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Embryology/Branchial Arches


Ear (Embryology)
22nd day              Otic placode is seen
5th week             Auricle starts forming
6th week             The cochlea and semicircular canals starts forming
8th week             The cochlea and semicircular canal assume their definitive external form
10th week           Scala vestibuli and scala tympani appear
7th month            External acoustic meatus gets canalized.

  1. Pinna:-
    1. Period of development:
      1. 38th day to 20 week
      2. 4-6th week (Adult configuration)
    2. Contributing arches: 1st arch &. 2nd arch.
    3. Six tubercles, 3 from each arch (called Hillock’s of His)- mesodermal.
    4. Site of development: At the upper part of the neck.

Fig: Development of pinna. Six hillocks around first branchial cleft and the corresponding parts of pinna which develop from them

  1. Process of Development
    The tissue condensations of the mesoderm of the first and 2nd branchial arch form six hillocks of His which fuse to form pinna​
Figure: Development of external auditory canal and middle ear:


Extra Edge. Chordoma arises from the remnants of notochord. Characteristic appearance on histology is physaliferous cells-foamy cells with compressed nuclei.
Extra Edge. Structures of ear fully formed by birth are: middle ear, malleus, incus, stapes, labyrinth and the cochlea.  i.e. middle ear & inner Ear, (External Ear not developed).

  1. Applied Anatomy
    1. Pre-Auricular Sinus:
      1. Formation: 1st and 2nd hillocks fail to fuse
      2. Opening: Is found in front of the ascending limb of the helix
      3. Treatment: surgical excision
    2. ​​Coll aural Fistula:
      1. Formation: Is a 1st branchial cleft anomaly arises from failure of fusion of the ventral part of the 1st cleft.
      2. Opening:
        Upper Part
        : opens in the floor of the external auditory canal
        Lower Part: Between the angle of the mandible and the sternocleidomastoid muscle.
  1. Surgical reconstruction of the pinna is performed at the age of 6 years ( size preschool)
  2. ‘Rib’ cartilage is used for its reconstruction or synthetic implants, multistage operation,

Extra Edge: Hematoma auris / cavlit lower ear / boxers ear ( blood under the perichondrium)

  1. Potter’s Syndrome.
    1. Features:
      1. Congenital abnormality of pinna (auricles are large and flat)
      2. Abnormal limb positioning
      3. Pulmonary hypoplasia
      4. Compressionfacial
    2. Cause: Oligohydramnios​
Syndromes associated with Pinna abnormality:
  1. Treacher’s Collins syndrome
  2. LADD syndrome


  1. Exostosis of external auditory canal are multiple and usually associated with cold water swimming while osteoma of external canal is usually single and occurs at suture lines, e.g. tympanomastoid.
  2. External auditory canal of an adult is 24 mm in length. Outer one-third (8 mm) is cartilaginous and inner two thirds (16 mm) are bony.

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