Head and neck embryology Flashcards
when do neural crest cells migrate
week 3-4 of development
2 teratogens that can destry neural crest cells
alcohol and retinoic acid (Accutane)
first arch syndrome
- from insufficient migration of neural crest cells
- treacher collins/robin sequence
- hemifacial microsoma
treacher collins syndrome
- malar hypoplasia (of zygomatic bone)
- mandibular hypoplasia
- eye, ear malformations
- autosomal dominant (also by teratogens)
robins syndrome
- triad complex:
- poor growth of mandible
- high posteriorly placed tongue
- cleft palate
DiGeorge syndrome
- from pharyngeal arch 3/4 differentiation failure (neural crest cells didnt migrate)
- hypoplasia of thymus
- no parathyroid glands
- CVS defects
- facial anomalies (cleft palate)
- poor prognosis
- chrom 22 deletion
- linked to teratogens
what does first pharyngeal pouch give rise to
epithelial lining of tympanic cavity and mastoid antrum (distal)
lining of eustachian tube (proximal)
second pharyngeal pouch gives rise to
surface of palatine tonsil, tonsillar fossa
third pharyngeal pouch gives rise to
dorsal: inferior parathyroid gland ( glandular epithelial cells that secrete PTH)
ventral: forms stroma of thymus
fourth pharyngeal pouch gives rise to
dorsal: glandular cells of superior parathyroid cells
ventral: ultimobrachial body (incorporate into thyroid as parafollicular cells)
what is derived from pharyngeal clefts
external auditory meatus from first cleft
what arises from pharyngeal membranes
tympanic membrane from first membrane
where are lateral cervical cysts found and what are they from
found laterally along SCM muscle
remnants of cervical sinus, usually below angle of jaw
branchial fistulas
occur when second arch doesnt grow over arch 2,3 and 4 leaving the clefts in contact with the surface epithelium by a narrow canal (internal or external)
when does tongue development start
during week 4
what starts tongue development
proliferation of endoderm (and mesenchyme) of pharyngeal floor (give rise to mucus membrane)
pharyngeal arch 1 gives rise to
anterior 2/3 of tongue
root of adult tongue formed by
tissue of third (which overgrows second) and fourth arch endoderm
muscles of tongue arise from
myotomes of occipital somites
sensory of tongue
- anterior 2/3
- general: lingual of CN V
- taste: chorda tympani of CN II
- root
- genreal: glossopharyngeal and vagus
- taste: glossopharyngeal
ankyloglossia
aka tongue tied
usually no intervention (frenulum stretches afer birth)
when does thyroid gland develop
day 24 (first of all glands)
when does synthesis of thyroid hormones start
week 12
when should thyroglossal duct degenerate
week 7
(if not, gives rise to throglossal cyst)
5 primordia of first pharyngeal arch
nasolacrimal groove becomes
nasolacrimal duct (upper end becomes lacrimal sac)
frontonasal process gives rise to
medial nasal prominences then intermaxillary segment then primary palate, philtrum, jaw with four incisor teeth
skeletal elements pharyngeal arch 1
- meckel’s cartilage
- EC ossification: incus, malleus, perichondrium, sphenomandibular ligament, anterior ligament of malleus
- IM ossification: maxilla, zygomatic squamous temporal bone, mandible, portion of palatine bone
skeletal elements pharyngeal arch 2
EC: stapes, styloid process, stylohyoid ligament, lesser horns and upper body of hyoid
skeletal elements pharyngeal arch 3
EC: lower body and greater horns of hyoid bone
skeletal elements pharyngeal arch 4
laryngeal cartilages
skeletal elements pharyngeal arch 6
laryngeal cartilages
arch artery pharyngeal arch 1
maxillary
arch artery pharyngeal arch 2
stapedial , hyoid
arch artery pharyngeal arch 3
common carotid, proximal ICA, ECA
arch artery pharyngeal arch 4
left: arch of aorta, left subclavian
right: right proximal subclavian
arch artery pharyngeal arch 6
pulmonary arteries, ductus arteriosus
muscles from pharyngeal arch 1
muscles of mastication, mylohyoid and anterior belly of digastric, tensor tympani and tensor veli palatine
muscles from pharyngeal arch 2
muscles of facial expression, posterior belly of digastric and stylohyoid, stapedius
muscles from pharyngeal arch 3
stylopharyngeous
muscles from pharyngeal arch 4
muscles of soft palate (except TVP), muscles of pharynx (except stylopharyngeous)
muscles from pharyngeal arch 6
intrinsic muscles of pharynx, upper esophagus
CN of pharyngeal arch 1
trigeminal
CN of pharyngeal arch 2
facial
CN of pharyngeal arch 3
glossopharyngeal
CN of pharyngeal arch 4
pharyngeal branch of vagus
CN of pharyngeal arch 6
recurrent laryngeal of vagus
which germ layer gives rise to thyroid gland?
- nerual crest/ectoderm: parafollicular cells of thyroid
- endoderm: follicular cells of thyroid
