Question

The function of tunica externa is to ________.

Answer 1

To protect and/or reinforce the blood vessels  

Answer 2

The tunica externa (New Latin "outer coat"), also known as the tunica adventitia (New Latin "additional coat")(or adventitia for short), is the outermost tunica (layer) of a blood vessel, surrounding the tunica media. It is mainly composed of collagen and, in arteries, is supported by external elastic lamina.