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*RACS ENT Fellowship > Anatomy - Ear > Flashcards

Anatomy - Ear Flashcards

1
Q

Vascular supply External Ear

A
  1. Posterior auricular artery (ECA)
  2. Superficial temporal artery (ECA)
  3. Deep auricular (1st part maxillary)
    - deeper part of meatus
    - enteres via squamotympanic fissure
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2
Q

Ex Ear Canal

Dimensions

A

1/3 cartilagenous (deficient posterosuperiorly), 2/3 bony

25mm posterosuperior, 31mm anteroinferior

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3
Q

Ext Ear Canal

Contents/landmarks

A

Fissures of Santorini - deficiencies in cartilage, allow mobility of the auricle/canal pathway for disease spread (to parotid)

Foramen of Huschke - bony deficiency anteroinferiorly in children up to 4 (lag in development of bony EAC floor). Also potential route of spread

Osseous canal - tympanic ring (ant/inf/post) and completed by squamous and petrous bone. 2 sutures tympanosquamous (ant) and tympanomastoid (post)

  • 2 areas of narrowings - B/C junction, isthmus (5mm lateral to TM)
  • Skin very thin (0.2mm)

Glands- sebaceous, ceruminous (modified apocrine)

Wax - recessive trait (Asians=dry, Cauc/Black=wet). Keratin, desquamated skin, sebaceous/ceruminous secretions

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4
Q

Ext Ear Canal

Blood Supply

A

Blood supply:

superficial temporal (anterior auricular), posterior auricular, occipital artery branch (small), deep auricular (from IMA via tympanosquamous fissure)

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5
Q

Ext Ear Canal

Nerve Supply

A

Nerve supply:

A/T (V3),

Greater auricular (C2,3),

Lesser Occipital (C2/3),

Arnold’s (X fibres- also receives from VII and auricular branch IX- not Jacobsen’s)

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6
Q

Auricle

Describe

A

Auricle:

  • Single layer elastic cartilage. Skin closely attached laterally, thin subdermal adipose layer medially
  • Pinna attached to skull by 3 extrinsic ligaments
  • 3 extrinsic muscles from galea aponeurotica (medial triangular fossa, spine of helix, medial surface cavum) - all supplied by VII
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7
Q

Ext Ear Canal

Relations

A

Superior: MCF

Ant:

  • Superfical temporal Artery & Vein
  • Auricultemporal N
  • Parotid
  • Preauricular lymph nodes

Lat: Outside

Post: Mastoid

Inf:

  • Carotid
  • Jug Bulb
  • VII
  • Styloid process
  • Parotid
  • Digastric
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8
Q

Pinna & EAC Nerve supply

A
  1. Lesser Occipital (C1-2)
    - Mastoid skin
    - Upper medial auricle
  2. Greater Auricular (C2-3)
    - Helix/antihelix, lobule not concha
    - Most of medial auricle
  3. Auriculotemporal Nerve (V3)
    - Anterosuperior auricle, EAC, TM
  4. Arnold’s Nerve (X)
    - Posterosuperior EAC, TM
    - Post-auricular skin crease
  5. Facial Nerve (VII) post-auricular nerve and branches from Fallopian canal to Arnold’s
    - Conchal bowl
    - Posterior EAM/EAC
    - Tragus, antitragus, antihelix

Significant overlap between these areas

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9
Q

Tympanic Membrane

Dimensions

Orientation

Area

A

Orientation:

Faces antero-infero-lateral, concave laterally (umbo at apex)

140 degrees to superior canal, 55 degrees to inferior canal

Size:

10mm vertical by 9mm horizontal. Thickness 70-80 microns

Area:

85mm2 total, 55mm2 vibrating

Pars tensa = 88%, pars flaccida = 12%

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10
Q

Tympanic Membrane

Structure

A

Structure:

  • Epidermis
  • Lamina propria: outer radial, inner circumferential (ORIC)

** pars flaccida has disorganised LP with collagen and elastin fibres (pars tensa only collagen) hence lacks rigiity of pars tensa

  • Mucosa
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11
Q

Tympanic Membrane

Blood & Nerve supply

A

Blood supply:

  • Lateral surface- deep auricular (peripheral vascular ring around annulus)
  • Medial surface- ant tympanic, stylomastoid

Nerve supply:

  • Lateral surface- A/T (anterosuperior), Arnold’s (posteroinferior)
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12
Q

IAC

Definition

Sections

Devisions

A

A neurovascular channel in petrous temporal bone between PCF and middle/inner ear compartments

Sections:

  • Porus (medial, faces postero-medially)
  • Canal
  • Fundus (lateral, faces antero-laterally)

Divisions:

  • Falciform crest (transverse)
  • Bill’s bar (vertical, only divides superior half)
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13
Q

IAC

Dimensions & Orientation

A

Dimensions: there is relative consistency between sides (>2mm diff is abnormal)

  • Horizontal = 4.68mm
  • Vertical = 3.72mm
  • Length- 8mm

Orientation:

  • 45 degrees with long axis of TB
  • Approx 90 degree angle with sagittal plane
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14
Q

IAC

Contents

A

Contents:

  • Meninges
  • Facial Nerve (NI lies beneath and behind motor VII)
  • Vestibulocochlear Nerve
  • Artery = Labyrinthine artery (branch of AICA in 80%)
  • Accessory AICA in 17%, PICA in 3%
  • Vein = labyrinthine vein to inf petrosal sinus
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15
Q

Relationship of VII & VII

in IAC

A

VIII-VII Relationship:

Close to brainstem, VIII is bigger than VII but not separated out

  • Towards IAC, components of VIII become more obvious
  • VII not seen initially in a retrosigmoid approach (obscured by VIII)
  • Achieve their complete separation at the fundus laterally
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16
Q
A

*RACS ENT Fellowship (19 decks)

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