Ossicle/Pediatric

ARCHES
Pinna forms from 6 hillocks: 1-tragus, 2-helical root, 3=helix, 4=antihelix, 5=antitragus, 6=lobule

Middle Ear & External Auditory Canal 1st branchial groove migrates inward forming EAC 1st and 2nd pouch migrate to form ME (where they meet is TM) Tympanic Membrane: squamous TM=ectoderm, fibrous=mesoderm, mucosal=endoderm 

SECOND BRANCHIAL CLEFT CYST and sinus tract: Lateral to IX and XII Passes between ICA and ECA Ends at medial constrictor or tonsillar fossaMOST COMMON

THIRD BRANCHIAL CLEFT CYST and sinus tract: <ul><li>Ascends Lateral to CCA<li>Passes posterior to ICA<li>Superior to XII and Inferior to IX<li>Courses medially to peirce lateral thyrohyoid membrane to open into pyriform sinus</ul></ul>

Dysphagia Lusoria - Dysphagia from retroesophageal subclavian artery<ul><ul> <li>Assoc with non-recurrent laryngeal 100%<li>From degeneration of Right 4th Arch</ul></ul>

Parathyroid Development<ul><ul><li> Superior Parathyroid - 4th Arch development; Posterior to RLN & posterior in mediastinum <li>Inferior Parathyroid - 3rd Arch development; Anterior to RLN & Anterior in mediastinum</ul></ul>