OROFACIAL DEVELOPMENT
OROFACIAL DEVELOPMENT
Results of folding1 -the cranial end of the embryo folds
Before the caudal end(growth of the brain is very fast).
2 -formation of stomatodeum (primitive oral (cavity
3 -part of the yolk sac is taken in the embryo forming the future gut. Foregut, midgut, and hindgut
Shallow depression surrounded by neural plate cranially and cardiac plate caudally.
Primitive stomatodeum
Early orofacial development
1 -Time:- Early somaite period 21 to 31 days.
2 -Number& Nature :- Formation of five mesodermal elevations, augmented by neural crest cells , and lined with ectoderm.
3 -Name one central large elevation (frontonasal process) , two maxillary processes , and two mandibular processes.
Differentiation of facial processes1 -The wide frontonasal present between
the developing eyes, forming forehead and nose.
2 -Two maxillary process------- lateral part of the upper lip, and cheek.
3 -Two mandibular process merge in the midline to form the lower lip and Jew.
Nasal placodesSpecialized epithelial thickening at the inferolateral corners of the frontonasal process.
Globular process
Origin 5th intrauterine two horseshoe shaped nasal processes demarcate and enclose the nasal placode forming anterior naresTwo medial processes fuse to form one large globular processe
Derivatives of globular process -:1 -tip of the nose
2 -columella.3 -philtrum.
4-labial tuberculum & frenum of upper lip.
5-primary palate.
Branchial arches
Branchial arches Number and nature:- five to six mesenchymal swellings augmented by neural crest cells.
site:- they are developed between the stomatodeum and future heart.( future
Mandibulocervical region. ) Size:- they decrease in size from first to sixth
Time:- fourth week of I.U .
Each arch is formed of:Derived from neural crest cells))1- central cartilageDerived from lateral mesoderm)) 2- vascular core
3-nervous elementFrom lateral mesoderm) )4- muscular component
nerve Artery Muscle Skeleton Arch
Mandibular.
External carotid
Muscles of mastication
Maxillamandible
Mandibular
facial Facial Muscles of facial expression
Hyoid bone Hyoid
glossopharyng
eal
Internal Commoncarotid
Pharyngeal muscle Lower of hyoid
Third
vagus Aortasubclavian
Pharyngeal muscle Thyroid cartilage
Fourth
vagus pulmonary Laryngeal muscle Laryngeal cartilage
Sixth
Fate Branchial grooves
1st PersistsForming External aoustic meatus
2nd ,3rd & 4thObliterated
By caudal overgrowth of 2nd arch .
Obliteration Failure
BRANCHIAL SACBRANCHIAL FISTULA
cleft derivatives1st external auditory
meatus, ectodermal aspect of tympanic membrane
2nd – 4th cervical sinus?
Derivatives Branchial grooves
Derivatives Branchial pouchesDORSAL VENTRAL
PARTPOUCH
Auditory tube.Tympanic membrane.
Obliterated by tongue
First
Palatine tonsil Obliterated by tongue
Second
parathyroid Thymus Thirduncertain uncertain FourthCalcitonin cells calcitonin Fifth
Formation of the tongue1 -It begins to develop at the 4th week of intra
uterine life, in relation to the first 4 branchial branches
2 -The anterior two thirds of the tongue is derived from the first (mandibular) arch.
Posterior one-third is derived from 3rd branchial arch.
3 -The posterior most part of the tongue is derived from the 4th arch , the same as the epiglottis
Sensory nerve of the tongue
1 -Anterior two thirds
Third arch
Mandibular nerveChorda tympani nerve
2 -Posterior one third
First arch
Glossopharyngeal nerve
3 -Posterior most partfourth arch Superior laryngeal branch of
vagus
Motor nerve of the tongue12th cranial nerve (Hypoglossal nerve )
supplies all muscles of the tongue
Dorsal and ventral aspects of the tongue
Epithelium covering of the tongue
Epithelium covering of the tongue1 -only one layer of epithelial cells
2 -stratified multilayered epithelial cells3 -appearance of circumvallate papillae on
(v) shaped sulcus. 8-12 ( from2nd to 5th month)
4 -development of taste buds. 5 -development of the crypts of palatine
tonsil at birth.
Formation of the palateThe palate is formed from three components-:
1 -the primitive palate.
2 – two palatal process from maxillary process which fuse to form the palate proper at the 7th week .
at late stage the palate undergoes intramemberanous Ossification to form hard palate . Ossification does not extend to the most posterior portion, which forms soft palate.
Development of the jaw
1 -About the six week of intrauterine life bone of the jaw is started to appear .
2 -Both of the maxilla and the mandible are developed from the first branchial arch .
3 -The maxilla formed within the maxillary process and the mandible within the mandibular process.
Development of the madible
Development of the mandible1 -the major part of the mandible mandible is
intramembranous ossification, only the tip of condlye process, cronoid process and the symphyseal region are of endochondoral
ossification .
2 -Meckel,s cartilage , the cartilage of the first branchial arch, act as a guideline for mandible formation, dense fibro-cellular tissue outside and lateral to the cartilage forming the mandible
through intramembranous ossification .
3 -the symphyseal cartilages ,two in number ,appear in the connective tissue between the two ends of Meckel,s cartilage but completely separated from it , they are obliterated within the first year of life.
Intra-membranous ossification
Development of the maxilla
1 -the maxilla is formed of maxilla proper and premaxilla.
2 -maxilla proper is formed as an extension of mandibular arch.(1st branchial arch)
3 -around the 6 week intra membranous ossification center appears near the part which
forms the enamel organ of the canine tooth .
4 -from this center of ossification bone spread below the orbit towards pre-maxilla.
5-maxillary air sinus appears at 16th week featal life as a projection from nasal cavity
6 -sinus increase gradually and separates the orbital surface from the dental surface, the final height Reached after eruption of all permanent teeth.
Development of (TMJ) tempero-mandibular joint
1 -It is an articular surface between two bones; mandible and temporal bone in the base of the skull
2 -at the 7th week of intra-uterine life Meckel,es cartilage extends from the chin to the base of the skull
3 -the formation of tempro-mandibula joint is established at the end of fetal life.
Development of salivary gland1-There are three pairs of major and
innumerable minor salivary glands in the oral cavity.
2 -the parotid and sub-mandibular buds appear during six week .
3 -bud of the sublingual gland appear during seventh week of intrauterine life
4 -the majority of glands are ectodermal in origin, some glands about the base of
the tongue are endodermal .
Clinical consideration1 -Nonuion .
2 -cleft lip and cleft palate4 -lateral facial cleft and macrostromia.
5 -Bifid tongue.6 -lingual thyroid.
1- Folding of the emberyo begins by the end ofa) Third week b) 7th week c) 15th week2- Folding of the emberyo is caused by a) Overgrowth of the nervous system b) overgrowth of the uterine wall c) overgrowth
of the placenta3- anterior two thirds of the tongue developes from a) First branchial arch b) first and third branchial archs c) fourth
branchial arch.4- the ossification center of the maxilla is near to a) enamel organ of the canine tooth b) enamel organ of the first molar tooth c)
enamel organ of the premolar tooth.5- maxillary air sinus get their final length only afterb) eruption of All the permanent teeth b) eruption of all the deciduous teeth c)
development of the tongue.6- The number of major salivary glands isc) Two pairs b) three pairs c) only one pair7- ------------------------------ is aguide for development of the mandible.d) Meckel cartilage b) alveolar bone c) prochord.8) Meckel cartilage participate in the formation of the mandible.a) True b) false.