Neuroscience 2022 Anatomy Dr. Doaa Shuaib of the ear Assistant Professor of Anatomy & Embryology Faculty of Medicine – Cairo University Email: doaa.shuaib@kasralainy.edu.eg Parts of the ear Malleus Incus Dr. Doaa Shuaib Stapes Middle ear Internal ear External ear Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) External ear Auricle External auditory meatus Tympanic membrane Parts • • • Auricle External auditory meatus Tympanic membrane Dr. Doaa Shuaib Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) a. Auricle Auricle • • It is formed of single yellow elastic cartilage covered with skin. Its lower part is called the lobule. b. External auditory meatus Lateral 1/3 (cartilage ) Medial 2/3 (bone ) Dr. Doaa Shuaib Source: Atlas of Anatomy, Anne M.Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) External Auditory Meatus - Site: It extends from the auricle to the tympanic membrane. Shape: It is an S-shaped tube Length: 24 mm in length Parts: Its lateral 1/3 is cartilaginous and its medial 2/3 is bony. Ismuth: the narrowest site of the tube (5 mm from tympanic membrane). Nerve supply: auriculotemporal nerve & auricular branch of vagus. c. Tympanic membrane (ear drum) Tympanic Membrane Tympanic Membrane Site Stretched obliquely at the medial end of the external auditory meatus • It has: - 2 surfaces - 2 parts - 3 layers • Dr. Doaa Shuaib Source: Atlas of Human Anatomy, Sixth Edition-Frank H. Netter, M.D Handle of malleus Inner surface Tympanic Membrane Surfaces Outer surface: - Concave - directed downwards laterally & forwards. Inner surface: - Convex - (point of maximum convexity is called umbo). Dr. Doaa Shuaib Outer surface Source: Atlas of Human Anatomy, Sixth Edition-Frank H. Netter, M.D Umbo Tympanic Membrane Pars flaccida Handle of malleus Umbo Dr. Doaa Shuaib Cone of light Pars tensa Source: Atlas of Human Anatomy, Sixth EditionFrank H. Netter, M.D Parts • • • Normal right tympanic membrane Source: http://otitismedia.hawkelibrary.com/normal/tm_2 Pars tensa (the major part) Pars flaccida (the small triangular upper part). The anteroinferior quadrant is called cone of light, because it reflects the light coming from the examiner’s otoscope Tympanic Membrane Dr. Doaa Shuaib Layers - Outer layer (skin) Intermediate layer (fibrous) which is abscent in pars flaccida Inner layer (mucosa of middle ear). Tympanic Membrane Nerve supply • • Outer surface is supplied by auriculotemporal nerve and auricular branch of vagus nerve. Inner surface is supplied by the tympanic plexus of nerves (mainly from glossopharyngeal nerve). Arterial supply • • Outer surface is supplied by the deep auricular artery (from maxillary artery). Inner surface is supplied by anterior tympanic artery (from maxillary artery) Middle ear (tympanic cavity) Dr. Doaa Shuaib Site • A small vertical space which lies within the petrous temporal bone tympanic cavity Source: kenhub Anatomy Shape • • • Biconcave lens Very narrow from side to side (2 mm) Longer anteroposterior & vertical diameters (15 mm). Source: Textbook of anatomy, HEAD, NECK AND BRAIN, Vishram Singh, 2nd edition (2014) Walls Posterior wall Roof Walls It has 6 walls: • Roof • Floor • Medial wall • Lateral wall • Anterior wall • Medial wall • Posterior wall Lateral wall Medial wall Dr. Doaa Shuaib Anterior Floor wall Dr. Doaa Shuaib Walls Lateral wall M L Tympanic membrane Tympanic membrane Anterior view Source: Atlas of Human Anatomy, Sixth Edition-Frank H. Netter, M.D Tygmen tympani Walls Dr. Doaa Shuaib P A Side view Tygmen tympani Source: Atlas of Anatomy, Anne M.Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) Roof - Tygmen tympani Tygmen tympani separates the middle ear cavity from the temporal lobe of the brain Walls Tympanic branch of 9th cranial nerve P A P A Dr. Doaa Shuaib IJV Floor Side view Jugular fossa Side view Source: Atlas of Anatomy, Anne M.Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) Floor - Thin convex plate of bone It separates the middle ear from the jugular fossa containing the superior bulb of internal jagular vein. Its pierced by the tympanic branch of 9th cranial nerve Oval window Walls Foot of stapes Horizontal part of facial canal Horizontal part of facial canal Tympanic plexus Promontory Promontory A P P A Dr. Doaa Shuaib Promontory Round window Side view Source: Atlas of Anatomy, Anne M.Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) Medial wall - - Round window Side view Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) Promontory: Rounded central bulging with tympanic plexus on it. Oval window: above & behind the promontory (is closed by stapes). Round window: below & behind the promontory (is closed by 2ndry tympanic membrane). Horizontal part of facial canal: it runs backwards above the promontory and oval window. Walls Canal for tensor tympani Tensor tympani Bony part of auditory tube Tensor tympani Dr. Doaa Shuaib P P A A Auditory tube Carotid canal Side view Side view Source: Atlas of Anatomy, Anne M.Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) Anterior wall - Internal carotid artery Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) Canal for tensor tympani The bony part of the auditory tube The ascending part of the carotid canal Mastoid antrum Walls Mastoid antrum Aditus Aditus Mastoid air cells Stapedius muscle Tympanic cavity Dr. Doaa Shuaib P P A A Vertical part of facial canal Pyramid Side view Source: Atlas of Anatomy, Anne M.Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) - Posterior wall - Facial nerve Pyramid Tendon of stapedius Side view Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) Aditus and antrum: the opening which communicates the upper part of the middle ear with the mastoid antrum. The pyramid: A small conical bony projection containing the origin of the stapedius Vertical part of facial canal: behind the pyramid. PM: promontory TP: tympanic plexus O: Oval window R: round window P: pyramid Source: Textbook of anatomy, HEAD, NECK AND BRAIN, Vishram Singh, PhD, 2nd edition (2014) Contents of middle ear 1. 2. 3. 4. Three ossicles: malleus, incus, stapes. Two muscles: tensor tympani, stapedius Two nerves: tympanic plexus, chorda tympani Arteries Contents Incus Aditus Facial canal Stapes Oval window Malleus Incus Malleus Head Head Short process Anterior process Dr. Doaa Shuaib L M Tensor tympani Ossicles Handle Head Tympanic membrane Anterior view Source: Atlas of Anatomy, Anne M. Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) Promontory Tendon of stapedius Long process Stapes Foot Source: Atlas of Human Anatomy, Sixth EditionFrank H. Netter, M.D Three ossicles articulating together by synovial joints, from lateral to medial they are: a- Malleus is fixed to the inner surface of the tympanic membrane. b- Incus lies between malleus and stapes. c- Stapes closes the oval window. Contents Tensor tympani Malleus Stapedius Dr. Doaa Shuaib L M A P Auditory tube Anterior view Source: Atlas of Anatomy, Anne M.Gilroy, Brian R. MacPherson, Lawrence M. Ross (2nd edition) Muscles • • Tensor tympani Auditory tube Side view Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) Tensor tympani and stapedius muscles Acting together reflexly to damp down the high noise by decreasing the vibration of the tympanic membrane and movements of stapes. Chorda tympani Facial nerve A P Contents Nerves • • Chorda tympani Tympanic plexus Side view Tympanic membrane Dr. Doaa Shuaib Side view Source: Atlas of Human Anatomy, Sixth Edition-Frank H. Netter, M.D Tympanic membrane Arteries - Anterior tympanic artery (branch of maxillary artery) - Posterior tympanic artery (branch of posterior auricular artery) - Superior tympanic artery (branch of middle meningeal artery) - Inferior tympanic artery (branch of ascending pharyngeal artery) Pharyngotympanic (auditory) tube Middle ear cavity Pharyngotympanic (auditory) tube Length Dr. Doaa Shuaib 36 mm Parts Bony cartilaginous Beginning Anterior wall of the middle ear Bony part Direction Downwards, forwards and medially Cartilaginous part Pharyngotympanic tube Nasopharynx Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) Inferior concha Pharyngotympanic (auditory) tube End • • In the nasopharynx 1cm behind the inferior concha Dr. Doaa Shuaib Source: Atlas of Human Anatomy, Sixth Edition-Frank H. Netter, M.D Opening of auditory tube Inner ear Internal auditory meatus Inner ear Inner ear Site • • Dr. Doaa Shuaib It lies in the petrous temporal bone between the medial wall of the middle ear and the bottom of the internal auditory meatus Parts • • Bony labyrinth Membranous labyrinth Internal auditory meatus Source: Gray's Basic Anatomy - Richard L. Drake, Wayne Vogl, Adam W.M. Mitchell (2012) Inner ear Cochlea Vestibule Dr. Doaa Shuaib Semicircular canals Vestibule Source: Atlas of Human Anatomy, Sixth EditionFrank H. Netter, M.D Bony labyrinth Cochlea Source: Sobotta Atlas of Anatomy, 15 edition - Consists of 3 bony parts: • Vestibule in the center (in the middle) • Cochlea in front (in front) • Semicircular canals behind (behind) Semicircular canals Inner ear Dr. Doaa Shuaib Foot of stapes in oval window Membranous labyrinth Cochlea of bony labyrinth Promontory Round window Endolymph Perilymph Source: Atlas of Human Anatomy, Sixth Edition-Frank H. Netter, M.D Membranous labyrinth - They are interconnected membranous cavities lying inside the bony labyrinth These cavities are filled with fluid called endolymph and separated from bony labyrinth by perilymph. Inner ear Semicircular canals Semicircular ducts Utricle Cochlear duct Vestibule Dr. Doaa Shuaib Saccule Endolymphatic duct Source: Atlas of Human Anatomy, Sixth Edition-Frank H. Netter, M.D Membranous labyrinth - It contains receptors of hearing & equilibrium. - It consists of: 1- Utricle and saccule: inside the vestibule. 2- Three semicircular ducts: within semicircular canals. 3- Cochlear duct: within the cochlea. 4- Endolymphatic duct: Lies in the aqueduct of vestibule Cochlea Thank you
