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Comparison of the structural and functional specialisations of cells lining the stomach with those of the cells lining the small intestine.

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Introduction

Page 1 Comparison of the structural and functional specialisations of cells lining the stomach with those of the cells lining the small intestine. The specialised cells lining the stomach and small intestine vary in structure and function; however, they are similar in the fact that they are both involved in the digestion process. The stomach is a j shaped organ with a wall of muscle which has lots of folds called rugae to enable the stomach to expand when food is present. There are three types of specialized stomach cells that are located in the glands of the stomach lining which is called the mucosal epithelium. These cells produce various gastric secretions necessary for the breaking down food into a soup like liquid called chyme. When this is complete, chyme is passed via the pyloric sphincter into the small intestine which continues digestion and absorbs nutrients into the blood stream or fats into the lymphatic system. The small intestine is approximately 7 metres long and is divided into three parts; the duodenum, jejunum and ileum. ...read more.

Middle

To protect and lubricate the stomach lining from the strong acid, goblet cells secrete mucus which create a less acidic microenvironment in the lumen. Goblet cells also produce gastrin which is a hormone and is secreted into the blood vessels in order to activate other epithelial cells in the gut. Finally, pepsinogen is produced by the chief cells and is converted into pepsin by HC1 to breakdown polypeptide chains and peptides. To complete the breakdown of peptides, the small intestine secretes amino peptidase. Together with caboxypeptidase secreted by the pancreas they convert them into free amino acids by each Page 3 removing one end of the peptide chain. For the amino acids to then be absorbed into the epithelial cells they require active transport (ATP) and use a process called cotransport to cross the epithelial membrane. Amino peptidase is just one of the enzymes produced by the specialised cells of the small intestine to break down protein. Others include dextrinase, lactase, sucrase and maltase and have their role in the breaking down of carbohydrates into monosaccharides; glucose galactose and fructose. ...read more.

Conclusion

The structure of the cells varies in that the stomach does not have a brush border as the small intestine does. This is because the structure of the cells serves their function and as the stomach is not involved in absorption, it does not need to increase surface area in this way. Instead, the stomach expands and contracts depending what is in it. The lining of the stomach also does not contain lymph nodes, blood vessels and enteric ganglia as the small intestine does. However, they are both invaginated to form glands containing secretery epithelial cells. In this way and the thick layer of mucus, they are protected in the stomach from the hydrochloric acid produced by the parietal cells. In contrast some enzymes are also located on the brush border of the small intestine which is exposed to the lumen. Page 5 The structure and function of the stomach cells, although different to the small intestine cells, are complementary. They are both crucial in the digestive process and are structured appropriately to primarily produce either gastric secretions or enzymes to digest food and absorb nutrients into the body. ...read more.

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