![]() Development of the biliary tree begins at the hilus and spreads outward to reach the subcapsular zone over time. The hepatic diverticulum is also the origin of the biliary epithelium. The gallbladder and the cystic duct arise from the caudal part of the hepatic diverticulum. Thus the essential sinusoidal arrangement of the liver is established very early in development. The primitive epithelial cells are arranged in close approximation with the vessels that form the vitelline venous plexus, a complex of vessels that drain the yolk sac. Primitive epithelial cells of the hepatic diverticulum extend into the adjacent mesenchymal stroma of the septum transversum, a sheet of cells that incompletely separates the pericardial and peritoneal cavity and that will develop into the connective tissue of the liver. The embryonic origin of the liver is an out-pouching of the embryonic endoderm forming the duodenum termed the hepatic diverticulum or the liver bud. As such, hepatic disorders have far-reaching consequences, given the dependence of other organs on the metabolic function of the liver. The liver also functions as an important organ of the innate immune system, integrated into the complex system of defense against foreign macromolecules. The liver plays a central role in processing dietary carbohydrates, lipids, amino acids, and vitamins in the synthesis and turnover of most plasma proteins and in the detoxification and biliary excretion of endogenous wastes and xenobiotic compounds. Liver injury or neoplasia foretells a poor future for many pharmaceuticals in development. The practice is continued in a fashion today. This interest is captured in a Biblical quote from Ezekiel 21β:β21, βFor the king of Babylon stands at the parting of the way, at the head of the two ways, to use divination he shakes the arrows, he consults the household idols, he looks at the liver.β Hepatoscopy was continued by the Greeks, Etruscans, and the Romans. In ancient Mesopotamia and Babylonia, the liver was used to divine the future using a technique termed hepatoscopy. However high our regard for the liver, it is dwarfed by the perspective of ancient civilizations that regarded the liver as the seat of life and window to the future. It is the guardian of homeostasis, the epicenter of the body's metabolic capability, a massive filter detoxifying the portal blood releasing cleansed blood to the systemic circulation, and a lymphoid organ protecting against infection. From a contemporary perspective, the liver is a marvel of biology.
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