Facial Development shabeel

Development of face

• Dr shabeel pn

MECHANISMS OF DEVELOPMENT 1

Cells proliferate to: Increase a cell mass, to cover a growing surface, or to create or increase the stratification of a layer or structure

Cells differentiate to specialized forms, e.g., mesenchymal cells to osteoblasts & cementoblasts

Cells migrate to new positions ,e.g., neural crest cells

Cells produce extracellular materials: fibers, matrix, cuticle, etc

Cell die by apoptosis and/ or digest their surroundings, so that some structures regress in size and disappear, e.g., Meckel’s cartilage, Hertwig’s root sheath

Differential growth of tissues, e.g., mesenchyme growing more than overlying ectoderm to yield protrusions or ridges, with clefts in between them

GENERAL


Differential growth of tissues, e.g., mesenchyme growing more than overlying ectoderm to yield protrusions or ridges, with clefts in between them

ECTODERM

MESENCHYME

Mesenchyme has grown more & unevenly

Surface is greater so that some ectodermal proliferation must have occurred

Basal lamina is important, but not shown GENERAL


Fate of clefts between ridges: (i) the cleft may deepen by further growth in the bulges; (ii) the cleft may be eradicated by disproportionate growth beneath it

GENERAL

MECHANISMS OF DEVELOPMENT 4Fate of clefts between ridges: (iii) the cleft may be bridged or covered over to form a duct-like structure, e.g., groove becoming a duct

Fusion

mark most growth

GENERAL

MECHANISMS OF DEVELOPMENT

Figs show that: (I) the duct thus formed is lined by ectoderm; (ii) the ectodermal cells (& endodermal) can attach to each other when meeting cells approaching from another direction

Fusion

This kind of fusion is very important in developmentGENERAL

MECHANISMS OF DEVELOPMENT 5Fate of clefts between ridges: (iv) base of the cleft forms a cord that separates, then is canalized -- constructs a tube , e.g., to form the nasolacrimal duct

Fusion

Cord canalizes

Proliferation a cord of cells

Loss of connection

GENERAL


Fate of fused ectoderm I Creation of epithelial diaphragm

Creation of epithelial diaphragm

Which may later disappear, e.g., bucconasal membrane

GENERAL


Fate of fused ectoderm II Penetration of dissolving fused ectoderm by mesenchyme

E.g., fusion of palatal processes

GENERAL



Mesenchyme later becomes bone

& CT

Some ectodermal cells become mesenchymal - an epithelio-mesenchymal conversion

Others die by apoptosis

GENERAL


Downgrowth of ectoderm into mesenchyme

Relies on an INDUCTIVE exchange of chemical messages between mesenchyme and ectoderm

Mitotic areaBUD CORD

e.g., for gland or hair follicle

LAMINA (sheet) e.g., dental or bucco-labial

OR

GENERAL


Ectodermal laminae can be used: LAMINA

At discrete points only, for making dental organs of tooth germs. The remainder of the lamina then breaks up and disappears, but a few ectodermal cells may remain as epithelial rests or pearls

The whole sheet may split to form a furrow lined by ectodermal epithelium on both sides, e.g., formation of vestibule from bucco-labial/vestibular lamina

Split

Split involves loss of cell-cell adhesion, apoptosis & continued proliferation

GENERAL

The whole sheet may split to form a furrow lined by ectodermal epithelium on both sides, e.g., formation of vestibule from bucco-labial/vestibular lamina

Split

Split involves loss of cell-cell adhesion, apoptosis & continued proliferation

GENERAL


Ectodermal cells can differentiate

Cord cells into DUCT & SECRETORY cells within a gland

Dental organ cells into outer epithelium, inner epithelium, stellate reticulum, & stratum intermedium cells

Stroma

TOOTH GERM

DENTAL LAMINA

Outer dental epithelium

Stellate reticulum

Inner dental epithelium

Stratum intermedium

GENERAL


Fate of diffferentiated cells (Not confined to ectodermal cells)

Might go back to a less active/differentiated state, e.g., cementoblasts to resting cementoblasts

May remain as they are, e.g., odontoblasts

May be resorbed or commit suicide/ apoptosis, e.g., root sheath cells

May fuse with other cells and lose their identity, e.g., reduced dental epithelium fuses with the gingival epithelium in eruption

GENERAL

CARDIAC BULGE

Remains of FRONTONASAL PROMINENCE after development of nasal placodes

OPTIC PLACODE

NASAL PLACODE

MAXILLARY PROCESS

MANDIBULAR ARCH

HYOID ARCH

STOMODEUM with perforating membrane

4-w/3.5mm EMBRYO Full-face

FACE

FACIAL DEVELOPMENT 1-7 wks

The slides to follow cannot convey the increase in size involved

First shown is the external story of the face, but this will be matched in subsequent slides by the internal oral developments for tongue, palate, etc

The change is continuous so that the Figs represent a just few ‘baby pictures’ as the elaborate events unfold FACE


At each ‘stage’ be able to analyze the view for its parts, and for what will happen to each part in transforming to the next ‘stage’

The change is continuous so that the Figs represent a just few ‘baby pictures’ as the elaborate events unfold

Stories for face, nasal cavity, palates, jaws & teeth, & tongue

FACE

FRONTONASAL PROMINENCE Brain developing behind

NASAL & OPTIC PLACODES thickenings of ectoderm

MANDIBULAR ARCH formed by early fusion of mandibular processes

CARDIAC BULGE

STOMODEUM oral depression - part that did not grow forward - with bucco/oro-pharyngeal membrane at bottom

4-w/3.5mm EMBRYO Full-face

FACE

OPTIC PLACODE

NASAL PLACODES are prime movers

CARDIAC BULGE

deepen to form NASAL PITS defi ning lateral from medial nasal processes These move medially allowing maxillary processes to move from sides of head to a frontal position & allowing eyes to move from sides to a more frontal position

Lateral processes will become alae of nose

Medial processes form midline nose & contribute to lip, central upper jaw & primary palate

4-w/3.5mm EMBRYO

FACE

CARDIAC BULGE

5.5-w/9mm EMBRYO

OLFACTORY/NASAL PIT

EYE

NASOMEDIAL PROCESS

NASO-OPTIC GROOVE

MANDIBULAR ARCH

HYOID ARCH

MAXILLARY PROCESS

Stomodeum

FACE

5.5-w/9mm EMBRYO

NASOLATERAL PROCESS

NASO-OPTIC GROOVE

or furrow between lateral-nasal & maxillary processes will later be covered over to form part of the nasolacrimal duct

MAXILLARY PROCESS

Stomodeum

FACE

5.5-w/9mm EMBRYO

NASOMEDIAL PROCESS

MAXILLARY PROCESS

grow to meet just off the midline, which is occupied by the fusing medial nasal processes

&

FACE

FRONTONASAL REGION gets squeezed back by merging nasomedial processes

7-w/19mm EMBRYO

EAR TUBERCLES

EYE

FOREHEAD

MOUTH

LOWER JAW

HYOID BONE

MAXILLARY PROCESS

LARYNGEAL CARTILAGESFACE

7-w/19mm EMBRYO

EAR TUBERCLES Ear will move posteriorly

FOREHEAD bulges forward as brain enlarges

MOUTH

MAXILLARY PROCESS

Joining of maxillary processes & mandibular arch moving medially reduces width of the mouth & contributes to cheek

LOWER JAW

FACE

7-w/19mm EMBRYO

becomes INTER-MAXILLARY SEGMENT(i) Philtrum of lip

(ii) Upper jaw region carrying 4 incisor teeth

(iii) Triangular primary palate

FACE

INTERMAXILLARY SEGMENT Sagittal cut

BRAIN

PHILTRUM of LIP

PRIMARY PALATE

LIP

4-INCISOR MAXILLA = INTER-MAXILLARY SEGMENT

12

3

PALATE

MATURE FACE: Sources

FRONTONASAL PROMINENCE

OPTIC PLACODE

NASAL PLACODE central part inside as olfactory mucosa

MAXILLARY PROCESS

MANDIBULAR ARCH

HYOID and

STOMODEUM

NASOMEDIAL PROCESS

NASOLATERAL PROCESSNASAL PIT

MANDIBULAR ARCHES

FACE

FACIAL DEFECTS: Developmental

OBLIQUE FACIAL CLEFT

MEDIAN CLEFT JAW

UNILATERAL MACROSTOMIA mouth too wide

(microstomia - too small)

MEDIAN CLEFT LIP Nose may also be cleft

UNILATERAL CLEFT LIP

FACE

FACIAL DEFECTS: Failures of processes to fuse

OBLIQUE FACIAL CLEFT

MEDIAN CLEFT JAW UNILATERAL MACROSTOMIA

MEDIAN CLEFT LIP


Mandibular & Maxillary

Maxillary & Nasolateral

Nasomedial & Nasomedial

Mandibular & Mandibular

Maxillary & Nasomedial

FACE


MOSTLY BY ALTERING PROPORTIONS

FACE

CHEEK

HAIRY SKIN

BUCCAL MUCOSA thick strat squam ep

BUCCAL GLAND mucous

MUSCLE

ADIPOSE TISSUE

MUSCLE Buccinator

CONNECTIVE TISSUE

GENERAL

BUCCAL MUCOSA

SKIN

MUSCLE

ADIPOSE TISSUE

MUSCLE Buccinator

CHEEK: Germ-layer Origins

MUSCLE migrated somitic MESODERM

BUCCAL MUCOSA Oral ECTODERM

SKIN Surface ECTODERM

CONNECTIVE TISSUE Neural crest MESECTODERM

GENERAL

FACIAL STRUCTURES thus depart from body plan

MUSCLE migrated somitic MESODERM

BUCCAL MUCOSA Oral ECTODERM

SKIN Surface ECTODERM

CONNECTIVE TISSUE Neural crest MESECTODERM

ECTODERM

MESODERM

ENDODERM

SKIN

GENERAL

FACIAL & ORAL STRUCTURES More sources

Neural crest MESECTODERM also forms cartilage, bone & some periodontal tissues

ORAL ECTODERM

also forms anterior salivary glands, dental organs & enamel

GENERAL

Mid-sagittal section

BRAIN

HEART

I II

CORD

CARDIAC BULGE

Full-face view 4-w embryo

What is going on inside the cranial end of the embryo? E.g., plans for nose & mouth?

GENERAL

PHARYNGEAL ARCHES covered by ectoderm & demarcated by

PHARYNGEAL GROOVES

Mid-sagittal section of 4-w embryo

BRAIN

HEART

ESOPHAGUS

MESECTODERM

PHARYNGEAL POUCHES lined by endoderm

AORTA

I II

CORD

CARDIAC BULGE

GENERAL

Mid-sagittal section of 1-m embryo

OLFACTORY PLACODE off the midline

STOMODEUM


BRAIN

PHARYNGEAL ARCHES covered by ectoderm

I II

NOSE

OLFACTORY PLACODE Lens & Otic similar

BRAIN ECTODERM

OLFACTORY PLACODE

Neural crest MESECTODERM

OLFACTORY PLACODE’s rims rise, so creating & deepening the nasal pit & forming two processes

NOSE

BRAIN WALL

NASAL PIT

ORAL CAVITY

NASOLATERAL PROCESS

NASOMEDIAL PROCESS

ORONASAL MEMBRANE

MANDIBULAR ARCH

TONGUE

START OF NASAL CAVITY & NOSTRIL (Naris)

NOSE

ORONASAL MEMBRANE breaks down, creating a passage - primitive choana - between nasal & oral spaces

BRAIN WALL

ORAL CAVITY

NASOMEDIAL PROCESS moves to fuse with its fellow & start primary palate

MANDIBULAR ARCH protrudes with the support of Meckel’s cartilage

TONGUE

NASAL CAVITY- next events

Upper nasal lining differentiates into olfactory mucosa

NOSE

TONGUE

Secondary PALATE will grow from maxillary process toward the midline

NASAL SEPTUM grows down in midline from frontonasal prominence

Nasomedial processes forming tip of nose & intermaxillary segment

NASAL CAVITY- more events & slightly later 1

nasal-

oral cavityPrimary palate growing back

NARIS

primitive choana NOSE

TONGUE

Protrusions for NASAL CONCHAE grow in from lateral nasal process

Respiratory mucosa diffferentiating

NASAL CAVITY- more events & slightly later 2

nasal

oral

NOSE

NASAL CAVITY at 3-m, just off the midline

TONGUE

LIP

BRAINNASAL CONCHAE

Olfactory bulb

JAW

SECONDARY PALATE

NARIS

LIP

PHARYNX

Hence no nasal septum

olfactory mucosa

NOSE

INTERMAXILLARY SEGMENT Sagittal

BRAIN

PHILTRUM of LIP

PRIMARY PALATE

LIP

4-INCISOR MAXILLA = INTER-MAXILLARY SEGMENT

12

3

PALATE

EYE

NASAL SEPTUM grows down in midline from frontonasal prominence & nasomedial process?

BRAIN

LATERAL PALATINE SHELF/PALATAL PROCESS

TONGUE

MECKEL’S CARTILAGE

PALATE

FRONTAL SECTION at 6-w

PALATE

EYE develops

NASAL SEPTUM grows down durther

BRAIN

LATERAL PALATINE

SHELVES grow inwards & elevate

TONGUE


degenerates to be replaced by mandibular bone

PALATE

FRONTAL SECTION at 6-w: next events

TONGUE drops below meeting palatine processes

LATERAL WALL grows in as conchae

PALATE

EYE

PALATE

FRONTAL SECTION at 8-w

TOOTH BUD

NASAL SEPTUM

LATERAL PALATINE SHELF


mandibular bone

NASAL CONCHAE

Maxillary bone

* Site for meeting and fusion of nasal septum & palatal shelves

BRAIN

TONGUE*



E.g., fusion of palatal processes

GENERAL

PALATE

PROXIMITY

Epithelial disintegration & conversion Mesenchymal continuity

FUSION

Epithelial & Mesenchymal differentiation

STEPS IN PALATAL-NASAL FUSION

PALATE

TONGUE

X

X

X

X

X

X

Mandibular bone

NASAL CONCHAE

FACIAL REINFORCEMENT

SEPTAL CARTILAGE

Maxillary bone

TOOTH BUD not seen in every section

HARD PALATE

VESTIBULAR LAMINA

X Skeletal muscle starting Tongue gets larger, develops papillae

XX

NARIS

INTER-MAXILLARY SEGMENT

PALATE FROM BELOW

GUM

LATERAL PALATINE PROCESS/SHELF

PRIMARY PALATE/ Median palatine process

NASAL SEPTUM (mostly from median nasal processes)

UPPER LIP

PALATE



Once the primary palate is fused in place, the lateral shelves meet & fuse zipper-like towards the rear

PALATE FROM BELOW

Fusion between

PALATE

PALATE FROM BELOW a little later



Once the primary palate is fused in place, the lateral shelves meet & fuse zipper-like towards the rear

fuses with

NASAL SEPTUM partly hidden by palate

Incisive foramen

PALATE

PALATE FROM BELOW 12-w

GUM

SOFT PALATE

UPPER LIP

HARD PALATE

PALATE

PALATE FROM BELOW 12-w

SOFT PALATE

Uvula last site to fuse

UPPER LIP

Developing 10 Incisors not yet erupted

Raphe of HARD PALATE

Incisive papilla

GUM Frenulum of

PALATE

PALATAL DEFECTS I: Partial failures to fuse


Lateral palatines


PALATE

CLEFT UVULA/ BIFID UVULA

ANTERIOR CLEFT PALATE Incomplete & UnilateralPrimary & Lateral palatines

PALATAL DEFECTS II: Failures to fuse

POSTERIOR CLEFT PALATE Complete

COMPLETE UNILATERAL ANTERIOR CLEFT Palate & Lip

Primary & Lateral palatines

PALATE

Can occur independently; can be partial; anterior can be bilateral


AND


ORO/BUCCO-PHARYNGEAL MEMBRANE


STOMODEUM

BRAINI II

TONGUE




Next slides will schematize & simplify floor of Arches I-IV

TONGUE

BRAINI II

Pouch pattern is more complicated & does not quite match arch pattern



Endodermal lining of pharyngeal pouch

ARCH I

II

Pharyngeal groove I

III

IV

Site of Tongue development: inside

Endodermal lining of pharyngeal pouch

Ectodermal covering

Mesenchymal coreArch cut intoTONGUE


Differential growth of tissues, e.g., mesenchyme growing more than overlying ectoderm to yield protrusions/ buds

ECTODERM

MESENCHYME

Mesenchyme has grown more & unevenly

Surface is greater so that some ectodermal proliferation must have occurred

GENERAL

Sources of Tongue development I

provides growing power to produce bulges/buds

Mesenchymal core

ARCH

I

II

III

IV

TUBERCULUM IMPAR Median tongue bud

LATERAL LINGUAL SWELLINGS

COPULA

HYPOBRANCHIAL EMINENCE

OCCIPITAL MYOTOMES muscle core

TONGUE

Sources of Tongue development

but not Arch II; & some structures lag & are incorporated

ARCH

I

II

III

IV

ARCH I

ARCH III

Terminal sulcus

TONGUE

Sources of Tongue development II

ARCH

I

II

III

IV


HYPOBRANCHIAL EMINENCE


TUBERCULUM IMPAR & COPULA leave no adult markTONGUE

TONGUE MALFORMATIONS I

ARCH

I

II

III

IV


Failure of these to fuse properly causes a DEEP MEDIAL SULCUS or at worst a BIFID TONGUE

Overgrowth - MACROGLOSSIA

Undergrowth - MICROGLOSSIA

TONGUE

TONGUE MALFORMATIONS II

FORAMEN CECUM from whence the thyroglossal duct set out to create the thyroid gland

Remnant of duct epithelium forms a LINGUAL CYST

Part of duct opens back to foramen -

“FISTULA”

TONGUE

TONGUE MALFORMATIONS III: Ankyloglossia

normal LINGUAL FRENULUM

short LINGUAL FRENULUM restricts tongue protrusion

Ankyloglossia = Tongue-tied

TONGUE

Tongue Innervation

TONGUE

Trigeminal V

ARCH

I

II

III

IV

Facial VII

Glossopharyngeal IX


Hypoglossal XII

Vagus X

CRANIAL NERVE

Tongue Innervation

TONGUE


Trigeminal V I

II

III

IV

Facial VII

Glossopharyngeal IX

Hypoglossal XII

Vagus X

Mandibular Trigeminal SENSORY

Hypoglossal MOTOR

Glossopharyngeal& Facial

TASTE

Vagus

Technology

Facial Development shabeel