Question

Haversian system observed in-

Answer 1

It is observed in bones. The blood vessels and nerve entering the bones remain in the Haversian canals

Answer 2

The channels are formed by concentric layers called lamellae. The haversian canals surround blood vessels and nerve cells throughout bones and communicate with bone cells (contained in spaces within the dense bone matrix called lacunae) through connections called canaliculi.

Clopton Havers (24 Feb 1657 (Stambourne, Essex) - Apr 1702) was an English physician who did pioneering research on the micro-structure of bone. He is believed to have been the first person to observe and almost certainly the first to describe what are now called Haversian canals and Sharpey's fibres." Wikipedia.
The osteon or haversian system /həˈvɜːr.ʒən/ (named for Clopton Havers) is the fundamental functional unit of much compact bone. Osteons are roughly cylindrical structures that are typically several millimeters long and around 0.2 mm in diameter.