Assignment on Tongue • Draw the dorsal surface of tongue & label the parts • Draw a neat diagram showing the sensory innervation of tongue • Draw the ventral surface of tongue and label the structures lying there • Draw the lymphatic drainage of tongue External ear • Has – Auricles – External auditory meatus • Lined – By skin Auricle • Made up of – Yellow elastic cartilage • Except lobule • Covered by – Perichondrium and skin • Has several depressions and elevations • Concha – Deepest depression • Helix – Elevated margin • Antihelix – Y shaped curved structure in front of helix • Tragus – Tongue-like projection overlapping the opening of the external acoustic meatus • Antitragus – Overhang the concha • Scaphoid fossa – Depressed region deep to helix • Intertragic notch – Bounds tragus inferiorly & separates it from antitragus Auricle Auricle - Outer Elevation • Outer elevated rim • Helix – Elevated margin – Has 2 limbs • Anterior – Crus • Posterior – Ends in Lobule • Fatty tissue – Lobule Auricle – Inner elevation • Anti helix – Prominent elevation – Lies infront of • Posterior part of helix – Upper end • Divides into – 2 crura » Anterior crus » Posterior crus – Triangular fossa » Between the 2 crura Auricle - Elevation • Tragus – Lies in front of external acoustic meatus – Small flap of cartilage • Antitragus – Lies behind the tragus • Intertragic notch – Depression in between tragus & antitragus Auricle -Depressions • Concha – Large depression – Leads towards • External acoustic meatus – Boundaries • • • • • Tragus Intertragal notch Antitragus Antihelix Inferior crus of the antihelix – and • Root of the helix • Parts – Cymba • Above the crus of Helix • Corresponds to – Suprameatal triangle – Cavum Auricle -Depressions • Scaphoid fossa – Depression between • Helix & antihelix • Triangular fossa – Depression between • 2 crura of helix Auricle - Muscles • Extrinsic – Attaches • Skull (mastoid process) or scalp to auricle – Auricularis anterior, posterior & superior – Moves the auricle as a whole • Intrinsic – Attaches • Between the parts of cartilage – Helicis major & minor, Tragicus & Antitragicus, Obliqus auricularis & Transversus auricularis – Alters the shape of auricle Auricle • Arterial supply – Posterior auricular • And – Superficial temporal arteries Auricle – Lymphatic drainage • Posterior aspect – Posterior auricular nodes • At mastoid tip • Tragus and upper part of the pinna – Preauricular nodes • Remainder of pinna – Deep cervical nodes • Medial surface Auricle - Nerves – Upper 1/3rd • Lesser occipital – Lower 2/3rd (Helix, antihelix and lobule) • Commonly called back – & • Helix, antihelix and lobule – Great auricular nerve • Lateral surface – Anterior to external acoustic meatus (Tragus crus of helix) • Auriculotemporal nerve • Concha and its eminence – Vagus • Helix, antihelix and lobule – Great auricular nerve Auricle – Applied anatomy • Lobule – Ear boring to wear rings • Cartilage, perichondrium and fat can be used for – Reconstructive surgery of Middle ear & Nose • Incisura terminalis – Space b/w crus of helix & tragus – Devoid of cartilage – Surgical importance • To approach external acoustic meatus • Right ear is better in hearing speech • Left ear is better in hearing music External auditory meatus • Extent – From • Concha – To • Tympanic membrane • Length – 24 mm • Shape – S-shape At examination Pull the auricle posteriorly and superiorly to straighten the canal) External auditory meatus • Consists of – Cartilaginous part (outer 1/3) • 8 mm in length • Formed by – Elastic cartilage – Covered by » Thick skin and contains hair follicles, sebaceous and ceruminous glands – Bony part (inner 2/3) • 16 mm in length • Tympanic plate of temporal – Below & front • Squamous part of temporal – Above & behind • Covered by – Skin Roof & posterior wall of EAC are shorter than floor & anterior wall External auditory meatus • Constrictions – Junction of bony and cartilaginous parts – Narrowest part • Medial to junction of bony & cartilaginous parts nearly 5 mm lateral to Tympanic membrane • Recesses – Anterior recess • Anterior wall of EAC goes sharply forward to the TM to form a blind pouch Nerve supply • Auriculo temporal nerve(V3) – Anterior wall & roof • Auricular branch of vagus (X) – Posterior wall & floor Applied anatomy • Ear wax – External acoustic meatus produces a waxy oil called cerumen (earwax) – Protects ear from dust, foreign particles and microorganisms • Dewax – Excessive wax may block hearing – Removing wax from external acoustic meatus Ceruminous glands: Modified sweat glands and react to same stimuli as other apocrine glands Tympanic membrane • Otherwise ear drum • Partition between – External auditory canal • and – Middle ear • Shape – Oval • Position – Obliquely placed – 55 with floor of EAC – In newborn babies - horizontal • Posterosuperior part more lateral than Anterioinferior part • 9-10 mm tall • 8-9 mm wide • 0.1 mm thick Tympanic membrane • Slotted into a groove – Tympanic sulcus – Deficient superiorly • Malleolar folds – Due to the deficiency of sulcus in upper part • From the 2 ends – Forms » Anterior malleolar fold » Posterior malleolar fold • Converge to the lateral process of malleolus Tympanic membrane • Subdivisions – Pars flaccida • Small triangular area • Loosely arranged • Above malleolar folds – Pars tensa • Rest of the tympanic membrane • Tight part Tympanic membrane - Surfaces • Outer surface – Concave • Inner surface – Convex – Handle of malleus is firmly attached as far as its center • So, the point where tip of handle attaches shows maximum convexity – That point is known as Umbo Tympanic membrane - structure • Consist of three layers • Outer cuticular layer – Stratified squamous epithelium (skin) – Ectodermal origin • Middle layer or lamina propria – Fibrous layer – Mesodermal origin • Inner mucous layer – Endodermal origin – Simple columnar epithelium Examination of tympanic membrane from canal • Cone of light – Seen in anteroinferior quadrant • Handle of malleus • Long process of incus • Chorda tympani nerve Tympanic membrane - development • Outer cuticular – Ectoderm • Dorsal end of first branchial cleft • Intermediate fibrous – Mesoderm of branchial arch • Inner mucous – Endoderm • Tubotympanic recess – Formed by union of dorsal ends of first & second pharyngeal pouches Tympanic membrane – blood supply • Outer surface – Deep auricular artery • Inner surface – Anterior tympanic artery – Posterior tympanic artery • Venous drainage – Outer surface • External jugular – Inner surface • Transverse sinus • Pterygoid venous plexus Tympanic membrane • Nerve supply – Lateral surface/cuticular layer • Anterior half – Auriculotemporal • Posterior half – Auricular branch of vagus – Medial surface / mucous layer • Glossopharyngeal (tympanic plexus) Nice to know …….. • • • • • • Landmarks Cone of Light Umbo Handle of Malleus Lat Process of Malleus A & P Malleolar Fold Inner Ear Internal ear • Part of ear • Organ of – Hearing and balance • Concerned with – Reception of sound • Converts sound waves into nerve impulses – Reception of equilibration • Responds to changes in equilibrium Internal ear • Lies in – Petrous part of temporal bone • Has 2 Parts – Bony Labyrinth – Membranous Labyrinth Bony Labyrinth • Hardest part of Petrous part of temporal bone • Has three parts – Vestibule – Cochlea – Semicircular Canals • Bony labyrinth is filled with a fluid – Perilymph Vestibule • Ovoid bony chamber • Measuring 4 mm • Situated between – Medial wall of middle ear (laterally) – Internal auditory meatus (medially) • Situated between – Cochlea (anteriorly) – Semicircular canals (posteriorly) Vestibule • Contains – Central Cavity – Lateral & Medial walls • Lateral wall – Fenestra vestibule • Oval window – Closed by base of stapes Vestibule • Medial wall (inner Surface) – 2 recesses • By vestibular crest • Spherical recesses – Anterior to vestibular crest – Lodges saccule • Elliptical recesses – Posterior to vestibular crest – Lodges utricle • Below elliptical recesses – Opening of vestibular aqueduct • Contains endolymphatic duct & a vein • Postero superior – 5 openings of SCC Vestibule • Anterior wall – Opening for scala vestibule of cochlear canal • Posterior wall – Has openings for semicircular canal Semi Circular Canals • 3 semi circular canals – Superior – Posterior – Lateral • Lie in planes at right angle to each other • Ampullary end – Each canal got – open in vestibule • Non-ampullary end – Lateral SCC open • Independentally – Post. SCC and Sup. SCC form a common opening • Called CRUS COMMUNE • Anterior part of bony Cochlea labyrinth • Coiled tube like the shell of snail– 35 mm • Two and half turns around a central bone called Modiolus • Basal turn forms a bulging into tympanic cavity – Promontory Modiolus • Pyramidal Shaped • Has 2 ends – Apex or cupola • • Forwards & laterally – Base • Directed towards the bottom of internal acoustic meatus • Vessels and Nerves enter cochlea Osseous Spiral lamina • Thin plate of bone winds spirally around modiolus – Like the thread of a screw • Gives attachment to – Basilar membrane – Divides the bony cochlea into • Scala Vestibuli • Scala Tympani • Scala media • Spiral canal of modiolus – At base of spiral lamina – Contains spiral ganglion of cochlear nerve Cochlear canal • Hollow canal • Around modiolus • Basal turn forms – Promontory on medial wall of tympanic cavity Cochlear canal - Divisions • Spiral lamina has – 2 lips • Upper lip gives attachment to – Vestibular/Reissner membrane • Lower lip gives attachment to – Basilar membrane • Vestibular & basilar membrane peripherally attaches with – Endosteum of cochlear canal • Cochlear duct – Space between the membranes • Above the Reissner membrane – Scala vestibule • Below the Basillar membrane – Scala tympani Scala vestibuli and scala tympani • They contain – Perilymph • Resembles CSF – Both cavity meets at • Helicotrema – At the apex of modiolus • Scala vestibuli – Continues posteriorly with • Vestibule • Scala tympani – Separated from middle ear cavity by • Secondary tympanic membrane – At Fenestra cochlea/round window scala vestibuli and scala tympani • Filled with perilymph • Communicate with each other – At the apex of cochlea through an opening called HELICOTREMA • Connected to Sub arachnoid space by aqueduct of choclea Cochlear duct • Part of membranous labyrinth • Present within bony cochlea • Separated from bony canal by – Perilymph • Connected with vestibule (Saccule) by – Ductus reuniens Cochlear duct • Begins at – Ductus reuniens • Ends at – Near helicotrema • Triangular section – Apex • At spiral lamina – Base • Outer wall of bony canal • Floor – Basilar membrane • Roof – Reissners membrane Spiral organ of Corti • Located on basilar membrane • Contains receptor (sensory) and supporting cells for hearing • Consists of – – – – Inner & outer rod cells Hair cells Supporting cells Membrana tectoria Spiral organ of Corti • Tunnel of Corti • Rod cells have – Base and apex • Base of rod cells – Attached with • Basilar membrane • Apex of rod cells – Contact with each other • Space between – Rod cells & basilar membrane Spiral organ of Corti • Hair cells • Supplied by – Peripheral process of bipolar spiral ganglion • Arranged in 2 rows – Inner hair cells • Single cell row • Internal to inner rod cells – Outer hair cells • 3 to 4 rows • External to outer rod cells – In between them • Supporting cells – Attached to basilar membrane Spiral organ of Corti • Membrana tectoria – Covers the organ of Corti – Acellular gelatinous structure Utricle • Lies in – Posterior part of vestibule – In the elliptical recess • Receives five openings of the three semicircular ducts • Connected to the saccule through utriculosaccular duct • Macula or utricle lies – On medial wall of utricle – Sensory epithelium of the utricle is called the macula Saccule • Lies – In spherical recess of vestibule – Anterior to urticle • Joins with duct of cochlea by – Ductus reuniens • Sensory epithelium of the saccule is called the macula Semicircular ducts • Correspond exactly to the three bony canals • Open in utricle • Ampullated end of each duct contains a thickened ridge of neuroepithelium called crista ampullaris Semicircular canals • 3 semi circular canals – Superior – Posterior – Lateral • They lie in planes at – Right angle to each other • Each canal got 2 ends – Ampullary (dilated) – Non-ampullary • Crus commune – Union of non ampullary ends of posterior and superior canals • All semicircular canals opens into – Posterior and superior part of vestibule by five openings Right Side Semicircular canals • Canals contain – Semicircular ducts – Perilymph • Between bony and membranous labyrinth Semicircular duct • Part of membranous labyrinth • Present in semicircular canals • Contains – Endolymph – CRISTAE AMPULARIS • Present at ampullary part of semicircular duct Semicircular duct • Ampullary crest contains – Hair cells • & – Supporting cells • Hair cells are – Sensitive to rotation of head – Supplied with peripheral process of vestibular ganglion Endolymphatic duct and sac • Y- shaped duct • Posterior limb – Utrriculosaccular duct – Starts from Utricle • Anterior limb – Starts from Saccule • Runs in – Vesibular aqueduct • Ends in – Saccus endolymphaticus • Which lies beneath duramater on posterior part of petrous part of temporal bone Internal ear - summary Membranous structure Sensory epithelium present Function Cochlea Choclear duct Organ of corti Hearing Vestibule Saccule & Utricle Maculae Static balance Semicircular Semicircular ducts Cristae canals Kinetic balance Assignment • Name the parts of tympanic membrane • Name the layers of tympanic membrane along with their structure & development • Enumerate the arteries supplying the medial & lateral surfaces of tympanic membrane • Name the nerves supplying the medial & lateral surfaces of tympanic membrane Assignment • Name the parts of internal ear • Enumerate the parts of bony labyrinth • Enumerate the parts of membranous labyrinth • Enlist the functions of • 1. Organ of corti • 2. Cristae • 3. Macula & saccule
