Question

Mucus is secreted by
(a) Stomach
(b) Duodenum
(c) Large intestine
(d) All the above

Answer 1

Hint: The submucosa layer of the alimentary canal has glands that secrete mucus to protect its lining. It is lined in all the organs that are included in the alimentary tract.

Complete answer:
The wall of the alimentary canal starting from the esophagus to the rectum is lined by four layers namely serosa, muscularis externa, submucosa, and mucosa. The layer formed by the loose connective tissue that contains nerves, blood vessels, and lymph vessels in the submucosa. This layer has glands specific to organs that secrete mucus. The stomach, large intestine, and duodenum are the parts of the alimentary canal.

Additional Information:
 - The first layer in the alimentary canal of humans is serosa which is made up of mesothelium with some connective tissue.
- Muscularis externa is the second layer of the alimentary canal made up of smooth muscle that is usually arranged into outer longitudinal and circular muscles.
- Submucosa is the third layer made up of loose connective tissue which contains glands that secrete mucus, blood vessels, nerves, and lymph vessels. Burner’s glands in the duodenum and large intestine, gastric glands in the stomach, secretes mucus.
- In the stomach mucosa forms irregular folds called gastric rugae in between many gastric glands. In the small intestine, mucosa forms small folds called villi. It is the innermost layer of the alimentary canal.
So, the correct answer is ‘all the above’.

Note: -The mucus secreted by the Brunner’s gland and gastric glands helps in the protection of alimentary canal lining from the acidic secretions of the stomach and enzymes secreted by the intestines.
-Gastric glands are of three types namely cardiac gland, pyloric glands, and oxyntic glands. All three glands secrete mucus along with other gastric secretions.