Development of face

DEVELOPMENT OF FACE

Moderator: Dr. Chaitanya

By: Dr. Muhammad.Haneef

Post Graduate Trainee 1st year OMFS

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

OUR FACE FROM FISH TO MAN

THE MOBILE MASK IN FRONT OF HUMAN BRAIN BEGAN TO ATTRACT OUR ATTENTION WHEN

WE WERE BABIES AND CONTINUES TO FASCINATE US AS LONG AS WE LIVE

W. K. GREGORY

CONTENTS


INTRODUCTION

An individual spends 9 months, 38 weeks, 266 days nearly 383040minutes of his life his mothers womb. Human development is continuous process and does not stop at birth. Human brain triples its weight between birth and 16 years.

Anatomical structures are more diverse in the mouth than in any other region.

DEVELOPMENT:

Todd “ Is progress towards maturity”.

Moyers “ All the naturally occurring unidirectional changes in life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death”.

Development is growth + differentiation + translocation.

Growth according to MOSS is change in morphological parameters which is measurtable.

SIGNIFICANCE

Progress in surgery, especially in the pediatric age group has made knowledge of human development more clinically significant. The understanding and correction of most congenital malformations (e.g. Cleft palate) depend on the knowledge of normal development and of the deviations that have occurred.

An understanding of common congenital malformations and their causes also enable doctors, dentists and others to explain the developmental basis of abnormalities often dispelling parental guilty feelings.

In 40 to 60% of persons with birth defects, the cause of congenital anomaly is unknown.

Genetic factors, such as chromosome abnormalities and mutant genes, account for approximately 15% of abnormalities.

Environmental factors produce approximately 10% of abnormalities.

Multifactorial inheritance produces 20 to 25%; Twinning causes 0.5 to 1% of abnormalities.

CONTENTS


EARLY EMBRYONIC DEVELOPMENT1. PERIOD OF OVUM- From fertilization to 14th day.

2. PERIOD OF EMBRYO- From 14th day to 56th day.

3. PERIOD OF FETUS- From 56th day till birth.

FETAL PERIOD

Last 7 months of fetal life are devoted to very rapid growth and repositioning of body components, with little further organogenesis or tissue differentiation.

- 4 months human face is seen - By 4th month sex of fetus is known- Last 2 months of fetal life fat is deposited

subcutaneously.

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT

DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

DEVELOPMENT OF BRANCHIAL/PHARENGIAL ARCHES APPEARS DURING THE 4th & 5th WEEK OF INTRA UTERINE

DEVELOPMENT.

CONSISTS OF BARS OF MESENCHYMAL TISSUE SEPARATED BY

DEEP CLEFTS KNOWN AS PHARYNGEAL (BRANCHIAL) CLEFTS.

ON DEVELOPMENT, A NO OF OUT POCKETING APPEARS, ALONG

THE LATERAL WALLS OF THE PHARYNGEAL GUT WHICH ARE THE

PHARYNGEAL POUCHES.

CONTRIBUTE NOT ONLY TO THE FORMATION OF THE NECK BUT

ALSO PLAY AN IMPORTANT ROLE IN THE FORMATION OF THE FACE.

THOUGH DEVELOPMENT OF THESE ( ARCHES, CLEFTS & POUCHES )

RESEMBLES FORMATION OF GILLS IN FISHES & AMPHIBIA,IN THE HUMAN

EMBRYO REAL GILLS ARE NEVER FORMED. THEREFORE THE TERM

PHARYNGEAL ARCHES HAS BEEN ADOPTED.

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES

DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

DEVELOPMENT OF FACE

Development of face depends upon the inductive activities of organizing centres

Procencephalic Rhombencephalic

Induces the inner ear apparatus and upper third of face

Induces the middle and external ear apparatus and the middle and lower third of face

Face develops from 5 prominences that surround the stomatodeum

- Frontonasal- Paired maxillary processes.- Paired mandibular processes.

Frontonasal prominence formed by proliferation of mesenchyme ventral to the forebrain. It forms

- Lateral optic diverticula eyes - Forehead (between the eyes)- Nasal placodes

Mesenchyme proliferates around the placodes producing medial and lateral nasal prominences

Lateral nasal prominence separated from maxillary process by nasolacrimal groove

Fusion of medial nasal prominences and the maxillary and lateral nasal prominences requires disintegration of nasal fin.

Failure of normal disintegration of nasal fin cause cleft of upper lip and anterior palate.

Midline merging of medial nasal process

Forms:- Philtrum of upper lip.- Tip of the nose.- Primary palate.

Merging of medial nasal and maxillary process

Continuity of the upper jaw and lip.Causes separation of nasal pits from stomodeum

Merging of mandibular process in midlineForms lower jaws and lips

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE

DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

DEVELOPMENT OF NOSE The nose is a complex of

contributions from:- Frontal prominence

The bridge.- Medial nasal prominence Median ridge and tip

- Lateral nasal prominence The alae

- The cartilage of nasal capsule the septum and nasal conchae

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE

DEVELOPMENT OF PARA NASAL SINUSES

DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

Paranasal Sinuses

Paranasal sinuses develop during late fetal life the remainder develops after birth.

They form as outgrowths or diverticula of the walls of the nasal cavities and become air filled extensions of the nasal cavities in the adjacent bone.Frontal EthmoidalMaxillary Sphenoidal

Expand in nasal fossae by growth of mucous membrane sacs- primary pneumatization

Enlarged by secondary pneumatization

Retain communication with nasal fossae through ostia

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES

DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

DEVELOPMENT OF PALATE

Palatogenesis begins towards the end of 5th week and is completed by about 12th week.

The palate develops from two primordia.Primary palateSecondary palate

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE

DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

EACH OF THE FIVE ARCHES CONTAIN

1. A CENTRAL CARTILAGE THAT FORMS SKELETON OF ARCH

2. MUSCULAR COMPONENT OR BRANCHIOMERE

3. VASCULAR COMPONENT

4. NEURAL ELEMENT

MANDIBLE IS THE DERIVATIVE OF THE FIRST PHARYNGEAL ARCH

DORSAL PORTION IS KNOWN AS MAXILLARY PROCESS

VENTRAL PORTION KNOWN AS MANDIBULAR PROCESS OR MECKEL’S CARTILAGE

DEVELOPMENT OF MANDIBLE STARTS AT 4TH WEEK I.U.L

CENTER OF FACE FORMED BY STOMODEUM, SURROUNDED BY FIRST PAIR OF PHARYNGEAL ARCHES

4 ½ week embryo

ROLE OF MECKEL’S CARTILAGE DERIVED FROM FIRST PHARYNGEAL ARCH AROUND

41TH – 45TH DAY I.U.L

EXTENDS FROM OTIC CAPSULE -THE MIDLINE OR SYMPHYSIS

FIRST OSSIFICATION CENTER ARISES AT 6TH WEEK I.U.L IN THE REGION OF BIFURCATION OF THE INFERIOR ALVEOLAR NERVE

THE CENTER IS LOCATED LATERAL TO THE MECKEL’S CARTILAGE

FROM THIS “PRIMARY CENTER”- OSSIFICATION SPREADS “BELOW AND AROUND” THE INFERIOR ALVEOLAR NERVE AND THEN MOVES “UPWARDS”

OSSIFICATION THEN SPREADS “DORSALLY AND VENTRALLY” TO FORM RAMUS AND THE BODY OF MANDIBLE

AS OSSIFICATION CONTINUES MECKEL’S CARTILAGE BECOMES SURROUNDED BY BONE

REMANANTS OF MECKEL’S CARTILAGE:

MAJOR PART OF THE MECKEL’S CARTILAGE DISAPPEARS DURING GROWTH

1. MENTAL OSSICLES

2. INCUS AND MALLEUS

3. SPINE OF SPHENOID

4. ANTERIOR LIGAMENT OF MALLEUS

5. SPHENOMANDIBULAR LIGAMENT

TYPES OF OSSIFICATION: MANDIBLE IS THE SECOND BONE IN THE BODY TO BE

OSSIFIED

THERE ARE TWO TYPES OF OSSIFICATION :

1. INTRAMEMBRANOUS TYPE :

FORMATION OF BONE IS NOT PRECEDED BY FORMATION OF CARTILAGENOUS MODEL

BONE IS DIRECTLY LAID INTO FIBROUS MEMBRANE

THERE IS CONDENSATION OF MESENCHYMAL CELLS

SOME CELLS FORM OSTEOBLAST AND SECRETE OSTEIOD

DEPOSITION OF CALCIUM SALTS INTO THE OSTEOID LEADS TO CONVERSION OF OSTEOID INTO LAMELLA

2. CARTILAGENOUS TYPE:

FORMATION OF BONE IS PRECEDED BY FORMATION OF CARTILAGENOUS MODEL

CONDENSATION OF MESENCHYMAL CELLS TO FORM CHONDROBLASTS-- LAY DOWN HYALINE CARTILAGE

CARTILAGE IS SURROUNDED BY PERICHONDRIUM —VASCULAR AND CONTAINS OSTEOGENIC CELLS

INTERCELLULAR CELLS SURROUNDING CARTILAGE CELLS CALCIFY DUE TO THE ACTION OF ALKALINE PHOSPHATASE

NUTRITION TO THE CELLS IS CUT– LEADING TO DEATH---FORMATION OF EMPTY SPACES— PRIMARY AREOLAE

BLOOD VESSELS AND OSTEOGENIC CELLS INVADE THE CALCIFIED CARTILAGENOUS MATRIX WHICH IS NOW REDUCED TO BARS OR WALLS– FORMATION OF LARGER SPACES----SECONDARY AREOLAE

PARTS OF MANDIBLE DERIVED FROM

1. INTRAMEMBRANOUS OSSIFICATION

i) WHOLE BODY OF MANDIBLE EXCEPT THE ANTERIOR PART

Ii) RAMUS OF MANDIBLE AS FAR AS MANDIBULAR FORAMEN

2. ENDOCHONDRAL OSSIFICATION

i) ANTERIOR PORTION OF THE MANDIBLE (SYMPHYSIS)

ii) PART OF RAMUS ABOVE THE MANDIBULAR FORAMEN

Iii) CORONOID PROCESS

iv) CONDYLAR PROCESS

SUMMARY MANDIBLE DEVELOPS FROM FIRST PHARYNGEAL ARCH

SEVERAL CHANGES OCCUR IN THE MANDIBLE DURING THE DEVELOPMENTAL PERIOD

ANY DISTURBANCE DURING THE NORMAL GROWTH OF THE MANDIBLE REFLECTS AS A ANOMALY

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS

DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

Associated with the formation of ear ossicles,

a new jaw joint

TMJ made its first appearance in mammals.

Secondary joint / Squamosodentary joint

[As it is present between squamous part of temporal bone and the mandible (dentary)].

- One can imagine this evolutionary transmission occurring by means of a bony process which appeared on the mandibular anterior to quadratoarticular joint which at one time became large enough to contact the skull.

Difference in

Mammalian jaw-joint Non mammalian jaw-joint

A) Concavo-Convex joint surface Concave

B) Intra-articular disk Absent

EMBRYOLOGY- Develops late in embryonic life.- Compared with large joints of extremities.- Associated with its late evolutionary development.- During the 7th prenatal week, the jaw joint lacks:- Condylar growth cartilage.- Joint cavities.- Synovial tissues- Articular capsule.

2 skeletal elements : mandible and temporal bone are not yet in contact with each other.

7 week old embryo- Meckel’s cartilage extends all the way from chin to base of the

skull. - Serves as a scaffolding or strutt against which the mandible

develops.- Provides a temporary articulation between mandible and base of

the skull until TMJ takes over.- Near end of fetal life Meckel’s cartilage completes its

transformation: - Incus- Malleus- Anterior ligament of malleus- Sphenomandibular ligament

Meckel’s cartilage plays an a basic role in setting the evolutionary stage for the emergence of this joint.

Articular Disc:- Earliest appearance in 6 week old embryo.- Muscular derivative of 1st branchial arch.- Disc analge- vague layer of mesenchyme

stretching across upper end of mandibular ramus.- No capsule.- No condyle.

Articular Disc:- At its anterior end, mesenchymal analge extends

laterally from superior border of Lateral pterygoid muscle, to medial side of masseter muscle.

- At the end of 6th week, lateral pterygoid inserts not on the mandibular but on the posterior end of Meckel’s cartilage.

- During 7th week – (lateral pterygoid) joins upper end of mandibular ramus; also continues posteriorly beyond this point with mesenchyme analge des abv; these 2 structures insert in common part of Meckel’s cartilage which becomes the malleus.

At 7 weeks: the future condyle is still only a condensation of mesenchyme resting on osseous lamella, which forms the mandibular ramus.

12 week – condylar growth cartilage makes its 1st appearance and begins to develop a hemi-spherical articular surface.

By 13th week – condyle and articular disc having moved up into contact with temporal bone.

Only when such articular contact has been made do the joint cavities develop.

Inferior space appearing first.

Disc begins to get compressed.

When central portion of disc is compressed this part becomes avascular.

The articular capsule:

- Becomes recognizable during twelth week as a faint cellular condensation along the medial and lateral sides of joint connecting mandible with temporal bone.

- Articular disc merges peripherally with these condensations.

- Formation of capsule posterior to joint does not occur until twenty-second week; when the Glaserian fissure; becomes narrow; encroaching upon Meckel’s cartilage as it passes into middle ear.

- Articular disc becomes intercepted at the Glaserian fissure, loses its continuity with malleus and develops definitive attachment to anterior lip of GF.

- Joint cavities are now lined by synovial tissue and according to Symons (1952), temporal bone now shows area of secondary cartilage in medial part of the joint.

By 26th week:

All components of TMJ present except articular eminence.

Meckel’s cartilage still extends through GF, but by thirty-first week is transformed into sphenomandibular ligament.

By 39th week:

Ossification of bones in this region has proceeded to the point where; ligament gains its apparent attachment to spine of sphenoid.

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ

DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

Tongue appears to begin to form in 4th week of intra uterine life from 1st pharangeal arch

Second swelling, copula/hypobronchial eminence is formed second third and partly fourth mesoderm arches.

Part of fourth arch forms the epiglottis. Behind this there is laryngeal inlet flanked arytenoid swelling.

CONTENTS


CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR

DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

Introduction

The oral cavity is kept moist by a film of fluid called saliva, this complex salivary fluid is secreted by the salivary gland which is exocrine in nature . Saliva’s important function is to maintain the well being of mouth hence any Individuals with a deficiency of salivary secretion experience difficulty eating, speaking, swallowing and prone to mucosal infections .

Types of salivary glands

I Based on anatomic location Parotid gland Sub mandibular gland Sub lingual gland Accessory glands (labial, lingual,

palatal buccal,glossopalatine and retromolar)

III Based on size and amount of secretion

Major salivary glands Minor salivary glands

II Based on type of secretion

Serous:parotid ,submandibular and von ebners glands

Mucous : sub lingual,labial ,buccal,palatine ,glossopalatine,posterir part of tongue

Mixed:sub mandibular, sub lingual ,anterio labial buccal and lingual minor glands

Anatomy Development :individual salivary glands arise as a proliferation of oral

epithelial cells,forming focal thickening that grows into underlying ectomesenchyme

Parotid : 6 th week of I U : corners of stomatidium

Sub mandibular : end of 6 th week of I U : floor of mouth

Sub lingual : 8 th week of I U: lateral to primordium

Minor salivary gland : 12 th week of I U :buccal epithelium

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS

DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

FORMATION OF DENTAL LAMINA

At about 21st day of embryonic life the embryo folds along two planes

rostocaudal and lateral.

The head fold is critical for the formation of primitive stomatodeum or oral

cavity, lined by stratified squamous epithelium, oral ectoderm.

Neural Crest Cells: This is ectomesenchymal tissue, termed neural crest from

its site of origin, arises from crest of neural fold, where neutralizing and

epidermalizing influences the interact.

- Pleuripotential cells with great migratory propensities.

Primary Epithelial Band: Roughly horse shoe shaped epithelial bands

corresponding in position to future upper and lower jaws.

Formed as a result of change in orientation of mitotic spindle and cleavage plain

of dividing cells and gives rise to dental lamina and vestibular lamina.

The band of epithelium that invades the underlying ectomysenchyme along each of horse shoe shaped future dental arches called Dental lamina at about 6th week of embryonic life.

Importance: Primordium for the ectodermal portion of deciduous teeth. Successional tooth buds . Buds for permanent molars from distal extension of dental lamina. Dental lamina degenerates at about 5th year of life. Remnants persist as epithelial pearls / islands. Vestibular Lamina / Lip Furrowband: Epithelial thickening labial and buccal to dental lamina in each

dental arches. Forms oral vestibule.

Dental lamina

STAGES IN TOOTH DEVELOPMENT

The stages are named after the shape of the epithelial part of the tooth germ.

1) BUD STAGE:

a) The ectodermal cells along the dental lamina multiply rapidly in to round or ovoid swellings at different points corresponding to the position of future deciduous teeth.

b) These form the primordium for the enamel organs of the tooth bud.

c) It consist of i. low columnar cells at periphery and polygonal cells at the centre.

ii. Dental papilla.

iii. Dental sac.

Bud stage

2) CAP STAGE:This stage is characterized by the shallow invagination on the deep surface of the bud as a result of continued proliferation.

In this stage cells of enamel organ can be histologically differentiated as follows:

Outer enamel epithelium (OEE). – peripheral cuboidal cells. Inner enamel epithelium (IEE) – columnar cells. Stellate reticulum

–polygonal cells located in the center.–provides cushion like effect, thus supports

and protects delicate enamel forming cells Enamel knot – the densely packed cells in the center enamel organ. Enamel cord – a vertical extension of the enamel knot between

inner and outer enamel epithelium. Dental papilla – the ectomesenchymal cells proliferate and

condense under the influence of proliferating epithelium. Dental sac – the dense fibrous layer.

Cap stage

3) BELL STAGE: The epithelial invagination deepens and the margins continue to grow,

thus the enamel organ assumes bell shape. Stage consist of IEE – Single layer of tall columnar cells called ameloblasts. Stratum Intermedium – squamous cells present in between IEE and

stellate reticulum. Shows high degree of mitotic activity. Stellate reticulum – star shaped cells. Collapses before enamel

formation. OEE – flattens to low cuboidal form.

– surface laid in folds at the end of bell stage prior to enamel formation begins.

Dental lamina Dental papilla – odonto blasts differentiation. membrane performativa. Dental sac – circular arrangement of fibers and resembles capsular

structure.

Advanced bell stage

Bell stage with permanent tooth bud

4) ADVANCED BELL STAGE : Future dentino enamel junction. Cervical portion of enamel organ forms the hertwig’s

epithelial root sheath.

Hertwig’s Epithelial Root Sheath and Root formation: Root development starts after enamel and dentin

formation reaches future cemento enamel junction. Enamel organ forms hertwig’s epithelial root sheath

consisting of inner and outer enamel epithelium. It modes the shape of roots and initiates radicular dentin formation.

The sheath looses its continuity after radicular dentin formation.

Cementoblast form cementum over dentin. Epithelial diaphragm – the inner and outer enamel epithelium

bend at the future CEJ into horizontal plane narrowing wide cervical opening. The cells proliferate along with adjacent connective tissue cells of pulp.

Apical foramen opening is narrowed by the deposition of dentin and cementum at the apex of root.

In multi rooted teeth the differential growth of epithelial diaphragm causes division of root trunk in to two or three roots.

The long tongue like extensions of the horizontal diaphragm develops two in mandible, three maxilla. Before this the free ends grow towards each other and fuse.

The cervical opening of coronal enamel organ is divided in to two or three openings and dentin formation starts on the periphery of each opening.

Cervical loop

Heartwig’s epithelial root sheath and forming root

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH

TERATOLOGY CONGENITAL ANOMALIES SUMMARY REFERENCES

Teratology

Defnition: The sceince that studies birth defects is teratology.

The agents called as Teratogens. Maximum susceptibility in from 3rd to 8th

week of gestational period; The period of embryogenesis.

Principles of Teratology

Susceptibility depends on genotype of conception and the manner of interaction with the environment

Developmental stage at the time of exposure Dose and duration of exposure Mechanisms of interaction of teratogens and

pathogenesis to anomaly Manifestations include death, retardation,

malformation and functional disorders,

6 general classes of congenital abnormalities

1. Agenesis like absence of teeth.

2. Full/partial aplasia = incomplete development like cleft palate

3. Hyperplasia = excessive development like macrognathia, maxillary hyperplasia

4. Embryonic survival like thyroglossal cyst

5. Hemartoma, misplacement of normal tissue like lingual thyroid

6. Blastoma like teratoma in which there is atypical differentiation of embryonic tissue

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY

CONGENITAL ANOMALIES SUMMARY REFERENCES

Defects involving the pharyngeal region

Involving the pharyngeal region

1. Ectopic thyroid and thymic tissue

2. Branchial fistulas

Neural crest cells and craniofacial defects1.Treacher collin syndrome/ first arch syndrome/

mandibulofacial dystosis syndromea) May be caused due to Vitamin A.

b) Arises as autosomal dominant trait.

c) May arise due to new mutations Due to retardation or failure of differentiation of maxillary mesoderm at or after 50mm stage of development of embryo.

-malar, zygomatic hypoplasia,

Mandibular hypoplasia.

-lower eyelid colobomas.

-malformed ears

-lower eyelid colobomas

2. Robin sequence – may occur independently or in association with other syndromes.

May occur in oligohydroaminos due to compression of chin against chest

-micrognathia with mandible being affected severely.

-cleft palate.

-glossoptosis – posteriorly placed tongue.

3. Di george anomaly – it in includes velocardiofacial syndrome or conotruncal anomlies of face.

Caused due to alcohol, maternal diabetes & retinoids. All part of spectrum called as CATCH22 Due to deletion of long arm of chromosome 22 and the

following: Cardiac defects Abnormal facies Thymic hypoplasia Cleft palate Hypocalcemia

5. CROUZON’S SYNDROME/ CRANIOFACIAL DYSTOSIS.

1.Associated with premature closure of the cranial sutures leading to one of the following

a. Boat shaped skull

b. Tower shaped skull

c. Clover leaf shaped skull or Brachecephaly

d. Egg shaped skull

2. Maxillary hyperplasia with high arched palate maybe associated with cleft

3.Increased interpupillary distance

4.Hypoplasia of the orbit

5. Congenital defects of the heart.

4. Hemifacial Microsomia/ Goldenhar syndrome/ oculoauriculovertebral syndrome.

Maxilla, zygomatic, temporal bone are tiny and flat Microtia/ anotia Tumours or dermoids in eyeball Fused hemivertebrae / spina bifida Assymmetry Cardiac abnormalities like

- teratology of fallot

- Venticulo-septal defects

Defects arising in tongue Tongue tie or ankyologlossia Aglossia Macroglossia Microglossia Lingual thyroid nodule Lymphoma of tongue Haemangioma of tongue Bifid tongue or scrotul or fissured tongue Lingual cyst Thyroglossal ductal cyst Ankyloglossum superiosum Lipoma of tongue Teratoma of tongue

Defects of thyroid1.Aberrant thyroid tissue2.Cyst or fistula

Facial clefts

Palatal clefts

Defects of teeth

Size Related Microdontia Macrodontia

Shape related cusp Gemination Twinning Fusion Concrscense Dens in dente Talons cusp Dilaceration Dens evaginatus Taurodontism

Number related Anodontia Onligodontia Supernumary tooth Supernumary roots

Structure related Ameoleogenesis imperfecta Dentino genesis imperfecta Enamel hypoplasia

Related to growth and eruption Impected tooth Transposition and ectopic

eruption

Congenital anomalies related to Salivary Glands Aberrancy/ ectopic salivary glands –

staffne’s cyst Aplasia Hypoplasia / hyperplasia Atresia- congenital occlusion or absence of

one or more major salivary gland ducts Accessory duct / accessory lobe

Congenital anomalies affecting TMJ

Hypoplasia of condyle – unilateral/ bilateral Hyperplasia of condyle – unilateral /

bilateral Double condyle Hyperplasia / hypoplasia of coronoid

process Malformed glenoid process or articular

tubercle

Defects in development of Eye and External Ear Ear – preauricular pits and appendages

Eye -

Cyclopia or synopthalmia with probescis

Absence of eye ie anopthalmia

Colobomas of eyelids

Congenital Ptosis

Fusion of eyelids-cryptophalmos

Epicanthal fold

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES

SUMMARY REFERENCES

SKELETAL SYSTEM

SKULL

NEURO CRANIUM

THE MEMBRANOUS PART

THE CARTILAGINOUS PART

OR CHONDROCRANIUM

VISCERO CRANIUM

BONES OF THE FACE.

FORMED FROM THE FIRST

TWO PHARYNGEAL ARCHES

MEMBRANOUS NEUROCRANIUM

CARTILAGINOUS NEUROCRANIUM OR CHONDROCRANIUM

DEVELOPMENT OF FACIAL SKELETON

THE FACE MAY BE CONVIENTLY,IF SOME WHAT

ARBITARILY DIVIDED INTO UPPER, MIDDLE & LOWER

THIRDS.

THE THREE PARTS CORRESPOND GENERALLY TO THE

EMBRYONIC STRUCTURES NAMELY THE FRONTO

NASAL, MAXILLARY & MANDIBULAR PROCESS.

UPPER THIRD OF FACE IS PREDOMINANTLY OF

NEUROCRANIAL COMPOSITION,WITH THE FRONTAL BONE OF

THE CALVARIA ,PRIMARILY RESPONSIBLE FOR THE FORE

HEAD.

INTIALLY GROWS MOST RAPIDLY KEEPING PACE WITH ITS

NEUROCRANIAL ASSOCIATION & THE PRECOCIOUS

DEVELOPMENT OF THE FRONTAL LOBES OF THE BRAIN.

ACHIEVES ITS ULTIMATE GROWTH POTENTIAL AT AN EARLY

AGE, PRACTICALLY CEASING THE GROWTH SIGNIFICANTLY

AFTER THE 12 YEARS OF LIFE.

MIDDLE THIRD OF FACE IS SKELETALLY THE MOST

COMPLEX,BEING COMPOSED IN PART OF THE CRANIAL BASE &

INCORPORATING BOTH THE NASAL EXTENSIONS OF THE

UPPER THIRD PART OF THE MAXILLARY APPARATUS.

GROWS MORE SLOWLY OVER A PROLONGED PERIOD, NOT

CEASING THE GROWTH UNTIL THE LATE ADOLESENCE.

THE LOWER THIRD OF FACE COMPLETES THE MASTICATORY

APPARATUS, BEING COMPOSED OF THE SKELETON OF THE

MANDIBLE & ITS DENTITION.

GROWS MORE SLOWLY , NOT CEASING THE GROWTH UNTIL

THE LATE ADOLESENCE.

FACIAL BONES DEVELOP INTRA MEMBRANOUSLY FROM

OSSIFICATION CENTERS IN THE NEURAL CREST MESENCHYME OF

THE EMBRYONIC FACIAL PROCESS.

IN THE FRONTONASAL PROCESS,INTRAMEMBRANOUS SINGLE

OSSIFICATION CENTER APPEARS IN THE 3RD MONTH.

DURING 8TH WEEK A PRIMARY OSSIFICATION CENTER APPEARS FOR

EACH MAXILLA AT THE TERMINATION OF INFRA ORBITAL NERVE

JUST ABOVE THE CANINE TOOTH DENTAL LAMINA.

FURTHER TWO INTRA MEMBRANOUS PREMAXILLARY CENTERS

APPEAR ANTERIORLY ON EACH SIDE IN THE 8TH WEEK & RAPIDLY

FUSE WITH THE PRIMARY MAXILLA.

THE MANDIBULAR PROCESS DEVELOP BILATERALLY FROM A SINGLE

INTRA MEMBRANOUS CENTRE.

THE ATTACHEMENT OF THE FACIAL SKELETON ANTERO –

INFERIORLY TO THE CALVARIA DETERMINES THE CHONDRO

CRANIAL INFLUENCE ON FACIAL GROWTH.

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY

CONCLUSION REFERENCES

CONCLUSION

JUST AS THE CLINICIAN NEEDS THE MEDICAL

HISTORY TO MAKE A LOGICAL DIAGNOSIS,

SO TOO THE GROWTH AND DEVELOPMENT

OF FACE IS ESSENTIAL FOR A LOGICAL

EXPLANATION OF ANY STRUCTURAL AND

FUNCTIONAL IMBALANCES IF IT DO OCCURS.

CONTENTS

INTRODUCTION EARLY EMBRYONIC DEVELOPMENT DEVELOPMENT OF BRANCHIAL ARCHES DEVELOPMENT OF FACE DEVELOPMENT OF NOSE DEVELOPMENT OF PARA NASAL SINUSES DEVELOPMENT OF PALATE DEVELOPMENT OF JAWS DEVELOPMENT OF TMJ DEVELOPMENT OF TONGUE DEVELOPMENT OF EXTERNAL EAR DEVELOPMENT OF SALIVARY GLANDS DEVELOPMENT OF TOOTH TERATOLOGY CONGENITAL ANOMALIES SUMMARY

REFERENCES

References

T.W. Saddler “Langman’s Medical Embryology”. 5th edition. G.H. Sperber “Craniofacial embryology”. 4th edition. W.R. Proffit “Contemporary orthodontics”. 3rd edition. S.I. Balaji “Orthodontics the art and science”. 2nd edition. A.R. Tencate “Oral histology”. 5th edition. Shafer “A textbook of Oral pathology”. 4th edition. B.D. Chaurasia “Human anatomy Head and neck”. 3rd edition. Orban’s oral histology &embryology Textbook of Pedodontics –Shobha Tandon Text book of oral medicine – Ghoms Text book of embryology – Inderbere singh Craniofacial Development, Geoffrey H. Sperber.

Thank you

Development of face

Health & Medicine

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