The malleus is so called because it resembles a hammer. It is the largest and the most laterally placed ossicle.
Incus or Anvil
It is so called because it resembles an anvil, used by blacksmiths.
Ossicles of the left ear
this bone is so-called because it is shaped like a stirrup. It is the smallest and the most medially placed ossicle of the ear.
Joints of the Ossicles
- The incudomalleolar joint is a saddle joint.
- The incudostapedial joint is a ball and socket joint. both of them are synovial joints. They are surrounded by capsular ligaments.
Muscles of the Middle Ear
The tensor tympani lies in a bony canal that opens at its lateral end on the anterior wall of the middle ear, and at the medial end on the base od the skull. The auditory tube lies just below this canal. Thus muscle arises from the walls of the canal in which it lies.
The tensor tympani is supplied by the mandibular nerve. It develops from the mesoderm of the first branchial arch.
The stapedius lies in a bony canal that is related to the posterior wall of the middle ear.
The muscle arises from the walls of this canal. It tendon emerges through the pyramid and passes forwards to be inserted into the posterior wall of the middle ear.
The muscle arises from the walls of this canal. Its tendon emerges through the pyramid and passes forwards to be inserted into the posterior surface of the neck of the stapes. The stapedius is supplied by the facial nerve. It develops from the mesoderm of the second branchial arch.
The bony labyrinth consists of three parts:
- Cochlea anteriorly.
- Vestibule, in the middle.
- Semicircular canals posteriorly.
Parts of the Membranous Labyrinth
It is in the form of a complicated, but continuous closed cavity filled with endolymph. Parts of the epithelium of the membranous labyrinth are specialized to form receptors for sound, the organ of Corti; for static balance, the maculae, and for kinetic balance the cristae.
Like the bony labyrinth, the membranous labyrinth also consists of three main parts.
The spiral dust of the cochlea or organ of hearing, anteriorly.
The utricle and saccule, the organs of static balance within the vestibule.
The semicircular ducts the organs of kinetic balance posteriorly.
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