Digestion Cycle

Anatomy of Digestive System

To know how acidity occurs, it is important to know how and where the food gets digested. Gastrointestinal (GI) tract, as the name says, is a long tract or ‘tube’ or ‘canal’ along which the food passes and breaks down producing energy. This tube where the digestion happens is approximately 6.5 meters long and is highly convoluted to fit into our abdomen.

The GI tract that forms the digestive system of the body is divided into many organs, each of which contributes to the digestion of the food in their own way. The following organs forms the organ system that performs digestion in the body,

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine

Apart from these organs, there are certain glands that contribute the chemicals necessary for digesting the food. These are,

  • The salivary glands
  • The pancreas
  • The liver
  • The gall bladder

The Mouth

Mouth is the first part of the digestive system that helps in grinding the food mechanically into smaller particles that can be easily digested. In mouth, the food is broken into small pieces and mixed with saliva. If you do not chew your food properly, it may increase your chances of having acidity.

The mouth contains the teeth, the tongue, and the salivary glands. The 32 teeth in an average adult help in grinding the food mechanically. The tongue helps in mixing the food with the saliva produced by the salivary glands, makes the food moist, and easily swallow able. The tongue helps in forming the round mass of food called bolus and helps in ‘pushing’ this ball into the canal that carries out the rest of the digestion. The tongue also helps in tasting the food. The taste buds present on the surface of the tongue are responsible for tasting the food. The salivary glands present in the mouth secrete saliva that helps in moistening the food and digesting it partially. Saliva contains an enzyme- salivary amylase that helps in digesting the carbohydrates into smaller molecules.


Pharynx is the region that connects the mouth to the esophagus. It is a region that forms the common passageway for food and the inspired air. The food is prevented from entering the lungs with the help of a flap like structure called ‘epiglottis’. Epiglottis covers the windpipe and prevents the entry of the food particles into it.


Esophagus is a connecting tube between the mouth and the stomach that comes after the pharynx. It helps in carrying the grounded food from the mouth to the stomach for further digestion. It does not contribute much to digestion but helps in conducting the food along the GI tract.


Stomach is an organ present to the left side of the abdomen below the diaphragm. This is the organ that helps in mechanically and chemically digesting the food. This muscular structure is made to ‘move’ in a particular fashion (peristaltic movements) that enables grinding of the food and mixing of the food with the digestive enzymes and hydrochloric acid secreted into its cavity.

The stomach is lined by many cells that produce various enzymes that help in digesting the food partially, before it is sent into the small intestine. Certain cells that line the stomach (parietal cells) secrete an acid called hydrochloric acid that kills the pathogens present in the food and protects the body.

Many blood vessels innervate stomach. These absorb certain ingredients in the stomach itself. The food that gets easily absorbed from the stomach is alcohol and water.

Apart from digestion of food, the stomach forms the major storage organ of food. The food gets stored here for a minimal period of at least two hours before it is passed into the small intestine. It can store nearly up to 2-3 liters of food.

Small Intestine- An amazingly long organ

It is the largest part of the GI tract that contributes to most of the digestion that takes place. It is a very long organ nearly 10 feet in length and 1 inch in diameter. It is amazing how a human body can accommodate such organs! It is highly convoluted to fit into our abdomen. The inner lining of the small intestine also has many folds that help in absorbing the digested food. The more the folds, the greater is the surface area for absorbing the digested food. The small intestine by itself does not contribute solely to the digestion. Many accessory glands secrete enzymes into the small intestine and help in digestion.

Liver And Gall Bladder

Liver is a very big organ located to the right side of the abdomen just below the diaphragm. This lies just above the small intestine and secretes bile salts and bile acids that help in breaking down the lipids and emulsifying them. It also contributes to many other metabolic activities as it is the region into which the blood ‘moves into’ after passing through the small intestine. No wonder it is called the ‘chemical factory’ of the body!

The gall bladder lies posterior to the liver and simply helps in storing the bile acids. It also helps in recycling the excess bile that is taken in from the small intestine.


This gland is a major contributor of many enzymes that help in digesting the food in the small intestine. It lies posterior to the stomach and secretes its enzymes into the small intestine.

The various enzymes that are secreted by the pancreas perform the Herculean task of digesting the food, and include:

  • Trypsinogen, chymotrypsinogen, pancreatic peptidase- that digest the proteins
  • Pancreatic lipases- that digest the lipids; nucleases- that digest the nucleic acids
  • Pancreatic amylase- that digest the carbohydrates

All of these enzymes digest the food and break them into smaller particles. These smaller absorbable particles are then absorbed all along the small intestine through the folds and villi (finger like projection extending into the inner side of the small intestine). From the small intestine, the nutrients are absorbed into the blood and the lymph through the blood vessels and the lymphatic vessels present in the villi. Blood then carries the nutrients to the liver and then all over the body.

Large Intestine

Large intestine extends down from the small intestine up to the anus. It is quite thicker than the small intestine and is 5 feet long. Large intestine forms a ‘border’ around the small intestine laterally and superiorly. These lateral and superior ‘borders’ are called the ascending colon, transverse colon and the descending colon. This is followed by the sigmoid colon, which ends up as rectum. The rectum is followed by anal canal and anus that forms the opening through which the digested food is excreted.

Large intestine contributes mostly to absorption of water, digestion of certain undigested foods and production of certain vitamins. It contains bacterial flora that secrete enzymes required for digesting certain foods. It also helps in producing Vitamin B and K. It also contributes to absorption of maximum amount of water from the food and produces soft mass- feces.

The formed feces then leave our body through the anus.

Any problem with any of these organs may potentially lead to acidity, so a well-functioning digestive system is very important for preventing acidity.