Gallbladder

Bile (containing water and electrolytes, mucus, cholesterol, lecithin, bile acids and bilirubin) is secreted by the liver, and stored in the gall-bladder. The mucosa can reabsorb water to concentrate the bile, secrete water to dilute it and also acidify it by secretion of hydrogen ions. The dilution of the bile occurs during periods of bile expulsion when there is activity of the smooth muscle. This activity can be initiated by hormones such as CCK and enhanced by vagal activity. Concentration of bile by reabsorption of water seems to occur during periods of low contractile activity. Hydrogen ion secretion can be enhanced by activity in the sympathetic nerves. Release of bile into the duodenum is governed by a complex set of controls involving the secretion of bile by the liver, the activity of the smooth muscle in the gallbladder and the contractions and relaxations of the sphincter of Oddi. Hormones and neuronal pathways are involved (see Fig. 9.29).

Bile acids

Local pathway

Bile acids

Local pathway

Fig. 9.29 Control of the bile flow into the duodenum. The secretion of bile from the liver is dependent on the extraction of bile from the blood and de novo synthesis from cholesterol by the hepatocytes, and also the secretion of electrolytes and water triggered by secretin (released into the blood in response to acids in the duodenum). The gallbladder contracts in response to vagal stimulation, and to the neuronal pathways involved in the migrating motor complex (MMC). It can also be inhibited, for instance via a pancreatic polypeptide (PP). CCK secreted from the upper small intestine in response to bile acids and products of digestion also constricts the gall-bladder and dilates the sphincter of Oddi. There is evidence for a local reflex from the gall-bladder that is involved with sphincter relaxation.

Fig. 9.29 Control of the bile flow into the duodenum. The secretion of bile from the liver is dependent on the extraction of bile from the blood and de novo synthesis from cholesterol by the hepatocytes, and also the secretion of electrolytes and water triggered by secretin (released into the blood in response to acids in the duodenum). The gallbladder contracts in response to vagal stimulation, and to the neuronal pathways involved in the migrating motor complex (MMC). It can also be inhibited, for instance via a pancreatic polypeptide (PP). CCK secreted from the upper small intestine in response to bile acids and products of digestion also constricts the gall-bladder and dilates the sphincter of Oddi. There is evidence for a local reflex from the gall-bladder that is involved with sphincter relaxation.

Relaxation Audio Sounds Relaxation

Relaxation Audio Sounds Relaxation

This is an audio all about guiding you to relaxation. This is a Relaxation Audio Sounds with sounds called Relaxation.

Get My Free MP3 Audio


Post a comment