Stomach

Definition:

The stomach is a muscular, hollow organ located in the upper abdomen, between the esophagus and the small intestine. It plays a vital role in the digestive system by breaking down food through mechanical movements and chemical secretions, preparing it for nutrient absorption in the small intestine.

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Parts of the Stomach:

1. Cardia:
   • The upper portion where food enters from the esophagus through the lower esophageal sphincter.
2. Fundus:
   • The rounded, dome-shaped section above the cardia, which stores undigested food and gases released during digestion.
3. Body (Corpus):
   • The largest central section where most of the digestive mixing occurs.
4. Antrum (Pyloric Antrum):
   • The lower portion that grinds food and regulates the passage of digested contents to the small intestine.
5. Pylorus:
   • The narrow region that connects to the small intestine through the pyloric sphincter, controlling the release of chyme into the duodenum.
6. Sphincters:
   • Lower Esophageal Sphincter: Prevents backflow of stomach contents into the esophagus.
   • Pyloric Sphincter: Regulates the movement of food into the small intestine.

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Functions of the Stomach:

1. Mechanical Digestion:
   • Churning and mixing food with gastric juices to form a semi-liquid mixture called chyme.
2. Chemical Digestion:
   • Secretes hydrochloric acid (HCl) to:
     • Break down food.
     • Kill harmful bacteria.
     • Activate the enzyme pepsin.
   • Produces digestive enzymes like pepsin for protein digestion.
3. Storage:
   • Temporarily stores ingested food and regulates its release into the small intestine.
4. Absorption:
   • Limited absorption occurs in the stomach, mainly for water, alcohol, and certain medications.
5. Protection:
   • Mucus secretion protects the stomach lining from self-digestion by hydrochloric acid.
6. Hormone Production:
   • Releases gastrin, a hormone that stimulates gastric acid production.

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