Esophagus and Stomach as Digestive Organs

Esophagus and Stomach as Digestive Organs Esophagus The esophagus is a long tube (± 25 cm) thin as the bolus passes from the mouth to the stomach. Function The esophagus serves as a route for the bolus from the mouth to the stomach.The inside of the esophagus is always wet with fluid produced by glands in the walls esophagus to keep the bolus wet and slippery.This situation will make it easier for the bolus to move through esophagus leads to the stomach. Movement of the bolus from the mouth into the stomach through the esophagus due to movement peristaltic in the muscles of the esophageal wall. Peristaltic movements can occur due to alternating muscle contractions in muscle layers which are arranged lengthwise and circularly. The process of bolus movement in the esophagus towards the stomach can be observed in figure below. The process of peristaltic movement of the bolus from the esophagus to the stomach Before a person starts eating, the back of the mouth (top) opens to allow air to flow from the nose. In the esophagus, the wavy-like epiglottis relaxes so that air enters the lungs. When eating, food is chewed and swallowed into the esophagus. As food moves towards the esophagus, the soft palate along with the wattle-like tissue at the back of the mouth () lifts upward and closes the nasal passages. Meanwhile, when food moves towards the tracheal cover, the epiglottis will close so that food does not enter the trachea and lungs but food still enters the esophagus. Position of the tongue and epiglottis during breathing (a) and when swallowing (b) Stomach The stomach is a digestive tract that is shaped like a sac, located under the bulkhead of the body cavity. The hull consists of three parts as follows. a. The upper part is called the cardiac, which is the part that borders the esophagus. b. The middle part is called the fundus, which is the body or middle part of the stomach. c. The lower part is called the pylorus, which borders the small intestine. The border area between the stomach and the esophagus contains the cardiac sphincter muscle which reflexively opens when a bolus enters. Meanwhile, in the pylorus there are muscles called the pyloric sphincter. These stomach muscles can contract like the muscles of the esophagus. When these muscles contract, they squeeze, squeeze, and mix the boluses into chyme . This squeezing motion is known as the mechanical digestion process. This digestion is caused by the muscles of the stomach wall. The stomach wall consists of smooth muscles that are elongated, circular and oblique. The structure of the stomach which is composed of muscle layers Meanwhile, chemical digestion is assisted by gastric juice. This sap is produced by glands located in the stomach wall below the fundus, while the inside of the stomach wall produces mucus which functions to protect the stomach wall from abrasion by stomach acid, and can regenerate if injured. This gastric juice can be produced due to bolus stimulation when it enters the stomach. Gastric juice contains various chemical substances, most of which consist of water. Gastric juice also contains HCl/gastric acid and digestive enzymes such as renin, pepsinogen and lipase. Gastric acid has the following functions. a. Activates several enzymes found in gastric juice, for example pepsinogen is converted into pepsin. This enzyme actively breaks down proteins in the bolus into proteoses and peptones which have smaller molecular sizes. b. Neutralizes the alkaline properties of the bolus coming from the oral cavity. c. Changes the solubility of mineral salts. d. Acidifies the stomach (pH drops 1-3), so it can kill germs that enter the stomach with the bolus. e. Regulates the opening and closing of the valve between the stomach and duodenum. f. Stimulates the secretion of intestinal juice. The renin enzyme in gastric juice functions to precipitate it casein or milk protein from breast milk. Hull in the atmosphere Acid can stimulate pepsinogen to become pepsin. Pepsin This functions to break down protein molecules into peptide molecules. Meanwhile, lipase functions to change fats into fatty acids and glycerol. Next, the chyme will enter the small intestine through athe small pyloric sphincter. If these musclescontracts, the chyme is pushed into the small intestine a littlelittle by little.