Anatomy of the Middle Ear - Boundaries ,Contents and Functions By Dr. Deekshith Reddy скачать в хорошем качестве

Anatomy of the Middle Ear - Boundaries ,Contents and Functions By Dr. Deekshith Reddy

Overview The middle ear is an air-filled, mucosa-lined cavity inside the petrous temporal bone, spanning from the tympanic membrane laterally to the lateral wall of the inner ear medially. Its core role is mechanical transmission and amplification of sound from the tympanic membrane to the oval window of the cochlea via the auditory ossicles. Subdivisions Tympanic Cavity (Mesotympanum) Lies directly medial to the tympanic membrane. Houses the complete chain of auditory ossicles—malleus, incus, stapes—suspended by ligaments and moved by tiny muscles. Epitympanic Recess (Attic) Air space superior to the tympanic cavity. Receives the heads/body of the malleus and incus and communicates posteriorly with mastoid air cells via the aditus to the mastoid antrum. Boundaries (Visualize a Rectangular Box) Roof (Tegmen Tympani) Thin plate of petrous temporal bone. Separates the cavity from the middle cranial fossa and temporal lobe dura. Floor (Jugular Wall) Very thin bony plate over the superior bulb of the internal jugular vein. Dehiscence here risks venous bleeding or pulsatile tinnitus if eroded. Lateral Wall Formed mainly by the tympanic membrane; superiorly by the lateral wall of the epitympanic recess. Manubrium of malleus is embedded in the membrane, forming the umbo landmark. Medial Wall (Labyrinthine Wall) Lateral wall of inner ear with key prominences. Promontory overlies the basal turn of the cochlea; oval window (fenestra vestibuli) receives the stapes footplate; round window (fenestra cochleae) allows pressure relief. Facial canal produces a horizontal ridge as the facial nerve courses posteriorly. Anterior Wall (Carotid Wall) Thin plate related to the internal carotid artery. Openings for the pharyngotympanic (auditory) tube and the canal for tensor tympani muscle. Posterior Wall (Mastoid Wall) Bony partition separating cavity from mastoid air cells. Superior opening—the aditus to the mastoid antrum—connects epitympanum with mastoid system; pyramidal eminence transmits stapedius tendon. Principal Contents Auditory Ossicles Malleus: handle attached to tympanic membrane; head projects into epitympanum; transmits vibrations to incus. Incus: body in epitympanum; long process articulates with stapes. Stapes: head articulates with incus; footplate fits into oval window to drive cochlear fluids. Muscles Tensor Tympani (V3): inserts on malleus handle; increases membrane tension to dampen low-frequency noise (e.g., chewing). Stapedius (Facial Nerve): inserts on stapes neck; reflexively reduces stapes movement to protect inner ear from loud sounds. Nerves Chorda Tympani (Facial Nerve branch): traverses the cavity between malleus and incus; carries taste from anterior two-thirds of tongue and parasympathetics to submandibular/sublingual glands. Tympanic Plexus (Glossopharyngeal via Jacobson’s nerve): on the promontory; provides mucosal sensation and forms the lesser petrosal pathway to the parotid. Facial Nerve (Canal): runs in the medial/posterior walls; close surgical and pathology relevance. Mucosa and Air Cells Respiratory mucosa lines the cavity and communicates with nasopharynx via the pharyngotympanic tube and with mastoid air cells posteriorly. Communications & Pathways Pharyngotympanic (Auditory) Tube Ventilates the middle ear, equalizes pressure, and clears secretions to the nasopharynx. Cartilaginous portion opens during swallowing/yawning via tensor veli palatini. Aditus to Mastoid Antrum → Mastoid Air Cells Provides posterior pathway for aeration and potential spread of infection. Core Functions Impedance Matching & Amplification Area difference (large tympanic membrane → small oval window) and ossicular lever action boost sound pressure to efficiently move cochlear fluids. Pressure Equalization & Drainage Eustachian tube maintains near-ambient middle-ear pressure; mucociliary clearance drains secretions to the nasopharynx for middle-ear health. Rapid-Fire Recap (MCQ-Style One-Liners) Roof of middle ear → Tegmen tympani; separates from middle cranial fossa. Floor relation → Superior bulb of internal jugular vein (jugular wall). Medial wall landmarks → Promontory, oval window (stapes), round window, facial canal ridge. Anterior wall openings → Pharyngotympanic tube and canal for tensor tympani; related to ICA. Posterior wall connection → Aditus to mastoid antrum leading to mastoid air cells. Muscle innervations → Tensor tympani by V3; stapedius by facial nerve. Nerve crossing cavity → Chorda tympani between malleus and incus. Primary function → Impedance matching via area and lever advantages to drive cochlear fluids. Common complication pathway → Otitis media → mastoiditis via aditus. Reflex that protects inner ear → Stapedius-mediated acoustic reflex.. #middleearanatomyanimation #middleear #drgbhanuprakash #middleeargrossanatomy #anatomyofmiddleear #middleearboundaries #middleearcontents #middleearfunctions #middleeargrossanatomy