Stomach: Introduction, Structure of Stomach, Sections of Stomach, Functions of Stomach, Clinical Significance of Stomach (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction to Stomach

  • It is a muscular, hollow organ in the gastrointestinal tract of humans.
  • It is located in the upper-left side of the abdomen just below the liver.
  • One should eat food slowly as the brain doesn՚t respond immediately after the stomach is full.
  • The digestion occurs smoothly with food being chewed properly.
  • Mucous, hydrochloric acid and digestive juices are secreted by the inner lining of the stomach.
  • Mucous performs an important function of protecting the lining of the stomach.
  • The acid kills many bacteria.
  • The protein is broken down into simpler substances using the digestive juices.

Small Intestine

  • This is highly coiled and is about 5 meters long.
  • There are thousands of finger-like outgrowths in the inner walls of the small intestine.
  • Small intestine:
    • Carries out most of the digestive process.
    • Absorbs almost all the nutrients you get from foods.
  • This intestine is classified into three regions:
    • ‘C’ shaped duodenum.
    • A long coiled middle portion jejunum.
    • A highly coiled ileum.
Schematic Drawing of the Digestive System

Large Intestine

  • This is wider and shorter than small intestine.
  • This intestine is about 1.5 metre in length.
  • Absorbing water and some salts from the undigested food material is the main function.

Ingestion

Digestion

Absorption

Assimilation

Egestion

Diagram of the Human Intestine

Structure

  • The stomach lies between the oesophagus and the duodenum in humans.
  • The top of the stomach lies against the diaphragm.
  • Pancreas lies behind the stomach.
  • The stomach is surrounded by:
    • Parasympathetic (stimulant)
    • Sympathetic (inhibitor)
    • Plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac, and myenteric)
      • Regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.

Sections of Stomach

Sections of Stomach

The Cardia

The contents of the esophagus empty into the stomach.

The Fundus

Formed in the upper curved part.

The Body

The main, central region of the stomach.

The Pylorus (From Greek ‘Gatekeeper’ )

  • The lower section of the stomach.
  • This empties contents into the duodenum.
Blood Supply to the Human Stomach

Functions of the Stomach

Digestion

  • The stomach releases proteases (protein-digesting enzymes such as pepsin) and hydrochloric acid. This in turn kills or inhibits bacteria and provides the acidic pH of 2 for the proteases to work.
  • Through muscular contractions food is churned by the stomach of the wall called peristalsis.
    • Reducing the volume of the bolus.
    • Before looping around the fundus.
    • The body of stomach as the boluses are converted into chyme.
  • Gastric juice in the stomach also contains:
    • Pepsinogen
    • Hydrochloric acid
  • Pepsin breaks down proteins into polypeptides.

Absorption

  • Some absorption of certain small molecules occurs in the stomach through its lining.
    • Water, if the body is dehydrated
    • Medication, such as aspirin
    • Amino acids
    • 10 – 20 % of ingested ethanol (e. g. , from alcoholic beverages)
    • Caffeine

Clinical Significance of Stomach

Clinical Significance of Stomach

Human Stomach Division in Classical Anatomy

The Cardia

This is the place where the contents of the esophagus empty into the stomach.

The Fundus

This is formed in the upper curved part.

The Body

This is the central region of the stomach.

The Pylorus

This is the lower section of the stomach that empties contents into the duodenum.