THE DIGESTIVE SYSTEM

The digestive system is used to convert food that has been eaten into useful forms within the body. A sequence of events takes place in order for the digested food to be transported to our cells.

 

MOUTH

 

The mouth is the first place that food enters. On our mouth we have different types of teeth which help in the initial digestion process. These teeth are known as;

 

·        Incisor (front/ used for cutting or biting)

·        Canine (pointed/ pierce food)

·        Premolar (crush and grind food)

·        Molar (crush and grind food)

 

Teeth have an outer layer of enamel. This is the hardest material in the body. Underneath this is the dentine. The root of a tooth is embedded in the gum, and covered by a material known as cement, (similar to bone). Teeth are held in place by periodontal fibres. In the centre of each tooth is the pulp cavity. It is here where you will find blood vessels and sensory nerves. Oxygen and food materials are delivered to this part of the tooth, and unwanted materials are removed.

When food enters the mouth a process which is called mastication takes place. The food is mixed with saliva, which is secreted by three sets of salivary glands.

Saliva is composed of 90/95% of water. In it are dissolved ions. These are known as sodium, chloride, potassium, phosphate and bicarbonate. An enzyme (known as salivary amylase) helps to catalyse the breakdown of starch to maltose.

 

SWALLOWING

 

This is a voluntary reflex action which ensures the bolus of food will go to the oesophagus and not into the respiratory system. During swallowing the tongue pushes the bolus against the soft palate, closing of the nasal cavity. The epiglottis then covers the glottis to prevent the food from entering the airways. The bolus is then pushed into the pharynx where the oesophagus meets with the trachea. The bolus is taken along the alimentary canal by a process contraction which is known as peristalis.