Facial Growth PDF

FACIAL GROWTH - To describe the process of facial growth and development ​ - Starts week 4 w 5 swellings around stomodeum (primitive mouth) - Max and mandib swellings from 1^st^ pharyngeal arch -\> lat each side of stomodeum - Mandib swellings form lower border + 5^th^ - Frontonas...

FACIAL GROWTH - To describe the process of facial growth and development ​ - Starts week 4 w 5 swellings around stomodeum (primitive mouth) - Max and mandib swellings from 1^st^ pharyngeal arch -\> lat each side of stomodeum - Mandib swellings form lower border + 5^th^ - Frontonasal process forms upper border of stomodeum - Max swellings form upper border of stomodeum - Max swellings grow forwards + move closer together to fuse at midline - Nasal placode -\> 2 thickenings on frontonasal process - Failure of max swelling fusion = unilateral/bilateral cleft lip - Max + mandib swelling fusion = cheeks -\> reducing mouth width Formation of palate: - Intermaxillary process -\> prim palate + pre-maxilla + front of ant palate (4 max incisors) + nasal septum - Week 7 = thin extensions form in inner wall of max process -\> palatine shelves -\> form initially on either side of lat tongue - Palatine shelves rotate upwards to midline as tongue lowers - Week 8 + 9 = shelves fuse to each other + prim palate + lower border of nasal septum Bone formation + growth: - Intramembranous ossification = form bone in membrane - Endochondral ossification = bone replace cartilage - Bone can form w both methods - Intramembranous = embryo development in sheets - Calvarium, facial bones, most of mandible, clavicle -\> intramembranous - Bones of face + skull joined by sutures - Bony infill @ sutures = response to force separating bones on either side - Growth causes mass of bone to move relative to neighbours = displacement - Remodelling + displacement can occur simultaneously on same bone - Cartilage in mandib condyle diff to rest of body - Condylar cartilage grows in response to other facial structures Control of craniofacial growth: - Genetic control greater for anteroposterior growth compared to vertical growth Theories: Sutural theory (Sicher): - Sutures have innate growth potential - Suture pushed bones apart - Not true -\> transplanted suture did nothing - Stretched suture = growth - They respond w passive deposition Cartilaginous theory (Scott): - Prim determinant for growth = cartilage - Transplant nasal septum cartilage into other tissues = some growth - 75% no impairment in growth in condylar fracture in growing children Functional matrix theory (Moss) -- capsular + periosteal matrices: - Genetic control expressed in soft tissues -\> determines size and shape of bone - 2 types of matrices -\> periosteal + capsular - Periosteal -\> teeth, muscles, blood vessels, nerves - Microskeletal unit has own periosteal matrix - Capsular matrix -\> organs - Congenital absence of eye = diminutive and rudimentary orbit Likely that both capsular + functional matrix theories play part in craniofacial growth Postnatal craniofacial growth - As face enlarges -\> grows forwards + downwards - Calvarium, cranial base, maxilla + mandible grow differently -\> finish by 7yo - face grows slows in puberty - max growth pattern closer to neural growth -\> declines at 12yo - max complex growth important for position of upper teeth - max grows downward and forward until 7yo by drift + remodelling - downward growth -\> drift of hard palate + vertical development of alveolar process as teeth erupt and root forms - lat growth = displacement of halves of max + infill at mid palatal suture - max complex slows at 7yo and basically stops at 12yo - mandib follows somatic growth -\> periosteal activity - alveolar process adds to vert height - mandible displaced forwards by tongue growth - remodelling = ↑ width posterior mandible + length + prominent chin - growth occurs 2-3mm mandib body -\> doubles at puberty - slows down 17yo girls 19yo boys - facial growth never completely stops Growth prediction: - bone maturation on hand-wrist radiographs poor correlation to jaw growth -\> better assessment using cervical vertebrae - To reveal different skeletal types and the corresponding general facial patterns ​ Assessed in 3 planes: anteroposterior, vertical, transverse - To define the epigenetics and its impact on facial growth and development ​ - Study of how cells control gene activity w/o changing gene sequence - Stable, heritable traits not explained by changes in DNA - Leads to individual differences in appearance, physiology, cognition + behaviur -\> phenotype - Genes responsible for craniofacial structures are basically the same but every face is unique - Mechs: histone modification - Neural crest cells origin of facial structures - Environment signals reach neural crest cell to activate chromatin state - To reveal the facial differences between male and female   ​ CHICKS DUDES -------------------------------------- ------------------------------------- More prominent eyes + cheeks \~2.4mm More prominent nose + mouth \~2.7mm More v shaped mandible Smaller nasiolabial angle Fuller lips Stronger forehead Lips closer to nose Flatter cheekbones