The structure and functions of the digestive systemThe digestive system is made up of a group of organsthat work together to breakdown food into small substances that our body canabsorb and use in metabolic reactions, growth and repair in cells.
Digestiontakes place in the alimentary canal starting at the mouth and ending at theanus. (Womens-health-advice.com, n.d.). The alimentary canal is also known asthe gastrointestinal (GI) tract, whenfood is broken down the useful products are separated from the unusableproducts. Useful products are transported to the body and the unusable productsare excreted from the body. The final product of digestion results in glucose,amino acids and fatty acids.
The five stages of food processing are, ingestion,digestion, absorption, assimilation and egestion. (Toktol.com, n.d.). The mouth is thecavity which food enters the GI tract, and is the location where the mechanicaland chemical digestion begins. Chewing food starts to break large chunks intosmall chunks that are easier to manage and swallow. In the mouth, the food ismixed with saliva secreted from salivary (paratoid, submandibular andsublingual) glands that contains the enzyme, amylase.
(Richardson, 2006). Amylaseis an extracellular enzyme as it works outside cells, it catalyses thehydrolysis of starch into maltose. (Parsons, 2015). Once the food has beenchewed and in bolus form it is pushed the back of the mouth by the tongue andinto the oesophagus. Its function is to take food from the mouth to the stomachfor further digestion. It is specialised for this function by having a mucusproducing membrane and involuntary muscle contractions so that food slideseasily down it. (Richardson, 2006) The stomach is amuscular bag that can expand to hold up to a litre of food.
The stomach is madeup of four layers that help in the digestion of food, the mucosa, producesenzymes and acids, which help in digestion and protection of stomach lining.The submucosa and muscularis that contact to churn the food. Finally, theserosa, which is the strong membrane keeping the stomach together.(Macmillan.org.uk, 2016).
The food is then stored in the stomach withhydrochloric acid for 30 – 60 minutes. (Taylor, n.d.) The partiallydigested food (chyme) leaves the stomach through pyloric sphincter and into theduodenum, the C-shaped tube part of the small intestine.
This is where thepancreas, gallbladder, liver and some glands all deliver their digestiveenzymes and alkaline mucus too. Once all the secretions have mixed with thechyme, the process of chemical digestion is complete. The carbohydrates, lipidsand proteins have now been broken down into their individual units and readyfor absorption. (Taylor, n.d.). Trypsin is one of the enzymes that is secretedby the pancreas into the duodenum, it is responsible for the hydrolysis ofproteins into amino acids. (Hocking, S.
, Sochacki, F. and Winterbottom, M,2015). The ileum is thefinal part of the long intestine and its soul function is the absorption of allrequired nutrients needed by the body. The ileum is highly specialised for thisrole as it is 3.5m in length, he walls have villi and then micro villi on themso it has a very large surface area.
The surface of the wall is moist, verythin and has a rich blood supply. These help in maximising the amount ofnutrients absorbed. (Encyclopedia Britannica, 2018).
The remaining matter that was not absorbed in the ileum carries ontraveling through the GI tract and into the colon. Any remaining nutrients andwater is absorbed but waste feces carry on moving along the colon and passedonto the rectum. The rectum stores feces until it passes out of the bodythrough the anus. (cancer.ca