Final answer:
Microscopic subunits of the liver consisting of a central vein and responsible for blood filtration and hepatocyte access are called hepatic sinusoids.
Step-by-step explanation:
The microscopic subunits of the liver, each consisting of a central vein passing down its core, are called hepatic sinusoids. Hepatic sinusoids are crucial for liver functionality, as they provide a space where the nutrient-rich blood from the hepatic portal veins and oxygen-rich blood from hepatic arteries come into close contact with hepatocytes. These fenestrated capillaries allow hepatocytes to process nutrients, toxins, and waste materials, secreting essential proteins, lipids, and carbohydrates back into the blood or bile canaliculi as needed. Furthermore, hepatic sinusoids are home to Kupffer cells, which are star-shaped reticuloendothelial cells, playing a role in the phagocytosis of foreign materials and cellular debris.