Digestion in Stomach
What is a Stomach? Stomach plays a vital role in the digestion. The majority of the physical and chemical digestion is carrying out by the stomach.
Stomach – Digestive System
The stomach is a pear-shaped, thick elastic, muscular pouch that helps in the breakdown and digestion of food. Stomach can be able to change its size and shape according to the body position and amount of food taken. Stomach has approximately 30 cm length, 15 cm width and 1-liter capacity for a well develop adult. Stomach functions as an important organ of the digestive tract.
In adults, the stomach near an empty volume is about 45 ml. Because it is a distensible organ, it can expand to hold 1 liter of food, but can hold as much as two to three liters. A newborn baby stomach can only hold about 30ml.
Bolus (masticated food) enters the stomach from the mouth through the esophagus. Bolus is churned (agitated vigorously) by the stomach’s muscular contractions. In addition, the stomach converts the food boluses into chyme (partially digested food). Depend upon the quantity of the meal; the stomach will digest the food into chyme within 40 minutes to a few hours.
Stomach contracts by three different movements:
- first small slow contraction waves on stomach walls originate from the upper part of the stomach to its lower part (which produces simple indentation of the stomach walls) and a backward wave’s sweep from the bottom of the stomach to the upper that results in back and forth movement to mix and crush the gastric content,
- Second contracting wave towards the pyloric sphincter this produces a deep indentation as a peristaltic contraction emptying the gastric content through the pyloric sphincter to the small intestine,
- The third type of contraction is considering as a tonic that decreases the size of the stomach lumen.
Pyloric sphincter is a strong smooth muscular ring serves as a valve at the end of the stomach through which food pass to the duodenum, where the extraction of nutrients begins. It prevents surge back of food from the intestine back into the stomach.
Stomach – Digestive Process
The stomach secretes proteases (enzyme that digest protein) and hydrochloric acid, which helps to maintain pH of two (which helps the protease is work effectively) and kills or inhibits harmful bacteria.