Phayngeal Arch Flashcards
When do the pharyngeal arches appear?
In the 4th - 5th week
What are the pharyngeal arches separated by externally?
Pharyngeal Clefts / grooves
What are the pharyngeal arches separated by internally?
Pouches
Which surfaces do ectoderm line?
Outer surfaces of the arches and inner surface of Arch 1
Which surfaces are lined by endoderm?
Inner surfaces of all arches except 1
What lines the outer surface of the pharyngeal arches?
Ectoderm
What lines the inner surface of the pharyngeal arches? Which is the exception?
Endoderm; Arch 1 is lined by ectoderm
What does each pharyngeal arch contain?
Nerve
Artery
Cartilage
Muscles
What is Arch 1 named?
Mandibular arch
Which processes make up Arch 1?
Mandibular process
Maxillary process
Which nerve supplies Arch 1?
CN V
Which arteries are found in Arch 1?
Maxillary
Carotid
Which cartilage is associated with Arch 1?
Meckel’s cartilage
Function of cartilage in Arch 1
Provides primitive support
What does Meckel’s cartilage form?
bones - incus, malleus
ligaments - sphenomandibular, sphenomalleolar
What structures do Arch 1 give rise to?
Body of tongue
Muscles of Mastication - ABD, mylohyoid, temporalis, masseter, pterygoids
Which disease is associated with Arch 1? What is it caused by?
Treacher-Collins syndrome - failure of neural crest cell migration
What is the name of Arch 2?
Hyoid Arch
Which nerve supplies Arch 2?
CN VII
What muscles do Arch 2 give?
Muscles of Facial expression + posterior belly of digastric
Which cartilage is found in Arch 2?
Reichert’s cartilage
What structures do Reichert’s cartilage give?
- stapes
- lesser horn and superior hyoid body
- styloid process, stylohyoid ligament
What structures do the 2nd Arch give rise to? x2
Tonsil
Thyroid gland
Which nerve supplies the 3rd Arch?
CN IX
Which muscle is given by the 3rd Arch
Stylopharyngeus muscle
What structures do the 3rd Arch form? x3
Greater horn of hyoid
Inferior hyoid body
Root of the tongue
Which nerve supplies the 4th Arch
CN X (Superior laryngeal branch of vagus)
Which muscles are given by the 4th Arch?
pharyngeal constrictors
soft palate muscles
4th arch cartilage?
Thyroid cartilage
Which structures do the 4th Arch give rise to? x2
Pharynx
Epiglottis
Which nerves supplies the 6th Arch?
CN X (Recurrent laryngeal branch of vagus)
What is the fate of the 5th Arch?
It rapidly disappears
What cartilages do the 6th Arch give?
Cricoid and Arytenoid cartilages
What does the 1st cleft give? x2
external auditory meatus
ear drum
What happens to the 2nd - 6th clefts?
they disappear / are obliterated by the proliferating 2nd arch
What does the 1st pouch give? x4
Eustachian tube
Middle ear cavity
Tympanic membrane
VENTRAL PART IS OBLITERATED BY TONGUE
What does the 2nd pouch give? x2
Tonsillar fossa
Palatine tonsil
Ventral part - obliterated by tongue
What does the 3rd pouch give? x2
Inferior parathyroid gland
Thymus
What does the 4th pouch give?
Superior parathyroid gland (will fuse with the inferior one)
