Development of Branchial Arches Flashcards
Branchial Pouch
Endodermal outpocketing from rostral foregut
Branchial groove
Ectodermal cleft between banchial arches
Branchia Membrane
Point of contact between branchial clefts and pouches
Stomadeum
Forms oral and nasal cavity; composed of ectoderm
Oropharyngeal membrane
Site of contact between stomadeum (ectoderm) and endoderm
-Pharynx begins here
Palatoglossal Arch
Site of oropharyngeal membrane
First Arch Strutures
CN (V)
Bones:
Malleus
Incus
Ligaments:
Anterior ligament of the malleus
Sphenomandibular Ligament
Muscles:
Muscles of Mastication Tensor tympani Tensor palati Mylohyoid Anterior belly of digastric
Second Arch Structures
CN (VII)
Bones:
Stapes
Styloid Process
Lesser Horn of hyoid bone (upper half)
Ligaments:
Stylohyoid ligament
Muscles:
Muscles of facial expression
Stapedius
Stylohyoid
Posterior belly of the digastric muscle
Structures of the Third Arch
CN (IX)
Bones:
Greater Horn of the hyoid bone; lower half
Muscles:
Stylopharyngeus
Structures of the Fourth Arch
CN (X)
Bones:
Structures of the larynx
Muscles:
Muscles of the larynx
Muscles of the pharynx (ex. stylopharyngeus)
Muscles of the palate (ex. tensor palati)
Structures of the Sixth Arch
CN (XI)
Muscles:
Trapezius
Sternocleidomastoid
Structures of the First cleft, membrane, and pouch
Cleft: External auditory meatus
Membrane: Tympanic membrane
Pouch: Auditory tube, Tympanic cavity
Structures of the Second Pouch
Crypts of the palatine tonsils
Structures of the third pouch
Inferior parathyroid gland
Thymus
Structures of the Fourth Pouch
Superior Parathyroid gland
C-cells of thyroid gland
Branchial Fistula
Channel connecting the pharynx to the skin of the neck; occurs due to malformation of first branchial pouch structures
Passes anterior to sternocleidomastoid and in between the internal and external carotid arteries
Branchial Cyst
Forms due to a remnant of the cervical sinus
Thyroid Development
- Begins as thickening at foramen cecum on the floor of the pharynx
- Elongates to form Thyroid diverticulum and descends anterior to hyoid and larynx
- Thyroglossal duct connects diverticulum to Foramen cecum`
Thyroglossal duct remnants
Can form cysts along descending path
Treacher-Collins Syndrome
“First Arch Syndrome”
Neural crest cells do not migrate to Arch 1
-mandibular hypoplasia, conductive hearing loss, facial malformation
Second Brancial Cleft Cyst
Most common
tract linked to palatine tonsils
