Hepatocytes, which are liver parenchymal cells, secrete bile.
Bile secretion is a critical function of the liver and is essential for digestion and absorption of fats and fat-soluble vitamins in the small intestine. This secretion isn't a simple process; it involves the coordinated activity of specific transport proteins located on different surfaces of the hepatocyte.
Bile Secretion Process:
The secretion process can be broken down as follows:
- Solute Uptake: At the basolateral (sinusoidal) membrane of the hepatocyte (the side facing the bloodstream), various transport proteins facilitate the uptake of bile acids, organic anions, and other solutes from the blood into the cell.
- Intracellular Transport: Once inside the hepatocyte, these substances are transported within the cell.
- Bile Excretion: At the apical (canalicular) membrane, which forms the bile canaliculus (a small duct), different transport proteins excrete the bile acids, organic anions, phospholipids, cholesterol, and other components of bile into the bile canaliculus. This requires energy. The canaliculi merge into larger bile ducts, which eventually drain into the gallbladder for storage or directly into the small intestine.
The Role of Hepatocytes:
Hepatocytes are highly specialized cells, making up about 70-85% of the liver's mass. Their structure and function are specifically adapted for bile secretion. They possess a large number of mitochondria to provide the energy required for active transport processes involved in bile secretion.
Summary
Therefore, the answer to the question is unequivocally the hepatocytes, the parenchymal cells of the liver, are the cells that secrete bile. They achieve this through a complex and highly regulated process involving specialized transport proteins.
