liver the only Organ that can Regenerate
肝再生是一个高度受控的过程，由高度冗余信号的复杂网络调节。已知几种信号通路刺激肝脏再生，包括细胞因子，生长因子，激素和核受体。在体内发现并研究了一些天然多组分肝再生物质 - 肝刺激物质，肝再生组，肝脏再生增强剂。
The liver is the only internal organ that can regenerate itself. In fact, you can lose up to 75 percent of your liver, and the remaining parts can regenerate itself into a whole liver again. Amazing stuff.
Liver regeneration is the process by which the liver is able to replace lost liver tissue from growth from the remaining tissue. The liver is the only visceral organ that possesses the capacity to regenerate. The liver can regenerate after either surgical removal or after chemical injury.It is known that as little as 25% of the original liver mass can regenerate back to its full size.The process of regeneration in mammals is mainly compensatory growth because only the mass of the liver is replaced, not the shape. However, in lower species such as fish, both liver size and shape can be replaced.
Liver regeneration involves replication of the liver cells, mainly hepatocytes, followed by other cells such as biliary epithelial cells and sinusoidal endothelial cells. Once cell proliferation is completed, the newly divided cells undergo restructuring, angiogenesis and reformation of extracellular matrix to complete the regeneration process. In most cases, liver function is only partially affected during liver regeneration. Whereas certain specialized functions such as drug metabolism decrease, many other primary functions such as albumin and bile production are not substantially affected.
Liver regeneration is a highly controlled process regulated by a complex network on highly redundant signals. Several signaling pathways are known to stimulate regeneration in the liver including cytokines, growth factors, hormones, and nuclear receptors. Discovered and studying in vivo some natural multicomponent liver regeneration substances – hepatic stimulator substance, hepatic regeneration set, augmenter of liver regeneration.
The ability for the liver to regenerate is central to liver homeostasis. Because the liver is the main site of drug detoxification, it is exposed to many chemicals in the body which may potentially induce cell death and injury. The liver can regenerate damaged tissue rapidly thereby preventing its own failure. However, a predictor of the true speed of liver regeneration depends on whether Interleukin 6 has overexpression. Liver regeneration is also critical for patients of liver diseases where the partial removal of the liver due to fibrosis or tumor is a common therapy that utilizes the ability of the remaining liver to generate back.
Two main types of models are used to study liver regeneration, including surgical removal, also referred to as partial hepatectomy (PHX), and chemical-induced liver damage. Whereas the mechanisms and kinetics of liver regeneration in these two models are different, many of the same signaling pathways stimulate liver regeneration in both pathways.
肝脏容易受缺氧的影响-肝脏的高代谢活性导致~1mL / g / 分钟的高灌注速率。在休息条件下，这大约是身体总血液供应的四分之一。肝动脉的富氧血液占总肝脏灌注的四分之一，在需氧量过大的情况下可能会大幅增加。复杂的血液供应使肝脏极易受到急性循环障碍的影响。肝损伤的严重程度和模式都取决于被动充血和灌注减少的相对贡献。
Liver has high demand on oxygen.
The high metabolic activity of the liver results in a high perfusion rate of ∼1 mL/g/min. Under resting conditions, this is about a quarter of the bodýs total blood supply. The oxygen-rich blood of the hepatic artery contributes to about a quarter of the total liver perfusion that may rise substantially under conditions of excessive oxygen demand. The complex blood supply makes the liver extraordinarily vulnerable to acute circulatory disturbances. Both the severity and the pattern of hepatic injury depend on the relative contribution of passive congestion and diminished perfusion.
Hypoxic Liver Injury
Hypoxic liver injury is defined as a massive, but transient, increase in serum transaminase levels due to an imbalance between hepatic oxygen supply and demand in the absence of other acute causes of liver damage. It typically occurs in elderly individuals with right-sided congestive heart failure and low cardiac output. Precipitating factors include arrhythmias or pulmonary edema. Symptoms include weakness, shortness of breath, and right upper quadrant pain. Less commonly, hypoxic liver injury is seen in patients with severe hypoxemia or septic shock. Characteristically, the transaminase level is elevated 20-fold but normalizes rapidly over several days. Imaging studies reveal hypoechoic or hypodense lesions that resolve completely with reversal of the initiating event. Treatment and prognosis depend on the underlying disease.
肝门静脉的血液是脱氧血液。通过肠道和脾脏的所有血液都通过肝门静脉输送到肝脏进行解毒。 肝脏还接收来自肝动脉的动脉血，携带氧气。 流向肝脏的血液是独特的，因为它接受氧合血液和脱氧血液。因此，门静脉血液的pO2和灌注压低于身体的其他器官。血液从门静脉的分支通过称为血窦的肝细胞“板”之间的空腔。血液也从肝动脉的分支流出并混入血窦中以向肝细胞供应氧气。这种混合物通过血窦渗透并收集在中央静脉中，其排入肝静脉。肝静脉随后排入下腔静脉。
肝脏由60~65％的实质细胞，即肝细胞和30％至35％的非实质细胞组成，即枯否细胞（Kupffer cell, KC)，肝星状细胞（HSC）和肝窦内皮细胞（LSECs）。