Friday 5 - Ach - Embryology of head and neck Flashcards
Where, embryologically, do the maxillary prominence and the mandibular prominence come from?
The first pharyneal arches
what pharyndeal arch never developes and dissapears
5 (pouch 5 disappears too)
what are the pharyngeal pouches made of?
endoderm. (epithelial endoderm……..)
they are part of the developing gut
where does the only permanent pharyngeal membrane form in human development
between the 1st and 2nd arch
do the pharyngeal arches develope to form neurocranium or viscerocranium?
viscerocranium.
where does the mesoderm come from that goes into the pharyngeal arches
the somites and somitomeres
Tounge precursor mesoderm comes from what somite
occipital somites
Do neural crest cells move in to the phar. arches?
what do they become
yup
become mesenchyme
somite and somitomere migration to the pharyngeal arches
vs
neural crest cell migration to phar. arches
somites and somitomeres-
more nonspecific migration
from mesoderm
NCC-
very specific migration to form mesenchyme (this mesenchyme is special because it is not formed from mesoderm, but rather ectoderm, because neural crest cells are formed from ectoderm)
*arches and the cranial nerves assoc.
1 2 3 4 6
- CN V - trigem
- CN VII - facial
- CN IX - glossopharyngeal
- CN X - vagus
- CN X - vagus
what is the muscle derived from the 3rd pharyngeal arch
stylopharygeus
bones derived from the first phar. arch
maxilla
zygomatic
squamous part of temporal bone
(intramembranous ossification)
Meckel’s cartilage
where
what does it become
Developes within the first pharyngeal arch,
posterior portion becomes malleus and incus
anterior part becomes the ligament of the malleus, spine of the sphenoid bone, and the spheno-mandibular ligament (attaches at the lingula) AND the cartilaginous core of the mandible
Muscles supplied by V3
come from which arch
Tense tense chew chew
tensor tympani
tensor veli palatini
all muscles of mastication
frist pharyngeal arch
Treacher collins syndrome general
definiency of neural crest cells migrating into the first arch
mandibulofacial dysostosis
eyelid malformation, hypoplastic (flat) cheek and jaw, “fish mouth” appearence
pierre robin syndrome general
deficiency of neural crest cells migrating into the arch
small jaw (micrognathia), large, posteriorly placed tounge leading to cleft pallate (soft palate)
skeletal derivs from second arch
Reichert’s cartilage-
stapes styloid process stylohyoid ligament lesser cornu of the hyoid bone upper body of the hyoid bone
nerves of second arch and what muscles they innervate
facial nerve
muscles of facial expression
posterior belly of digastric
stylohyoid
stapedius
Goldenhar syndrome
1st and 2nd arch syndrome
hypoplastic maxilla, mandible, and temporal bone usually unilaterally
skeletal derivs of the third arch
lower body of hyoid
greater cornu of the hyoid bone
nerve of third arch, what muscle(s) does it innervate?
glossopharyngeal
only muscle it goes to is the stylopharyngeus
skeletal derivatives of the fourth and sixth arches
thyroid cartilage
cricoid cartilatge
arytenoid cartilage
other small laryngeal cartilages
what branch of the vagus nerve comes out of the fourth phary. arch
what does it do
superior laryngeal,
carries sensation from the above the vocal folds
supplies muscles of the soft palate (except for tensor veli palatini (V3))
supplies muscles of the pharynx (except stylopharyngeus (glossopharyngeal))
sixth arch what branch of vagus comes out of it
what does it do
recurrent laryngeal branch of vagus
innervates intrinsic muscles of larynx (except cricothyroid)
sensation for larynx below the vocal folds
First pharyngeal pouch
becomes
tubotympanic recess becomes epithelial lining of:
auditory tube
tympanic or middle ear cavity
mastoid air cells
second pharyngeal pouch
becomes
epithelial component of the palatine tonsils
Third pharyngeal pouch
becomes
Thymus (ventral part of third pouch)
inferior parathyroid glands (dorsal part of third arch)
fourth pharyngeal pouch becomes
parafollicular cells of thyroid (c cells)
superior parathyroid glands (dorsal)
the parathyroid glands from the third pouch develop and move _________ to the parathyroid glands of the fourth pouch
caudally (this makes there position variable apparently…)
ectopic
somewhere where something is not normally found
DiGeorge Syndrome
no thymus or parathyroids resulting in diminished immunity, hypocalcemia
What does the first pharyngeal membrane become
tympanic membrane
how does the cervical sinus come about?
what is it lined with
what happens if it doesn’t dissapear
overgrowth of 2nd arch across the 3rd and 4th clefts leads to this sinus
lined with endothelial cells
lateral cervical cists if it doesn’t disappear
how does the thyroid develop
evagination of the the endoderm from the floor of the pharynx between 1st and 2nd pouch (call thyroid diverticulum)
two things that come together to form the thyroid
thyroid diverticulum -> follicular cells of thyroid
4th pharyngeal pouch -> ultimobranchial body -> parafollicular (C) cells
if you see an adult with a mass in their neck it is what until proven otherwise
in a child?
adult - cancer
child - developmental abnormality
branchial vs thyroglossal cyst
branchial - lateral neck
thyroglossal cyrst - middle neck
anterior 2/3rds of toung come from
posterior
1st pharyngeal arch
3rd pharyngeal arch
what forms the intrinsic muscles of the tounge
occipital myotomes
what muscle of the tounge is not supplied by the hypoglossal nerve
palatoglossal (vagus)
ankyloglossia
tounge tied (lingual frenulum is still attached)
