Human Stomach – Class 11 | Chapter – 16 | Biology Short Notes Series PDF

Human Stomach: The stomach is an organ of the digestive system, specialized in the accumulation and digestion of food. Its anatomy is quite complex; it consists of four parts, two curvatures and receives its blood supply mainly from the celiac trunk. Innervation is provided via the vagus nerves and the celiac plexus.

Functions of the Human Stomach

  1. The major function of the stomach is to store and digest the food and liquid one consumes during meals.
  2. It produces hydrochloric acid and enzymes to help digest food and other foreign objects like bacteria.
  3. This acidic environment of the stomach kills the unwanted microorganisms.
  4. The stomach muscles contract at regular intervals to churn the food ingested and thus helps in digestion.

The stomach connects the oesophagus to the first part of the small intestine known as the duodenum. It is an enlargement of the alimentary canal that lies directly inferior to the oesophagus. As we are going to discuss the human stomach and functions of stomach it is important to note that the primary function of the stomach is to store the bolus (bolus is the chewed food mixed with saliva from the buccal cavity), while digestion is considered as the secondary function of the stomach. 

Parts of the Human Stomach

Your stomach has five distinct sections:

  • 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.

Structure of Human Stomach

Several layers of muscle and other tissues make up Human Stomach:

  • 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.

How does the Human Stomach work with the rest of the GI tract?

Each part of your GI tract breaks down food and liquid and carries it through your body. During the digestive process, your body absorbs nutrients and water. Then, you expel the waste products of digestion through your large intestine.

Food moves through your GI tract in a few steps:

  1. Mouth: As you chew and swallow, your tongue pushes food into your throat. A small piece of tissue called the epiglottis covers your windpipe. The epiglottis prevents choking.
  2. Esophagus: Food travels down a hollow tube called the esophagus. At the bottom, your esophageal sphincter relaxes to let food pass to your stomach. (A sphincter is a ring-shaped muscle that tightens and loosens.)
  3. Stomach: Your stomach creates digestive juices and breaks down food. It holds food until it is ready to empty into your small intestine.
  4. Small intestine: Food mixes with the digestive juices from your intestine, liver and pancreas. Your intestinal walls absorb nutrients and water from food and send waste products to the large intestine.
  5. Large intestine: Your large intestine turns waste products into stool. It pushes the stool into your rectum.
  6. Rectum: The rectum is the lower portion of your large intestine. It stores stool until you have a bowel movement.

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By Team Learning Mantras