Ossicle/Pediatric

Pediatric and Developmental

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

ARCH	CN Assoc	ARTERIES	MUSCLES	CARTILAGE/BONE
FIRST	CN V	-none-	Masticators & Tensors	Meckel's Cartilage, mandible, head of maleus, body of incus
SECOND	CN VII	Stapedial	Facial, Stylohyoid, posterior belly Digastric	Reichart's cartilage, manubrium of malleus, long process incus, stapes, lesser cornu hyoid, Part of hyoid body
THIRD	CN IX	ICA	Stylopharyngeus	Greater cornu of hyoid, rest of hyoid body
FOURTH	CN X (Sup Laryngeal)	L=Aorta R=Subclav	Cricothyroid	Thyroid Cartilage
FIFTH	CN X (Recur Laryngeal)	PA's, Ductus	Intrinsic mm of larynx	cricoid, arytenoid, corniculate cartilages

SECOND BRANCHIAL CLEFT CYST and sinus tract:

• Lateral to IX and XII
• Passes between ICA and ECA
• Ends at medial constrictor or tonsillar fossa
• MOST COMMON

THIRD BRANCHIAL CLEFT CYST and sinus tract:

• Ascends Lateral to CCA
• Passes posterior to ICA
• Superior to XII and Inferior to IX
• Courses medially to peirce lateral thyrohyoid membrane to open into pyriform sinus

Dysphagia Lusoria - Dysphagia from retroesophageal subclavian artery

• Assoc with non-recurrent laryngeal 100%
• From degeneration of Right 4th Arch

Parathyroid Development

• Superior Parathyroid - 4th Arch development; Posterior to RLN & posterior in mediastinum
• Inferior Parathyroid - 3rd Arch development; Anterior to RLN & Anterior in mediastinum