Discuss the different sections of the small intestine and what is absorbed.

Small intestine refers to a part of the gastrointestinal tract that lies between the stomach and large intestine. It is the principal organ where most of the absorption of food occurs. The small intestine is about seven metres long, and it is the second-largest organ of the gastrointestinal tract after large intestine.

The small intestine is divided into three regions: duodenum, jejunum, ileum.

1. Duodenum is the primary fraction of the small intestine, and it is responsible for linking small intestine with the stomach. After mixing of food with digestive juices in the stomach, the food is directed to the duodenum. The food gets mixed with secretions of gallbladder and pancreas that is bile and other digestive juices in this part.
2. The jejunum is the second part of the small intestine. This part of the small intestine is encircled by a particular type of cell known as enterocytes. These cells are primarily responsible for absorption of small molecules of nutrient that has been first digested in the duodenum.
3. The last part of the small intestine is the ileum. This part is responsible for linking small intestine with the large intestine. The function of ileum is to absorb the food from the stomach and small intestine.

The majority of nutrient absorption occurs in the small intestine include-

Vitamin B9 get absorbed in the jejunum and duodenum. The absorption of vitamin B12 and salts of bile takes place in the terminal part of the ileum. The absorption of water occurs throughout the intestine by the phenomenon of osmosis and absorption of lipids occur by passive diffusion. The sodium bicarbonate is absorbed in the intestine using active transport. The co-transportation method is used for glucose and amino acid absorption. Fructose absorption is done by using facilitated diffusion.