Orofacial Embryology Flashcards
branchial refers to…
gills- eventually the precursor for neck and lower 2/3 of face like mouth ear and neck
4 components of pharyngeal apparatus
- arches- bulge outward from neck region
- cleft/groove- external invagination b/w arches
- pouch- internal invagination b/w arches
- membrane- tissue separating cleft and pouch
when and where do the arches arise
week 4, cranial to caudal
1,2,3,4,6
give rise to lower 2/3 of face, oral cavity, ear, neck
3 layers of arches
- external- from ectoderm
- filling/core- from mesoderm and neural crest, neural crest must migrate into arches for proper skeletal tissue formation
- internal- from endoderm, forms GI tract lining
innervation of the 5 arches
1=5 2=7 3=9 4=10 6=10
5 areas that give rise to the face
frontonasal process and 2 maxillary processes and 2 mandibular processes
meet at the mouth eventually
arch 1 gives rise to… (bones)
lower 2/3 of face- skin, muscle, bone
bone:
- maxillary process, forms that bone, palate, zygomatic, squamous temporal
- lower jaw, mandibular process: mandible, sphenoid spine, malleus, incus
- sphenomandibular ligament, anterior ligament of malleus
what is meckel cartilage
origin of mandibular process of arch 1
arch 1 muscle derivatives
muscle: all innervated by CN5, muscles of mastication
- mylohyoid, masseter, temporalis, anterior digastric, tensor tympani, tensor veli palatini
formation of lower lip and jaw
arch 1 mandibular processes fusing at midline, rare anomalies
formation of upper lip and jaw
more common- 3 areas are fusing
2 maxillary processes fusing w/ medial nasal process (philtrum)
anomolies more common, cleft lip and palate
difference b/w cleft lip and palate, incomplete vs complete
cleft lip: clefting anterior to incisive foramen (meeting of processes)
cleft palate: clefting posteriror to foramen
incomplete- partial lack of fusion
can be unilateral or bilateral
skeletal derivatives of arch 2
aka hyoid arch
starts w/ reichert cartilage- forms lesser horn of hyoid, stylohyoid ligament, styloid process, stapes
muscles from arch 2
all from CN7
muscles of facial expression- posterior digastric, stylohyoid, stapedius
skeletal derivatives of arch 3
starts w/ cartilage, forms body and greater horn of hyoid
muscles from arch 3
from CN 9
stylopharyngeus
skeletal derivative of arch 4,6
from cartilage- laryngeal cartilage (cricoid, thyroid, arytenoids, etc)
muscles from arch 4,6
all from CN10
arch 4: pharyngeal constrictors, cricothyroid, levator veli palatini
arch 6: all laryngeal except cricothyroid
describe phayngeal arch vasculature and what they become
each arch as 1 artery called aortic arch
1,2,5 disappear
3=common carotid
4= right subclavian and arch of aorta
6= pulm arteries
arch contribution to the tongue
arch 1: anterior 2/3 (CN5 for somatic, 7 for taste)
arch 3: posterior 1/3 (CN9 for somatic and taste)
arch 4: base and epiglottis (CN 10 for both)
think cranial to caudal
what happens to branchial clefts
2-4 disappear as arch 2 covers them up, temporarily creates cervical sinus
cleft 1 becomes external acoustic meatus- from ectoderm
what is a branchial cleft cyst
persistent cervical vesicle/sinus
along anterior border of SCM muscle
derivatives of 4 pouches
note these are internal, endoderm
- eustachian tube
- palatine tonsil
- thymus, inferior parathyroids
- superior parathyroids
etiology of diGeorge syndrome
abnormal development of pouch 3 and 4- lack of thymus and parathyroids causes immune deficiency, hypocalcemia, facial/palate problems
derivatives of branchial membranes
2-4 disappear under arch 2 overgrowth
1 becomes tympanic membrane (pouch 1 was eustachian tube)
describe formation of ear, preceding structures (4)
arch 1,2: auricle
cleft 1: external accoustic meatus
membrane 1: tympanic membrane
pouch 1: eustachian tube
list some facial characteristis of fetal alcohol syndrome
small head, low nose, thin upper lip, small eye openings
some due to neural crest cell injury or impaired migration
