What Is The Small Intestine? By Jane Thurnell-Read

The small intestine is between the stomach and the large intestine. It is the main organ of digestion. Complex sugars are turned into simpler sugars. Fats are turned into fatty acids and glycerol. Peptones (from proteins) are turned into amino acids. The nutrients are then absorbed through the wall of the small intestine.

The opening to the small intestine is through the pylorus. When the food in the stomach reaches the correct degree of acidity in the area next to the pylorus, the pyloric sphincter opens to allow some of the food into the small intestine. Acid levels in the digestive tract are affected by stress, so stress can have a big affect on nutrient absorption and waste excretion.

Food is digested and absorbed through the wall of the small intestine. Villi increase the surface area of the small intestine.

At the end of the small intestine is the ileo-caecal valve, which controls the entry of the chyme into the large intestine. The small intestine is divided into:

• The duodenum
• The jejunum
• The ileum

3 hormones are secreted in the duodenum to ensure proper sequence of digestion:

• Secretin
• Cholecystokinin (CCK)
• Gastric inhibitory peptide

The gall bladder and liver are connected to the duodenum by ducts. Lymphatic nodes deal with any bacteria absorbed with the food.

Digestion is carried out by:

• Pancreatic juices (containing trypsinogen, amylase, lipase and sodium bicarbonate)
• Bile from the liver and gall bladder
• Intestinal juices

The intestinal juices are secreted in response to the food and also to the hormone secretin (produced in intestine). The intestinal juices contain enzymes: enterokinase, peptidase, maltase, sucrase, lactase and lipase. These are mixed with the food by peristalsis.

The enzymes change peptones (from proteins) into amino acids convert complex sugars into simple sugars (e.g. glucose). These are then absorbed through the intestinal wall into the blood stream.

The bile and the juices emulsify fats. Lipase converts fats into fatty acids and glycerol, which are water-soluble. These are absorbed through the intestinal wall and transported via the lymph system into the blood stream. Water is absorbed passively as a result of sodium being actively absorbed. Most vitamins and minerals diffuse through the small intestine walls, but some have an active carrier mechanism (e.g. iron is taken into the cells by carrier proteins).

Copyright 2008 Jane Thurnell-Read Natural Nutritional Products