Understanding the Liver, Pancreas, and Spleen: Anatomy and Function
The Liver: Anatomy and Function
The liver is a vital organ located primarily in the right upper quadrant and epigastrium, extending into the left upper quadrant. Weighing approximately 1.5 kilograms, it features a superior diaphragmatic surface that conforms to the diaphragm and an inferior visceral surface in contact with other abdominal organs.
The upper liver is divided into right and left lobes by the falciform ligament, which attaches it to the diaphragm. On the liver’s inferior surface, grooves form an “H” shape:
- The right posterior sulcus houses the inferior vena cava.
- The right anterior groove contains the gallbladder.
- The left grooves contain ligaments, including the ligamentum teres (in the left anterior groove) and the venous ligament (ligamentum venosum or Arancio) in the left posterior sulcus.
The crossbar of the “H” marks the hilum, where the hepatic artery and other structures enter and exit the liver.
Additional lobules include the quadrate lobule (between the gallbladder and the round ligament) and the caudate lobule (between the inferior vena cava and the ligament of Arancio).
The liver attaches to the abdominal wall via the diaphragm on its upper surface. The posterior border, a thick structure, connects to the posterior abdominal cavity via the coronary ligament. The round ligament attaches to the abdominal cavity anterior to the navel.
The gastro-hepatic omentum attaches at the level of the “H”. The hepatic veins emerge at the posterior border, draining into the inferior vena cava before it enters the heart.
Bile, the liver’s excretory product, exits through the bile duct from the gallbladder. The gallbladder, pear-shaped and holding up to 50 milliliters of bile, connects to the cystic duct. The union of the cystic duct forms the common bile duct, which carries bile to the duodenum. The sphincter of Oddi controls the flow of bile into the duodenum.
Hepatic Lobules
Hepatic lobules are ovoid structures, polygonal in section, measuring approximately 2 mm wide by 1 mm long. Composed of hepatocytes, they are defined by vasculobiliary complexes at their angles, with the central vein at the axis. Liver cells are arranged in radial lamellae. Bile canaliculi, formed between hepatocyte plates, drain into perilobular bile ducts.
Arterial blood enters the lobule through arterioles from perilobular branches of the hepatic artery, providing nutrition and oxygenation. Venous blood from the portal vein connects to the central vein via intralobular sinusoids, detoxifying and phagocytizing, before draining into the hepatic veins and the inferior vena cava.
Interlobular tissue thickens to form a capsule around the liver.
The Pancreas: Anatomy and Function
The pancreas, comma-shaped, resides in the concavity of the duodenum. Its head lies within the concavity, while the tail extends towards the left retroperitoneal space (peritoneum passes ahead), attaching to the intraperitoneal spleen via the splenic-pancreas omentum.
Its primary role is to produce pancreatic juice, a digestive fluid that drains into the second portion of the duodenum. Additionally, it functions as an endocrine organ, regulating blood glucose levels.
The Spleen: Anatomy and Function
The spleen is an ovoid organ located in the left hypochondrium, positioned far back. Its convex side contacts the diaphragm, while the opposite side facilitates the entry and exit of blood vessels.