early embryology and branchial arch

Question 1

when is the critical period for orofacial dev

Answer 1

month 2-3

Question 2

when is morula/blastocyst, implantation

Answer 2

morula day 4
blastocyst day 5-6
implantation day 6-7

Question 3

whats the cluster of cells, outer layer and other space called

Answer 3

-outer space - trophoblast
inner space = blastocoele
-embryoblast is the cluster

Question 4

what occurs in the 3rd week of development

Answer 4

gastrulation
bilaminar embryonic disc converted to trilaminar dis
-cells of inner cell mass begin to differentiate as amnion forms. travel inward, make indent and outer layer is ecto, inner meso etc.

Question 5

what happens in the 3-4 weeks after gastrulation

Answer 5

• neural tube formation
• cephalic folding (formation of primitive oral cavity and foregut)
• neural crest formation (cells that leave from closing neural tube to throughout body)

Question 6

how does the neural tube form

Answer 6

ectodermal layer at the rostral end of embryo forming the neural plate

• neural folds make a deepening/midline depression (neural groove). proceeds cranial/caudal
• closes at 4th week ish, and the nervous system is established

Question 7

what are homebox genes

Answer 7

genes for pre-determined ‘migration’ paths . they have a common sequence element of 180 base pairs

Question 8

what are hox genes

Answer 8

group of related patterning genes that determine the basic structure and orientation of an organism

Question 9

which transcription factors orchestrate migration and pattern formation

Answer 9

Msx, Dlx, Barx

Question 10

what is external and internal composition of branchial arches

Answer 10

externally arches are separated by branchial grooves, covered by ECTODERM

internallly separeated by pharyngeal pouches, lined by endoderm

Question 11

what is the buccopharyngeal membrane made of

Answer 11

ectoderm and endoderm. separates stomatodeum from foregut. breaks down so they can communicate at one point

Question 12

what 4 things does each branchial arch have

Answer 12

• cartilage
• aortic arch
• cranial nerve
• muscle

Question 13

what derives from branchial arch 1 and nerve?

Answer 13

• CN V (trigeminal)
• mandible and maxilla
• sphenomandibular ligament
• formation of external auditory meatus

Question 14

what derives from branchial arch 2 and nerve

Answer 14

• cn VII or facial
• styloid process of temporal bone
• stylohyoid ligament
• lesser horns of hyoid bone

Question 15

what derives from branchial arch 3 and nerve

Answer 15

CN IX or glossopharyngeal

-greater horns of hyoid bone

Question 16

what derives from branchial arch 4 and nerve

Answer 16

CN X or vagus

-cartilages of larynx

Question 17

what are the derivatives of the 5 pouches

Answer 17

1- auditory tube (tympanic membrane, mastoid antrum, eustachian tube)
2-palatine tonsil
3-inferior parathyroid (III) and thymus glands
4-superior parathyroid (IV) and thymus (vestigial) glands
5- postbranchial body. source of parafollicular or C cells of thyroid gland

Question 18

where do the 3 sections of the tongue derive from and what nerve innervates them SENSORY? MOTOR?

Answer 18

tip of tongue (anterior); CN V (ARCH 1)
middle of tongue ; CN IX (ARCH 3)
posterior of tongue ; CN X (ARCH 4)

little sliver on the anterior /mid part = arch 2

MOTOR INNERVATION = XII (hypoglossal)

Question 19

where does the muscle of the tongue arise from

Answer 19

post-occipital somites (segments of mesoderm extending caudally)

Question 20

what two conditions can occur due to neural crest migration issues

Answer 20

pierre-robin syndrome and treacher-collins syndrome

Question 21

what are the 3 landmarks on developing tongue

Answer 21

lingual swellings (2 bulges)

• tuberculum impar (small at base of lingual swellings
• hypobranchial eminence along tongue