External Ear Anatomy and Tympanic Membrane

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Questions and Answers

What is the total length of the external auditory canal?

  • 24mm (correct)
  • 20mm
  • 16mm
  • 28mm

What portion of the external auditory canal is cartilaginous?

  • 1/4 (6mm)
  • 1/2 (12mm)
  • 1/3 (8mm) (correct)
  • 2/3 (16mm)

Which section of the external auditory canal is primarily bony?

  • Medial section (correct)
  • Superior section
  • Anterior section
  • Lateral section

Which anatomical structure allows communication between the parotid gland and the external auditory canal?

<p>Fissure of Santorini (C)</p> Signup and view all the answers

What is the correct division of the external auditory canal in terms of cartilaginous and bony sections?

<p>1/3 cartilaginous, 2/3 bony (D)</p> Signup and view all the answers

Which statement about the Foramen of Huschke is true?

<p>It can be found in the bony part of the external auditory canal. (A)</p> Signup and view all the answers

What fraction of the external auditory canal is bony?

<p>2/3 (A)</p> Signup and view all the answers

What is the function of the Parotid Duct?

<p>Drain saliva into the oral cavity (A)</p> Signup and view all the answers

What is the narrowest portion of the external auditory canal?

<p>Isthmus (C)</p> Signup and view all the answers

At what location is the isthmus found in relation to the tympanic membrane?

<p>6mm lateral (A)</p> Signup and view all the answers

Which communication is not associated with the narrowest portion of the external auditory canal?

<p>Isthmus (D)</p> Signup and view all the answers

What is the primary purpose of straightening the external auditory canal?

<p>To visualize the tympanic membrane (D)</p> Signup and view all the answers

How is the external auditory canal typically straightened in adults?

<p>By pulling it upwards, backward, and outwards (C)</p> Signup and view all the answers

What anatomical feature is the largest depression in the external ear?

<p>Cavum concha (D)</p> Signup and view all the answers

Which structure is present only in pars tensa and absent in pars flaccida?

<p>Annulus (A)</p> Signup and view all the answers

What angle is the tympanic membrane placed at in relation to the canal?

<p>45 degrees (C)</p> Signup and view all the answers

Which nerve supplies the roof and the anterior wall of the external auditory canal?

<p>Auriculotemporal nerve (B)</p> Signup and view all the answers

What is the effective vibrating area of the tympanic membrane?

<p>90 mm² (D)</p> Signup and view all the answers

How is the side of the tympanic membrane identified based on the cone of light?

<p>3 o'clock to 6 o'clock - Right (A)</p> Signup and view all the answers

What type of perforation involves all the quadrants of the pars tensa but leaves the annulus intact?

<p>Subtotal perforation (B)</p> Signup and view all the answers

What is the length of the external auditory canal, and how is it divided into cartilaginous and bony parts?

<p>24mm; 1/3 cartilaginous, 2/3 bony (A)</p> Signup and view all the answers

What is the narrowest portion of the external auditory canal, and where is it located?

<p>Isthmus; 6mm lateral to the tympanic membrane (C)</p> Signup and view all the answers

In the upper portion of the tympanic membrane, which layer is absent?

<p>Endothelial layer (D)</p> Signup and view all the answers

Flashcards

External auditory canal length

The external auditory canal (ear canal) is 24mm long.

Cartilaginous part of EAC

The outer 1/3 (8mm) of the external auditory canal is cartilaginous.

Bony part of EAC

The inner 2/3 (16mm) of the external auditory canal is bony.

Fissure of Santorini

Connects the parotid gland to the cartilaginous part of the ear canal.

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Parotid Gland

A gland located near the ear that produces saliva.

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Parotid Canal

A structure not present, there isn't a parotid canal.

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Foramen of Huschke

An opening potentially present in the bony part of the ear canal, not in the cartilaginous part.

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Parotid Duct

Drains saliva from the parotid gland to the oral cavity (mouth).

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Narrowest part of the EAC

The isthmus is the narrowest part of the external auditory canal, located 6mm lateral to the tympanic membrane.

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Isthmus location

The isthmus, the narrowest part of the external auditory canal, is located 6mm lateral (away from) the tympanic membrane.

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Why is the isthmus important?

The isthmus is prone to wax impaction and foreign body lodgment, meaning things can get stuck there easily.

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Straightening the EAC

To visualize the tympanic membrane, the external auditory canal needs to be straightened.

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How to straighten the EAC in adults

To straighten the EAC in adults, pull the pinna (outer part of the ear) upwards, backward, and outwards.

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How to straighten the EAC in children

To straighten the EAC in children, pull the pinna downwards and backward.

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Tympanic membrane angle

The tympanic membrane (eardrum) sits at a 45-degree angle to the floor of the external auditory canal.

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Pars flaccida and annulus

The pars flaccida, a part of the tympanic membrane, lacks the annulus, a ring of tissue present in the pars tensa.

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Auriculotemporal Nerve

This nerve provides sensory innervation to the roof and anterior wall of the external auditory canal (ear canal).

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Tympanic Membrane Vibrating Area

The effective vibrating area of the tympanic membrane (eardrum) is approximately 90 square millimeters.

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Cone of Light - Right Ear

In a right ear, the cone of light, a reflection of light on the tympanic membrane, appears between 3 o'clock and 6 o'clock positions.

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Subtotal Perforation

A tympanic membrane perforation involving all quadrants of the pars tensa (main part) with the outer ring (annulus) remaining intact.

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Narrowest Part of EAC

The narrowest portion of the external auditory canal is called the isthmus, located 4 mm lateral to the tympanic membrane.

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Lempert Incision

This incision is used during ear surgery to prevent cartilaginous necrosis (tissue death) in the ear canal.

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Study Notes

External Auditory Canal Anatomy

  • Length: 24mm
  • Cartilaginous portion: 1/3 (8mm), lateral
  • Bony portion: 2/3 (16mm), medial
  • Important communication: Fissure of Santorini connects the parotid gland to the cartilaginous EAC.

Tympanic Membrane

  • Effective vibrating area: 90mm²
  • Cone of light: Used to determine the side of the tympanic membrane (e.g., 3 o'clock to 6 o'clock - Right).
  • Pars tensa perforation types:
    • Central: Involves more than one quadrant
    • Large: Involves more than one quadrant
    • Attic: Varies; doesn't necessarily include all quadrants
    • Subtotal: Includes all quadrants but annulus stays intact.

External Ear Anatomy

  • Narrowest portion (EAC): Isthmus, 6mm lateral to the tympanic membrane
  • Important landmarks in EAC:
    • Fissure of Santorini: Communication with the parotid gland
    • Foramen of Huschke: Opening in bony portion, not cartilaginous
  • Angles: Tympanic membrane is angled 45 degrees.
  • Important Structures (EAC Anatomy):
    • Cavum Concha: Largest depression in the external ear.
    • Lempert endaural incision: An incision to prevent cartilage necrosis; incisura terminalis is the specific site.
  • Tympanic membrane layers:
    • Pars tensa: Has all layers
    • Pars flaccida: Lacks the epithelial layer.

Additional Notes

  • External auditory canal is S-shaped; needing to be straightened for visualization.
  • Pulling the pinna outwards, upwards, backwards is used for visualization in adults.
    • Pinna downwards, backwards in children

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