Umbo is also a term for a shield boss and for the swollen (oldest) part of a bivalve (clam, mussel, etc) shell near the ligament that holds together the two shell valves.

The umbo is the most depressed part of the tympanic membrane.

Depression

The manubrium of the malleus is firmly attached to the medial surface of the membrane as far as its center, which it draws toward the tympanic cavity; the lateral surface of the membrane is thus concave, and the most depressed part of this concavity is named the umbo.

External links

• Diagram at unmc.edu
• Diagram at aap.org