Problem 70 - Objective Biology for NEET

Question

Structural and functional unit of liver is (a) Cystic duct (b) Hepatocyte (c) Hepatic lobules (d) Kupffer cells

Step-by-Step Solution

Answer

The structural and functional unit of the liver is the Hepatocyte (option b).

Step 1: Understand the Terminology

It's vital to comprehend the meaning of each presented option:(a) Cystic duct - This is a part of the biliary system that carries bile from the gallbladder. It doesn't refer to a liver structure though.(b) Hepatocyte - These are the main cells of the liver, performing most of the liver's functions.(c) Hepatic lobules - The liver is composed of many hepatic lobules; however, they are more of an anatomical rather than a functional unit.(d) Kupffer cells - These cells participate in the liver's immune functions. They play a role, but they are not the main functional and structural units.

Step 2: Identify the Correct Option

The question asks about the main structural and functional unit of the liver. Hepatocytes are the main cells of the liver, making up 70-85% of the organ's mass. They are responsible for a large range of functions such as protein synthesis, detoxification, and production of bile. Therefore, option (b) Hepatocyte is the correct answer.

Key Concepts

Hepatocytes

Hepatocytes are the powerhouse cells of the liver. They account for 70-85% of the liver's mass and perform many of its crucial functions. These cells are polygonal, making them fit together like a mosaic inside the liver. This structure allows them to execute multiple tasks efficiently. Hepatocytes are heavily involved in protein synthesis. They produce many proteins essential for blood clotting, such as albumin and fibrinogen. Additionally, they play a significant role in detoxification by metabolizing drugs and toxins. Another vital function of hepatocytes is the production of bile. This greenish secretion aids in breaking down fats in our diet.
Besides these roles, hepatocytes store vital nutrients such as glycogen, vitamins, and minerals, releasing them into the bloodstream as needed. This ensures that the body remains in balance both during fasting and feeding periods.
Given these extensive functions, hepatocytes are indeed the main structural and functional units of the liver.

Hepatic Lobules

Hepatic lobules are the basic building blocks of the liver's structure. Each lobule is hexagonal and comprised of stacks of hepatocytes radiating outward from a central vein. It can be visualized as a honeycomb within the liver. This geometric arrangement ensures that each hepatocyte is in contact with a blood supply.
The organization in lobules permits efficient processing of blood components. Blood flows from the periphery of the lobule toward the central vein, passing by hepatocytes in the process. This flow pattern allows hepatocytes to filter the blood, extract nutrients, and remove toxins.
While hepatic lobules provide the structural framework of the liver, they are considered more of an anatomical unit rather than a functional one. This means that while they house the functional cells (hepatocytes), themselves aren't directly performing the liver's jobs but rather facilitating the work environment.

Kupffer Cells

Kupffer cells are specialized immune cells within the liver, part of the body's defense mechanism. They reside inside the blood-filled spaces of the liver's lobules and are essential in protecting the liver from pathogens that enter via the portal vein.
These cells have a few specific duties:

• Phagocytosis: They engulf and destroy bacteria, dead cells, and other debris in the blood.
• Immune response: Kupffer cells stimulate other immune cells to activate an adaptive immune response when needed.
• Cytokine production: They can release signaling molecules that modulate immune functions and inflammation.

Although Kupffer cells are crucial for the liver's immune defense, they are not considered the main structural or functional units of the liver like hepatocytes. Instead, they support the liver by keeping it free from infection and contributing to its overall health and resilience.