embryo pharyngeal arches Flashcards
the pharyngeal arches contribute to the formation of thr
nasal cavities, larynx, pharynx, mouth, and neck
when do the arches begin to form? arches 1-6 development next to what primordial structures?
- begin in 4th week when neural crest cells begin to migrate into future head and neck from hindbrain
- 1st arch (primordial jaws- maxillary and mandibular) forms lateral to developing pharynx
- 2-4th arch develop next to developing head and neck
- 5/6th are rudimentary, or 5th might not form at all
what part of the hindbrain does the neural crest cells of the pharyngeal arches come from? (be specific)
-rhombomeres (R1-7) from hindbrain
- PA1 - R1-2
- PA2- R4
- PA 3-4 - R6-7
mesenchyme comes from ____
neural crest cells that migrate into arches
**core of arch surrounded by ectoderm and endoderm
maxillary and mandibular prominences come from
1st pharyngeal arch- neural crest cells
right after NCC migrate and differientiate into mesenchyme
how is the cervical sinus formed? what happens to it?
- in 5th week it is made by the second PA overgrowing and covering PA 3 and PA 4 (ectodermal depression)
- it is degenerated by the 7th week
what forms all the connective tissue (dermis and smooth muscle) of structures from the PA
NCC
where does myogenic mesoderm come from ? what does it make?
- from paraxial mesoderm
- moves into each arch to make a central core of muscle primordium
where does angioblasts come from ? what do it make?
- from lateral plate mesoderm
- become endothelium of blood vessels
what plays an essential role in regulating the development of the arches
pharyngeal endoderm
a typical PA contains what structures
- artery (from trunks arteriosus)
- cartilaginous rod (forms bone of arch structures) NCC
- muscular component (from paraxial and prechondral M0
- sensory and motor nerves (from brain )
describe what happens to PA 1 cartilage? what is another name for it ?
PA 1 cartilage = Meckels Cartilage
- dorsal part = malleus and incus. the perichondrium will make the anterior ligament of the malleus, sphenomandibular L.
- ventral part = primordium of mandible. cartilage will disappear as bones from laterally
describe what happens to PA 2 cartilage? what is another name for it ?
PA2 = Riecherts
-( plus dorsal anlage) = stapes , styloid process of temporal bone. perichondrium = sphenomandibular L .
-ventral - lesser or of hyoid
what does PA 3 cartilage become
greater horn of hyoid
what does PA 4 and 6 cartilage becomes
fuse to make laryngeal cartilages (except epiglottic cartilage)
how does the body of the hyoid bone form
-from the hypopharyngeal eminence coming from PA 3 and PA4 prominence in floor of primordial pharynx
what muscles do paraxial mesoderm make? prechordal?
paraxial = facial
prechordal = ocular
the muscular portions of the PA’s from what muscles
PA 1 - muscles of mastication PA 2- muscles of facial expression PA 3- stylopharyngeus M. PA 4 - pharyngeal constrictors, cricothyroid, levator veli palatini PA 6 - intrinsic laryngeal muscles
what branch of trigeminal CN does not supply PA
V1 (ophthalmic )
what arteries are made in the 3rd arch
common and root of internal carotids
how does external carotid form
de novo from common
how does distal internal carotid for
continuation of dorsal aorta
how are pharyngeal pouches made ? what structures do they form
- the primordial pharynx is from forgeut endoderm. this endoderm lines the internal aspect of the pharyngeal arches and pouches. the 5 pouches are made cranioncaudally between the arches, 1st pouch b/t 1st and 2nd arch.
- the endodermally epithelial lining of the pouches forms the organs of the head and neck
what forms the tympanic cavity and mastoid antrum
cavity of the tubotympanic recess proximally
from 1st PA pouch
