Describe the morphologic changes associated with different patterns of inflammation
Before defining the types of inflammation, I'll start by giving a general definition of inflammation. Inflammation is a non-specific response to tissue injury, in which various mediators are released that attracts various components of the immune system to come and fight off the threat.
Acute inflammation is a short-term inflammatory response. The main signs of acute inflammation are tumor (swelling), rubor (redness), calor (heat), dolor (pain), and loss of function in the inflamed area (e.g. inflamed joints are harder to move). Acute inflammation can appear in many different ways:
- Purulent/suppurative- Pus-forming.
- Abscess- Collection of pus in tissue.
- Empyema- Collection of pus in an anatomical space, such as in the pleural or pericardial cavities.
- Serous/serositis- Protein-rich exudate at serous surfaces.
- Fibrinous- Similar to serous inflammation, but with leakage and activation of large proteins such as fibrin.
- Ulcerative- Erosion of a mucosal surface.
Chronic inflammation is a longer-term response that can last over weeks or months. It may develop from acute inflammation or from some other kind of persistent damage, such as a long-term infection or long-term exposure to a toxic chemical. Chronic inflammation is characterised by infiltration of mononuclear cells, such as macrophages, lymphocytes, and plasma cells. There is also evidence of attempts to heal, such as scar tissue formation and growth of new blood vessels.
Granulomatous inflammation is a type of chronic inflammation where the infectious agent or foreign body cannot be eradicated. Granulomas are made of clusters of histiocytes (tissue macrophages) that are surrounded by lymphocytes, and sometimes giant cells (which are made of multiple macrophages fused together) as well. Granulomatous inflammation can be necrotising or non-necrotising. Necrotising granulomatous inflammation is usually associated with infections such as tuberculosis. Non-necrotising granulomatous inflammation, on the other hand, is not usually associated with inflammation.
Describe the vascular and cellular changes that occur in acute inflammation
The main steps of inflammation are recognition, recruitment, activation, and elimination. However, as not all threats can be eliminated, sometimes the elimination stage does not occur, and you get perpetuation of the response and/or progression to chronic inflammation instead.
Firstly, tissues recognise when they are damaged due to various receptors in cell membranes, circulating proteins, or various other sensors of cell damage known as the inflammasome. Once the threat has been recognised, various mediators are released that recruit leukocytes (white blood cells) to the site of injury. Various mediators also dilate blood vessels to increase blood flow, as well as increase the permeability of the blood vessels. In doing this, these mediators improve the rate at which cells migrate to the site of injury and allow these cells to enter the tissue and do their job.
In the activation phase, cells respond to the injurious stimuli directly or to the various mediators that have been released. Depending on the cell type, they can respond in different ways. For instance, phagocytic cells may eliminate harmful microbes by eating them, whereas other cells may continue to secrete mediators to coordinate the inflammatory response. If all goes well, the cause of inflammation may be eliminated and the tissue is restored to normal. If not, inflammation may be perpetuated and/or progress to chronic inflammation.
Understand the initiating events and potential sequelae of inflammation
Inflammation is a double-edged sword. We need it to protect from dangerous pathogens and toxic agents, but if left unchecked, it can cause serious problems. Just ask anyone with an autoimmune disease, where the body attacks itself, or with an allergy, in which the immune system goes apeshit over something harmless.
Explain the mechanisms by which wounds and injuries are repaired
Discuss the differences between resolution, regeneration, repair and healing (scar formation)
- Resolution- The return of tissue to its pre-injury state, albeit with possible long-term consequences. This usually only happens when the injury was mild enough to maintain most of the tissue.
- Regeneration- The regrowth of tissue to replace damaged areas.
- Repair/healing by scar formation- The growth of connective tissue to replace a damaged area. This connective tissue lacks many of the features that the original functional tissue would have had. For instance, scar tissue replacing heart muscle is unable to contract in the way that heart muscle normally would.
Discuss the systemic and local factors that participate in wound healing
There are many factors that participate in wound healing. Local factors that participate in wound healing are those related to the injury itself: a more severe injury with a poor blood supply will take longer to heal than a well-perfused small injury. Systemic factors are those related to the patient as a whole: if they have poor nutrition or have some medical condition that impacts healing (e.g. diabetes), they will take longer to heal than a well-nourished person with no medical conditions.
Describe the major cells involves in healing and repair
As far as I can see, this lecture didn't really cover this point. By the looks of things, the main cells you need are phagocytic cells (such as macrophages) to clean up the debris, and then some kind of immature cell (such as fibroblasts) to proliferate and regenerate some new tissue. Watch this space for more details, I guess...?
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