The liver is the largest gland in the body. It’s a huge organ that sits roughly in the middle of your abdomen. It is a hugely important gland that is responsible for a wide range of metabolic and chemical reactions that are vital to living. You wouldn’t live long without a functioning liver. This article will take a looks at some of the smaller, cellular structures in the liver and what those structures do.
The liver is massively complex. Because it does so many things, it must have a correspondingly complex structure, even at the cellular level. If you were to take a slice of liver tissue and look at it under a microscope, you would see a series of criss-crossed bands of tissue. This roadwork of connective tissue serves to divide the liver in to functional groups, known as “lobules”. There are thousands of lobules in a healthy adult liver.
Lobules in the liver are “fed” by a central vein. They are (very) approximately shaped like a hexagon. Note that this is a common textbook description, but biological structures rarely take on perfectly symmetrical shapes, so don’t expect all six sides to be exactly the same size.
Each of the lobules has a series of “tubes” going in and out that are called the “portal triad”. These structures help move chemicals in and out of the lobule, along with the central vein.
If we increase the magnification of our virtual microscope, we will eventually be able to see the functional cells of the liver. These cells are called hepatocytes. They are approximately shaped like little pyramids, but again, these shapes are not perfect. Hepatocytes are connected to each other by something called an “anastomosing plate”. The plates allow the hepatocytes to “communicate” with each other and to pass chemicals back and forth very efficiently.
Because hepatocytes are primarily involved in metabolism and chemical processing, you’d expect that they would be mostly filled with organelles that serve these functions. And you’d be right. While they may not have as many mitochondria as a muscle cell, they are stuffed full of Golgi aparatus and Endoplasmic retuculum (both rough and smooth). If you aren’t familiar with these terms, do a search for the basics of cellular structure. Liver cells also store a lot of lipids and fat.
Hepatocytes must be able to make contact with the blood stream. They do this in areas known as sinusoids. Also in the sinusoids are specialized “trash collector” cells known as Kupffer Cells. These cells serve to clean up junk and swallow up foreign invaders such as bacteria and viruses. They do this by literally swallowing their target. Yummy!
One of the more important functions of the liver is to make bile. Bile is a chemical that is stored in the gallbladder and is used to help your body digest fats. Bile is made in the hepatocytes and transferred to the gallbladder in a series of channels called caniliculi. These come together to form interlobular bile ducts, and ultimately a single large bile duct.
There is obviously a lot of detail in the histology of the liver that this article cannot go in to. Medical school will spend several weeks of intense lectures on the structure and function of liver cells – making it impossible to condense this information in to a small space such as this. This article should provide a basic starting point to understanding the cells of the liver and what some of them do.