The three bones of the middle ear, malleus (m), incus (i) and stapes (s) are shown in panel A as they articulate with each other. In panel B, the ossicles are shown in isolation so that their parts can be viewed.
The malleus is the lateral most ossicle. It consists of a head (h) located in the epitympanic recess, neck (n), lateral process (lt), anterior process (ap) and handle or manubrium (mm). The manubrium and lateral process are attached to the eardrum laterally. The radial fibers in the middle layer of the eardrum insert into the perichondrium of manubrium. The inferior tip of the manubrium is located at the umbo of the eardrum. The articular facet (af) on the head of the malleus forms a joint with the body of the incus. In addition to its attachments to the eardrum and incus, the malleus is held in place by the superior, anterior and lateral malleal ligaments and the insertion of the tendon of the tensor tympani muscle into the medial side of the manubrium. Embryonic origin - Head and neck from the mandibular (first) arch; manubrium from hyoid (second) arch.
The incus is the second ossicle. It consists of a body (b) and short process (sp) located in the epitympanic recess, a long process (lp) and a lenticular process (not visible). The articular facet (af) of the incus forms a joint with the head of the malleus while the lenticular process articulates with the head of the stapes. The long process projects inferiorly nearly parallel to the manubrium of the malleus. The short process projects posteriorly into the fossa incudis where it is held in position by the posterior incudis ligament. The superior ligament attaches the body of the incus to the tegmen tympani. Embryonic origin - Body and short process from mandibular arch; long and lenticular processes from the hyoid arch.
The stapes is the third ossicle. It consists of a head (sh), anterior (ac) and posterior crura (pc) and footplate (fp). The head of the stapes articulates with the lenticular process of the incus while the footplate is fitted into the oval window and held there by the annular ligament. The tendon of the stapedius muscle inserts into the posterior portion of the stapes head. Embryonic origin - Head and crura from hyoid arch; footplate from otic capsule.
Plates A and B modified from the companion slides with Vidic' and O'Rahilly, An Atlas of the Anatomy of the Ear, W. B. Saunders, 1971.