Histology of the Alimentary Canal - Practice Questions & MCQ

The alimentary canal is composed of four layers of tissues. Each layer has its specific tissues and functions. Starting from the lumen of the digestive tube, the layers are arranged as follows:
 

1. Mucosa: It is composed of simple epithelium cells and a thin connective tissue - areolar tissue. The layer of areolar connective tissue is called lamina propria. In addition, the mucosa has a thin, smooth muscle layer, called the muscularis mucosa. Mucosa forms glands in the stomach (gastric glands) and crypts in between the bases of villi in the intestine (crypts of Lieberkuhn).

2. Submucosa: The submucosa is relatively thick, is highly vascular and serves the mucosa. It is made up of dense connective tissue. It also contains glands and nerve plexus.It also contains MALT (Mucosal Associated Lymphoid Tissue) 

3. Muscularis: It is also the muscularis externa. The muscularis is composed of two layers of muscle: an inner circular and outer longitudinal layer of smooth muscle. The stomach contains an additional layer of oblique muscles. In Stomach, oblique muscles form the innermost layer, circular muscles are the middle layer and longitudinal muscles are the outermost layer

4. Serosa: It is present only in the region of the alimentary canal within the abdominal cavity. Instead of serosa, the mouth, pharynx, and oesophagus have a dense sheath of collagen fibres called the adventitia

Four layers of Alimentary canal surrounding the lumen are seen in the diagram below :