5.4
炎症反応I：血管と細胞
炎症反応は、細菌、外傷、毒素、熱による感染、損傷、または刺激からの身体の防御です。炎症は、病原体を見つけて破壊し、損傷した組織要素を体を癒すために除去するのに役立ちます。この初期段階では、液体、血液製品、栄養素が傷ついた部位に移動し、赤み、熱、腫れ、痛み、機能の喪失が生じます。さらに、全身性の炎症の…
炎症反応は、感染、損傷、または刺激に対する体の防御メカニズムです。
それは、数日または数週間続く急性のものもあれば、数か月から数年続く慢性のものもあります。
炎症は、病原体を特定して破壊し、損傷した組織要素を取り除き、体が治癒できるようにします。
この応答は、血管レベルと細胞レベルで見られます。どちらも急性炎症過程の重要な構成要素です。
血管段階では、損傷部位の近くの小さな血管が最初に収縮して失血を防ぎます。
その領域に血液を供給する細動脈と細静脈が拡張し、血流が増加し、局所的な発赤と熱を引き起こします。
さらに、ヒスタミン、ブラジキニン、プロスタグランジンなどの細胞メディエーターが損傷領域に放出されると、タンパク質や免疫細胞が豊富な液体に対する血管透過性が高まり、腫れ、痛み、機能喪失を引き起こします。
細胞期では、白血球(WBC)が血管を通過して損傷部位に急いで到達し、全体的なWBC数が増加します。
好中球や単球などの白血球は、病原体を飲み込み、細胞の破片や異物を摂取します。病原体食作用の結果として、発熱物質が放出され、発熱を引き起こします。
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Q1: What is the inflammatory response and why does the body trigger it?
The inflammatory response is a defense mechanism against infection, injury, or irritation from bacteria, trauma, toxins, or heat. It helps locate and destroy pathogens while removing damaged tissue elements to promote healing. This response occurs at both vascular and cellular levels, with fluid, blood products, and nutrients migrating to the injured area, resulting in redness, heat, swelling, pain, and loss of function.
Q2: What happens to blood vessels during the vascular stage of inflammation?
During the vascular stage, small blood vessels near the injury site initially constrict to prevent blood loss. The arterioles and venules then dilate, increasing blood flow and causing local redness and heat. Cell mediators like histamine and bradykinin are released, increasing vascular permeability and allowing protein-rich fluids to flow into the area, causing swelling and pain.
Q3: How do white blood cells respond during the cellular stage of inflammation?
During the cellular stage, white blood cells, including neutrophils and monocytes, pass through blood vessels and rush to the injury site, increasing overall WBC count. These cells engulf pathogens through phagocytosis and ingest cell debris and foreign material. This phagocytic activity releases pyrogens from bacterial cells, which trigger fever as part of the systemic inflammatory response.
Q4: What role do cell mediators play in the inflammatory response?
Cell mediators such as histamine, bradykinin, and prostaglandins are released in the injured area during inflammation. These mediators increase vascular permeability, allowing protein- and immune-cell-rich fluids to escape blood vessels and enter surrounding tissue. This fluid accumulation causes the characteristic swelling, pain, and temporary loss of function associated with acute inflammation.
Q5: How long can inflammation last and what are the different types?
Inflammation can be acute, lasting days or weeks, or chronic, lasting several months to years. Acute inflammation is the initial response to injury or infection, characterized by vascular and cellular changes. Chronic inflammation represents a prolonged response when the body cannot fully resolve the initial insult, potentially leading to tissue damage and systemic complications.
Q6: What systemic signs indicate that inflammation is occurring throughout the body?
Systemic inflammation produces signs beyond the local injury site, including fever, increased white blood cell count, malaise, anorexia, nausea, and vomiting. Lymph node enlargement may also occur as lymphoid tissues respond to infection. In severe cases, organ failure can develop, indicating that the inflammatory response has become widespread and potentially harmful.
Q7: Why does fever develop as part of the inflammatory response?
Fever develops when white blood cells engulf pathogens through phagocytosis during the cellular stage of inflammation. This phagocytic activity releases pyrogens from bacterial cells, which are fever-inducing substances. Pyrogens circulate through the bloodstream and act on the body's temperature-regulating center, raising the set point and causing fever as part of the systemic inflammatory defense.