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.