The stomach!!! By Hannah Bayfield and Esme Gray! Year 12 King Edward VII High School! Introduction What is the stomach??? The stomach is an enlarged and muscular saclike organ of the alimentary canal. It is the principal organ of digestion. It is situated between the oesophagus and the intestines and nearly every animal has a stomach. It changes size and shape according to it’s position in the body and the amount of food inside it. Structure of the stomach! •The stomach is composed of five layers which starts from the inside and works its way out. •The inner most layer is called the mucosa. This is where the stomach acid and digestive juices are made. •The next layer is called the submucosa which is surrounded by the muscularis (a layer of muscle that moves and mixes the stomach contents). •The next two layers are the subserosa and the serosa and are the wrapping for the stomach. A cross section of the stomach. Quick questions! The stomach is the ………………….. Organ of digestion??? Principal How many layers does the stomach have??? Five The stomach wall The wall of the stomach is structurally similar to other parts of the digestive tube, with the exception that the stomach has an extra oblique layer of smooth muscle, which aids in performance of complex grinding motions. What protects the stomach? The stomach is lined with epithelial cells (goblet cells), which produce and secrete a bicarbonate-rich solution that coats the mucosa. Bicarbonate is an alkaline and neutralizes the acid secreted by the parietal cells, producing water in the process. This is the main way that your stomach protects itself from auto digestion (the stomach digesting itself) and the overall acidic environment. Goblet cell Quick questions??? What does the smooth Aids performance of oblique extra layer of the complex grinding stomach help it to do??? motions. What do the epithelial A bicarbonate- cells that line the stomach produce??? rich solution Cells in the stomach There are four major types of secretory epithelial cells that cover the surface of the stomach. They are: Mucous cells: These secrete an alkaline mucus that protects the epithelium against shear stress and acid. Parietal cells: These secrete hydrochloric acid. Chief cells: These secrete pepsin, a proteolytic enzyme. G cells: These secrete the hormone gastrin . A parietal cell. Can you name the organelles in this cell? Rough endoplasmic Mitochondria reticulum. Nucleus Golgi body Thank you for watching our presentation!!!