Bile canaliculus

Bile Canaliculus

The bile canaliculus is a small duct within the liver that transports bile from hepatocytes to the bile ducts. The canaliculi form a complex network that allows for the efficient transport and modification of bile, a critical process in the digestion and absorption of fats.

Structure

The bile canaliculus is a thin tube, approximately 1 micrometer in diameter, that is lined by the canalicular membrane of adjacent hepatocytes. These cells are polarized, meaning that they have distinct structural and functional differences between their two surfaces. The surface that faces the canaliculus, known as the canalicular pole, contains numerous microvilli that increase the surface area for secretion and absorption.

Function

The primary function of the bile canaliculus is to transport bile from the hepatocytes, where it is produced, to the bile ducts, which carry it to the gallbladder for storage and concentration. Bile is a complex fluid that contains bile acids, cholesterol, phospholipids, and bilirubin. It plays a crucial role in the digestion and absorption of dietary fats, as well as the excretion of waste products.

The transport of bile across the canalicular membrane is an active process that requires energy. It is driven by the bile salt export pump (BSEP), a protein that is located in the canalicular membrane and pumps bile acids into the canaliculus against their concentration gradient.

Clinical significance

Defects in bile canaliculus function can lead to a variety of liver diseases. For example, mutations in the gene that encodes BSEP can cause progressive familial intrahepatic cholestasis (PFIC), a severe liver disease that often requires liver transplantation. Other conditions, such as primary biliary cholangitis and primary sclerosing cholangitis, involve inflammation and damage to the bile ducts, which can also affect the function of the bile canaliculi.

See also

• Hepatocyte
• Bile duct
• Gallbladder
• Bile
• Bile salt export pump
• Progressive familial intrahepatic cholestasis
• Primary biliary cholangitis
• Primary sclerosing cholangitis