formation. Here’s a detailed identification of the types of recovery reactions, mechanisms of tissue regeneration, and recovery through connective tissue deposition: Types of Recovery Reactions 1.​ Regeneration: This reaction involves the restoration of tissue architecture and function by the proliferation of residual cells that survived the injury, along with tissue stem cells. It primarily occurs in tissues that can replace their lost components effectively, such as epithelial tissues and some parenchymal organs, like the liver. 2.​ Scar Formation (Connective Tissue Deposition): When regeneration is not possible, especially if the tissue is severely damaged or if it includes non-dividing cells, repair occurs through the deposition of connective tissue. This processing leads to scar formation, which does not restore normal architecture but provides structural stability to the injured tissue. Mechanisms of Tissue Regeneration 1.​ Cell Proliferation: Critical to regeneration, this involves the division of surviving cells and tissue stem cells, stimulated by growth factors and the integrity of the extracellular matrix (ECM). Key cell types involved include: 2.​ Labile tissues: Continuously dividing cells like hematopoietic stem cells and surface epithelial cells can regenerate effectively.  3.​ Stable tissues: These cells, like those in the liver and kidney, are quiescent but can proliferate in response to injury, although their regenerative capacity is limited. 4.​ Permanent tissues: Cells in this category, such as neurons and cardiac muscle cells, are terminally differentiated and typically do not regenerate, leading to scar formation when injured. 5.​ Stem Cell Activation: Tissue stem cells play an essential role in regeneration. When injuries occur, signaling from the injury site activates quiescent stem cells to proliferate and differentiate, contributing to tissue repair. Recovery Through Connective Tissue Deposition 1.​ Formation of Granulation Tissue: This initial step in scar formation involves the migration and proliferation of fibroblasts along with the deposition of loose connective tissue and new blood vessels, providing the framework for further repair. 2.​ Remodeling of the Connective Tissue: Following granulation tissue formation, the repair process involves maturation and reorganization, leading to a stable scar. This process includes increased collagen deposition and structural modifications to strength the scar tissue. Key Growth Factors: Several growth factors, including TGF-β, PDGF, and others, play crucial roles in stimulating fibroblast proliferation and connective tissue synthesis during the repair process. Both regeneration and connective tissue deposition are complex processes that involve delicate balance and interactions among different cell types and extracellular matrix components.