embryology Flashcards
when do the pharyngeal arches develop?
weeks 4 and 5
which arch is most cranial?
arch 1
how many arches are there?
5 (1,2,34,6) number 5 doesnt develop
what germ layer are the pharyngeal arches from?
all-endo, meso and ectoderm
what do the otic placodes give rise to?
inner ear
which part of otic vessels gives rise to the cochlea?
saccular
which part of otic vessels gives rise to the semicircular canals?
utricular
when do the semicircular canals develop?
week 6
internal indentation ?
pouch (endoderm lining)
external indentation ?
cleft (ectoderm lining)
what are the 2 skeletalcomponents of the first arch?
maxillary process(dorasl portion)and mandibular process(ventral portion)
what muscles arise from arch 1?
muscles of mastication, mylohyoid, tensor tympani and tensor palatini (all supplied by CN V3)
skeletal components from second arch?
stapes, styloid process and stylohyoid ligament, lesser horn and upper part of body of hyoid
muscles and nerves from second arch?
muscles of facial expression, strapedius, stylohyoid.. all supplied by facial nerve
when does cochlea develop?
between week 8 and 8
what does the 3rd arch give rise to?
greater horn and lower part of body of hyoid
stylopharyngeus muscles - CN IX supply
what does the 4th and 6th arch give rise to?
layngeal cartilages
muscles of 4- cricothyroid, levator palatini, pharyngeal constrictiors
muscles of 6- intrinsic layngeal
what does the 1st pouch turn into?
middle ear, eustachian tube, tympanic membrane
what does the 2nd pouch turn into?
palatine tonsil
what does the 3rd pouch turn into?
thymus
inferior parathyroid gland
what does the 4th pouch turn into?
superior parathyroid gland and C cells of thyroid
what does the 1st cleft turn into?
external auditory meatus
what does the 2nd -4thcleft turn into?
they gradullay disappear
what is microtis?
small ear
how many facial swellings are there?
5
when do the facial swelling develop?
from week 4
name the 5 facial swellings
frontonasasl prominence
maxillary prominence x2
madiubular prominence x2
how many nasal swellings are there?
4
name the nasal swellings?
medial x2
lateral x2
when do the nasal swellings develop/
week 5
where does the nasolacrimal groove lie?
between maxillary prominence and lateral nasal prominance
what fuses to for the primary palate?
medial nasal prominences to give intermaxillary segement - the palatal component of this gives the primary palate
what forms the secondary palate?
palatine shelves
what form the upper lip?
2 medial nasal prominences and 2 maxillary prominences
what forms the lower lip?
mandibular processes
what forms the noses bridge and septum?
frontal prominences
what forms the noses chest and tip?
medial prominences
what forms the alae of the nose?
lateral prominences
when do nasal cavities develop?
week 6
