Digestion and Teeth

Concept : Digestive System

What is the Digestive System?

• The digestive system comprises the alimentary canal that starts from our mouth and ends at the anus.
• The alimentary canal is a series of hollow organs that play different roles in the process of digestion.
• The food undergoes an incredible journey while passing through the alimentary canal and gets converted into the form that is absorbed by the body to produce energy for vital life processes.

Functions of the digestive system:

• The digestive system plays a vital role in converting the complex food we eat into simpler forms suitable for getting absorbed in the bloodstream, thereby assisting in the production of energy.
• The digestive system breaks the complex food into simple nutrients like sugars, fatty acids and amino acids that get readily absorbed.

Importance of the digestive system:

• The digestive system is responsible for processing food eaten by an individual to meet the body's energy demands.
• In the absence of a digestive system, there would be no energy production in the body despite eating food.

Organs in the digestive system:

The series of organs involved in the digestive system is given below—

Glands associated with the digestive system:

• Glands are the organs in our body that secrete specific chemical substances.
• These chemical substances have different functions to perform in the body.
• Glands associated with the digestive system are as follows—

Salivary gland:
• Three pairs of salivary glands are found in the buccal cavity.
• They are responsible for the secretion of saliva, which plays a vital role in the digestion of carbohydrates.

Liver:
• It is the largest gland present in our body.
• The liver is responsible for the secretion of bile juice which helps digest fats.
• Bile is stored in the gall bladder.

1. Pancreas:
   • The pancreas secretes pancreatic juices that help digest proteins and fats.
   • Pancreas also plays a vital role in maintaining the sugar level in the body by secreting the hormones insulin and glucagon.
Gall Bladder:
• It is a pear-shaped gland attached to the liver with a tube.
• It lies just beneath the liver and stores bile secreted by the liver.

Role of the organs of the digestive system:

Buccal cavity:
• It comprises teeth, tongue and salivary glands.
• The tongue helps in the mastication of food by making it soft. It facilitates the mixing of food with saliva.
• Teeth help convert large pieces of food into small ones to be appropriately swallowed.
• Salivary glands secrete saliva, which moistens the food. Amylase, an enzyme present in saliva, helps digest carbohydrates and converts them into simple sugars like glucose.
• When swallowed, the soft mass of chewed food, also known as bolus, is transferred to the food pipe or oesophagus.

Oesophagus:
• It is a tube-like structure located behind the wind pipe and in front of the spine.
• Oesophagus receives the food from the buccal cavity once we swallow it.
• It then passes the food to the stomach by continuous contraction and relaxation of muscles present in the tract, called peristalsis.
• Peristalsis is an involuntary movement, i.e. we cannot control it.
1. Stomach:
   • The stomach is a J-shaped muscular organ.
   • It helps in the churning of food.
   • The cells in the stomach wall secrete hydrochloric acid, which is necessary for digestion.
   • The enzymes secreted by the pancreas are activated only in the acidic medium.





2. Small intestine:
   • It is the largest part of the alimentary canal.
   • The small intestine is about 20 feet long and is divided into three parts—duodenum, jejunum and ileum.
   • The enzymes from the liver and pancreas are secreted into the small intestine.
   • The small intestine is also called the ‘site of complete digestion of food’ as the complete breakdown of food occurs here.
   • Absorption of food takes place in the small intestine.
   • The wall of the small intestine has finger-like projections called villi.
   • These villi are embedded with the blood vessels, and here, the nutrients get absorbed while passing through the small intestine.

3. Large intestine:
   • It is also called the colon.
   • The large intestine is the site of water absorption, which is present in the digested food.
   • The large intestine is hence called the ‘site of absorption of water’.
   • Once all the water is removed, the undigested food or waste to be eliminated is passed to the next part of the alimentary canal called the rectum.
4. Rectum:
   • The rectum is an 8-inch chamber that connects the large intestine and anus.
   • The opening and closing of the rectum are regulated by sphincters.
   • Here, the stool is stored by the body before the bowel movement.
5. Anus:
   • It is the last part of the alimentary canal and is 2 inches long.
   • The anus is surrounded by the sphincter muscles, which help in the passage of stool.
   • On relaxation of the sphincter muscles, the stool is egested out of the body, eliminating the undigested waste material.

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