What is bile?
Bile is a yellow to dark green liquid that consists of around 80 percent water. The remaining 20 percent or so consists mainly of bile acids, but also of other substances such as phospholipids (such as lecithin), enzymes, cholesterol, hormones, electrolytes, glycoproteins (proteins with a carbohydrate content) and waste products. It also contains metabolic breakdown products, such as bilirubin, which is produced during the breakdown of red blood cells and is responsible for the color of the secretions.
What is the function of bile?
Bile acids activate fat- and protein-splitting enzymes from the pancreas and small intestine. They emulsify the fats that have been ingested with food so that they can be broken down by the fat-splitting enzymes. With the breakdown products (free fatty acids, monoglycerides), the bile acids form so-called micelles (spherical aggregates) and thus enable their absorption, but remain in the intestine themselves and can “continue to work”.
In the lower sections of the small intestine, most of the bile acids are absorbed and returned to the liver via the portal vein (enterohepatic circulation) – they are therefore recycled to a certain extent and only need to be constantly produced in small quantities.
Where is bile produced?
Bile is produced in the liver cells (about 0.5 to 1 liter per day) as a thin secretion. This is known as liver bile. It is secreted into the tubular gaps between the cells, the so-called bile capillaries or tubules. The small tubules merge to form larger ones and ultimately lead into the common hepatic duct. This bifurcates into two branches: one opens into the gallbladder as the common bile duct. The other leads on to the duodenum, the uppermost section of the small intestine, as the large bile duct.
What problems can bile cause?
Biliary colic or high intestinal obstruction can lead to bile vomiting (cholemesis).
If the bile contains excessive amounts of cholesterol or bilirubin, these can precipitate and form “stones” (cholesterol stones, pigment stones). Such cholelithiasis can lead to further complications such as jaundice (icterus) or inflammation.
