Results of folding1- the cranial end of the embryo foldsBefore the caudal end(growth of the brain isvery fast).2- formation of stomatodeum (primitive oralcavity3- part of the yolk sac is taken in the embryoforming the future gut. Foregut, midgut, andhindgut
1- Time:- Early somaite period 21 to 31 days.2- Number& Nature :- Formation of fivemesodermal elevations, augmented byneural crest cells , and lined with ectoderm.3- Name one central large elevation(frontonasal process) , two maxillaryprocesses , and two mandibular processes.
Differentiation of facial processes1- The wide frontonasal present betweenthe developing eyes, forming forehead andnose.2- Two maxillary process------- lateral partof the upper lip, and cheek .3- Two mandibular process merge in themidline to form the lower lip and Jew.
Nasal placodes Specialized epithelial thickening at the inferolateral corners of the frontonasal process.
Globular processOrigin 5th intrauterine two horseshoe shaped nasalprocesses demarcate and enclose the nasal placodeforming anterior naresTwo medial processes fuse to form one largeglobular processe
Derivatives of globular process:-1- tip of the nose2- columella.3- philtrum.4-labial tuberculum & frenum of upper lip.5-primary palate.
Branchial archesNumber and nature:- five to six mesenchymalswellings augmented by neural crest cells.site:- they are developed between thestomatodeum and future heart.( futureMandibulocervical region) .Size:- they decrease in size from first to sixthTime:- fourth week of I.U.
Each arch is formed of:1- central cartilage Derived from neural crest cells)2- vascular core Derived from lateral mesoderm)3-nervous element4- muscular component From lateral mesoderm)
Arch Skeleton Muscle Artery nerveMandibular Maxilla Muscles of External Mandib mandible mastication carotid ular .Hyoid Hyoid bone Muscles of facial Facial facial expressionThird Lower of Pharyngeal muscle Internal glossop hyoid Common haryng carotid ealFourth Thyroid Pharyngeal muscle Aorta vagus cartilage subclavianSixth Laryngeal Laryngeal muscle pulmonary vagus cartilage
Formation of the tongue1- It begins to develop at the 4th week of intrauterine life, in relation to the first 4 branchialbranches2- The anterior two thirds of the tongue isderived from the first (mandibular) arch.Posterior one-third is derived from 3rd branchialarch.3- The posterior most part of the tongue isderived from the 4th arch , the same as theepiglottis
Sensory nerve of the tongue First arch Mandibular nerve1- Anterior two thirds Chorda tympani nerve Third arch2- Posterior one third Glossopharyngeal nerve fourth arch Superior laryngeal branch of3- Posterior most part vagus Motor nerve of the tongue 12th cranial nerve (Hypoglossal nerve ) supplies all muscles of the tongue
Dorsal and ventral aspects of the tongueEpithelium covering of the tongue
Epithelium covering of the tongue1- only one layer of epithelial cells2- stratified multilayered epithelial cells3- appearance of circumvallate papillae on(v) shaped sulcus. 8-12 ( from2nd to 5thmonth)4- development of taste buds .5- development of the crypts of palatinetonsil at birth.
Formation of the palateThe palate is formed from three components:-1- the primitive palate.2 – two palatal process from maxillary process whichfuse to form the palate proper at the 7th week.at late stage the palate undergoes intramemberanousOssification to form hard palate . Ossification does notextend to the most posterior portion, which forms softpalate.
Development of the jaw1- About the six week of intrauterine life bone ofthe jaw is started to appear.2- Both of the maxilla and the mandible aredeveloped from the first branchial arch.3- The maxilla formed within the maxillaryprocess and the mandible within the mandibularprocess.
Development of the mandible1- the major part of the mandible mandible isintramembranous ossification, only the tip ofcondlye process, cronoid process and thesymphyseal region are of endochondoralossification.2- Meckel,s cartilage , the cartilage of the firstbranchial arch, act as a guideline for mandibleformation, dense fibro-cellular tissue outside andlateral to the cartilage forming the mandiblethrough intramembranous ossification.
3- the symphyseal cartilages ,two in number,appear in the connective tissue between thetwo ends of Meckel,s cartilage but completelyseparated from it , they are obliterated withinthe first year of life.
Development of the maxilla1- the maxilla is formed of maxilla proper andpremaxilla.2- maxilla proper is formed as an extension ofmandibular arch.(1st branchial arch)3- around the 6 week intra membranousossification center appears near the part whichforms the enamel organ of the canine tooth.
4- from this center of ossification bone spreadbelow the orbit towards pre-maxilla.5-maxillary air sinus appears at 16th weekfeatal life as a projection from nasal cavity6- sinus increase gradually and separates theorbital surface from the dental surface, the finalheight Reached after eruption of all permanentteeth.
Development of (TMJ) tempero-mandibular joint1- It is an articular surface between twobones; mandible and temporal bone in thebase of the skull2- at the 7th week of intra-uterine lifeMeckel,es cartilage extends from the chin tothe base of the skull3- the formation of tempro-mandibula jointis established at the end of fetal life.
Development of salivary gland1-There are three pairs of major andinnumerable minor salivary glands in theoral cavity.2- the parotid and sub-mandibular budsappear during six week.3- bud of the sublingual gland appearduring seventh week of intrauterine life4- the majority of glands are ectodermalin origin, some glands about the base ofthe 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 bya) Overgrowth of the nervous system b) overgrowth of the uterine wall c) overgrowth of the placenta3- anterior two thirds of the tongue developes froma) 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 aftera) 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 isa) Two pairs b) three pairs c) only one pair7- ------------------------------ is aguide for development of the mandible.a) Meckel cartilage b) alveolar bone c) prochord.8) Meckel cartilage participate in the formation of the mandible.a) True b) false.