Pharyngeal Arches Flashcards
Pharyngeal Apparatus consists of…
Pharyngeal Arches
Pharyngeal Pouches
Pharyngeal Grooves/Clefts
Pharyngeal Membrane
How do pharyngeal arches begin to form?
o Begin to develop early in the fourth week as neural crest cells migrate into the head and neck region
Where do Neural crest cells come from and what direction do they travel?
NCC come from the developing neural plate
They migrate posterior/dorsal neural tube region to anterior ventral
Major events on day 24 due to rapid proliferating mesenchyme
Stomodaeum forms laying ectoderm throughout oral cavity (most oral cavity forms from this)
Stomodaeum and parynx are seperated by the buccopharyngeal membrane
Buccopharyngeal membrane ruptures to open the oropharynx
Each arch contains
Nerve, artery, cartilage, muscles
Arch I Artery
Terminal branch of maxillary artery
Arch I Skeletal
Derived from arch cartilages (from NCC):
Max cart –> Incus
Meckels cart –> Melleus
Derived by direct ossification from arch dermal mesenchyme
maxilla, zygomatic, squamos protion of temporal, mandible
Arch I Muscles
Muscles of mastication
Mylohyoid
Anterior belly of digastric
Tensor Tympani
Arch I Nerves
Trigeminal nerve V (5)
-Max and Mand division
Arch II Artery
Stapedial artery (embryonic)—> Corticotympanic artery (adult)
Arch II Skeletal
Stapes
Styloid process
Part of Hyoid
Arch II Muscle
Facial expression
Posterior belly of digastric
Stylohyoid
Stapedius
Arch II Nerve
Facial Nerve VII (7)
Arch III Artery
Common carotid artery
root of internal carotid
Arch III Skeletal
Part of Hyoid
Arch III Muscle
Stylopharyngeus
Arch III Nerve
Glossopharyngeal IX (9)
Arch IV Artery
Arch of aorta
Right Subclavian artery
Arch IV Skeletal
Thyroid
Arch IV Muscles
Constrictors of pharynx
Arch IV Nerve
Vagus X
-Superior laryngeal branch
Arch VI Artery
Ductus Arteriosus
Pulmonary arteries
Arch VI Skeletal
Circoid
Arch VI Muscles
Intrinsic muscles of larynx
Arch VI Nerve
Vagus Nerve X
Recurrent laryngeal branch
Derivatives Of Pharyngeal Clefts/ Grooves
Cleft I: External Auditory Meatus
Paryngeal Arch II: Mesenchyme rapidly proliferate and cover remaining clefts
Clefts 2-4: Cervical Sinus
Cervical Cysts
-Cause, characteristics
Failure of resorption during cervical sinus formation
Forms at LATERAL border of neck, anterior to sternocleidomastoid
Can be isolated or fistulated, may be infected or purulent (pus)
Formation of Pharyngeal Pouches
Internal endoderm forms outline of oropharynx
Pharyngeal pouches form around oropharynx, and eventually form pharyngeal derivatives
Pouch I
Pharyngotympanic tube
Pouch II
Palatine tonsil
Pouch III
Inferior Parathyroid and thymus
Pouch IV
Superior Parathyroid and Ultimo Branchial Body
Ultimo Branchial Body
Joins thyroid and forms Follicular C cells which produce Calcitonin
Thyroid Primordium Migration
Forms at midline of pharynx below tuberculum impar
2 lobes migrate from foramen cecum –> below cricoid
Forms thyroglossal duct during migration
Thyroglossal Duct Cysts Location
Found at the MIDLINE of the neck
Form by improper degeneration of thyroglossal duct
Confined or fistulated through the oral duct
Can be infected, purulent, obstruct airway
Development of Tongue
Oral Part
Fusion of:
Lateral lingual swellings
Madian tonhue bud (Tuberculum par)
Development of Tongue
Paryngeal Part
Fusion of Copula (hypobranchial eminence)
formed from arches 2, 3, 4 –> fuse to form terminal sulcus
Tongue Muscles
Arise from Occipital Somites which migrate into tongue area
Pharyngeal Arch Defects
Facial Clefting
Micrognathia (small mouth)
Hemifacial Microstomia (Lower half of face underdeveloped)
