Ear Anatomy & Tibbo
Transcript of Ear Anatomy & Tibbo
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Embryology and Anatomy of
the External EarJamie Tibbo
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General Embryology
3 Embryonic Layers: Ectoderm (Grooves) Mesoderm (Arches)
Endoderm (Pouches) 4x Grooves 5x Arches (5 th arch called 6 th arch) 4x Pouches
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General Embryology
ArchNerveArteryCartilage bar
Arch mesoderm
differentiates
MusclesBones
Vessels
Cartilage
Reference: K.J. Lee
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Overview
Development of External & Middle Ear1. External Auditory Canal2. Tympanic Membrane3. Middle Ear Cavity4. Ossicles
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Embryology of External Ear
EAC begins ( 4 th wk) Hillocks become evident
(5 th wk) Hillocks distinct ( 6 th wk)
Auricle identifiablestructures ( 8 th wk)
Auricle has adult form(18 th wk)
Meatal plug begins todisintegrate ( 20 th wk)
EAC fully open ( 28 th wk)
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Ligaments of the External Ear
Extrinsic Ligaments Anterior Ligament : attaches helix and tragus to
zygomatic process Superior Ligament : attaches spine of helix to
superior margin of bony EAC Posterior Ligament : attaches medial surface ofconcha to mastoid process
Intrinsic Ligaments
A fibrous band connects the antihelix and thecauda helicis A strong fibrous band connects the tragus to the
beginning of the helix (completing the meatusanteriorly)
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Extrinsic Muscles of the Ear
Anterior Auricular Muscle Origin : anterior part of fascia of temporal region Insertion : spine of helix Action : displaces auricle anterosuperiorly Innervation : temporal branches of CN VII
Superior Auricular Muscle Origin : fascia of temporal region Course: converges to thin, flattened tendon Insertion : upper part of cranial surface of auricle Action : displaces auricle superiorly Innervation : temporal branch of CN VII
Posterior Auricular Muscle Origin : mastoid as 2 or 3 fasciculi Insertion : cranial surface of convexity of concha Action : displaces auricle backward Innervatio n: post-auricular branch CN VII
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Intrinsic Muscles of the Ear
Rudimentary muscles extending fromone part of the auricle to another
1. Helicus Minor Muscle
2. Antitragus Muscle3. Transverse Muscle of the Auricle4. Oblique Muscle of the Auricle
5. Helicus Major Muscle
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Anatomy of the External Ear
Motor: post auricular branch of facial innervatesanterior, superior, posterior auricular muscles
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Anatomy of the External Ear
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Anatomy of the External Ear
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Vasculature of the Auricle
Arteries (3 main): Posterior Auricular Artery (Ext. Carotid) Anterior Auricular Artery (STA)
Occipital Artery (Mastoid Branch) Veins:
Superficial Temporal Vein Drains into Retromandibular vein
Drains into Internal Jugular
Posterior Auricular Vein Drains into External Jugular
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Innervation of the Auricle
Motor Innervation: Temporal Branch of CN VII
Anterior auricular muscle
Superior auricular muscle Post-auricular branch of CN VII
Posterior auricular muscle Intrinsic muscles of the cranial aspect of the
pinna
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Lymphatics of the External Ear
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Anatomy of the External EarExternal Auditory Canal
4 cm from tragus to TM 2.5 cm from concha to TM TM positioned obliquely
Anterior Canal & Floor 6 mm longer thanthe roof and Posterior Canal
Has an S-Shape External part directed anterosuperiorly Middle part directed posteriorly
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Anatomy of the External EarExternal Auditory Canal
Has 2 constrictions (isthmuses):1. Cartilagionous Isthmus
Narrowest segment of EAC
Located medial end of cartilagionus segmentof canal
2. Bony Isthmus Lies 2 cm from inferior aspect of concha, just
lateral to the inferior tympanic recess
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Anatomy of the External Ear
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Embryology of the Middle Ear
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Embryology of Middle Ear:Tympanomastoid compartment
3rd wk tubotympanicrecess (1 st branchial pouchendoderm) approaches 1 st cleft ectoderm 6 th wk Malleus & incusidentifiable as cartilaginousmodels
5th wk
10 th wk
27 th wk
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Embryology of Middle Ear:Tympanomastoid compartment
20 th wk tympanic cavitybegins to open 22 nd wk extension toform mastoid antrum 30 th wk - malleus & incusossified 34th wk ossicles liewithin open MEC, mastoidair cells begin to develop
5th wk
10 th wk
27 th wk
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Embryology of Middle Ear: Ossicles
1st
Branchial Arch Meckels Cartilage Malleus head & neck Incus Body and Short
process Ant. Malleal ligament Sphenomandibular ligament Mandible
Mesoderm Tensor tympani muscle Masticator muscles Ant. Belly digastric Tensor palati muscle
Nerve Semilunar ganglion (CN V3)
Artery degenerates
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Embryology of Middle Ear: Ossicles
2nd Branchial Arch Reicherts Cartilage
Manubrium of malleus Long process of malleus Lenticular process Stapes (except
vestibular part offootplate)
Styloid process,pyramidal eminence
Stylohyoid ligament Lesser cornu of hyoid Part of body of hyoid Lower half facial canal
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Embryology of Middle Ear: Ossicles
2nd Branchial Arch Mesoderm:
Platysma Stapedius muscle & tendon Facial muscles Auricular muscle Posterior belly of digastric Stylohyoid muscle
Nerve:
Geniculate ganglion (CN VII) Artery:
Degenerates (stapedial artery)
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The End
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3 weeks: Developing auditory placode (ectoderm) and gut endoderm (willcontribute to inner and middle ear) Invagination into otic pit , andmigration of otocyst
7 weeks: Labyrinths are recognizable,cochlea has one turn, first sensorycells in utricle, saccule
11 weeks: CN VIII attaches, cochlea has 2 turns Adult size, active by week 21
Inner Ear Development
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