Study Material

What is the role of acid in our stomach?

As we know, our stomach, a bag-like structure is an important part of the digestive system. It plays a major role in the digestion process. This process is aided by the secretion of acids in stomach. Let us see how. Happy learning!

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Posted by Kunduz Tutor, 8/11/2021
What is the role of acid in our stomach?

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The food we eat is digested by the act of various organs of the digestive system. Along with this many enzymes and acid also helps in digestion. Let us learn the process of digestion. We will also discuss what is the role of acids in our stomach.

Author – Parisa Gupta


Digestion is one of the processes of nutrition. It means breaking down complex molecules into simple ones.

“It is the catabolic process by which non-diffusible complex biomolecules convert into simple and diffusible biomolecules by hydrolysis.”

Let us learn about the digestive system of humans.

Human digestive system

The digestive system of humans contains many organs that help in digestion. We will discuss them one by one in detail.


In the mouth, teeth are present for crushing the food. The tongue helps in mixing the saliva with the food. Furthermore, saliva also helps in making the food wet for easy passage.

The salivary glands present in the mouth produce saliva which contains the enzyme salivary amylase. The function of Salivary amylase is to break down the starch into simple sugar.

Moreover, Mucus in the saliva helps in lubricating and adhering the masticated food particles into a Bolus. The bolus passes into the pharynx and then passes into the oesophagus by swallowing or deglutition.


The food (bolus) moves by peristaltic movement through the oesophagus and passes into the stomach. It is also known as the food pipe. However, no digestion of food takes place in the oesophagus.

Furthermore, the oesophagus and trachea open into the pharynx. Also, there is a cartilaginous flap called epiglottis which prevents the entry of food into the glottis


It is a bag-like structure that can expand when the food enters it. Sphincter muscles regulate the entry and exit of food in the stomach. Furthermore, it has three parts namely- cardiac portion, fundic region, and pyloric portion.

The wall of the stomach help in mixing the digestive juice (enzymes) with the food, because it has gastric glands which produce digestive juices.

Moreover, the mucosa of the stomach has a gastric gland. The gastric gland has the following three major types of cells:

  1. Mucus neck cell which secretes mucus.
  2. Peptic or chief cell which secretes proenzyme pepsinogen.
  3. Parietal or oxyntic cells which secrete HCL and intrinsic factor( factor essential for the absorption of vitamin B12)
Main components of the stomach:
1. HCl (hydrochloric acid):
  • Produced by the upper part of the stomach (fundus).
  • It helps to activate the protein digestive enzyme pepsin.
  • It also helps to kill microorganisms present in the food.

2. Mucus:

  • Mucus protects the wall of the stomach from HCl.

3. Pepsin:

  • It is a protein digestive enzyme and is activated only in an acidic medium.


The liver is the largest gland. It produces bile, which helps in emulsifying the fats that break them down into smaller globules that are further digested by the enzymes.

Furthermore, the bile secreted by the hepatic cells passes through the hepatic duct and is stored and concentrated in the thin muscular sac called the gallbladder. In addition, the duct of the gallbladder, which is the cystic duct, and the hepatic duct, form the common bile duct.


It secret pancreatic juice which helps the following enzymes:

  • Trypsin: digest proteins
  • Lipase: digest lipids
  • Amylopsins: digest starch

It also produces two hormones:

  • Insulin
  • Glucagon

In addition, The pancreatic juice contains inactive enzyme trypsin, chymotrypsinogen, procarboxypeptidase, amylase, lipase, and nuclease. However, trypsinogen is activated by an enzyme enterokinase secreted by the intestinal mucosa into active trypsin which in turn activate other enzymes in the pancreatic juice

Small intestine:

The complete digestion of proteins, fats, and carbohydrates takes place inside the small intestine with the help of intestinal juice. Furthermore, the walls of the intestine secrete the intestinal juice.

Intestinal juice converts the following:

  • Proteins into amino acids
  • Carbohydrates to glucose
  • Fats to fatty acids and glycerol

It has numerous finger-like projections on its wall called villi. They increase the surface area of the wall for absorption.

Large intestine:

The large intestine helps in the reabsorption of water from the undigested food which is discarded through the anus. Hence, there is no role of acids here.

Click here to read about Alimentary Canal- human digestive system, to know more about the parts of digestive system.

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