Embryology

Question 1

Pharyngeal arches

Answer 1

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

Question 2

arch 1

Answer 2

trigeminal (V)
forms the face: bones(viscerocranium) , CT, dermis, muscles of mastication, digastric, MH
oropharyngeal membrane separates the pharynx and oral cavity

Question 3

arch 2

Answer 3

facial (VII)

skeletal derivatives of temporal bones
muscles of facial expression
stylohyoid, posterior belly of digastric, stapedius

Question 4

arch 3

Answer 4

glossopharyngeal (IX)

greater horn and inf portion of hyoid
stylopharngeus

Question 5

arch 4

Answer 5

vagus (X)

with the 6th arch, forms all laryngeal cartilages
muscles of pharynx, cricothyroid

Question 6

arch 6

Answer 6

vagus via recurrent laryngeal (X)

fwith 4th arch, forms all laryngeal cartilages 
laryngeal muscles (-cricothyroid) and skeletal muscles of esophagus

Question 7

Pouch 1

Answer 7

contributes to the formation of the middle ear and auditory tube

Question 8

pouch 2

Answer 8

forms the stroma of palatine tonsil and tonsillar fossa

Question 9

pouch 3

Answer 9

inferior parathyroid

ventral—>thymus

Question 10

pouch 4

Answer 10

dorsal: suerior parathyroid glands
ventral: ultimobranchial body—> C cells

Question 11

First cleft

Answer 11

formation of the external ear

Question 12

Thyroid gland formation

Answer 12

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

Question 13

tongue development

Answer 13

1st arch—> anterior 2/3 (GSA from V)
3rd arch—> posterior 1/3 (GSA from IX)
4th forms epiglottic region(GVA from X)

Question 14

ectopic thyroid or PT tissue

Answer 14

remnants of thyroid tissue can remain along the course of migration (tongue, ant to hyoid, ant to thyroid)

Question 15

lateral cervical cysts

Answer 15

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

Question 16

Thyroglossal cysts

Answer 16

remnant of thyroglossal duct

always located on or near the MIDLINE of the neck

Question 17

Neural crest disorders

Answer 17

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

Question 18

venticular zone

Answer 18

thick pseudostratified epithelium call neuroepithelium gives rise to all neurons and glia of spinal cord (simple layer of ependymal cells in adults)

Question 19

Mantle zone

Answer 19

zone superficial to neuroepithelium that is composed of neuronal cell bodies

alar and basal plates

Question 20

alar plate

Answer 20

form sensory, dorsal horn

Question 21

basal plate

Answer 21

form motor, ventral horn

Question 22

marginal zone

Answer 22

outermost layer that is composed of nerve processes (axons and dendrites (white matter)

Question 23

telencephalon

Answer 23

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

Question 24

diencephalon

Answer 24

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

Question 25

mesencephalon

Answer 25

forms the midbrain and cerebral aqueduct | associated with CN III and IV

Question 26

metencephalon

Answer 26

forms the pons AND cerebellum from the marginal layer alar--->sensory basal--->motor V, VI, VII, VIII

Question 27

myelencephalon

Answer 27

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)

Question 28

cerebellar development

Answer 28

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

Question 29

meroencephays

Answer 29

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

Question 30

encephalocele

Answer 30

skull (at the lambda or foramen magnum) does not seal, causing the CNS to protrude thru meningocele, meningoencephalocele, or meningohydroencephalocele (brain, meninges, and ventricles)

Question 31

congential hydrocephalus

Answer 31

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

Question 32

Arnold Chiari syndrome type I

Answer 32

skull defect (posterior cranial fossa is too small) cerebellum herniates thru the foramen magnum often asymptomatic, spina bifida cysitica