The thympanic membran has a round or oval structure and is tilted a little to the side in comparison to the outer ear canal. It is tilted to the lower front medial and to the upper back side to the lateral side. It is quite small: 10-11 mm in high and around 9 mm wide. It is around 0,1 mm thick.
The ear drum is surrounded by the cartilage ring, the so-called Anulus fibrocartilagineus. It brings tension to the ear drum, just like in the musical instrument where the name derives from. In the otoscopy the ring is visible as a white edge. The ring itself is grown together with the surrounding bone structure and hooked into a indention (Sulcus tympanicus), which is disconnected at the top (Incisura tympanica).