Cirrhosis definition pathology
When cells are injured or damaged, and die off, usually that dead tissue, that was previously full of living cells, becomes fibrotic, meaning it becomes thickened with heaps and heaps of protein and forms scar tissue. So, when your liver is constantly forced to process alcohol, likealcoholic liver disease, or subject to a viral attack for a long time, likeHBV, or anything else that causes a long term, or chronic, state of liver cell, or hepatocyte, destruction and inflammation, your liver can become seriously scarred
and damaged to the point where it's no longer reversible, at which point it becomes fibrotic, and,the liver, we call this process cirrhosis. Because it's usually irreversible, cirrhosis is often referred to as â€œend stageâ€� or â€œlatestageâ€� liver damage. When liver cells are injured, they start to come together and form what are called regenerative nodules. You can think of these as colonies of living liver cells. And these are one of the classic signs of cirrhosis,
and are why a cirrhotic liver is more bumpy, as opposed to a smooth, healthy liver. Also, with cirrhotic liver tissue, you'll see that,between these clumps of cells, or nodules, is fibrotic tissue and collagen. Here's a classic histology image of cirrhotic tissue, this clump of cellsthe middle is the regenerative nodule, and these blue stains surrounding it are the bands of protein from the process of fibrosis.
If we zoom out a bit and look at it with the naked eye, we'll again see these nodules, which have fibrotic protein bandsbetween. Alright, but how do these bands of fibrotic tissue form thoughé Well, fibrosis is a process mediated by these special cells called stellate cells, that sit between the sinusoid and hepatocyte, known as the perisinusoidal space. Here's a pretty basic layout of the basic functional unit of the liver, you've got the portal vein and the hepatic artery that combine into a sinusoid,
which then goes into the central vein, and these are all lined with hepatocytes, righté Along with these though, you've also got a bile duct, and all these three constitute a portal triad. So the perisinusoidal space, which literally means â€œaround the sinusoidal spaceâ€�, and stellate cells are about here. And usually,healthy tissue, these guys' main function is to store vitamin A,
and are, otherwise, consideredquiescent, or sort of dormant. When the hepatocytes are injured though, they secrete paracrine factors that â€œactivateâ€� and sort of change the stellate cells. When activated, these stellatecells lose vitamin A, proliferate, and start secreting secreting transforming growth factor beta1, or TGFbeta, which then causes them to produce collagen,