Right Liver Lobe

The right liver lobe is the larger of the two lobes by six times. The inferior and posterior surfaces are divided into four lobes by five fossae, which are arranged in the form of the letter H. The left limb of the H marks on these surfaces the division of liver into right and left lobes.

Left Liver Lobe

The left liver lobe is the smaller and flatter of the two liver lobes. The inferior and posterior surfaces are divided into four lobes by five fossae, which are arranged in the form of the letter H. The left limb of the H marks on these surfaces the division of liver into right and left lobes.

Abdominal Veins and Arteries

Veins usually carry blood straight to the atria of the heart, but those of the abdominal tissues are exceptions. These come from networks in the stomach, intestines, pancreas, and spleen, and carry blood from these organs through a "portal vein" to the liver. There, the blood enters capillarylike "hepatic sinusoids," called the "hepatic portal system." The tributaries of the portal vein include (1) the right and left "gastric veins" from the stomach; (2) the "superior mesenteric vein" from the small intestine, ascending colon, and transverse colon, and (3) the "splenic vein" from a number of merging veins from the spleen, pancreas, and part of the stomach. Its largest tributary is the "inferior mesenteric vein," which brings blood up from the descending colon, sigmoid colon, and the rectum. After passing through the portal veins of the liver, blood is carried through a series of merging vessels into the "hepatic veins." These empty into the "inferior vena cava," and return the blood into circulation. The corresponding arteries of the same names are taking oxygenated blood to these sites in paths parallel to those of the veins.

Falciform Ligament

The falciform ligament is the line of attachment that divides the liver into two parts, known as the right and left lobes.

Coronary Ligament

The coronary ligament are the folds of peritoneum connecting the posterior surface of the liver and the diaphragm.

Caudate Lobe

The caudate lobe is situated upon the dorsal surface of the right lobe bounded by the inferior vena cava, and on the left by the fissure of the ductus venosus.

Qaudrate Lobe

The qaudrate lobe is situated on the visceral surface of the right lobe to the left of the fissure for the gallbladder.

Liver (An Overview)

The liver has two major lobes and two minor lobes. Anteriorly, the right lobe is separated from the smaller left lobe by the falciform ligament. Inferiorly, the caudate lobe is near the inferior vena cava, and the quadrate lobe is adjacent to the gallbladder. The falciform ligament is responsible for attaching the liver to the anterior abdominal wall and the diaphragm by way of the coronary ligament, the upper layer of which is exposed as if the liver were to be pulled away from the diaphragm. A ligamentum teres is continuous along the free border of the falciform ligament and is a remnant of the umbilical vein of the fetus. The porta of the liver is where the hepatic artery, portal vein lymphatics, and nerves enter the liver and where the hepatic ducts exit. Although the liver is the largest internal organ of the body, it is only one to two cells thick. This is due to the fact that hepatocytes, or liver cells, are only one to two cells thick and separated from each other by large capillary spaces called sinusoids. The plate structure of the liver and high permeability of the sinusoids allow each hepatocyte to be in close contact with the blood. The hepatic plates are arranged into functional units called liver lobules. In the middle of each lobule is a central vein and at the periphery of each lobule are branches of the hepatic portal vein and hepatic artery, opening into spaces between hepatic plates. Arterial blood and portal venous blood, containing nutrient molecules absorbed in the gastrointestinal tract mix as the blood flows from the periphery of the lobule to the central vein. The central veins of the lobules will converge to form two hepatic veins which will carry blood from the liver to the inferior vena cava. Bile is produced in the liver by the hepatocytes and secreted into thin channels called bile canaliculi located within each hepatic plate. The canaliculi are drained peripherally by bile ducts which in turn drain into hepatic ducts that carry bile away from the liver. As a result, blood travels in the sinusoids and bile travels in the opposite direction so blood and bile never mix in the lobules of the liver under normal conditions. Cirrhosis, an irreversible liver disease destroys large numbers of liver lobules and replaces them with a permanent type of connective tissue from hepatocytes called regenerative nodules. These nodules don't have the plate-like structure of normal liver tissue and are consequently, less functional. Cirrhosis is often accompanied by the presence of ammonia from the hepatic portal vein on into systemic circulation. Any disease that attacks liver cells such as viral hepatitis or chemicals affecting the liver such as seen in chronic alcohol abuse may bring about sclerosis.

Gallbladder

The gallbladder is an active storage shed, which absorbs mineral salts and water received from the liver and converts it into a thick, mucus substance called "bile," to be released when food is present in the stomach. The gallbladder is a small, pear-shaped sac which is situated just below the liver and is attached to it by tissues. It stores bile and then releases it when food passes from the stomach to the duodenum (the first part of the small intestine) to help in the process of digestion. It has a capacity of around one and one-half fluid ounces. When food leaves the stomach, a secretion causes the gallbladder to contract and expel its contents into the duodenum, where the bile disperses the fats in the food into liquid. Pythagoras, the 6th Century BC Greek mathematician, believed that life is based on the four elements of earth, air, fire and water which correspond to the body's "humors": blood (hot and moist), phlegm (cold and moist), yellow bile (hot and dry) and black bile (cold and dry). The perfect or imperfect balance of these humors supposedly determined one's health and intelligence. We still speak in terms of "melancholia" (excess black bile, leading to depression) and "phlegmatic" (sluggish or impassive) and scientists have named the heavy mucus secreted in the respiratory passages - phlegm. Pythagoras was kind of a "square". Oh, come on; where's your sense of "humor"?

Bile Duct

Within the liver lobules, there are many fine "bile canals" that receive secretions from the hepatic cells. The canals of neighboring lobules unite to form larger ducts, and these converge to become the "hepatic ducts." They merge, in turn, to form the "common hepatic duct." The "common bile duct" is formed by the union of the common hepatic and the cystic ducts. It leads to the duodenum, where its exit is guarded by a sphincter muscle. This sphincter normally remains contracted until the bile is needed, so that bile collects in the common bile duct and backs up to the cystic duct. When this happens, the bile flows into the gallbladder and is stored there.

Sinusoids

The sinusoids are capillary-like vessels which the blood is conveyed to the inferior vena cava by the hepatic veins.

Inferior Vena Cava

The inferior vena cava is a large vein ascending through the abdomen. It collects blood from the hepatic veins, the lumbar veins, gonadal veins, renal veins, and phrenic veins. These vessels usually drain regions that are supplied by arteries with corresponding names. The inferior vena cava enters the heart through the right atrium.