The primordium of the liver, gall bladder and biliary duct system appears from the foregut during the 4th week of the development. The liver primordium, called hepatic diverticulum or liver bud, appears in' the form of an outgrowth from the ventral wall of the
caudal part of the foregut (future duodenum). As the duodenal loop is formed, the hepatic diverticulum is seen to be located at the apex of this loop. The hepatic diverticulum grows ventrally and upwards toward the sep- i turn transversum. As it reaches the | septum transversum, the hepatic diver-ticulum divides into two parts: (1) a larger cranial part called pars hepatica, from which the liver and intrahepatic biliary ducts develop, and (2) a smaller caudal part known, as pars cystica, which gives rise to the gall bladder and cystic duct.