What are the functions of the four tissues of the duodenum?
Histologically, the duodenum is similar to the other tubes that comprise the gastrointestinal tract. It therefore possesses similar tissues (groups of cells working together for a common purpose) as other parts of the digestive system (e.g., the esophagus, large intestines, etc.). These tissues are: 1.) the Mucosa, 2.) the Submucosa, 3.) the Muscularis, and 4.) the Adventitia (in the duodenum specifically, this is a combination of an adventitia and a serosa).
Themucosa of the duodenum is lined with villi and microvilli, which together create a “brush border.” The mucosa is primarily responsible for the absorption of nutrients from small particles of food that have not been digested by the pancreas. Surface absorptive cells are rich in disaccharidases and dipeptidases, which absorb sugars, amino acids, fatty acids, monoglycerides, electrolytes, water, and other substances.
The submucosa possesses the Meissner’s Plexus, which is an interlacing series of nerves which supply the smooth muscle of the duodenum. The submucosa also supplies the intestines with blood. Finally, Brunner’s glands are located in the submucosa, which produce an alkaline substance that buffers the acidic chyme entering the intestines from the stomach.
Thistissue consists of striated bits of smooth muscle, which maintain peristalsis in the duodenum and further down the small intestine. The muscularis also stimulates the release of substances from various glands by contracting above-lying tissue.
Anouter layer of tissue that both holds the duodenum in place and protects it from friction by preventing it from rubbing up against adjacent organs in the abdominal cavity.
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