Orofacial Development (Exam 1) Flashcards
Primary Palate develops from:
The medial Nasal process of the frontonasal region (5th-7th week)
Describe the stages of primary palate formation and upper lip:
Stage 1: Formation of inter-maxillary segment: Due to fusion of medial nasal processes of frontonasal region
Stage 2: Nasal septum browns inferiorly from the roof of nasal cavity toward oral cavity
Stage 3: Differentiation of inter maxillary segment
Stage 4: Formation of upper lip (7th week): Fusion of thesis two regions of soft tissue:
Labial component of maxillary process and labial part of inter maxillary segment (philtrum)
** Note lower lip is fusion of soft tissue of mandibular processes
Two components of the inter maxillary segment that can be recognized in stage 3 are:
- Labial component: Philtrum of upper lip
- Palatal component: Primary palate containing maxillary incisors
* Bone of primary palate= Premaxilla in adult forms by intramembranous ossification
Definitive Palate =
Primary and Secondary palates
When does the formation of the secondary palate form?
6-10th weeks
AKA: Secondary palatogenesis
Stage 1 of Secondary palate development (Prior to palatal elevation)
(6 weeks)
- Proliferation of ectomesenchyme in the lateral palatal shelves of the maxillary processes
- Palatal shelves are in a vertical orientation located on either side of tongue
- Lower jaw needs to grow forward, pulling tongue downward into floor
Stage 2 of Secondary Palatogenesis:
(8th week)- Palatal elevation stage:
- Lower jaw grows forward and tongue drops from nasal cavity into floor of mouth
- Palatal shelf elevation depends on proliferation of ectomesenchyme and ECM proteins (collagen ex)
- Elevation of palatal shelves to a horizontal position and growth of palatal shelves toward midline
- Nasal septum (Cartilaginous nasal capsule) grows downward to separate nasal cavity and fuse with secondary palate
Stage 3 of Secondary Palatogenesis:
(10th Week) Completion of Palatogenesis:
- Bilateral fusion of palatal shelves anteriorly with primary palate (premaxilla);
- midline fusion of the lateral palatal shelves with each other= secondary palate
- Inferior edge of descending nasal septum fuses with completed future hard palate–
- Collectively the primary and secondary palates together form the definitive/ complete palate
Intrinsic factors controlling palatal fusion:
Signaling b/w ectoderm- Ectomesenchyme controls:
- Survival of ectomesenchyme and adequate proliferation allowing shelves to elevate and touch
- Apoptosis of ectoderm– at medial epithelial seam to allow fusion of areas to occur
- Fusion/confluence of ectomesenchyme throughout the completed palate
- Differentiation of remaining epithelium on palatal and nasal surface and differentiation of bone. Muscle migrates into region
Extrinsic factors controlling palatal fusion:
Growth of Head and Skull
- Downward and forward growth of mandible must occur to accommodate shelf elevation
- Growth of mandible lowers the tongue out of nasal cavity and into floor of the oral cavity
Stage 4 of Palatogenesis:
(11th week)
- INtramembranous ossification of anterior portion of palate occurs -> Forms definitive hard palate
- Skeletal muscle differentiates in posterior portion of secondary palate: Will form the muscle of the soft palate
- Note: Muscles of soft palate originate from paraxial/head mesoderm migrating from the region 4th arch. EXCEPTION: Tensor veil palatine is paraxial mesoderm of 1st arch
What are the five primary ossification sites?
Region of:
- Incisive foramen (1) ossification center; spreads anterolateral
- Palatine foramen (4) ossification centers; ossification bilaterally spreads medial, anteriorly, posteriorly
What are the skeletal muscles of the Palate:
Palatopharyngeus Platoglossus Musculus Uvulae Levator veli palatini Tensor Veli Palatini*** 1st PA
TMJ develops from the:
Ectomesenchyme of 1st PA
Primary Temporal joint develops from:
Meckel’s cartilage (malleus) and Palatopterygo-quadrate cartilage (incus)
