14 DAY TRIAL // 1.Digestion takes place inside a 9 m (30 ft) long duct called digestive tube. It starts in the mouth and even if the food stays very little here, this is the place where the break down of the starches begins. The taste detects food's flavor, size, composition, texture and temperature. By chewing the food, the surface of the aliments exposed to the action of the digestive juices is increased.
2.The saliva, secreted by 3 pairs of glands, is 98 % made of water, the rest being made of amylase (that breaks down starches to maltose) and lysozyme, that kills bacteria. There is always some saliva in the mouth so that teeth and cheeks do not rub themselves during the speaking.
3.The food is pushed through the pharynx (the muscular organ located in the back part of the mouth) into the esophagus. The pharynx is where digestive and respiratory pathways cross. During the swallowing, breathing is interrupted, larynx is raised and a tap cartilage (epiglottis) covers the respiratory ways. If food enters the respiratory ways, we start coughing to bring it out. Through a peristaltic movement, the esophagus transports the food into the stomach; gravitation does not affect this, so that we can eat even standing on the head or in the cosmic space, devoid of gravitation. The mucus secreted by the esophageal glands also helps. Food passes from esophagus into the stomach through the orifice called cardia, after the contraction of the esophageal smooth muscles have increased the pressure enough to allow this.
4.The stomach has a bagpipe shape and three parts: cardia (mouth), fornix (bottom) and terminal end (pylorus). The stomach is very muscular and produces a strong acid (chlorhydric) that helps breaking down proteins and kills many germs. Its absence causes slow digestion (dyspepsia) while an overproduction causes ulcer, the burning of the stomach wall and that of the neighboring segments (esophagus and duodenum). Pepsin is a stomach enzyme starting the break down of the proteins. It is secreted as inactive pepsinogen by the stomach's wall cells and activated by the chlorhydric acid. In this moment, the wall's cells are protected by mucus, thus the enzyme does not digest the stomach itself. If the mucus is damaged, the pepsin contributes to the development of ulcer.
5.Through belching, the air swallowed with the food and drink and accumulated in the upper part of the stomach is eliminated.
6.The release of stomach juices is made both by nerves and hormones. The secretion can start even when we just saw or smelt the food, preparing the stomach for digestion. If we do not eat when the stomach is already "ready", the stomach juices can cause problems. The hormone named gastrin, released by pylorus, is also involved in the release of stomach juices. Through peristaltic movements, the food processed in the stomach passes into the small intestine, in its first part called duodenum.
7.The passing of the whole stomach's content can last 2 to 6 hours. Carbohydrates-rich foods stay very little in the stomach, while protein-rich foods stay longer, and fat-rich foods have the slowest transmission to the intestine.
8.Very few aliments can pass from the stomach into the bloodstream. Amongst them are water, salt, some drugs and alcohol. The total breakdown of the aliments takes place in the small intestine, and the nutrients are absorbed into the bloodstream through its wall.