What is inside the small intestine?
The small intestine is the part of the intestines where 90% of the digestion and absorption of food occurs, the other 10% taking place in the stomach and large intestine. The main function of the small intestine is absorption of nutrients and minerals from food.
The intestinal epithelium is the layer of cells that forms the luminal surface or lining of both the small and large intestine (colon) of the gastrointestinal tract. It is composed of simple columnar epithelium.
- Endothelium refers to cells that line the interior surface of blood vessels and lymphatic vessels, forming an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. It is a thin layer of simple, or single-layered, squamous cells called endothelial cells.
- The outermost layer of the intestine, the serosa, is a smooth membrane consisting of a thin layer of cells that secrete serous fluid, and a thin layer of connective tissue. The muscularis is a region of muscle adjacent to the submucosa membrane. It is responsible for gut movement (also called peristalsis ).
- The innermost layer of the bladder is the mucosa layer that lines the hollow lumen. Unlike the mucosa of other hollow organs, the urinary bladder is lined with transitional epithelial tissue that is able to stretch significantly to accommodate large volumes of urine.
The entire luminal surface of the small intestine has villi, small projections of mucosa. The villi are lined with simple columnar epithelial cells, also called enterocytes. The cells are tall with middle to basal nuclei and have an apical brush border, also known as microvilli.
- The intestines are a long, continuous tube running from the stomach to the anus. Most absorption of nutrients and water happen in the intestines. The intestines include the small intestine, large intestine, and rectum. The small intestine (small bowel) is about 20 feet long and about an inch in diameter.
- The gastrointestinal wall surrounding the lumen of the gastrointestinal tract is made up of four layers of specialised tissue – from the lumen outwards: Mucosa. Submucosa. Muscular layer.
- The small intestine is the major place for digestion and absorption. Pancreas is the major source for enzymes. However, the small intestine does make some of its own enzymes, including protease and amylase.
Like the rest of the gastrointestinal tract, the small intestine is made up of four layers of tissue. The mucosa forms the inner layer of epithelial tissue and is specialized for the absorption of nutrients from chyme.
- The small intestine has three parts:
- +Duodenum. The duodenum is the first part of the small intestine. The main role of the duodenum is to complete the first phase of digestion.
- +Jejunum. The jejunum is the second part of the small intestine.
- +Ileum. The ileum is the third part of the small intestine.
- Small intestine cancer is a rare disease in which malignant (cancer) cells form in the tissues of the small intestine. Diet and health history can affect the risk of developing small intestine cancer. Signs and symptoms of small intestine cancer include unexplained weight loss and abdominal pain.
- Three organs play a pivotal role in helping the stomach and small intestine digest food:
- Pancreas. Among other functions, the oblong pancreas secretes enzymes into the small intestine.
Updated: 2nd October 2019