#Stomach

#Biology

#HumanDigestiveSystem

Introduction

• The gastrointestinal tract (GI tract) is the digestive system of the body. It takes food that is consumed by an organism and processes it into usable molecules. Then it packages the waste for elimination.

• The human GI tract consists of the mouth, esophagus, stomach, small intestine, large intestine, and the rectum.

  
  

• The stomach is a muscular organ that is located in the upper abdomen in between the esophagus and the small intestine.

• The size of the stomach varies from person to person, but the average size is about 10 inches. It is also bigger when it is full and collapses when it is empty.

• The function of the stomach is to store food temporarily and to then digest the food. It contracts and relaxes, produces enzymes and acids, and breaks down food before sending it to the small intestine.

• Your stomach’s purpose is to digest food and send it to your small intestine. It has three functions:

  • Temporarily store food.

  • Contract and relax to mix and break down food.

  • Produce enzymes and other specialized cells to digest food.

Anatomy

• The stomach is a J-shaped organ in the upper gastrointestinal tract, primarily responsible for the digestion of food.

• It has five main anatomical divisions:

• The cardia is the top part of your stomach. It contains the cardiac sphincter, which prevents food from traveling back up your esophagus.

  
  

• The fundus is a rounded section next to the cardia. It's below your diaphragm (the dome-shaped muscle that helps you breathe).

  
  

• The body (corpus) is the largest section of your stomach. In the body, your stomach contracts and begins to mix food.

  
  

• The antrum lies below the body. It holds food until your stomach is ready to send it to your small intestine.

  
  

• The pylorus is the bottom part of your stomach. It includes the pyloric sphincter. This ring of tissue controls when and how your stomach contents move to your small intestine.

• The wall of the stomach consists of four layers: mucosa, submucosa, muscularis externa, and serosa, each playing vital roles in digestion and protection.

• Mucosa is your stomach’s inner lining. When your stomach is empty, the mucosa has small ridges (rugae). When your stomach is full, the mucosa expands, and the ridges flatten.

• Submucosa contains connective tissue, blood vessels, lymph vessels (part of your lymphatic system) and nerve cells. It covers and protects the mucosa.

  
  

• Muscularis externa is the primary muscle of your stomach. It has three layers that contract and relax to break down food.

  
  

• Serosa is a layer of membrane that covers your stomach.

Gastric Cells

• Parietal or oxyntic cells -

  These large cells are located in the gastric glands in the fundus of the stomach. They secrete hydrochloric acid (HCl) and intrinsic factor, which helps the body absorb vitamin B12.

  
  

• Chief or peptic cells -

  These cells are located in the base of the gastric glands in the fundus. They secrete pepsinogen and gastric lipase, which help break down food.

  
  

• Mucous cells -

  These cells line the stomach and protect it from gastric acid by secreting mucus.

  
  

• Enterochromaffin-like (ECL) cells-

  These cells are a key regulatory cell for the secretion of gastric acid.

  
  

• Gastric stem cells -

  These cells have self-renewal and multipotent properties, and are the origin of specialized gastric epithelial cells.