Branchial (Pharyngeal) Arch Structures: 

Neural Crest Cells: Set of ectodermal, pluripotent cells that migrate into the region of the head and neck and Induce the differentiation of the tissue they invade.

Pharyngeal Arches: Originate from these neural crest cells, surround pharyngeal endoderm and mesoderm. Each arch is separated by pharyngeal grooves externally, pharyngeal pouches internally.  

1st Arch: a Massive list of M’s. 

• Nerve: Maxillary and Mandibular nerves 
• Artery: Maxillary artery 
• Cartilage: Meckel’s Cartilageà gives rise to: 

• Mandible + sphenoMandibular ligament 

• Malleus + Incus 

• Muscles: Think: MAT x 2 

• Muscles of Mastication 
• Mylohyoid  
• Anterior belly of digastric 

• Anterior 2/3 of tongue 
• Tensor veli palatini 
• Tensor tympani 

second arch: Second: ‘S’s”> 

• Nerve: Seventh nerve (facial nerve) 

• Artery: Stapedial artery and hyoid artery 
• Cartilage:  

• Stapes 
• Styloid 
• Stylohyoid ligament 

• leSSer horn of hyoid 

• Muscles:  

• Muscles of facial expression (Smiling) 
• Stapedius 
• Stylohyoid 

• poSSSterior belly of digastric 

third arch: Glossopharyngeal nerve

• Nerve: Glossopharyngeal nerveà taste sensation from post 1/3 of tongue 
• Cartilage: Greater horn of hyoid 

• Muscle: Stylopharyngeus 

 

fourth arch: Swallowing + The exceptions to the 6th arch below

• Nerve: Superior Laryngeal (branch of vagus)  
• Cartilage: Thyroid cartilage 

• Muscles:  

• Pharyngeal constrictors 
• Levator veli palatini 
• Cricothyroid 

6th Arch: Speaking (Laryngeal)

• Nerve: Recurrent laryngeal nerve (branch of vagus) 
• Cartilage: All laryngeal cartilages except thyroid cartilage 
• Muscles:  All instrinsic laryngeal muscles except cricothyroid, which as mentioned is part of the 4th arch structures.  

Pharyngeal Grooves: 

• Groove 1: Becomes external auditory canal 

• Grooves 2-4: Create cervical sinusà failure to obliterate results in: 

• pharyngeal cleft cysts (sealed within neck) 
• Sinuses: end in a blind sac 
• Fistulas: connect with pharynx 

• Anomalies often detected second decade of life, palpable at anterior border of SCM 

• Anomalies from groove 2 are most common, run between internal and external carotid arteries toward the tonsillar fossa 

Pharyngeal Pouches:

• Pouch 1: Internal auditory canal 
• Pouch 2: Palatine tonsil 
Pouch 3: Inferior parathyroid and thymus 

• Pouch 4: Superior parathyroid (migrates above pouch 3) 
• Pouch 5: Thyroid C cells 

Formation of the Face:

The face develops from 5 prominences: Frontonasal (1), maxillary (2), and mandibular (2)

• Frontonasal prominence: Pulled ventrally and caudally, forms the forehead, nasal dorsum, medial and lateral nasal prominences 

• Nasal Placodes: develop into nasal pits, eventually forming the nares 
• Medial nasal prominence: forms primary palate, midmaxilla, midlip, philtrum, central nose and septum 
• Lateral nasal prominence forms the nasal alae 

• Maxillary prominences: migrate medially to form the secondary palate, lateral maxilla, and lateral lip 

• Junction with the lateral nasal prominences forms the nasolacrimal groove and nasolacrimal duct system 

• Failure of fusion with the lateral nasal prominences results in an oblique facial cleft (Tessier 3) 

• Mandibular prominences: form mandible, lower lip and lower face 

Thyroid:

• From endodermal proliferation of foramen cecum of the tongue, thyroid descends with a trailing thyroid diverticulum to its final position distal to the cricoid cartilage 

• Thyroglossal duct cysts can form anywhere along this pathà Painless, MIDLINE neck mass 

• Lingual thryoids: failure of descent of the thyroid 

Tongue:

• Anterior 2 thirds: from pharyngeal arch 1, innervated by lingual nerve (V3) 
• Posterior third: 3rd and 4th arches, innervated by CN IX (taste) and X 

External Ear:

• Forms at junction of pharyngeal arch 1 and 2 
• Arch 1: three anterior hillocks (tragus, root of helix, superior helix) 
• Arch 2: three posterior hillocks (antitragus, antihelix, lobule) 

Dentition:

• Pediatric (primary/deciduous) dentition: 20 teeth 

• 4 incisors, 2 cancines, 4 molars per arch 
• No premolars in pediatric dentition 
• Pediatric dentition referenced by letter beginning with upper right second molar to upper left second molar (A-J) and continuing with lower left second molar to lower right second molar 

• Mixed dentition: marked by eruption of the first adult tooth (commonly mandibular first molar) 
• Adult: 32 teeth, 4 incisors, 2 canines, 4 premolars, 6 molars, referenced by number beginning with upper right third molar 

• Eruption sequence: first molars: 6-7 years, incisors 6-9 years, canines 9-12 years, first premolars: 10-11 years, second premolars 11-2 years, second molars 11-13 years, third molars 17-21 years.  

• Stages of tooth development: 

• Initiation/Proliferation 
• Bud stage: appearance of tooth bud without a clear arrangement of cells 

• Cap stage: first sign of arrangement of cells 
• Bell stage à known for morphodifferentiation that takes place: failure leads to an anomaly of enamel/dentin/cementin composition 
• Advanced Bell stage 

• Tooth anatomy 

• Three components: root (in the bone), neck, crown (covered by enamel) 

• External to internal: gingiva, Bone with nerve and blood vessels, cement (covers tooth root only), dentine (yellow layer), pulp cavity, root canal 

Hyperdontia is an anomaly of number of teeth and occurs most frequently in the maxilla (90%). It occurs during the initiation or proliferation stage. It is more common in males (2:1). It is 5 times more common in permanent dentition than in primary dentition. Finally, ectodermal dysplasia is associated with hypodontia. 

Dental Cysts:

• Periapical: Most common cyst, develops from necrotic pulp after a tooth infection/ associated with mandible fractures. Also known as a radicular cyst.
• Dentigerous Cyst: Develops in the follicle of an unruptured tooth. Lined with non-keratinizing epithelium, second most common 

• Odontogenic/Primordial cyst: Develops inside of a tooth. Epithelial lined 
• Gingival: superficial cyst in the gingiva, contains keratin 
• Residual: Retained periapical cyst after tooth has been removed 

Benign Dental Tumors:

• Ameloblastoma: slow growing, occurs in 4th or 5th decade, from odontogenic epithelium. On xray- radiolucent, multicystic, unilocular lesion. Tx: segmental mandibulectomy and reconstruction 

• Keratocystic odontogenic tumor: aggressive locally, occurs late in life, also from odontogenic epithelium. Tx: enucleation and chemoablation with Carnoy’s solution 
• Neurofibromas: expansile lesions of the inferior alveolar nerve canal 

Carotid artery Anatomy:

• External Carotid a: Some Attendings Like Freaking Out Potential Medical Students (less colorful): 
• Superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, maxillary, superficial temporal 

Zones of Injury of penetrating Neck traumas:

• Zone 1: (inferior-most): clavicle to cricoid cartilage: 

• Great vessels (subclavian vessels, brachiocephalic veins, common carotid arteries, aortic arch, jugular veins) 
• Trachea, esophagus, lung apices, cervical spine, spinal cord, cervical nerve roots 

• Zone 2: Cricoid cartilage to angle of mandible 

• Carotid and vertebral arteries, jugular veins 
• Pharynx, larynx, trachea, esophagus, cervical spine, spinal cord 

• Zone 3: (superior-most): angle of mandible to base of skull 

• Salivary and parotid glands 
• Esophagus, trachea, vertebral bodies, carotid arteries, jugular veins, spinal cord 

Skull Foramens (exiting of cranial nerves)

• Facial nerve: stylomastoid foramen 
• ICA: foramen lacerum 
• V2: foramen rotundum 
• V3: foramen ovale 

• III, IV, VI: superior orbital fissureà superior orbital fissure syndrome 

• Orbital apex syndrome = superior orbital fissure syndrome + CN II (optic n) involvement 

• Middle meningeal artery and vein: foramen spinosum 
• Glossopharyngeal (IX), vagus (X), spinal accessory (XI): jugular foramen 

Sinus Drainage into Nose:

• Superior meatus: drains sphenoid sinus and posterior ethmoid air cells 
• Middle meatus: drains maxillary sinus 
• Inferior meatus: drains nasolacrimal duct (important for placement of Crawford tube) 

Relevant Nerve Anatomy, Anomalous innervation:

• Arnold’s nerve: sensation to palate and external auditory meatus 

• Glossopharyngeal (IX) nerve: parasympathetic innervation to parotid gland 
• Frey’s syndrome: Causes Gustatory sweating (ie after parotidectomy), anomalous reinnervation of auriculotemporal nerve which normally supplies sensation to the upper helical rim.  

• Can also occur after repair of condyle fracture 

Parotid (not tumors)

• Parotid (stenson’s) duct injuryà sialocele 

• Located adjacent to the maxillary second permanent molar 
• can cause salivary fistulae 
• tx: abx + anti-sialogogues