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The Middle Ear and Ossicles

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The Middle Ear and Ossicles Disclosures Difficult Head & Neck • None Anatomy: The Middle Ear & Ossicles Benjamin Huang, MD,MPH University of North Carolina at Chapel Hill Objectives Lecture Organization By the end of this lecture, you should be • Middle ear overview able to: • Ossicles • Name the compartments of the middle ear and • Muscles and tendons their contents • Facial nerve • Describe the anatomy of the ossicles • Identify normal muscles and ligaments in the • Windows, spaces and recesses middle ear • Describe the tympanic course of the facial nerve • Identify key anatomic windows and spaces associated with the middle ear The Tympanic Cavity The Tympanic Cavity Epitympanum Epitympanum Mesotympanum Aditus ad Antrum Hypotympanum Mastoid Antrum The Tympanic Cavity NPC Causing Mastoid Effusion Protympanum Mesotympanum The Ossicles Malleus • Malleus → Incus → Stapes • Transmit and amplify sound vibrations from tympanic membrane to oval window • Mnemonic: “M I S O” Top image: By Oreilleinterne.jpg: Marc GiaconeSVG version/translation: Angelito7 - Oreilleinterne.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/ w/index.php?curid=59840795 Malleus Incus Head Neck Lat. Proc. Manubrium Suspensory Ligaments of the Incus Ossicles Suspensory Ligaments Short Long • Anterior malleal Proc. Proc. • Lateral malleal • Superior malleal • Posterior incudal Sag. “Molar Tooth” View Manubrium Lenticular Malleus Incus Proc. Stapes Muscles in the Middle Ear Two middle ear muscles: • Tensor tympani – Runs in canal along roof of bony Eustacian tube – Turns at cochleoriform process before inserting on malleus neck – Innervation: CN V3 • Stapedius – Smallest muscle in human body – Located adjacent to FN in pyramidal eminence – Inserts on stapes neck – Innervation: CN VII Tensor Tympani Stapedius Muscle Stapes neck Incus lenticular process Stapedius tendon Stapedius belly Facial Nerve Facial Nerve Windows and Recesses Windows • Oval window • Round window Spaces & Recesses • Prussak’s space • Facial recess • Sinus tympani • Supratubal (anterior epitympanic) recess Oval Window Fenestral otospongiosis Round Window Prussak’s Space Left image courtesy of Dr Piotr Gołofit, Radiopaedia.org, rID: 43407 Epitympanic Cholesteatoma Facial Recess & Sinus Tympani Pyramidal Eminence Facial Sinus Recess Tympani Anterior Epitympanic Summary (Supratubal) Recess • Middle ear compartments Supratubal • Ossicular anatomy Recess Epitympanic – “M I S O” Cog • Muscles & tendons – Only 2: Tensor tympani & stapedius Epitympanum • Facial nerve • Windows, spaces & recesses – Put these in your checklist Geniculate CN7 - CROSS SECTIONAL ganglion Labyrinthine ANATOMY Epitympanum REVIEW Additus ad antrum Koerner septum Mastoid antrum AXIAL CT ANATOMY AXIAL CT ANATOMY Anterior malleal lig. Head of malleus Head of malleus Tensor Additus Incus body tympani ad antrum and short process Mastoid CN7 – antrum tympanic segment AXIAL CT ANATOMY AXIAL CT ANATOMY Tensor tympani tendon Manubrium of malleus Neck of malleus Cochleoriform process Pro- Incudo- tympanum Incus long stapedial process joint Oval Round window CN7 – window Facial descending (stapes footplate) recess (mastoid) segment Stapes crura Pyramidal eminence Sinus tympani (CN7 & Stapedius) CORONAL CT ANATOMY CORONAL CT ANATOMY Tegmen tympani Tegmen tympani CN7 – tympanic CN7 segment Head of malleus Incus body & long process Prussak’s Tensor space tympani tendon Scutum Neck & lateral Incus - Lenticular Stapes entering process of malleus Process oval window CORONAL CT ANATOMY CORONAL CT ANATOMY Superior SCC Lateral Incus SCC short Posterior process SCC CN7 – Round mastoid window segment Internal jugular CN7 – vein tympanic segment Stylomastoid foramen .
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