Head and Neck Development: Skull & Face Audrone Biknevicius 2005-CPC2

CRANIOFACIAL ANOMALIES One-third of all congenital defects Etiology: Multifactorial inheritance Teratogens: alcohol, retinoic acid, toluene, smoking, radiation, hyperthermia Genetics

4 Week Embryo – Sagittal Section From Carlson, l999 Primordial tissues Stomodeum Frontonasal prominence

4 Week Embryo - Lateral View From Carlson, l999

4-8 Week Embryo – Frontal View From Carlson, 1999

Pharyngeal Arches Cranial nerve Aortic arch (from mesoderm) Muscle component (from mesoderm) Cartilaginous rod (from neural crest cells)

Skull Neurocranium (brain case) Viscerocranium (face)

Intramembranous ossification Endochondral ossification Development of Skull

PRIMARY DETERMINANT OF GROWTH & DEVELOPMENT MembranousCartilagenous Neurocraniumintracranial pressure genetics Viscerocraniumadjacent soft tissues genetics (tongue, eye)

Neurocranium Primarily derived from neural crest cells Cartilaginous neurocranium (chondrocranium) – skull base Membranous neurocranium – cranial vault

Cartilaginous Neurocranium – Skull Base Sphenooccipital synchondrosis site of AP cranial base growth until ~ 20 yo From Larsen, 1997

Achondroplasia Premature closure of primary growth plates Sphenooccipital synchondrosis - AP short cranial base, moon-shaped profile Autosomal dominant; most common form of dwarfism (1/26,000 live births) /syndication/

anatomy/skel/fetal.htm Cartilaginous Neurocranium – Stylomastoid Foramen Undeveloped mastoid process Ring-shaped external auditory meatus Superficial position of stylomastoid foramen

Forceps-Assisted Delivery pages/s_ob5.html To protect facial nerve: Avoid placing forceps immediately behind ear

From Larsen, 1997 Membranous Neurocranium – Skull Vault Flat bones of the skull Sutures and fontanelles

Gardner, Gray & O’Rahilly Anatomy Childbirth – yielding without cracking Growth - expansion of cranial vault with growth of brain Sutures and Fontanelles

anatomy/skel/fetal.htm Anterior Fontanelle Palpable during 1 st year If small – premature fusion If bulged – increased intracranial pressure If depressed – dehydration Venipuncture

Hydrocephaly

From Carlson, 1999 From Larsen, 1997 Craniosynostosis (premature fusion) ScaphocephalyAcrocephalyCrouzon syndrome Sagittal suture Most common (>50%) Coronal suture Aperts syndrome >2 sutures (coronal, sagittal) Face, teeth, ear

Viscerocranium Primarily derived from neural crest cells Membranous viscerocranium – face (below orbits) – derived from PA 1 (forehead = membranous neurocranium) Cartilaginous viscerocranium – middle ear bones, hyoid bone, laryngeal cart.

Face Formation 4-8 Week Embryo – Frontal View From Carlson, 1999

Development of Face BONE EMBRYOLOGY FACE Forehead Cheek, upper jaw, lateral upper lip Philtrum, medial upper lip Lower jaw, lower lip, chin Frontal Maxilla Premaxilla Mandible Frontonasal prominence Maxillary process Intermax. seg. Mandibular prominence

From Carlson, 1999 Initial sites of development: Optic vesicles - laterally Auditory vesicles – inferiorly Nasal pits – frontal but widely separated Eyes, Ears and Nose

Frontonasal Prominence Defect: Excessive Tissue - Frontonasal dysplasia From Carlson, 1999 Broad nasal bridge & hypertelorism Can be associated with other defects (e.g., tetralogy of Fallot)

Defects of the Frontonasal Prominence: Deficient Tissue - Holoprosencephaly Defective formation of prosencephalon (forebrain) Common olfactory abnormalities Most severe – cylcopia (fusion of op[tic primordia) Etiology: week 3 alcohol consumption, autosomal recessive, excessive retinoic acid, multifactorial From Larsen, 1997

Palate Formation From Carlson, 1999

Development of Palate Primary Intermaxillary palate segment Hard Palate Maxilla Palatine Lateral palatine processes/ shelves Soft Palate BONE* EMBRYOLOGY PALATE *Primary palate: premaxillary part of maxilla (houses incisors) Secondary palate: maxilla and palatine

Palate & Nasal Septum Formation From Carlson, 1999

Face Formation, Facial Clefting From Carlson, 1999

Distinct malformations Both are multifactorial, genetic, teratogens Cleft Lip Hypoplasia of maxillary process Failure of fusion of maxillary and nasomedial processes Most common congential malformation of H&N Cleft Palate Failure of fusion of palatal shelves or palatal shelf with primary palate Cleft Lip and Cleft Palate

Cleft Palate

Cleft lip repair craniofacial.html

Why are babies so cute? Somatic tissues Neural tissues AGE SIZE Adult size GROWTH PATTERNS ~2 yo ~16 yo

phd/mbchb/stroke/stk1.html Development of Paranasal Sinuses Form as invaginations of nasal epithelium into diploe of cranial bone

anatomy/skel/fetal.htm Paranasal sinuses Maxillary & ethmoid sinuses begun to develop in the fetus but are small at birth Sphenoid & frontal sinuses develop postnatally

image.htm Dental Development Permanent teeth dental formula I,C,P,M/I,C,P,M 2,1,2,3/2,1,2,3 (panoramic radiograph ) Deciduous (milk) teeth dental formula I,C,M/I,C,M 2,1,2/2,1,2 (lateral radiograph ) sumerdoc.blogspot.com