Pharyngeal Apparatus Flashcards
when and how do pharyngeal arches appear
- week 4
- as pairs of bulges overlaying head and neck bc migration of neural crest cells
components of pharyngeal apparatus
- arches
- clefts/grooves
- pouches
- membranes
arches
- 4 pharyngeal arches
- condensations of mesenchye in ant pharynx
- 5 not visible
- 4 and 6 paired together
- layer of mesenchyme btwn surface ectoderm and pharyngeal endoderm
clefts
- depressions btwn arches
- lined w/ ectoderm
- on exterior of pharynx
pouches
- outpouchings btwn arches lined w/ endoderm
- on interior of pharynx
- 4 pair
membranes
-where clefts and pouches come together
mesenchymal origins of apparatus
- neural crest cells: skeletal elements
2. paraxial mesoderm: striated mm, dermis, endothelium of BVs, vertebrae
max process of pharyngeal arch I derivatives
cart: max bones (inf nasal choncae), zygomatic bones, vomer
skeletal: sphenomand lig, ant lig of malleus, malleus, incus, mand canal
muscle: MOM, mylohyoid, ant belly of digastric, tensor twins
CN: V
mand process of pharyngeal arch I derivatives
cart: mandible, squamous portion of temp bone
* all else same as max process
Arch II derivatives
skeletal: Reichert cartilage, lesser cornu of hyoid bone, stapes, styloid process, stylohyoid lig
muslce: facial expression, stapedius m , post belly of digastric
CN: VII
arch III derivatives
skeletal: hyoid bone, greater cornu of hyoid bone
muscle: stylopharyngeal m
CN: IX
arch IV derivatives
skeletal: thyroid cartilage, cricoid cartilage
muscle: pharyngeal m
CN: X
1st pair of groove derivatives
- only groove contributing to a post-natal structure
- ext acoustic meatus
2nd-4th groove derivatives
- arch 2 overgrows arches 3-4
- grooves 2-4 unite to form the cervical sinus (gives rise to cervical vessicle)
cervical (branchial) cyst
- may develop from remnants of cervical sinus
- fluid filled, just below angle of mandible, lateral
germ layers of tympanic membrane
endoderm and surface ectoderm
pouch I structures
- tubotympanic recess (extension of eustachian tube connecting middle ear cavity and pharynx)
- middle portion of tubotympanic recess = tympanic cavity + mastoid antrum
- contributes to endoderm of tympanic membrane
pouch II structures
-palatine tonsils
pouch III structures
- dorsal buds: inf parathyroid glands
- ventral buds: fuse at midline to form thymus
- will migrate caudally to adult locations
pouch IV structures
- dorsal buds: superior parathyroid glands
- ventral buds: ultimopharyngeal body (elongated portion of each ventral bud that will fuse w/ thyroid gland) *cells w/in bodies become parafollicular āCā cells producing calcitonin
origin of thyroid gland
penetrates down thru foramen cecum in tongue (btwn ant 2/3 and post 1/3), creating thyroglossal duct
thyroglossal duct cyst
- results from imperfect closure of thyroglossal duct
- forms at midline, may move with tongue when swallowing
pharyngeal arch contributions to tongue
- median lingual swelling and 2 lat ling swellings develop at 1st arch level
- lat swellings grow and fuse at midline, covnering median and forming ant 2/3 tongue
- post tongue forms from elevations in floor of pharynx (copula = 2nd arch, hypopharyngeal eminence = 3rd/4th arch)
terminal sulcus
v shaped line separating ant 2/3 and posy 1/3 tongue
