* Alimentary canal
* 4 layers
* Buccal cavity
* Small intestine
* Large intestine
Nutrition is the process of acquiring energy and materials for cell metabolism, including the maintenance and repair of cells and growth. In humans, digestion and absorption occur in the alimentary canal or gut. As the gut wall is continuous with the outside surface of the body, the food in the gut is considered to be outside of the body, the gut is specialised into different regions, each designed to carry out a different role in the overall processes of digestion and absorption.
The human gut is a coiled, muscular tube extending from the mouth to the anus. Accessory digestive organs are connected to the main system by a series of ducts. These produce compounds that contribute to digestion and release them into the gut. The gut consists of four distinct layers; the mucosa, submucosa, muscularis externa and serosa. Draw diagram of the digestive system
The buccal cavity is the chamber just inside the mouth where the chewing action of teeth and jaws and the tongue begin the mechanical breakdown of food into smaller pieces. The tongue has taste buds with receptors sensitive to substances. The eye and the olfactory receptors in the nose are important for stimulating the salivary glands in the mouth to secrete saliva. Salivary amylase begins the digestion of starch into maltose. Eventually the semi-solid, partially digested food particles are stuck together to form a bolus by the tongue, which then pushes it towards the pharynx from where it is swallowed into the oesophagus as a result of a reflux action. To prevent the food from entering the trachea and lungs, the larynx closes, the soft palate is pulled up and a flap of tissue called the epiglottis covers the entrance to the...