Embryology Development of Face, Skull, Palate Flashcards
what two embryological tissue types give rise to all of the skull
neural crest
sclerotome portion of somite
neural crest disorder?
facial defects
anterior portion of the skull forms from what
neural crest cells
posterior portion of the skull forms from
paraxial mesoderm
when do the anterolateral fontanelles close?
about 6 months
when do the posterolateral fontanelles close?
about 6 months
when does the anterior fontanelle close
18 months
what are fontanelles
soft spots- large sheets of CT
allow for growth of skull postnatally
allow calvaria to undergo changes in shape (molding) during birthing
anterior, posterior, posterolateral, anterolateral
the flat bones grow together postnatally but the cranial sutures remain flexible throughout childhood
what is craniosynostosis and what are the two types?
abnormal sutures (close to early, etc.)
scaphocephaly
scaphocephaly
early fusion of SAGITTAL suture
skull is long A-P and narrow (transverse)
brachycephaly
early fusion of coronal suture
skull is short (A-P) and wide transverse
what does the face form from
three, paired prominences (from 1st arch) form most of the features of the face
what does the frontonasal prominence form
a. Forehead
b. Bridge of nose and nasal septum
c. Medial nasal prominences – apex of nose, philtrum of upper lip
d. Lateral nasal prominences – ala of nose
what does the maxillary prominences form
a. Upper cheek
b. Lateral portions of upper lip
what does the mandibular prominences form
Chin, lower cheek region
b. Lower lip
c. Part of external ear
what are nasal placodes?
thickening of surface ectoderm that forms on frontonasal prominence and the invaginates to form nasal pits
what do medial and lateral nasal prominences form from
mesenchyme surrounding the margins of the nasal pits proliferates to form these two structures
what is the development of medial nasal prominences
pushed towards midline and will fuse with one another (forming the intermaxillary segment)
what is the upper lip formed from
intermaxillary segment fusing with adjacent maxillary prominence
what else does the intermaxillary segment gives rise to besides part of the upper lip
philtrum and primary palate
what does the nose develop from ?
frontonasal prominence, lateral nasal prominence and medial nasal prominence
what does the upper lip develop from?
medial nasal prominence and maxillary prominence
lower lip develops from what?
mandibular prominence
how does the nasolacrimal duct form
- The maxillary prominence fuses with the lateral nasal prominence along the nasolacrimal groove.
- The nasolacrimal duct forms from the ectoderm of nasolacrimal groove.
how do the nasal cavities and paranasal sinuses form?
nasal pits deepen and grow dorsally, produce nasal sacs
nasal sacs are separated from oral cavity by oronasal membrane
oronasal membrane ruptures by 6th week, replaced by palate
olfactory epithelium and CNI develop from nasal sac ectoderm
paranasal sinuses develop slowly through puberty
what do the olfactory epithelium and CN I develop from
nasal sac ectoderm
muscles of mastication are derived from which pharyngeal arch ?
1st pharyngeal arch (trigeminal)
muscles of facial expression form from which pharyngeal arch?
2nd pharyngeal arch (facial n)
what does the primary palate form from and what does it fuse with
- The maxillary prominence fuses with the lateral nasal prominence along the nasolacrimal groove.
- The nasolacrimal duct forms from the ectoderm of nasolacrimal groove.
what do lateral palatine shelves form from
maxillary prominences
how does the secondary palate form
- During weeks 7-8, the palatine shelves migrate superiorly and fuse with one another, the primary palate, and in the midline with the nasal septum.
- Ossification occurs in anterior 2/3rds of palate to form hard palate.
- The incisive foramen is the landmark between primary and secondary palates.
what does the incisive foramen demarcate ?
the landmark b/w primary and secondary palates
what is the most common craniofacial anomaly
clefts of the lip and palate
what is the cause of anterior clefts?
separates the primary from the secondary plate
caused by failure of maxillary prominence to fuse with mideal nasal prominence (intermaxillary segment)
what is the cause of a median cleft of lip ?
failure of medial nasal prominences to merge (rare)
what is the cause of a posterior cleft?
lack of fusion of lateral palatine plates
cleft palate and/or uvula
what is the cause of an oblique facial cleft
failure of maxillary process to fuse with lateral nasal prominence
runs from mouth towards eye
results in nasolacrimal duct not being incorporated into the face
what do craniofacial defects result from many times?
disruption of nasal crest cell migration or differentiation in the face
Examples include Treacher collin’s
DiGeorge anomaly
DiGeorge
Chromosome 22
-Cardiac defects
-Abnormal facies
-Thymic aplasia
-Cleft palate
-Hypocalcemia
(parathyroid
deficiency)
