The vascular and cellular responses of living tissue to an injury
Inflammation
Inflammation is derived from the words?
Derived from “to inflame” or “to set fire to”
Inflammation is described as-
• The vascular and cellular responses of living tissue to an injury
• A protective response that serves to destroy, dilute or wall of the injurious agent and injured tissue
A protective mechanism because protective factors such as Ab, complement and phagocytic cells from the blood stream are able to go to the site of the injured tissue in order to destroy the invader
• The reaction is similar regardless of the inciting agent, though it may vary depending on the severity and persistence of the irritant as well as some host factors (e.g. location and type of tissue)
Inflammation
Outcome of inflammation according to main description
•The outcome of inflammation is also variable, if the response is successful, healing may occur, if not, further tissue reaction which may harm the host can occur
• In order to understand many disease processes and surgical processes, one has to fully understand inflammation and its role in tissue repair and regeneration
Cardinal signs of Inflammation:
Rubor (redness)
Tumor (swelling)
Dolor (pain)
Calor (heat)
Loss of function
Purposes of the Inflammation:
a. To minimize the effect of the irritant or injury
b. To repair the damaged tissue and restore the tissue to normal
Causes of Inflammation:
Pathogenic agents e.g. bacteria, viruses, fungi, protozoa, etc.
Chemical agents or poisons
Physical agents e.g. heat, cold, trauma, irradiation
Immunologic reactions/injury
Summary of events in Acute Inflammation
1. Transient or momentary vasoconstriction of arteriole (occurs only for a few seconds to about 5 minutes)
a. Followed by increase blood flow to terminal vascular bed due to dilation of all the blood vessels in the injured area
b. Accompanied by opening of new capillary beds and venules
2. Increase permeability of the terminal vascular bed accompanied by the exudation or outflow of plasma factors into tissues = tissue swelling, retardation of blood flow and hemoconcentration in the vascular bed
3. Margination – when *(leukocytes attach to the wall of blood vessels with migration of leukocytes** and exudation of erythrocytes into the tissues
; the process that attracts cells into the tissues is known as chemotaxis
4. Phagocytosis or removal of injurious agents by leukocytes,
breakdown of necrotic tissues by phagocytes and drainage or reabsorption thru lymph vessels or into the venules
5. Repair and regeneration
a. Regeneration – when dead cells are replaced by similar cells thru mitosis of viable
b. Repair – when fibrous connective tissue replaces damaged tissue if regeneration cannot occur
c. Both a and b can occur in a tissue
when leukocytes attach to the wall of blood vessels with migration of leukocytes and exudation of erythrocytes into the tissues;
Margination
when dead cells are replaced by similar cells thru mitosis of viable
Regeneration
when fibrous connective tissue replaces damaged tissue if regeneration cannot occur
Repair
The Inflammatory process in inflammation
- Vascular response
- Cellular response
increase blood flow or hyperemia in arterioles and capillaries; increase in venous blood causing passive congestion and contributes to vasodilation
Dilation of small vessels
(Vascular response)
B. Increase permeability of small vessels probably as a result of direct damage to endothelial cells or due to loosening of their attachments to other cells
• Increase permeability and increase hydrostatic pressure due to increase blood flow = exudation of fluid and plasma factors into the tissue spaces leading to swelling of the inflamed area
- Vascular response of Inflammatory process
2 Phases of Vascular Permeability:
a. An immediate transient phase that lasts than 1 hour followed by a prolonged phase that lasts for 3-4 hours or may be longer if the stimulus persists;
b. A third phase which is delayed in onset but lasts for several days have also been observed
Early stages of inflammation are characterized by margination which is the adherence of platelets and leukocytes to the endothelium
Cellular response
Many cells are observed to line the endothelium by a process known as
pavementing
- Cellular response
The slowing down of blood flow and sludging of RBCs id due to:
a. **Hemoconcentration that results from fluid loss*((or when fluid goes into the extravascular space)
b. Increase resistance to flow = increase adherence of cells to each other and to the endothelium
The cellular response is characterized by migration of the following cells to the injured site =
a. Tissue macrophage – considered as the 1st inflammation line of defense during
• During the onset of inflammation, the macrophages present in injured tissues becomes phagocytic • They are activated by inflammatory products so that they enlarge rapidly
• The attached macrophages become mobile and active during the 1st hour of the inflammatory process
• Principal phagocytic cells responsible for completing the destruction of the irritant and clearing the necrotic and degenerating tissues in the site of inflammation
b. Neutrophils – 2nd line of defense; migrates form the blood to the tissues and capable of phagocytosis
• Leukocytes are able to migrate from blood vessels to tissues by pseudopods in the intercellular junctions of endothelial cells thus enlarging the opening to enable them to squeeze thru via diapedesis
• This will also allow RBC to pass via passive extravasation• Leukocytes are attracted to the injured tissue via chemotaxis
• There is leakage of blood from the damaged vessel wall to extravascular tissue = clot formation called hematoma or hematocyst
The process of ingestion or engulfing of particulate matter by the cell.
Phagocytosis
Formed when the cell membrane invaginates to enclose a particle.
Phagosome
Considered the most important defense system of the body.
Phagocytosis
Substances that enhance phagocytosis, they are mainly antibodies and complement components like C3b.
Opsonins
