Internal structure of liver

The liver is a vital organ in the human body, playing a crucial role in various physiological processes that are essential for maintaining homeostasis. Its internal structure is intricate and highly organized, reflecting its multifunctional nature. In this comprehensive exploration, we will delve into the anatomy of the liver, examining its macroscopic and microscopic features, as well as its functional units, blood supply, and overall significance in human health.

Internal structure of liver

Macroscopic Anatomy:

The liver is the largest internal organ in the human body, located in the upper right quadrant of the abdomen, just below the diaphragm. It has a reddish-brown color and a soft, pliable texture. The liver is divided into two main lobes: the right lobe and the left lobe. The right lobe is significantly larger than the left lobe, reflecting the asymmetry of the organ.

Moreover, each lobe is further divided into lobules, which are the basic functional units of the liver. These lobules are hexagonal in shape and are arranged around a central vein. The entire liver is encapsulated by a fibrous tissue known as Glisson's capsule, which provides structural support and protection.

Microscopic Anatomy:

Hepatic Cells and Plates:

At the microscopic level, the liver is composed of hepatocytes, the primary functional cells of the organ. Hepatocytes are polygonal in shape and are arranged in plates that radiate outward from the central vein. The arrangement of hepatocytes in plates facilitates the efficient exchange of substances between blood and liver cells.

Sinusoids:

The spaces between adjacent plates are occupied by sinusoids, which are vascular channels that carry blood through the liver. Sinusoids are lined with endothelial cells and are surrounded by hepatocytes. This intricate network allows for the exchange of nutrients, oxygen, and waste products between the blood and hepatocytes.

Kupffer Cells:

Scattered among the sinusoidal lining are Kupffer cells, specialized macrophages that play a vital role in the immune system. Kupffer cells are responsible for phagocytosing foreign particles and cellular debris, contributing to the liver's role in detoxification.

Bile Canaliculi:

Hepatocytes secrete bile, a digestive fluid that emulsifies fats. Bile is transported through a network of small ducts called bile canaliculi. These canaliculi run between adjacent hepatocytes and merge to form larger bile ducts that eventually lead to the hepatic duct.

Functional Units - Liver Lobules:

The liver lobule is the functional unit of the liver, representing a hexagonal structure centered around a central vein. Each lobule is approximately 1-2 millimeters in diameter and consists of multiple hepatic plates radiating outward from the central vein. The arrangement of hepatocytes in plates allows for efficient processing of blood and ensures that each hepatocyte has access to the sinusoidal blood supply.

Portal Triad:

At each corner of the hexagonal lobule, there is a portal triad, which consists of three main structures: a branch of the hepatic portal vein, a branch of the hepatic artery, and a bile duct. These structures provide the liver with the necessary nutrients, oxygen, and the raw materials for bile production.

Blood Supply:

The liver receives a dual blood supply from both the hepatic portal vein and the hepatic artery. The hepatic portal vein carries nutrient-rich blood from the gastrointestinal tract, providing the liver with absorbed nutrients and potentially harmful substances. In contrast, the hepatic artery delivers oxygenated blood to support the metabolic needs of hepatocytes.

These two blood supplies converge within the sinusoids, creating a unique microenvironment that allows the liver to filter and process blood efficiently. This dual blood supply is a key feature of the liver's ability to regulate nutrient levels, detoxify harmful substances, and maintain metabolic homeostasis.

Hepatic Circulation:

The hepatic circulation within the liver lobule is orchestrated to ensure optimal function. Blood entering the liver lobule flows through the sinusoids, allowing hepatocytes to extract nutrients and oxygen. As blood progresses through the sinusoids, it merges into central veins, ultimately forming the hepatic vein that carries blood out of the liver and back to the general circulation.

Functions of the Liver:

The liver performs a myriad of vital functions, reflecting its complex internal structure and cellular composition. Some of the key functions include:

1. Metabolism:

Hepatocytes are central to the metabolic activities of the liver. They regulate glucose levels by storing excess glucose as glycogen and releasing it when blood glucose levels drop. The liver is also involved in lipid metabolism, synthesizing and storing triglycerides, as well as cholesterol metabolism.

2. Detoxification:

Kupffer cells and hepatocytes work together to detoxify blood by removing and processing harmful substances. The liver metabolizes drugs, toxins, and other foreign substances, making them more water-soluble for excretion.

3. Bile Production:

Hepatocytes synthesize bile, a digestive fluid that aids in the emulsification and absorption of fats in the small intestine. Bile is transported through the bile canaliculi and bile ducts before being released into the duodenum.

4. Protein Synthesis:

The liver is a major site of protein synthesis, producing a variety of proteins, including clotting factors, albumin, and enzymes. These proteins are essential for maintaining blood clotting, osmotic pressure, and various metabolic processes.

5. Storage:

The liver serves as a storage reservoir for important substances such as vitamins, minerals, and glycogen. It stores fat-soluble vitamins (A, D, E, and K), iron, and glycogen, releasing them into the bloodstream as needed.

Liver Diseases and Disorders:

The intricate internal structure of the liver makes it susceptible to various diseases and disorders. Some common liver conditions include:

1. Cirrhosis:

Cirrhosis is a chronic liver disease characterized by the replacement of healthy liver tissue with scar tissue. This condition can result from long-term liver damage caused by factors such as chronic alcohol abuse, viral hepatitis, or fatty liver disease.

2. Hepatitis:

Hepatitis is the inflammation of the liver, often caused by viral infections (hepatitis A, B, C, etc.) or exposure to toxic substances. Chronic hepatitis can lead to more severe liver damage and contribute to conditions like cirrhosis or liver cancer.

3. Fatty Liver Disease:

Non-alcoholic fatty liver disease (NAFLD) is characterized by the accumulation of fat in liver cells. This condition is associated with obesity, diabetes, and metabolic syndrome, and it can progress to more severe forms, such as non-alcoholic steatohepatitis (NASH).

4. Liver Cancer:

Liver cancer can originate in the liver itself (primary liver cancer) or spread to the liver from other parts of the body (metastatic liver cancer). Hepatocellular carcinoma is the most common form of primary liver cancer.

Conclusion:

In conclusion, the internal structure of the liver is a marvel of biological complexity, reflecting its crucial role in maintaining homeostasis and sustaining various physiological processes. The liver's microscopic and macroscopic features, its functional units, and its intricate blood supply collectively contribute to its ability to perform a wide range of essential functions.

Understanding the internal structure of the liver is pivotal for comprehending the mechanisms underlying liver diseases and disorders. Advances in medical