Development of Growth and Jaw Flashcards
(37 cards)
what are the head and neck formed from?
the frontal prominence and branchial arches.
what is the lower jaw formed from?
the first branchial arch / mandibular branch
what is the maxillary developed formed from?
develop from the mandibular process
what is the branchial arch?
growth and lateral extension of mesoderm in the head and neck region of the developing vertebrae embryo.
what cells is the branchial arch developed from?
the cranial neurocrest cells, which form the ectomesenchymal cells.
what does the branchial arch form?
jaw, middle ear and specialised structures in the head and neck.
how does the face begin to develop?
frontal and frontonasal/medial nasal processes develop from the frontal prominence. Process characterized by proliferation and migration of ectomesenchymal cells -> induce localised thickening of mesenchyme.
What 3 features are present in a 6/7 week old embryo?
Lateral nasal process, medial nasal process, maxillary process.
When does palatogenesis occur?
6-8 weeks
What is palatogenesis?
Formation of a secondary/ definite palate. 3 outgrowths in oronasal cavity - nasal septum and 2 palatine processes.
During the 6th week of intrauterine life, what is present?
Primary palate, primary nasal cavities, primary nasal septum.
How does the nasal septum develop?
Downward growth from the frontonasal process along the midline. Primary palate also formed from extension of frontonasal processes.
How do the 2 palatine processes develop?
Extend from maxillary processes downward and vertically on each side of tongue. Behind primary palate.
How does palatogenesis occur?
Primary nasal septum develops by downard growth from frontonasal processes down midline. Primary palate also formed. (6 weeks) 2 palatine processes extend from maxillary processes downward and vertically on each side of tongue (7 weeks). Tongue drops. Palatal processes elevate above tongue. Horizontal growth. Fuse along midline and primary palate. Converge with nasal septum Forms secondary palate and separates primary oral cavity into oral and nasal. (8 weeks)
When is palatal fusion complete by?
Week 12.
What is mandible formed from?
Band of Meckel’s cartilage
Describe mandible development.
Mandible appears from band of Meckel’s cartilage. Bone develops intramembraneously. Ossification centre forms (7th week) and bone spreads rapidly backwards, forwards and upwards. Bone on lateral side spreads (future body of mandible). Mandible extends towards midline, separated by fibrous mandibular symphysis.
Upward extension of lateral and medial plates of bone above and around nerve canals forming alveolar bone development. 3 Secondary growth cartilages form via endochondral bone formation between 10th and 14th weeks.
What is Meckel cartilage formed from?
From 1st pharyngeal arch.
What is the proximal end of Meckel’s cartilage connected to?
Ear capsules, which form the ossicles of middle ear and ligaments.
What is the centre of primary ossification located close to?
To division of inferior alveolar branch nerve (incisive and mental branch)
Describe intramembranous bone formation?
Bone formed directly within mesenchyme. Condensation of vascularised mesenchyme. Mesenchyme osteoprogenitor cells lead to osteoblast differentiation. Bone matrix formation and development of bone spicules called trabeculae. Surrounding periosteum leads to appositional bone growth. Does not directly involve cartilage. Developed directly from condensed mesenchyme.
What are remnants of Meckel’s cartilage formed into?
Ear ossicles and sphenomandibular and disco-malleolar ligaments.
What are teeth separated by?
Interdental septa.
How does the maxilla develop?
Develops intramembraneously. (Week 6-7). Develops in maxillary process. Ossification centre is in a band of tissue outside nasal capsule between alveolar and infra-orbital nerves. Spreads backwards to developing zygomatic processes, forward to future incisor region, upwards to form frontal-nasal processes and downards to form alveolar processes.
