Digestion

Organs of the Digestive System

The organs of the digestive system aim at breaking down the complex foods into simple nutritional forms that can be absorbed by human body. Several organs contribute to the process of breaking of food. The digestive system is classified into two basic types –

  • Upper gastrointestinal tract
  • Lower gastrointestinal tract

Various organs make up the above digestive system. Besides the upper and lower gastrointestinal tracts, several other organs are also involved in the process of digestion. These are called auxiliary organs which aim at maintaining a healthy digestion.

Upper Gastrointestinal Tract

The primary function of the upper gastrointestinal tract is simplification of the ingested food into forms of nutrition that can be assimilated by the lower gastrointestinal tract. The process of digestion starts even before the food enters the digestive system. Different organs produce gastric and digestive juices based on the signals from the eye, nose, ear and tongue. Physical simplification of the food is done inside the oral cavity of the human body. The following organs are involved in the upper gastrointestinal tract –

    • Mouth –

        • Tongue

      The tongue contains taste buds, which makes us realize the delicacy of any food. Tongue helps in the proper movement of the food inside the mouth to ensure proper chewing and then swallowing (called deglutination).

        • Salivary Glands

      The salivary glands secrete saliva, which contains digestive juices to breakdown the food. The saliva also helps in the lubrication of the food to allow free chewing. The saliva also contains disinfectant properties to a certain extent. The amylase produced by the salivary glands scan break starch into glucose.

        • Teeth

      The teeth grind and mash the food by vigorous chewing. They break the food physically so that the rest of the digestion is performed well. It makes digestion easier.

Mouth is the first organ that contributes to the process of digestion. The mouth has teeth, tongue and salivary glands inside it, which plays an active role in the initial processes of the digestion.

    • Pharynx –

The pharynx lies behind the mouth (buccal cavity). The pharynx is the vital organ that prevents the food from entering into the voice box (larynx). It forces the food to enter the esophagus instead. It plays no role in the physical or chemical simplification of the food.

    • Esophagus –

The esophagus is a 25cm long muscular tube stretched to connect the mouth to the stomach. It allows the food to pass through it to enter the stomach for further digestion. The food undergoes a systematic, symmetrical, rhythmic movement to reach the organ. This movement is called peristalsis, which is the alternate contraction and relaxation of the body muscles to allow passage of the bolus (partially digested food).

    • Stomach –

        • The cardia

      This portion of the stomach receives the partially digested food and is handed over to the adjacent part.

        • The fundus

      The curvature of the stomach is called the fundus. The cardia sends the food to the fundus, where it is stored.

        • The corpus

      The food is then allowed to enter the central portion of the stomach, called the corpus body. This is the part where the breakdown of the food takes place ultimately. Until complete simplification is done, the food undergoes treatment with various acidic gastric juices. The entire chemical breakdown takes place inside the corpus body of the stomach. The food is broken down into its basic form od nutrients; the vitamins, fat, proteins, minerals and carbohydrates.

        • The antrum –

      The main purpose of the antrum is to receive the simplified food from the corpus body and pass it to the small intestine (lower gastrointestinal tract).

The whole food is completely broken down inside the stomach. The stomach is divided into four different parts to ease the task –

Lower Gastrointestinal Tract

The lower gastrointestinal tract helps in assimilation of the nutrients by the body. Following the complete breakdown of the ingested foods in the upper gastrointestinal tract, the simpler forms of the food are absorbed by the body. The lower gastrointestinal tract consists of two basic organs –

  • The small intestine
  • The large intestine

Small Intestine –

The small intestine is divided into three different parts –

    • The duodenum

This is the shortest part of the small intestine. The duodenum is connected to the end of the stomach and hence, receives the simplified food from it. Irrespective of its size, it is capable of a lot of chemical digestive processes. The digestive juices from the liver and the pancreases mix inside the duodenum to carry complete digestion.

    • The jejunum

The middle portion of the small intestine is called jejunum. It helps in sorting of the nutrients from the digested food and transferring the remaining food into the other portion.

    • The ileum

The nutrients that could not be absorbed by the jejunum or missed, are absorbed by the ileum. Most of the vitamins are absorbed here.

Large Intestine –

The large intestine is also divided into three parts –

    • The cecum

The connecting pouch which acts as a bridge between the small and large intestine is called cecum. It is attached to the appendix.

    • The colon

The water and salts are absorbed in the colon. This lies next to the cecum.

    • The rectum

The third portion of the large intestine is the rectum. This is the link between the intestine and the anus. It stores fecal wastes inside it.

Anus –

The body wastes (solid) is excreted out through the opening called anus.

Auxiliary Organs

Some organs which are neither included in the lower or upper gastrointestinal tract, but are very important for the digestive system are called Auxiliary organs. These include –

    • Gallbladder –

The gallbladder stores bile in it, which is important during fat assimilation.

    • Liver –

The liver secretes several digestive juices and biochemical ingredients which help in protein digestion. The liver is important for the detoxification of the food.

    • Pancreas –

The pancreas secretes pancreatic juice. It contains several digestive juices. These are extremely important for the simplification of the carbohydrates, fat and proteins.

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