Digestion system also known as alimentary canal it is a series of oral organs that helps in the digestion of food.

It is composed of the GI tract or gastro intestinal tract which contains the organs involved in digestion like the mouth, pharynx, esophagus, the stomach, intestine large and small intestine and the accessory organs which contains the organs that assist in digestion and are not part of GI tract example the teeth, the tongue, the liver, gallbladder and the pancreas.

The GI tract is made up of four layers serosa the outer most layer, muscularis composed of smooth muscle called circular and longitudinal muscles, submucosa secretes mucous and mucosa secretes large amount of mucous.

Along the GI tract are the mouth which is the starting point of digestion, it helps in the formation of bolus keeps food in place, the pharynx prevents food from entering the respiratory tract allowing it move down the esophagus to the stomach. Esophagus pushes food down the stomach by peristalsis the contraction of smooth muscles, stomach which helps in the digestion of food, absorption, mixing food chyme, as a storage, secretes digestive juices and HCl which deal with bacteria in food and stop the action of salivary amylase to allow pepsin work and also pushes food down the duodenum. The duodenum secretes lot of mucus to prevent intestines from acidic chyme and also secretes digestive enzymes, the jejunum secretes digestive enzymes, the ilium this is where most absorption of nutrients occurs it secretes digestive system that digest carbohydrates proteins and fats. The large intestine is in parts also the Caesium, ascending colon, transverse colon, descending colon, sigmoid colon and the rectum, it is in the large intestine where digestion of vegetables and fermentation occurs.

Accessory organs; the teeth helps the break food for physical digestion, the tongue helps in swallowing, mastication of food and for the formation of bolus. The liver secretes bile, stores glycogen form of energy, deamination if old red blood cells, extract urea from protein as a byproduct or waste product and release it into the blood then taken to the kidney for elimination, removes toxins such as alcohol and drugs. Gallbladder stores bile. Pancreas secretes digestive juices which digest carbohydrates proteins and fats.

DIGESTION

This is the breaking down of complex food into small and simple ones so it can be absorbed and enter the bloodstream to be used as energy.

Types Of Digestion

There are two main types of digestion, These include,

Physical digestion; the digestion of large particles of food into smaller pieces by using teeth called chewing.

Chemical digestion, the digestion that involves chemicals or enzymes to break molecules of food into very small and simple molecules suitable for absorption.

STEPS OF DIGESTION

Digestion is in steps. These includes,

1. Ingestion: this is the intake of food into the mouth.

2. Digestion: this is the breakdown of large molecules of food into smaller pieces.

3. Absorption: this is the uptake of nutrients or food into the body by the walls of the digestive tract

4. Assimilation: this is the intake of absorbed good or nutrients into the bloodstream.

5. Egestion: this is the removal of unusable or indigestible materials out of the body.