Head and Neck Neuroembryology Flashcards
head and neck derivatives of the ectoderm
neural tube (CNS motor neurons, preganglionic ANS), neural crest (PNS, post ganglionic ANS), epithelial skin, nasal pit, external ear, olfactory, lens, otic (from placodes)
head and neck derivatives of the endoderm
epithelial lining (pharynx, larynx, trachea, esophagus, pharyngotympanic tube, middle ear), glands (thymus, parathyroid, tonsil, thyroid, mucosal)
head and neck derivatives of the mesoderm
notochord (nucleus pulposus), somites that form bones, muscles, connective tissue, sclerotome (bone and cartilage), dermatome (dermis), myotome (muscles)
neural crest derivatives related to the head and neck
PNS postganglionic autonomic nervous system, connective tissue and bone of face and skull, cranial nerve ganglia, skin of face, DRG, parasymapthic and sympathetic chain ganglia, adrenal medulla, schwann cells, satellite cells, meninges, melanocyte
which aortic arch is vestigial and does not develop?
5th aortic arch
what forms the auricle?
mesenchymal and condensations associated with the 1ST AND 2ND pharyngeal pouches
which pharyngeal CLEFT forms the external auditory canal?
1st pharyngeal cleft
which pharyngeal POUCH forms the pharyngotympanic tube and middle ear cavity?
1st pharyngeal pouch
what lines the outside of the tympanic membrane? what lines the inside of the tympanic membrane?
ectoderm; endoderm; there is mesoderm in between.
what do the pharyngeal arches develop from?
neural crest cells that proliferate and migrate around the sides of the developing pharynx
how does the 2nd pharyngeal arch form the smooth skin over the neck?
it overgrows the 3rd and 4th pharyngeal clefts
what is the cervical sinus? how does it form?
2nd, 3rd, 4th pharyngeal grooves merge to form it;
where would a branchial cyst be located in the neck? is there a surface landmark that can be used to describe its location?
it would be located above the lateral part of the SCM muscle, between it and the larynx
which cranial nerve innervates muscles derived from the 1st, 2nd, 3rd, 4th pharyngeal arches?
trigeminal (V), facial (VII), glossopharyngeal (IX), and vagus (X), respectively
what are the skeletal derivatives from the 1st, 2nd, 3rd, 4th pharyngeal arch cartilages?
1st: malleus, incus
2nd: stapes, styloid process, superior half of hyoid (stylohyoid ligament)
3rd: inferior half of body and greater horn of hyoid
4th: thyroid, epiglottic cartilages
where does the thyroid begin as an outpocketing of endoderm?
thyroid diverticulum (at the posterior edge of the 1st pharyngeal arch)
what path does the thyroid take to migrate to its final resting position? what structure could you identify on a cadaver that marks this pathway?
from the foramen cecum, through thyrogossal duct, down in front of the hyoid bone; adams apple?
what is a thyroglossal duct cyst? where would it be located?
it would be located at the foramen cecum where it meets the thyroglossal duct; protruding through the upper anterior neck.
what are the derivatives of the 1st, 2nd, 3rd, 4th pharyngeal POUCHES?
1st pouch: pharyngotympanic tube, middle ear
2nd pouch: palatine tonsil (epithelial crypts)
3rd pouch: inferior parathyroid, thymus
4th pouch: superior parathyroid, ultimobranchial body
what symptoms would a px display if glands developing from the 3rd pharyngeal pouch fail to develop properly?
hypocalcemia, recurrent infections due to T cell inadequacy
which parts of the developing face form the upper and lower jaw?
1st pharyngeal arch has both maxillary and mandibular parts that form the upper and lower jaw regions respectively
what parts of the face does the frontonasal process form?
philtrum, external nose
the medial nasal swellings fuse to form what part of the developing face?
intermaxillary segment that will develop into the external nose, philtrum of upper lip and primary palate.
where is the nasolacrimal groove located in the developing face? what two structures form its boundaries?
cleft between the lateral nasal swelling and the maxillary part of the 1st arch.
what causes an oblique facial cleft?
failure of fusion of between the lateral nasal swelling and the maxillary process of the 1st arch.
which three structures fuse to form the hard palate? does the intermaxillary segment contribute to the hard palate?
fusion of the primary palate, 2 secondary palates; yes the intermaxillary segment is the primary palate, and it contributes to the hard palate.
how does a cleft lip form?
results from failure of the medial nasal and maxillary prominence to fuse
how does a cleft palate form?
failure of the palatine processes to fuse with each other
what develops fro occipital myotomes?
tongue muscles
what structures fuse to form the anterior 2/3 of the tongue? which pharyngeal arch does this arise from?
lateral lingual swellings from the 1st pharyngeal arches fuse
what structures fuse to form the posterior 1/3 of the tongue? does the 2nd pharyngeal arch contribute to any structures in the developing tongue?
2 caudal lingual swellings from the 3rd and 4th pairs of pharyngeal arches; 2nd pharyngeal arches are overgrown and only give rise to taste buds in the anterior 2/3 of the tongue.
how many somites are formed during normal development? how many for each region of the adult vertebral column?
start with 42-44 pairs; some disappear and leave only 36-38 (3 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 3-5 coccygeal)
describe the developmental event that causes spinal nerves to lie between vertebrae in the adult?
resegmentation: they end up at the level of the IV disk where they exit the vertebral column through the IV foramina
what normal embryological process has been interrupted to cause the formation of a hemivertebrae?
defect of formation of the vertebral column
what occurs if you do not have proper resegmentation of the developing vertebrae?
block vertebrae or bar vertebrae, or ‘unilateral bar and hemivertebrae’
