Symbiotic bacteria present in the colon of the large intestine of humans produce:

Select the correct sequence of the layers of the alimentary canal from the inside to the outside.

What is the another name of gastro-oesophageal sphincter?

Identify $X, Y$ and $Z$ from the following figure.

The mucosa of the stomach is thick and folded. What are the advantages of this?

The esophagus is a thin,long tube which extends posteriorly passing through the neck,thorax,and diaphragm to lead to a '$J$' shaped bag-like structure called the stomach.