Question

Describe the four fundamental tissue layers of the alimentary canal

Contrast the contributions of the enteric and autonomic nervous systems to digestive system functioning.

Answer 1

The alimentary canal consists of four layer of tissues namely mucosa, submucosa, muscularis and serosa.

The innermost layer of tissues is known as mucosa layer. It consists of connective tissues and also a layer of smooth muscle. This layer of tissues are in direct contact with the ingested food and also as per the name, the mucosa layer secrets mucus which lubricates the food for easy movement in the alimentary canal.

The submucosa layer consists of loose connective tissue and contains the lymphatic and blood vessels which helps in the absorption and transportation of nutrients after digestion of food. This layer also contains nerve tissues and submucosal glands responsible for digestive secretions.

The third layer is the muscularis made up of smooth muscles : inner circular and outer longitudinal muscle layer. This layer of tissue contracts and helps in mechanical digestion of food and also gives more exposure to the digestive juices.

Serosa is the outermost layer of tissues which helps in keeping the alimentary canal attached to the vertebral column and also helps in protecting the alimentary canal from friction caused due to its movement during mechanical digestion of food.

The alimentary canal is connected by the enteric nervous system from oesophagus to the anus. The autonomic nervous system consists of sympathetic and parasympathetic nervous system. The enteric nervous system is only responsible for the functioning of the digestive system (alimentary canal) while the autonomic nervous system controls the activity of whole body. Enteric nervous system is divided into two plexuses. The myenteric plexus is connected to the muscularis layer and control the motility of the alimentary canal especially the contraction and relaxation of the muscularis layer. The submucosal plexus is connected to the submucosal layer of alimentary canal and responsible for the secretion from the submucosal layer of the alimentary canal.

The presence of food in the mouth is recognized by the receptors in the mouth of the nervous system and starts recognizing the taste of the food and digestion process.

The autonomic nervous system consists of sympathetic and parasympathetic nervous system which make intervention to the enteric nervous system. The sympathetic nervous system inhibits the action of enteric neurons and decreases the digestive activities while the parasympathetic nervous system activates the enteric neurons increasing the digestive activities by increasing the movement of alimentary canal and also the digestive secretions.