part of part of has part has part overlaps overlaps in taxon develops from develops from adjacent to adjacent to contributes to morphology of Testudines membrane organ external acoustic meatus external ear middle ear tympanic membrane A thin membrane that separates the external ear from the middle ear, consisting of two epithelia (one part of the the external accoustic meatus epithelium, the other part of the tympanic cavity epithelium) with a fibrous layer between them. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles. Rupture or perforation of the eardrum can lead to conductive hearing loss. [WP,unvetted]. MESH:D014432 VHOG:0001146 XAO:0000212 FMA:9595 GAID:870 UMLS:C0041445 paries membranaceus cavi tympani The tympanic membrane (TM) has three layers, two epithelia provided by the external acoustic meatus (EAM) and the MEC, derived respectively from the first pharyngeal cleft and pouch, and a mesenchymally derived fibrous stratum EMAPA:19062 The thin membrane which closes externally the cavity of the middle ear and is deeply sited at the bottom of the external auditory meatus. [Dorian_AF, Elsevier's_encyclopaedic_dictionary_of_medicine, Part_B:_Anatomy_(1988)_Amsterdam_etc.:_Elsevier][VHOG] UBERON:0002364 membranous wall of tympanic cavity Wikipedia:Tympanic_membrane MA:0000257 In particular, a tympanic membrane was not present in the earliest tetrapods (...). An ear utilizing a tympanic membrane evolved independently at least three times in tetrapods: (1) in the lineage that leads to anurans (frogs), (2) in the line of evolution to turtles and diapsids, and (3) in the late synapsid lineage that gave rise to mammals.[well established][VHOG] ear drum eardrum NCIT:C12502 myrinx Rivinus' membrane most AOs consider this part of the middle ear, so we go with this and place it in the middle ear as a border to the external, although it could be considered to overlap the external ear in that it has an EAM layer as part - for this reason we do not consider middle and external ear to be spatially disjoint. SCTID:181180005 lateral wall of tympanic cavity tympanum tympanic cavity inner epithelial layer of tympanic membrane pharyngeal membrane of 1st arch outer epithelial layer of tympanic membrane intermediate layer of tympanic membrane