Eustachian Tube

EMBRYOLOGY:
  • Develops from tubo-tympanic recess, derived from endoderm of 1st & 2nd pharyngeal pouch.
ANATOMY:
  • 36 mm long in adults.
  • Directed anteriorly, inferiorly & medially from anterior wall of M.E., forming angle of 450 with horizontal
  • Eustachian tube opens into middle ear cavity at Medial wall
  • Enters naso-pharynx 1.25 cm behind posterior end of inferior turbinate.
  • Opens during swallowing
Parts:
  1. Lateral 1/3 is bony
  2. Medial 2/3 is fibro-cartilaginous(25mm).
  • Junction b/w 2 parts is isthmus, narrowest part of Eustachian Tube.
  • Anatomy of medial 2/3rd:Cartilage plate lies postero-medially & consists of medial + lateral laminae separated by elastin hinge. Fibrous tissue + Ostmann’s fat pad lie antero-laterally.
  • Lining epithelium: pseudo stratified ciliated columnar
  • Levator veli palatine causes opening of Eustachian tube
  • Muscle which helps to open Eustachian tube while sneezingTensor veli palatini & Levator veli palatini
BLOOD SUPPLY & LYMPHATICS:
  • Arterial supply: ascending pharyngeal & middle meningeal arteries
  • Venous drainage: pharyngeal & pterygoid venous plexus
  • Lymphatic drainage: retropharyngeal node
NERVE SUPPLY:
  • Tubal mucosa – tympanic branch of cranial nerve IX
  • Tensor veli palatini - Mandibular branch of trigeminal
  • Pharyngeal plexus -Levator veli palatini & Salpingopharygeus
ENDOSCOPIC ANATOMY:
  • Medial end forms tubal elevation / torus tubarius
  • Lymphoid collection over torus is called Gerlach’s tubal tonsil.
  • Postero-superior to torus is fossa of Rosenm├╝ller.
ADULT vs. CHILD
PROPERTIES: ADULT INFANT
Length 36 mm 18 mm
Angle with horizontal 45 0 10 0
Lumen Narrower Wider
Angulation at isthmus Present Absent
Cartilage Rigid Flaccid
Elastic recoil Effective Ineffective
Ostmann’s fat More Less
Elastin content high Low
CLINICAL SIGNIFICANCE:
  • Eustachian tube gets blocked if pressure difference is more than 90 mm Hg
  • Tests for Eustachian tube patency are
  1. Valsalva test
  2. Methylene blue test
  3. Sonotubometry
  4. Politzer test 
  5. Toynbee test
  6. Frenzel maneuver
  7. Catheterization
  8. Inflation - Deflation test
Exam Question
  • Eustachian tube opens at the level of inferior turbinate
  • Eustachian tube opens into middle ear cavity at Medial wall
  • The length of Eustachian tube is 36mm
  • Inner 2/3rds of eustachian tube is cartilaginous 
  • Eustachian tube Opens during swallowing
  • Levator veli palatine causes opening of Eustachian tube
  • Higher elastin content in adult's Eustachian tube
  • Eustachian tube develops from 1st & 2nd pharyngeal pouch
  • Muscle which helps to open Eustachian tube while sneezing Tensor veli palatini & Levator veli palatini
  • Length of the cartilaginous part of Eustachian tube is 25mm 
  • Eustachian tube gets blocked if pressure difference is more than 90 mm Hg
  • Tests for Eustachian tube patency are Valsalva, Methylene blue ,Sonotubometry, Politzer ,Toynbee ,Frenzel maneuver, Catheterization & Inflation - Deflation test Ostmann fat pad is related to eustachian tube
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