Development of Orofacial structures Flashcards
Neurocranium:
Derived from mesenchyme
Gives rise to bones that enclose brain
Has cartilagenous and membranous components
Viscerocranium:
Derived from mesenchyme
Gives rise to bones of the facial skeleton
Has cartilagenous and membranous components
Intramembranous ossification:
Mesenchymal origin, does not involve cartilage
Neovascularization occurs
Osteoblasts produce the osteoid and produces bone and osteocytes
Endochondral ossification:
Uses preexisting cartilage model (e.g. long bones)
Diaphysis has the primary ossification centers
Chondrocytes undergo hypertrophy and matrix will calcify
Cartilagenous part of the neurocranium:
Occipital bone
Body of sphenoid
Ethmoid
Petrous and mastoid parts of the temporal bone
Membranous part of the neurocranium:
Frontal and parietal bones
Cartilagenous parts of the viscerocranium:
Malleus and Incus (PA1)
Stapes, styloid process and lesser horn (PA2)
Greater horn (PA3)
Laryngeal cartilage (PA4)
Derived from neural crest
Membranous parts of the viscerocranium:
Maxillary prominence
Squamous part of temporal bone
Maxilla
Zygomatic bone
Craniosynostosis:
Premature fusion of cranial sutures
Scaphocephaly
Brachycephaly
Plagiocephaly
Trigonocephaly
Involves sagittal suture, wedge shaped cranium (from superior view)
Involves entire coronal suture. Tower like cranium
Involves one side of the coronal suture, twisted and asymmetric cranium
Involves the frontal suture
What drives the shape/rate of growth of the head?
Brain development
What is the precursor structure for head development?
Appears?
Separated by? When does this rupture?
Facial primordia
Appears during week 4 and surround the stomodeum
Separated from the primordial pharynx by oropharyngeal membrane (ruptures at day 26)
Parts of the facial primordia:
2 maxillary prominences
2 mandibular prominences
1 frontonasal promince
Identify the parts of the facial primordia
Refer to drawings
Mandibular prominence
Derivatives:
Chin, lower lip and cheek
Incomplete fusion of mandibular prominence results in …
Chin dimple
Draw the development of the facial primordia
Refer to drawings
Maxillary prominence:
Derivatives:
Upper lip, maxilla and secondary palate
Grows medially and merges laterally with mandibular prominence
PA2 mesenchyme invade primordial lips and cheeks and give rise to facial muscles
Frontonasal prominence:
Derivatives:
Forehead, dorsal nose
Will go and surround the ventrolateral part of the forebrain
Nasal placodes and development:
Bilateral oval thickenings of surface ectoderm on inferolateral portion of frontonasal prominence
Proliferation forms horse shoe shaped elevations that form the medial and lateral nasal prominences, nasal pits and primordial nares