Amoeba digestion

Amoeba digesting a bacteria(also known as phagocytosis)

The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. The digestive system is responsible for taking whole foods and turning them into energy and nutrients to allow the body to function, grow, and repair itself. The functioning and structure of Digestive system in microorganisms and very small organisms is quite simple but in large organisms it is quite complex: as in the case of humans.

Human Digestive SystemEdit


Food begins its journey through the digestive system in the mouth, also known as the Oral Cavity. Inside the mouth are many accessory organs that aid in the digestion of food—the tongue, teeth, and salivary glands. Teeth chop food into small pieces, which are moistened by saliva before the tongue and other muscles push the food into the pharynx.
  • Teeth. The teeth  are 32 small, hard organs made of calcium(Just like bones) found along the anterior and lateral edges of the mouth. Each tooth is made of a bone-like substance called dentin and covered in a layer of enamel—the hardest substance in the body.The teeth are designed for cutting and grinding food into smaller pieces. 
  • Tongue. The tongue is located on the inferior portion of the mouth just posterior and medial to the teeth.The outside of the tongue contains many rough papillae for gripping food as it is moved by the tongue’s muscles. The taste buds on the surface of the tongue detect taste molecules in food and connect to nerves in the tongue to send taste information to the brain. The tongue also helps to push food toward the posterior part of the mouth for swallowing. 
  • Salivary Glands. Surrounding the mouth are 3 sets of salivary glands. The salivary glands are accessory organs that produce a watery secretion known as saliva. Saliva helps to moisten food and begins the digestion of carbohydrates. The body also uses saliva to lubricate food as it passes through the mouth, pharynx, and esophagus.

Oesophagus(Food Pipe)

The Oesophagus is a muscular tube connecting the pharynx to the stomach. It carries swallowed masses of chewed food along its length. At the inferior end of the esophagus is a muscular ring called the lower esophageal sphincter or cardiac sphincter(or simply sphincter muscles). The function of this sphincter is to close of the end of the esophagus and trap food in the stomach.


The stomach is a muscular sac that is located on the left side of the abdominal cavity just below the diaphragm. This major organ acts as a storage tank for food so that the body has time to digest large meals properly. The stomach also contains hydrochloric acid and digestive enzymes that continue the digestion of food that began in the mouth.

Small Intestine

The small intestine is a long, thin tube about 1 inch in diameter and about 10 feet long. It is located just inferior to the stomach and takes up most of the space in the abdominal cavity. The entire small intestine is coiled like a hose and the inside surface is full of many ridges and folds(or finger like projections). These folds are called as villiused to maximize the digestion of food and absorption of nutrients by large surface area. By the time food leaves the small intestine, around 90% of all nutrients have been extracted from the food that entered it.

Large Intestine

The large intestine is a long, thick tube about 2 ½ inches in diameter and about 5 feet long. It is located just inferior to the stomach and wraps around the superior and lateral border of the small intestine. The large intestine absorbs water that aids in the breaking down of wastes to extract some small amounts of nutrients. Faeces in the large intestine exits the body through the anal canal.


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Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.

In addition to the alimentary canal, there are several important accessory organs that help your body to digest food but do not have food pass through them. Accessory organs of the digestive system include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas. To achieve the goal of providing energy and nutrients to the body, six major functions take place in the digestive system:

  • Ingestion
  • Secretion
  • Mixing and movement
  • Digestion
  • Absorption
  • Excretion

Video explaining Digestive System

The Digestive System

The Digestive System

A video explaining Digestive System.



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