消化辅助器官

Accessory digestive organs secrete enzymes and other substances into the primary digestive tract to facilitate digestion. The first of these are the salivary glands in the mouth that secrete amylase. This enzyme starts the breakdown of starches and other carbohydrates.

The remaining organs secrete digestive enzymes into the duodenum where most digestion occurs. The liver and gallbladder work in tandem to distribute bile, a substance produced by the liver but stored and released by the gallbladder. Bile is a concoction of water, bile salts, cholesterol, and bilirubin, a waste product of hemoglobin breakdown.

Bile salts are both hydrophobic and hydrophilic, which helps to emulsify large globules of fat into smaller ones.

Lipase from the pancreas can then hydrolyze the dietary fats into fatty acids and glycerides. Additional pancreatic enzymes, trypsin and chymotrypsin, break down proteins into peptides, which are catabolized into amino acids by carboxypeptidase. Amylase, which digests carbohydrates, is also released by the pancreas.

Lastly, the pancreas secretes bicarbonate into the duodenum to neutralize the chyme, a mixture of food and stomach acid, and protect the intestines from the acidity.