What is tunica externa and what does it do?

The tunica externa, also known as the adventitia, is the outermost layer of blood vessels, composed mainly of connective tissue. Its primary function is to provide structural support and protection to the vessel, anchoring it to surrounding tissues. In larger blood vessels, it may also contain nerves and smaller blood vessels that supply the vessel wall itself. Overall, the tunica externa helps maintain the integrity and stability of the vascular system.