Embryology Flashcards
Pharyngeal arches
core of mesenchyme
neural crest will give rise to ct components
parxial mesoderm—>muscles
each has its own nerve and blood supply
6 total but 5th regresses
arch 1
trigeminal (V)
forms the face: bones(viscerocranium) , CT, dermis, muscles of mastication, digastric, MH
oropharyngeal membrane separates the pharynx and oral cavity
arch 2
facial (VII)
skeletal derivatives of temporal bones
muscles of facial expression
stylohyoid, posterior belly of digastric, stapedius
arch 3
glossopharyngeal (IX)
greater horn and inf portion of hyoid
stylopharngeus
arch 4
vagus (X)
with the 6th arch, forms all laryngeal cartilages
muscles of pharynx, cricothyroid
arch 6
vagus via recurrent laryngeal (X)
fwith 4th arch, forms all laryngeal cartilages laryngeal muscles (-cricothyroid) and skeletal muscles of esophagus
Pouch 1
contributes to the formation of the middle ear and auditory tube
pouch 2
forms the stroma of palatine tonsil and tonsillar fossa
pouch 3
inferior parathyroid
ventral—>thymus
pouch 4
dorsal: suerior parathyroid glands
ventral: ultimobranchial body—> C cells
First cleft
formation of the external ear
Thyroid gland formation
formed from endoderm of the proximal pharynx
descends down the neck, remaining connected to the tongue via thyroglossal duct (pyramidal lobe)
parafollicular C cells are derived from the ultimobranchial body of the 4th pouch
tongue development
1st arch—> anterior 2/3 (GSA from V)
3rd arch—> posterior 1/3 (GSA from IX)
4th forms epiglottic region(GVA from X)
ectopic thyroid or PT tissue
remnants of thyroid tissue can remain along the course of migration (tongue, ant to hyoid, ant to thyroid)
lateral cervical cysts
aka branchial cysts
when the cervical sinus fails to regress ( second arch should overgrow the 3rd and 4th clefts)
causes external (anywhere along the LATERAL SCM) or internal fistulas
Thyroglossal cysts
remnant of thyroglossal duct
always located on or near the MIDLINE of the neck
Neural crest disorders
all NCDs have a craniofacial defect
bc the NC of the 1st arch forms all of the bones of the face, which is where neural crest cell migrates
ex treacher collins, robin sequence, diGeorge anomaly
venticular zone
thick pseudostratified epithelium call neuroepithelium gives rise to all neurons and glia of spinal cord (simple layer of ependymal cells in adults)
Mantle zone
zone superficial to neuroepithelium that is composed of neuronal cell bodies
alar and basal plates
alar plate
form sensory, dorsal horn
basal plate
form motor, ventral horn
marginal zone
outermost layer that is composed of nerve processes (axons and dendrites (white matter)
telencephalon
cerebral hemispheres, basal ganglia
Lumen of telencephalon creates the LV
**most superior (NOT cranial) portion
new cells migrate thru, youngest cells are superficial (via radial glial cells)
CN I
diencephalon
forms the thalamus, hypothalamus, optic vesicles,pineal gland, pituitary gland (epithalamus) and cavity form 3V
*cranial most portion of the neural tube, eventually overgrown by cortex
CN II
mesencephalon
forms the midbrain and cerebral aqueduct
associated with CN III and IV
metencephalon
forms the pons AND cerebellum from the marginal layer
alar—>sensory
basal—>motor
V, VI, VII, VIII
myelencephalon
forms the medulla and 4V: most caudal
pontine flexure causes alar plate to move laterally
basal plate forms distinct nuclei (form CN VIII, IX, X, XII)
cerebellar development
from alar plates of the metencephalon—>cerebellar plate
Gray matter forms externally with white matter forms internally, with deeper nuclei located within the white matter
meroencephays
anencephaly is a failure of the brain to form, failure of the cephalic portion of the neural tube to form
**brainstem still forms, so the fetus will survive for a while, just no higher structures
encephalocele
skull (at the lambda or foramen magnum) does not seal, causing the CNS to protrude thru
meningocele, meningoencephalocele, or meningohydroencephalocele (brain, meninges, and ventricles)
congential hydrocephalus
increased CSF within the ventricles resulting from imbalance b/w production and absorption of CSF- often obstruction at foramen of monroe or aqueduct
skull expands, thinning bones of calvaria
Arnold Chiari syndrome type I
skull defect (posterior cranial fossa is too small)
cerebellum herniates thru the foramen magnum
often asymptomatic, spina bifida cysitica
