Introduction
Inflammation is an innate component of the immune system. It is typically characterized by rubor ( redness of the affected area) and calor (warmth). It is caused by increased blood flow to the affected area and tumor (swelling). As a result of all these, an increase in the surface temperature can be seen(dolor). The extravasation of leukocytes, fluid, and plasma proteins involved in inflammation are all the result of the actions of the local microvasculature. There are two types of inflammation, acute and chronic. Acute inflammation is the response to a sudden injury in the body. On the other hand, in chronic inflammation, the body has been trying to prevent injury for some time.
What Is Inflammation?
Inflammation is the protective response of the human body to any attack by a foreign body. It isolates and destroys the foreign body that causes damage to the body and helps the tissues in the body to prepare for repair and healing. This is usually short-lived and temporary. The body returns to normal after the tissue damage has been repaired. However, in some cases, the immune system continues to attack healthy cells and destroy them. This condition is called autoimmune disease. The microvasculature plays an important role in initiating and regulating the immune response. It undergoes a variety of structural and functional changes during an inflammatory process.
What Are the Symptoms of Inflammation?
The common symptoms of inflammation can include;
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Flushed skin at the site of injury.
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Pain.
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Swelling.
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Heat.
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Loss of function.
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Redness.
The signs of inflammation are commonly defined as rubor (or redness), tumor (or swelling), calor (heat or an increase in the body temperature), and dolor (or pain). An extreme sign of inflammation can be the loss of function in the area.
How Is the Blood Vascular System Organized?
The blood vascular system is organized into two loops running in two different segments. They are the systemic and pulmonary circulation systems. Larger arteries arising from the heart give rise to several smaller arteries that supply to the various organs in the body. The arteries give rise to further branches within the organ. The smaller arteries end up as arterioles, which have their diameters in micrometers. The arterioles further branch to give rise to capillaries. They are the surface for exchanging gasses, fluids, and gasses between the blood and the tissues.
How Does the Blood Vasculature Help in Maintaining Homeostasis?
Under normal conditions, normal blood vasculature has four primary functions:
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Keeps the blood fluid.
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Regulation of perfusion in various organs.
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Preventing the inappropriate activation of leukocytes.
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Regulation of macromolecules between the blood and the tissues.
Preventing coagulation is a general function of the entire vascular system.
How Does the Blood Flow Change During an Inflammation?
The vascular blood system and lymphatics get involved when there is inflammation. There will be significant changes in the tissue blood flow when there is inflammation. The direction and magnitude of the blood flow change as the inflammation progresses. During the early stages of an inflammatory process, the blood flow to the area increases (hyperemia). This causes redness over the area. This is probably due to the action of the arterioles in response to the injury. The mast cells, macrophages, fibroblasts, parenchymal cells, and the vessel wall causes a release of vasoactive mediators like histamine, bradykinin, neuropeptides, and prostaglandins. The hyperemic response benefits the host as it helps the foreign body or the body, causing injury to be destroyed, thereby reducing the injury. The increased blood flow facilitates the delivery of leukocytes to the site of inflammation.
Studies show that in chronic inflammatory conditions, there occurs a reduction in the blood flow to the tissue rather than an increase. In inflammatory bowel diseases, intestinal microvascular perfusion increases during the active phase of the disease. On the other hand, a reduction in flow is detected in the chronically inflamed and remodeled intestine. The blood vasculature remains enlarged, hyperpermeable, and activated with high expression of adhesion molecules in chronic inflammation. This causes continuous extravasation of inflammatory cells and fluids into the inflamed tissue.
The lymphatic system also plays an essential role along with the vascular system in inflammation. It regulates the inflammatory response by transporting fluids, extravasated leukocytes, and antigen-containing cells from the inflamed tissue to the lymph nodes and other secondary lymphoid organs. The secondary lymphoid organs include the spleen, the tonsils, and some tissues in various membrane layers, like the bowels.
What Is the Role of Circulating Blood Cells?
The leukocytes produce many factors that are capable of increasing vascular permeability. The adhesion and movement of leukocytes within the inflamed blood vessels are associated with endothelial barrier dysfunction in acute and chronic inflammation. (The endothelial barrier dysfunction occurs due to stimulating inflammatory agents, activated blood cells, and other diseases).
What Is the Role of Perivascular Cells?
Mast cells in the perivascular areas also play an essential role in the endothelial barrier dysfunction accompanying inflammation. Mast cell degranulation is a common feature of inflammation. It is characterized by producing and releasing superoxide, amines like histamine and serotonin, leukotrienes, proteases, and cytokines. All of these can diminish endothelial barrier function. The microvasculature in mast cell-rich tissues (like the intestine and the lung) shows dependence on mast cells in the increased vascular permeability response to inflammation.
Conclusion
Inflammation is a part of the healing process in the body. It activates the immune system to send out cells that help to fight the foreign bodies that try to harm the body. These cells release secretions or work to destroy these foreign bodies and reduce tissue injury. There is no definite evidence of vascular remodeling in humans during chronic inflammation. Though different anti-inflammatory drugs are available, none affect the pathological vascular supply in an inflammatory process, according to recent studies. The blood vascular system helps to control tissue homeostasis. Understanding the role of blood in inflammation is still under study and requires clarity in many aspects.
