or o facial embryology

Orofacial EmbryologyPrenatal Development Wendra,dr.,M.Kes Anatomy Dept of Medical Faculty General Achmad Yani Univ. Wendra/Anatomy/FK Unjani/2011

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Fertilization & Development in Utero-fertilization in the upper third of the oviduct/fallopian tube -fertilization = union of egg and sperm -after fertilization = zygote -first period of prenatal development = preimplantation period -first week of development-development of the unattached zygote/embryo -immediately prior to the union of egg and sperm nuclei the egg must complete the final stages of meiosis (meiosis I is completed as the egg primordium then stops) -fertilzation result in the combination of the haploid egg and sperm = diploid zygote -called an embryo once it begins to divide (within 24 hours) -division = mitosis

Wendra/Anatomy/FK Unjani/2011

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Embryonic terms to consider induction first process to occur during embryogenesis interaction between developing embryonic cells

morphogenesis may also be called morphodifferentiation development of form and specific tissues results from migration of embryonic cells and inductive interactions between these cells

patterning specification of the embryo through segmentation

differentiation process of specialization of embryonic cells

proliferation controlled levels of mitosis

interstitial growth growth deep within a tissue of organ as opposed to appositional growth growth at the periphery through the addition of additional Wendra/Anatomy/FK Unjani/2011 cell layers3

Prenatal development 10 lunar months three phases (first two = embryonic stage) first after fertilization and spans the first 4 weeks largely cellular proliferation and migration some differentiation

next 4 weeks of development largely the differentiation of all major internal and external organs = morphogenesis very vulnerable stage

remaining phase fetal stage largely a matter of growth and maturationWendra/Anatomy/FK Unjani/2011 4

-preimplantation period first week -embryonic stage week 2 to week 8

OVIDUCT: -union of sperm and egg nuclei (zygote) -> first mitotic cell division (embryo) -> cell division continues -> formation of the morula UTERUS: -morula forms a blastocyst or blastula (assymetrical ball of cells with a cavity) -> implantation into the endometrium


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-formation of the blastula marks the beginning of morphogenesis - shaping of the embryo, migration of dividing cells to specific locations -blastula = blastocyst - hollow ball of cells -outer layer = trophoblast - forms extraembryonic tissues (e.g. placenta, yolk sac) -inner mass of cells at one end - totipotent embryonic stem cells or embryoblasts


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Third week of development -migration of epiblast cells through the primitive streak towards the hypoblast eventually creates three tissue layers called the germ layers 1. ectoderm 2. mesoderm 3. endoderm

humans are deuterostomesWendra/Anatomy/FK Unjani/2011 7

Fourth week of embryonic development

differentiation of cells from the ectoderm forms the neuroectoderm -a neural plate forms -this plate thickens with proliferation invaginates centrally and forms the neural groove -this groove deepens and is surrounded by the two neural folds -development of the neural crest cells from these neural folds


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Fourth week of embryonic development the neural folds meet superior to the neural groove and forms the neural tube neural folds also form the cells of the neural crest migratory population of cells multipotent gives rise to ectodermal tissues and mesenchyme in specific areas of the head/faceWendra/Anatomy/FK Unjani/2011 9

development of a head fold is critical folding results in the formation of the primitive oral cavity = stomatodeum separated from the developing and expanding gut by a buccopharyngeal membrane (or oropharyngeal membrane)


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Branchial arches also called pharyngeal arches figure 4-11 fourth week: development of a frontal prominence forms the stomatodeum below this is the formation of the first branchial arch (mandibular arch) 6 pairs U shaped core of mesenchymal tissue formed from neural crest cells that migrate in to form the arches covered externally by ectoderm and lined internally by endoderm each has its own developing cartilage, nerve, vascular and muscular components

these arches separate the stomatodeum from the developing heartWendra/Anatomy/FK Unjani/2011 11

Branchial arches separated laterally by branchial grooves/clefts medially they are separated by pharyngeal pouches first arch (mandibular arch) maxillary and mandibular processes second arch (hyoid arch) - hyoid bone, part of the temporal bone (VII nerve) cartilage = Reicherts cartilage the mesoderm of this arch will form the muscles of facial expression, the middle ear muscles

third arch tongue (IX nerve) fourth arch tongue, most of the laryngeal cartilages (IX and X nerves) fifth arch becomes incorporated into the fourth sixth arch most of the laryngeal cartilages (IX and X nerves)


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Pharyngeal Pouches four well-defined pairs of pharyngeal pouches develop from the lateral walls of the pharynx first pouch (betwen the 1st and 2nd arches) cavum tympani, tympanic membrane, and eustachian tube second pouch palatine tonsils third pouch inferior portion of parathyroid glands, fourth pouch superior portion of parathryoid gland fifth pouch -becomes incorporated into the fourthWendra/Anatomy/FK Unjani/2011 13


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Pharyngeal grooves /clefts 5 week of embryo pharyngeal cleft First clefts meatus four

external auditory

2nd to 4th clefts cervical sinus disappearsWendra/Anatomy/FK Unjani/2011 19


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Development of the Face forms from the fusion of 5 face primordia which develop during week 4 and fuse during weeks 5 through 8 primordia = ectodermal swellings or prominences that are filled with mesodermal and neural crest cells frontonasal prominence mandibular prominences (2) from branchial arch #1 maxillary prominences (2) from branchial arch #1Wendra/Anatomy/FK Unjani/2011 23

Stomatodeum primitive stomatodeum forms a wide shallow depression in the face limited in its depth by the buccopharyngeal membrane


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Early development of the head and neck begin in early embryonic life, and continues in the postnatal in the late teems Stomodeum oropharyngeal membran break down /first embryonic month relation with gut primitivum


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43Wendra/Anatomy/FK Unjani/2011 26

Development of the Face


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Development of the Upper Face within the fourth week (weeks 5 8) the frontonasal prominence develops two sets of placodes (nasal and lens) formation is dominated by the proliferation and migration of ectomesenchyme cells MAJOR EVENTS development of medial and lateral nasal processes or swellings which encircle the nasal pits fusion of the medial nasal processes at the midline = intermaxillary/premaxillary process or process

formation of the upper portion of the face is faster than the lower portion (finally cease to grow at puberty)Wendra/Anatomy/FK Unjani/2011 34

Development of the Upper Face day 24: development of the frontal prominence (covers the rapidly expanding forebrain) beginnings of the mandibular and maxillary processes from the 1st branchial arch well-defined boundaries of the stomatodeum results

day 26: well-formed maxillary and mandibular processes day 27: appearance of the nasal placode and the odontogenic epithelium day 28: localized thickenings develop within the frontal prominence = olfactory placodes Wendra/Anatomy/FK Unjani/2011

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Upper lip formation during the fourth week fusion of the maxillary processes with each medial nasal process this contributes to the lateral sides of the upper lip together with the medial nasal processes which contribute to the medial aspect of the upper lip the maxillary processes also fuse with the lateral nasal processes results in a nasolacrimal groove which extends from the medial corner of the eye to the nasal cavityWendra/Anatomy/FK Unjani/2011 36

Development of the Palate involves the formation of a primary palate, a secondary palate and fusion of their processes Primary palate forms from an internal swelling of the intermaxillary/premaxillary process (fusion of medial nasal processes)

Secondary palate forms from the two lateral palatine shelves or processes develop as internal projections of the maxillary prominencesWendra/Anatomy/FK Unjani/2011 37

fusion of the median nasal processes gives rise to the median palatine process fuses to form the primary palate

Primary palate

MOVIES


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http://www.indiana.edu/~anat550/hnanim/face/face.html


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Secondary Palate only after the development of the secondary palate can oral and nasal cavities by distinguished three outgrowth appear in the oral cavity nasal septum: grows downward through the oral cavity it encounters the primary and secondary palates

two palatine shelves

closure of the secondary palate is likely to involve the hardening of the palatine shelves mechanism remains unknown + the withdrawl of the tongue


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Palatine shelves


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Cleft lip and palate


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Cleft lip and palate


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Nose complex combination of contributions of the frontal prominence (forms the bridge), the merged medial nasal prominences (form the median ridge and tip of nose), the lateral nasal prominences (form the alae) and the cartilage nasal capsule (forms the septum and the nasal conchae) the external nasal region develops from the superficial alar field gives rise to the alae Nasal pits and cavities separate anteriorly from the stomatodeum by fusion of the medial nasal, lateral nasal and maxillary prominences form the nostrils separate posteriorly from the stomatodeum by the oronasal membrane the developing nasal cavities are separated from the oral cavity by the intermaxillary process (forms the floor of the nasal cavity)

Nasal capsule and nasal septum condensation of the mesenchyme within the frontonasal prominence forms the precartilagenous nasal capsule the capsule develops as two masses around the nasal cavities the median mass becomes the progenitor of the nasal septum the lateral masses will form the conchae and nasal alar cartilages Wendra/Anatomy/FK Unjani/2011 45

nasal cavity early development of the face is dominated by the formation of the primitive nasal cavities rapid proliferation of the underlying mesenchyme around the placodes bulges the frontal eminence forward and produces the nasal pit the lateral arm of this pit = lateral nasal process the media arm = medial nasal process in between these nasal pits is the frontonasal process where the nose develops the two medial processes + the frontonasal give rise to the medial portion of the nose and upper lip, the anterior portion of the maxillaWendra/Anatomy/FK Unjani/2011 and palate

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Nose formation


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Nasal and Paranasal tissues nasal cavity lined with a respiratory mucosa like the rest of the respiratory system pseudostratified columnar epithelium with cilia interspersed are goblet cells which rest on the basement membrane very vascular lamina propria warms the air roof of the nasal cavity is a specialized area that contains the olfactory epithelium on the medial wall are the three nasal conchae paranasal sinuses frontal, sphenoid, maxillary and ethmoid sinuses provide mucus for the nasal cavity respiratory mucosa of ciliated pseudostratified columnar epithelium but is thinner than the nasal mucosa also has fewer goblet cells no erectile tissueWendra/Anatomy/FK Unjani/2011 50

Development of Sinuses and Nasal cavity paranasal sinuses some develop during late fetal life frontal and sphenoid not present at birth at 2 years the two most anterior ethmoid sinuses grow into the frontal bone visible on X-rays by age 7 two most posterior ethmoid sinuses grow into the sphenoid bone sinuses are important in the size and shape of the face during infancy and the resonance of the voice

the rest develop after birth form as outgrowths of the wall of the nasal cavity become air-filled extensions in the adjacent bones the original openings of these outgrowths persist as the orifices of the adult sinusesWendra/Anatomy/FK Unjani/2011 51

Maxilla formation centers of ossification develop in the mesenchyme of the maxillary processes of the first branchial arch spreads posteriorly below the orbit towards the developing zygoma and anteriorly toward the future incisor region and superiorly to form the frontal process ossification also spreads into the palatine process to form the hard palate at the union between the palatal process and the main body of the developing maxilla is the medial alveolar plate together with the lateral plates development of the maxillary teeth a zygomatic or malar cartilage appears in the developing zygomatic processes and contributes to the development of the maxilla


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Development of the Lower Face within the fourth week two bulges form inferior to the stomatodeum


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Mandible formation the cartilage of the first branchial arch associated with the formation of the mandible = Meckels cartilage 6 weeks: Meckels cartilage forms a rod surrounded by a fibrocellular capsule the two cartilages do not meet at the midline but are separated by a thin line of cartilage = symphysis on the lateral aspect of this symphysis a condensation of mesenchyme forms at 7 weeks intramembranous ossification begins in this mesenchyme and spreads anteriorly and posteriorly to form the bone of the mandible the bone spreads anteriorly to the midline of the developing lower jaw the bones do not fuse at the midline mandibular symphysis forms (from meckels cartilage) which fuses shortly after birth

the ramus develops from rapid ossification posteriorly into the mesenchyme of the first archWendra/Anatomy/FK Unjani/2011 54

Mandible formation-growth of the mandible until birth is influences by the appearance of three secondary (growth) cartilages 1. condylar 12th week, developing ramus by endochondral ossification, a thick layer persists at birth at the condylar head (mechanism for post-natal growth of the ramus = endochondral) 2. coronoid 4 months, disappears before birth 3. symphyseal appears in the connective tissue at the ends of the Meckels cartilage, gone after 1 year after birth


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Development of the Tongue begins to develop about 4 weeks localized proliferation of the mesenchyme results in formation of several swellings in the floor of the oral cavity the oral part (anterior twothirds) develops from the fusion of two distal tongue buds or lateral lingual swellings and a median tongue bud (tuberculum impar)MOVIE: http://php.med.unsw.edu.au/embryology/images/8/88/Tongue.gif


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Development of the Tongue the pharyngeal part or root of the tongue (posterior one-third) develops from the copula and the hypobranchial eminence (forms from the 2nd, 3rd and 4th branchial arches) these parts fuse (adult = terminal sulcus) muscles of the tongue arise from occipital somites which migrate Wendra/Anatomy/FK Unjani/2011 into the tongue area

B.As #1,2 and 3

hypobranchial arch overgrows the 2nd arch

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HEAD FORMATION rostral or head fold anterior portion of the neural tube expands as the forebrain, midbrain and hindbrain the neuroectoderm in this region will form the olfactory, orbital and otic placodes the hindbrain forms 8 bulges = rhombomeres migration of neural crest cells into this region provides the embryonic connective tissue (mesenchyme) required for development of the craniofacial structures these neural crest cells arise from the midbrain and the first two rhombomeres as two streams Wendra/Anatomy/FK Unjani/2011

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Refrences : 1. T W Sadler Langman`s medical embryology seven edition , william & wilkins 1995 2. Keith l moore before we are born fourth edition W B saunders company 1993 3. Bruse M Carlson human embryology and developmental biology third edison mosby 2004.


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or o facial embryology

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