Prenatal Growth

Question 1

Ectoderm

Answer 1

epidermix, nasal & oral mucosa, tooth enamel, lens, oragns of hearing/equilibrium

Question 2

Endoderm

Answer 2

lining of posterior tongue, pharynx, tympanic cavity, respiratory tract, parts of thyroid

Question 3

Mesenchyme

Answer 3

bones, muscles, & connective tissues of the head (and all other parts of the body)

head mesenchyme is from two sources:

paraxial mesoderm (somitomeres & somites)

neural crest (via surface ectoderm)

Question 4

mesenchyme from neural crest

Answer 4

bones & connective tissues of face & anterior skull (vault + base)

Question 5

mesenchyme from paraxial mesoderm

Answer 5

all skeletal mm., bones & connective tissues of posterior skull (vault + base)

Question 6

Ossification pathways: intramembranous

Answer 6

mesenchymal tissue located just below the dermis transforms directly into bone

lateral

Question 7

ossification pathways: endochondral

Answer 7

mesenchyme forms a hyaline cartilage model; the cartilage is then replaced by bone tissue

medial

Question 8

palatogenesis

Answer 8

inferior views of medial nasal prominences merging together to form primary hard palate (premaxilla)

medial nasal prominences give rise to: premaxilla and upper incisors

inferior view of lateral palatine processes merging to form secondary hard palate

Question 9

Cleft lip &/or anterior cleft palate

Answer 9

results from mesenchyme deficiences; failure of tissues to merge; vascular defects; etc. in maxillary prominences & median nasal prominences

maybe uni or bilateral

Question 10

posterior cleft palate (aka isolated cleft)

Answer 10

results from growth distortions in palatine shelves causing defective midline fusion & w/ nasal septum

soft palate may or may not be involved

Question 11

Lateral facial cleft: macrostomia

Answer 11

poor merging of max and man prominences; condition manifests as a large mouth on one or both sides

Question 12

congenital craniofacial defects

Answer 12

most craniofacial malformations occur during the embryonic period (weeks 2 to 8)

deformations and growth disturbances (diruptions) occur in the fetal period (weeks 9 to 40)

Question 13

Fetal alcohol syndrome

Answer 13

caused by maternal intake of alcohol

different effects due to timing of exposure(s)

affects development of all structures; apoptosis of early cell populations; damaged DNA; cognitive defects

may stimulate premature differentiation of mesenchyme of facial primordia

characteristic facial features

Question 14

Holoprosencephaly

Answer 14

defective formation of forebrain resulting in malformation of structures depending on molecular signaling from this region; reduction in frontonasal process structures

Question 15

Frontonasal dysplasia

Answer 15

excessive tissue in frontonasal process structures

Question 16

Pierre Robin Sequence (Robin Syndrome)

Answer 16

occurs in 1:8

may be caused by intrauterine constriction of mandibular growth; neurologic conditions affecting jaw movements; genetic

results in sequence of effects on 1st arch structures; tongue interferes w/ formation of secondary palate

triad of micrognathia, cleft palate, & glossoptosis (retracted tongue)

normal intelligence