kaksteistsõrmiksoole

Kaksteistsõrmiksool, also known as the duodenum, is the first section of the small intestine in humans and most vertebrates. It extends from the pyloric sphincter of the stomach to the jejunum. The name "duodenum" is derived from the Latin word duodeni, meaning "twelve," referring to its approximate length, which is about 12 fingerbreadths.

This vital organ plays a crucial role in digestion. It receives partially digested food from the stomach, known as chyme. The duodenum then mixes this chyme with digestive juices from the pancreas and the liver. These juices contain enzymes that break down carbohydrates, proteins, and fats, and bile, which aids in fat digestion. The acidic chyme is neutralized by bicarbonate secreted by the duodenum and from the pancreas, creating an optimal environment for enzymatic activity.

The wall of the duodenum contains glands that secrete mucus, which protects the lining from the acidic chyme and digestive enzymes. It also has a muscular wall that contracts rhythmically to mix the chyme with digestive juices and propel it forward into the jejunum. The surface of the duodenum is lined with villi and microvilli, which greatly increase the surface area available for absorption of nutrients, although most absorption occurs further down the small intestine. Key nutrients absorbed here include iron and calcium. The duodenum is susceptible to various conditions, including ulcers and inflammation.