Chapter 26: Digestion in Human being

How digestion works
Digestion ensures that larger sized nutrients are broken down into smaller sizes so as to pass through the walls of cell membranes. Digestive enzymes are responsible for digesting these nutrients, different enzymes digests different nutrients. Amylase acts on starch, a form of carbohydrate, to produce Maltose, a complex sugar. After which,  Maltase acts on maltose to produce glucose, simplest form of carbohydrate. Protease acts on proteins to  produce the simplest form of proteins, amino acids. Lastly, Lipase acts on fats to produces fatty acids and glycerol. These enzymes, which can be reused, speed up chemical reactions and remain unchanged through out the whole process as they act like scissors that breaks down large molecules into smaller ones. 


The different organs that makes up the Human digestive system

1.  The Mouth                                                                                                    Food enters from the mouth. In the mouth, food is broken down into smaller pieces as the food is chewed by the teeth and the surface area of the food increases which quickens the rate of digestion. While the salivary glands present in the mouth produces saliva that contains amylase digests starch into sugar and wets the food for easier swallowing. The tongue then rolls the food into balls which pushes its way down the oesophagus.
2. The Oesophagus                                                                                             The Oesophagus is a long muscular tube, connected to the stomach. No digestion occurs in this tube, however, the amylase in the food balls continues to digest the food as the muscles contract and relax to squeeze the food down the tube to the stomach. 
3. The Stomach                                                                                                      The stomach is like a muscular bag that contains gastric juice. The gastric juice consists of proteases that digests proteins and hydrochloric acid that assists proteases to work and kills all bacteria in the food. After which, digested food is passed to the small intestine bit by bit.
4. The Small intestine                                                                            The small intestine is also a muscular tube which the liver and the pancreas are connected to. In the small intestine, there are intestinal juices that produces Maltase, proteases and lipase, Pancreatic juice from the pancreas that contains amylase, proteases and lipase and  bile from the liver. As mentioned earlier, Amylase acts on starch, a form of carbohydrate, to produce Maltose, a complex sugar. Maltase acts on maltose to produce glucose, simplest form of carbohydrate. Protease acts on proteins to  produce the simplest form of proteins, amino acids. While Lipase acts on fats to produces fatty acids and glycerol. While the bile carries out emulsification, that is breaks fats down into smaller oil droplets and increase the surface area of the oil which speeds up the rate of digestion. Digestion ends here. Together with undigested food, fiber, water and mineral salts will be passed to the large intestines.
5. The Large intestine                                                                            In the large intestine, water and mineral salts are absorbed. The rest of the undigested, unwanted matter, known as faeces, are then stored in the rectum before being passed out.

a image of human digestive system

sources: google image