Filling And Emptying Of Gallbladder
Usually, the sphincter of Oddi is closed during fasting and the pressure in the biliary system is only 7 cm H2O. Because of this pressure, the bile from liver enters the gallbladder.
While taking food or when chyme enters the intestine, gallbladder contracts along with relaxation of sphincter of Oddi. Now, the pressure increases to about 20 cm H2O. Because of the increase in pressure, the bile from gallbladder enters the intestine. Contraction of gallbladder is influenced by neural and hormonal factors:
1- Neural Factor:
stimulation of parasympathetic nerve (vagus) causes of gallbladder by releasing acetylcholine. The vagal stimulation occurs during the cephalic phase and gastric phase of gastric secretion.
2- Hormonal Factor:
When a fatty chyme enters the intestine from stomach, the intestine secretes the cholecystokinin, which causes contraction of the gallbladder.