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Dr. Ahmed Fathalla Ibrahim THE EAR • • 1. 2. 3. Is an organ of hearing & balance Consists of three parts: External Ear Middle Ear Internal Ear THE EXTERNAL EAR • AURICLE • EXTERNAL AUDITORY MEATUS AURICLE: • Shape: consists of a thin plate of elastic cartilage • Function: collects air vibrations • Motor supply: facial nerve EXTERNAL AUDITORY MEATUS • Shape: a curved tube formed of elastic cartilage (outer 1/3) & tympanic plate of temporal bone (inner 2/3) • Function: conducts sound waves from auricle to tympanic membrane THE MIDDLE EAR (TYMPANIC CAVITY) • Definition: air-containing cavity in petrous part of tympanic bone, lined with mucus membrane • Function: transmits vibration of tympanic membrane to perilymph of internal ear • Communications: 1. Anteriorly: with nasopharynx (through auditory tube) 2. Posteriorly: with mastoid antrum 3. Nerve supply: tympanic branch of glossopharyngeal nerve THE MIDDLE EAR • Roof: tegmen typani (thin plate from petrous temporal bone), separates middle ear from temporal lobe of brain • Floor: thin plate of bone, separates middle ear from superior bulb of internal jugular vein THE MIDDLE EAR • Anterior wall: 1. Superiorly: has 2 openings (for auditory tube & for canal of tensor tympani) 2. Inferiorly: thin plate of bone separating middle ear from internal carotid artery THE MIDDLE EAR • Posterior wall: 1.Superiorly: has an opening (aditus to mastoid antrum) 2.Inferiorly: a conical projection (pyramid) for emergence of stapedius • THE MIDDLE EAR Lateral wall: tympanic membrane • Medial wall: 1. Promontory: rounded projection formed by cochlea 2. Fenestra vestibuli: oval opening, above & behind promontory, closed by base of stapes 3. Fenestra cochleae: round opening below promontory, closed by secondary tympanic membrane 4. Prominence for facial nerve canal: runs backward above promontory & fenestra vestibuli then curves downward behind pyramid THE TYMPANIC MEMBRANE • Shape: a thin fibrous membrane between external & middle ear, has a small depression (umbo) produced by handle of malleus, divided into pars flaccida & pars tensa • Nerve supply: • Outer surface: auricular branch of vagus • Inner surface: tympanic branch of glossopharyngeal AUDITORY OSSICLES MALLEUS: • Head: articulates with body of incus • Neck • Handle: firmly attached to medial surface of tympanic membrane, receives insertion of tensor tympani • Anterior process • Lateral process: attached to anterior & posterior malleolar folds of tympanic membrane AUDITORY OSSICLES INCUS: • Body: articulates with head of malleus • Long process: articulates with head of stapes • Short process: attached to tympanic cavity AUDITORY OSSICLES STAPES: • Head: articulates with long process of incus • NecK: receives insertion of stapedius • Base: attached to fenestra vestibuli MUSCLES OF OSSICLES TENSOR TYMPANI: • Origin: auditory tube • Insertion: handle of malleus • Nerve supply: mandibular of trigeminal • Action: damps down vibration of tympanic membrane STAPEDIUS: • Origin: pyramid • Insertion: neck of stapes • Nerve supply: facial • Action: damps down vibration of stapes FACIAL NERVE • Course: runs in facial canal then emerges through stylomastoid foramen • Branches: 1. Nerve to stapedius 2. Chorda tympani: carries taste fibers from anterior 2/3 of tongue & preganglionic parasympathetic fibers to submandibular & sublingual salivary glands 3. Greater petrosal nerve: carries taste fibers from soft palate & preganglionic parasympathetic fibers to lacrimal, nasal & palatine glands THE INTERNAL EAR • Lies in petrous part of temporal bone • Consists of: 1. Bony labyrinth 2. Membranous labyrinth BONY LABYRINTH • 1. 2. 3. • Consists of: Vestibule 3 semicircular canals Cochlea They are cavities inside bone, filled with perilymph in which membranous labyrinth is suspended MEMBRANOUS LABYRINTH • Lodged within bony labyrinth • Filled with endolymph & surrounded by perilymph • Consists of: 1. Utricle & saccule: in vestibule 2. 3 semicircular ducts: in semicircular canals 3. Cochlear duct: in cochlea VESTIBULOCOCHLEAR NERVE • Divides into: 1. Vestibular nerve: supplies utricle, saccule & semicircular ducts 2. Cochlear nerve: supplies cochlear duct