5.20
Sirroz II: Patofizyoloji
Sirroz, uzun süren iltihaplanma, aşırı fibrotik yeniden yapılanma ve rejenerasyonun bozulmasıyla oluşan ilerleyici kronik karaciğer hasarıdır. Zamanla…
Sirroz, tekrarlayan karaciğer hasarıyla başlar ve bu da üç ana süreci tetikler: iltihap, bağışıklık sistemi aktivasyonu ve hücre ölümü.
Bu süreçler birlikte ilerleyici karaciğer hasarına yol açar.
İltihaplanma, bağışıklık hücrelerini karaciğere çeker ve tümör nekroz faktörü-alfa ve interlökin-1 gibi inflamatuar sitokinlerin salınımına yol açar.
Bu sitokinler, fibrozun ana itici kaynağı olan transformasyon büyüme faktörü-betanın salınımını uyarır.
Bağışıklık sistemi aktivasyonu, hepatik yıldız hücrelerinin aktive olmasını ve fazla kollajen ile ekstrasellüler matriks proteinleri üretmesini tetikler.
Sürekli aktivasyon, karaciğer dokusunda yoğun lifli bantların birikmesine yol açar, bu da karaciğerin normal yapısını bozur ve kan akışını engeller.
Bu değişikliklerle birlikte hepatosit apoptozu ve nekrozu da ortaya çıkar ve fibroz ilerledikçe düzensiz yenilenmeye yol açar.
Bu düzensiz rejenerasyon, yoğun fibrotik doku ile çevrili karaciğer hücrelerinin nodüllerine yol açar.
Ortaya çıkan bozulma, portal kan akışına karşı direnci artırır ve portal hipertansiyona neden olur.
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Q1: What three main processes drive cirrhosis development?
Cirrhosis develops through inflammation, immune system activation, and hepatocyte death. Inflammation recruits immune cells that release cytokines like tumor necrosis factor-alpha and interleukin-1, triggering transforming growth factor-beta production. These processes activate hepatic stellate cells, stimulate collagen production, and cause liver cell death, collectively driving progressive liver damage and fibrosis.
Q2: How do hepatic stellate cells contribute to cirrhosis?
Hepatic stellate cells normally store vitamin A in a quiescent state. When activated by inflammatory signals, they transform into myofibroblasts and produce excess collagen and extracellular matrix proteins. Continuous activation leads to dense fibrous tissue accumulation that replaces normal liver tissue, distorting the liver's architecture and impairing its function.
Q3: What happens to the liver's structure as fibrosis progresses?
As fibrosis progresses, dense fibrous bands accumulate within liver tissue, distorting normal architecture. Hepatocyte death triggers disorganized regeneration, creating regenerative nodules—clusters of liver cells surrounded by fibrous tissue. These nodules further distort vascular and biliary structures, increasing resistance to portal blood flow and leading to portal hypertension.
Q4: How does cirrhosis lead to portal hypertension?
Fibrosis and regenerative nodules in the liver distort normal vascular architecture, increasing resistance to portal blood flow. This elevated pressure in the portal vein causes portal hypertension, which can trigger serious complications including ascites, splenomegaly, and bleeding from esophageal or gastric varices.
Q5: What role does inflammation play in cirrhosis pathophysiology?
Chronic liver injury triggers inflammation that recruits immune cells and promotes oxidative stress and reactive oxygen species production. Inflammatory cytokines damage liver tissue, disrupt cellular balance, and initiate fibrogenesis. This sustained inflammation accelerates hepatocyte injury and perpetuates the cycle of liver damage and fibrotic remodeling.
Q6: How does impaired liver regeneration affect cirrhosis progression?
Hepatocyte apoptosis and necrosis accelerate liver damage, prompting regeneration attempts. However, surrounding fibrosis disrupts this regenerative process, resulting in disorganized regeneration and regenerative nodules rather than normal tissue repair. This impaired regeneration perpetuates structural distortion and progressive functional decline in the liver.
Q7: What metabolic complications can result from advanced cirrhosis?
Advanced cirrhosis reduces the liver's ability to detoxify substances, allowing toxins like ammonia to accumulate and cause hepatic encephalopathy. The liver's diminished metabolic capacity also leads to kidney dysfunction, hormonal problems, and potential multi-organ failure in severe cases of decompensated cirrhosis.