The duodenum is a highly specialized part of the small intestine. Identify and explain how the structure of the different tissue types relates to their functions in the duodenum.

 

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The duodenum has four layers. The innermost layer, or mucosa, consists of columnar epithelium with microvilli that increase the surface area for digestion. The submucosa contains Brunner's glands that secrete alkaline mucus. Surrounding the submucosa is a layer made of circular and longitudinal muscle tissue that generates peristalsis. The outermost layer or serosa consists of simple squamous epithelial cells. Its function is to prevent friction between the duodenum and the adjacent organs.

The partially digested food or chyme enters the duodenum from the stomach. The mucus neutralizes the acid in the chyme, protects the walls of the duodenum, and helps the chyme to achieve an optimal pH for digestion. The peristaltic movement of the duodenum propels the chyme towards the ampulla of Vater, a cavity in the middle of the duodenum. The ampulla receives the common bile duct (from the liver and gallbladder) and the pancreatic ducts. The secretions contain peptidases (that breakdown peptides into amino acids), and lipase (that breaks down neutral fats into fatty acids and glycerol). There are four enzymes, sucrase, maltase, isomaltase, and lactase that split disaccharides into monosaccharides.

The microvilli in the mucosa help to absorb the nutrients, and the peristaltic movements of the duodenum propel the chyme towards the jejunum.

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The duodenum is a highly specialist part of the small intestine. Identify and explain how the structure of the different tissue types relate to their function.

The duodenum is the first part of the small intestine. It receives partially digested food directly from the stomach and introduces digestive enzymes from the pancreas, gall bladder, and liver to complete the digestive process. It also absorbs nutrients.

The inner lining of the duodenum is called the mucosa. This layer is made of simple columnar epithelial tissue covered in a layer of microvilli that increase the surface area of the tissue to facilitate absorption of nutrients. This layer contains mucus-secreting glands that help to lubricate the surface of the tissue and protect it from damage by the acidic mix of digestive fluids called chyme.

Surrounding the mucosa is a layer of connective tissue called the submucosa. This layer provides support and elasticity to the duodenum.

Outside the submucosa is the layer of smooth muscle that mixes and propels food through the GI tract, called the muscularis.

This is contained by an outer skin, called the serosa. This tissue is made of squamous epithelial cells, and it provides a smooth, slick surface to prevent friction between the duodenum and other surrounding organs. It secretes serous fluid to aid this lubrication process.

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