Which part of our body serves as a habitat for symbiotic microorganisms?

The central axis of each hepatic lobule is formed by:

Teeth are chiefly made up of

Given below are two statements.
Statement $I$: Since human beings have different kinds of teeth fitted in two jaws,the dentition is described as diphyodont.
Statement $II$: Human beings have four different kinds of teeth,hence it is described as heterodont.

Describe the external structure of the small intestine and large intestine.

The wall of the rectum lacks: