Evolution & Development of Face

EVOLUTION & DEVELOPMENT OF FACE

Dr. mohd ullah khan

CIDS

CONTENTS

Evolution of face

Introduction

Definition

Theories of evolution

Concepts of evolution of human face

Development of face.

Introduction

Pharyngeal arches , pouches, grooves , clefts.

Development of face

Clinical aspects

Conclusion

References

EVOLUTION OF FACE

INTRODUCTION

The history of the planet Earth begins 4.6 billion years ago.

At each age one type of life has dominated over all other forms, so much that there is a direct relationship between climatic and geologic condition and the dominating type of life existing.

From the biologic point of view we see that as environment changed there was a corresponding change in the form & structure of the animal and plant kingdoms

To understand the face thoroughly, it is only fair to assume that we should start at the bottom of the ladder in the scale of life & inspect the simplest type of face & then trace upwards through the stages of development of face & see how it has gradually changed and molded in form to that of modern man,

DEFINITION OF EVOLUTION

A continuous process of change from one state, condition or form to another.

Stedman’s medical dictionary

A developmental process in which an organ or organism becomes more and more complex by differentiation of its parts; a continuous & progressive change according to certain laws and by means of resident forces.

Dorland medical dictionary

THEORIES OF EVOLUTION

Four main theories to explain the method by which species of life that exist today have evolved from earlier simpler form:-

1. The Lamarckian theory

2. The theory of orthogenesis.

3. The theory of natural selection

4. The Mendelian theory

THE LAMARCKIAN THEORY

Characters acquired and changes taking place during life of an organism are inherited after the acquired character and changes have persisted for a long time.

They are due to change in environment and to the concerned effects of use and disuse.

E.g. giraffes with long necks

THEORIES OF ORTHOGENESIS(DEVELOPMENT IN STRAIGHT LINE)

Put forth by Haldane & Julian Huxley

They considered that evolution proceeds in any particular direction, not because of any advantages gained by the race or because of direct molding effect by the surrounding, but because of some inner urge, some necessity for the hereditary constitution to change in just that particular way.

NATURAL SELECTION OR SURVIVAL OF THE FITTEST

Charles Darwin propounded this theory of organic evolution.

This theory assumes that every life on earth was developed from previous form.

He attributed changes in living organism to the action of natural selection and in many instances to the effect of use and disuse.

This theory can be summarized as:

1. Struggle for existence

2. Natural selection

3. Heredity

4. Survival of the fittest.

MENDEL’S LAW OF INHERITANCE

Mendel discovered the fact of segregation o dissociation of characters from each other in the course of formation of germ cell.

His research work was on edible pea.

EVOLUTION OF HUMANS

AUSTRALOPITHECUS AFRICANS

3-3.5 million years ago

Cranial capacity—500cc

Size of cranium & portions closely resembles that of chimpanzees.

Head– dolichocephalic

Facial profile convex

Dental feature are intermediate between those of apes and modern man.

AUSTRALOPITHECUS ROBUSTUS

2.0-1.0 million years ago


More sturdier

Cheek bone projecting forward

Lower jaw is very large

His degree of prognathism is present

Back teeth are twice larger than the expected hominid size.

AUSTRALOPITHECUS BOSIEI


Cranial capacity 600cc

Tool maker and food gatherers

They could express and communicate simple ideas with sound

Face– long and broad

Facial & zygomatic portions of maxilla are large.

HOMO HABILIS


Cranial capacity—600-650cc

Associated with stone tools

Greater body size

Dental reduction orthognathy

HOMO ERECTUS

1.8-300000 years ago

Cranial capacity-850

Thick cranial vault

Size of posterior teeth are decreased and anterior were larger than modern humans

Upper incisors are distinctively shovel shaped

HOMO NEANDERTHALS

150000-300000 years ago

Ruggedly built and short stocky body

Developed skilled stone tool technology

Had larger brain

Dentition as a whole is placed forward relative to the skull vault

HOMO SAPIENS


Skull is high rounded

Orthognathic face.

Face is tucked under the enlarged brain case.

Teeth is progressively reduced in size, concurrently with the reduction in masticatory apparatus.

EVOLUTION OF FACE

CONCEPT 1

Man is one of the few truly bipedal mammals

The designs of the toes, foot bones, arch of the foot, ankle, leg bones, pelvis, and vertebral column all interrelate in the anatomic composite that provides upright body stance.

The head is in a balanced position on an upright spin.

The arms and hands have become freed.

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CONCEPT 2

Enlargement the brain of have caused a “ flexure” (bending) of the h human cranial base.

This relates to two key features:-

First, the spinal cord is aligned vertically.

Second the orbits have undergone a rotation in conjunction with frontal lobe expansion.

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CONCEPT 3

The large size of the human brain also relates to a rotation of the orbits towards the midline. This results in a binocular arrangement of the orbits.

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CONCEPT 4

The nasal region above and the oral region below are two sides of the same coin, that is, the palate. Reduction in nasal protrusion is accompanied by a more or less equivalent reduction of the jaw.

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Facial rotation has led to the development of the human maxillary sinus.

Because of its adaptation to facial rotation, the human maxilla is uniquely rectangular, rather than rectangular like that of most other mammals.

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The human face is exceptionally wide because the brain and cranial floor are wide.

This also relates to the rotation of he orbits into vertical, forward facing positions as well as to the rotation of the face as a whole into a downward backward position.

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NASOMAXILLARYCONFIGURATION

In man it is uniquely rectangular. This is caused by a rotation of the occlusion into a horizontal plane to adapt to the vertical rotation of the whole midface.

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DEVELOPMENT OF FACE

INTRODUCTION

The embryonic period extends from the beginning of the fourth week till the end of the eighth week.

The trilaminar embryonic area differentiates as follows:

1] ectoderm

2] endoderm

3] mesoderm

The fourth week is characterized by the differentiation of the three germ layers and the folding of the embryo

In the second month the organs and tissues are laid down and the embryo has a distinct human appearance

Langman's Medical Embryology 8th edition

PHARYNGEAL ARCHES

The most typical feature in the development of the head and neck is formed by the pharyngeal or branchial arches.


NERVE SUPPLY


FIRST PHARYNGEAL ARCH

Meckels’s cartilage.

Consists of two portions:

Dorsal:-also known as the maxillary process , giving rise to premaxilla ,maxilla, zygomatic bone and part of the temporal bone.

Ventral:- also known as the mandibular process , which contains the MECKEL’S CARTILAGE. During further development , Meckel’s cartilage disappears except for two small portions at it’s dorsal end that persist and form the Incus and Malleus.


Nerve supply to the muscles of the 1st arch is provided by Mandibular branch of Trigeminal nerve.

Sensory supply of the skin of the face is provided by Ophthalmic , Maxillary and Mandibular branches of the Trigeminal nerve.

Muscles of the different arches do not always attach to the bony or cartilagenous components of their own arch but sometimes migrate into surrounding regions. The origin of these muscles can be traced ,since their nerve supply is derived from the arch of origin.


SECOND PHARYNGEAL ARCH

The cartilage of the second arch (hyoid arch)is called as REICHERT’S CARTILAGE

THIRD PHARYNGEAL ARCH

The cartilage of this arch produces the lower part of the body and the greater horn of the hyoid bone.

Muscle of this arch is the Stylopharyngeus muscle which is innervated by the Glossopharyngeal nerve.


FOURTH AND SIXTH PHARYNGEAL ARCHES

Cartilagenuos components of the 4th and 6th pharyngeal arches fuse to form the thyroid, cricoid , arytenoid , corniculate and cuneiform cartilages of the larynx.


PHARYNGEAL POUCHES

The human embryo has five pairs of pharyngeal pouches.

The last one of these is atypical and is considered as a part of the 4th

First pharyngeal pouch:

It forms a stalk like diverticulum –the tubotympanic recess;

one side of this comes in contact with the external auditary meatus

The distal aspect of this widens in a sac like structure ,the primitive tympanic or middle ear cavity

The proximal part remains narrow forming auditary (eustacian )tube.

The lining of the tympanic cavity forms the tympanic membrane or the eardrum


Second pharyngeal pouch:

The epithelial lining forms the primordium of the palatine tonsil.

Third pharyngeal pouch:

It is characterized by a dorsal and a ventral wing .The dorsal wing proliferates to form the inferior parathyroid gland and the ventral wing forms the thymus


Fourth pharyngeal pouch:

Epithelium of the dorsal wing of this pouch forms the superior parathyroid gland.

Fifth pharyngeal pouch :

The 5th pouch is the last one to develop and is considered to be a part of the 4th pouch.This pouch leads to the development of ultimobranchial body which in future leads to the development of thyroid gland.


PHARYNGEAL CLEFT

The 5 week embryo is characterized by the presence of 4 pharyngeal clefts of which only one contribute to the development of the definitive structure of the embryo.

The dorsal part of the 1st cleft gives rise to the external auditory meatus


CLINICAL CORRELATES

Branchial fistulas :

When the 2nd pharyngeal arch fails to grow caudally over the 3rd and the 4th

arches , leaving remnants of the 2nd 3rd &4th clefts in contact with the surface by a narrow canal.

Internal branchial fistulas :

It is very rare and in this the cervical sinus is connected to the lumen of the pharynx by a small canal which usually opens in the tonsillar region.

Langman's Medical Embryology 8th editionLangman's Medical Embryology 8th edition

DEVELOPMENT OF FACE

DEVELOPMENT OF NOSE

DEVELOPMENT Of NASOLACRIMAL DUCT

DEVELOPMENT OF FACIAL MUSCLES

DEVELOPMENT OF CHEEK

DEVELOPMENT OF EAR

DEVELOPMENTOF EYE

DEVELOPMENT OF LIP


Early development of face is dominated by the proliferation & migration of ectomesenchyme involved in the formation of primitive nasal cavity.

At about 28 days , localized thickening develops with in the ectoderm of the frontal prominence, just above the opening of stomatodeum.these thickenings are NASAL PLACODES.

Rapid proliferation of underlying mesenchyme around the placode produce a horse shoe shaped ridge that converts the placode into NASAL PIT.

The lateral arm of the horseshoe is called LATERAL NASAL PROCESS & the medial arm the MEDIAL NASAL PROCESS. Between the 2 nasal process is the depressed area of frontonasal process

NOSE

The nose is formed from five facial prominences the frontal prominence gives rise to the bridge; the merged medial nasal prominences provide the crest and tip; and the lateral nasal prominences form the sides


Nasal pit are cut off from stomatodeum

External nares formn and approach each other.

Frontonasal process becomes narrower and forms nasal septum from deeper part

As nose become prominent external nares come to open downwards

Established.


DEVELOPMENT OF NASOLACRIMAL DUCT

NASOLACRIMAL DUCT

Obstructed Duct - failure of duct to canalize;is opened surgically for tears to drain to nasal cavity


DEVELOPMENT OF FACIAL MUSCLES

During 5th & 6th weeks myoblasts with in the mandible arch begin proliferation. The muscle cells become oriented to the sites of origin & insertion of the masticatory muscle which they will form

By 7th week the mandible muscle mass has begun to differentiate into the 4 muscles of mastication

Muscle cell migration occurs prior to the time that the skeletal ossification centers of mandible begin to appear.

At 7th week muscle cells with in the hyoid arch undergo proliferation & muscle cells in occipital myotomes have begun proliferation & anterior migration toward the floor of the mouth to become the muscles of the tongue.

Muscle cells of hyoid arch continue migration over the mandible muscle mass & by 10th week have migrated up over the face. These muscle cells forms a thin sheet as they extend up over the face, with one group of cells extending anterior to the ear & a 2nd group extending posterior to it. They initially follow a path like the location of platysma muscle up the side of the neck over the mandible.

DEVELOPMENT OF CHEEK

In lateral part of mouth (stomatodeum) it is bounded laterally by maxillary process and below by mandibular process.

These process undergo progressive fusion with each other to form cheeks.


DEVELOPMENT OF EAR

The external ear is formed around the dorsal part of ectodermal cleft.

The auricle, or pinna is formed from about six mesodermal thickening called tubercles or hillocks that appears on the mandibular and hyoid arches, around the opening of the dorsal part of first ectodermal cleft.

Mandibular arch forms tragus.

Hyoid arch forms rest of auricle

The three parts of the ear-

-External

-Middle and

-Internal ,arise from separate ,diverse embryonic origins .


DEVELOPMENT OF EYE

The light sensitive portion of the eye retina ,is the outgrowth from the forebrain ,projecting bilaterally as the optic vesicles which are connected to the brain by the optic stalks, this results in a thickening called as lens placodes.

These placodes invaginates in it’s centre by the development of peripheral folds .

The optic vesicles invaginate partly to form the double layered optic cusps and the optic stalk becomes the optic nerve .

The outer layer of the optic cup acquires pigmentation to become the pigmented layer of the retina.

DEVELOPMENT OF LIPS

Lower lip :The mandibular processes of the two sides grow towards each other and fuse in the midline ,they form the lower margin of the stomatodeum .

Upper lip :Each maxillary process now grows medially and fuses, first with the lateral nasal process and the with the medial nasal process.


CLINICAL ASPECTS

Cleft lip and palateClassification systems

Facial clefting. A, Absence of the intermaxillary segment with hypotelorism. The maxillary processes form the normal lateral thirds of the upper lips. Absence of prolabium, incisors, and primary palate.

B, True midline cleft of the upper lip and philtrum with hypertelorism. The nose is normal. A 7-month-old girl with transethmoidal cephalocele and left optic nerve dysplasia (morning glory syndrome).

C and D, Midline cleft lip is also found in association with Mohr syndrome (orofacial digital syndrome II [OFD II]). The presence of reduplicated great toes bilaterally helps to identify OFD II and to distinguish it from OFD I.

Facial clefting. A, Right unilateral common cleft lip and palate in a 4-day-old girl. The cleft extends into the base of a widened nostril.

B, Bilateral common cleft lip and cleft palate with discordant forward growth of the intermaxillary segment in a 4-year-old boy. The normal canthi, alae nasi, and lateral thirds of the lip and jaw indicate normal formation and merging of the maxillary and nasolateral processes. The abortive prolabium, premaxillarysegment, and central incisors attach to the vomer and project well anterior to their expected position, because failure to merge the facial processes.

C and D, Bilateral common cleft lip and palate prior to (C) and following (D) surgical repair. There is near-symmetric restoration of the nose and upper lip, with some residual distortion caused by scar.

Facial clefting. Bilateral oblique oroocular clefts with bilateral common cleftlip. A, Frontal view. B, Lateral view

Facial clefting. Unilateral transverse facial cleft and macrostomia in an infant girl.

Facial clefting. Nonanatomic clefts in a 12-year-old mentally retarded girl with the syndrome of amnionic bands. Lateral view. A long, thin band-like scar extends across the scalp and face from the temporoparietal region through the cheek and the corner of the mouth to the lower lip. The large posterior zone of atrophic skin, absent hair, tissuebulging, and inferior displacement of the ear indicate the site of an associated temporoparietal encephalocele. Imaging studies showed notching and separation of teeth where the band crossed the alveolar ridge.

Median cleft face syndrome, typical facies. A, Sedano facies type A in 3-month-old boy. B,Sedano facies type B in 4-day-old boy.C, Sedano facies type C in a young boy after repair of concurrent bilateral common cleft lip and palate. D, Sedano facies type D in a 31⁄2- year-old boy.

Typical facies associated with holoprosencephaly. Five types.A, Facies 1: cyclopia. The complete upper lip, with a hint of a labial tubercle in the midline, could represent either fusion of the nasomedialprocesses independent of the frontonasal process or fusion of the two maxillary processes across the midline.

B, Facies 2: ethmocephaly.

C, Facies 3: cebocephaly with synophrys (fusion of the two eyebrows across the midline).

D, Facies 4: absent intermaxillary segment, flat nasal bridge, and rudimentary alae nasi .

E, Facies 5: hypotelorism with an intermaxillary rudiment (white arrowhead ).

Microtia and hemifacial microsomia in two patients.A, Microtia. The pinna is deformed. The face appears normal. B, Hemifacial microsomia. The line formed by the two palpebral fissures and the line formed by the mouth converge to the region of the deformed, hypoplastic pinna. The right orbit, right eye, and entire right side of the face are asymmetrically smaller. The skin tag falls along the line between the pinna and the mouth.

Hemifacial microsomia. Goldenhar syndrome. •This 4-month-old girl shows a large coloboma of the medial portion of the left upper lid (between the curved white arrows) and a whitish choristoma (straight white arrow).•There is a second, small coloboma of the lower lid medial to the choristoma.

•Treacher Collins syndrome in an 8-year-old boy.• Three-dimensional CT of the skin surface. A to D, Malformed pinnae bilaterally, an antimongoloid slant of the transverse orbital axis, malar hypoplasia with deficient lateral orbital walls bilaterally, hypoplastic mandible with prominent antegonialnotch, narrow anterior vault, and overprojection of the central face.

•Pierre Robin sequence in a 21⁄2-year-old boy with no catch-up growth of the mandible.• A and B, Lateral 3D CT of the skin surface (A) and facial skeleton •(B) show severe retrognathia and micrognathia.

•C, Coronalbone CT shows marked buttressing of the mandibular condyle.

•D, Axial CT section shows a vertical orientation of the maxillary incisors but a horizontal course of the mandibular dentition.

Fetal alcohol syndrome:Alcohol exposure in i.u, life . Most sensitive period of exposure is the first trimester of pregnancy.Women having 2 – 4 drinks per day are at a risk of having smaller birth size.

Clinical features:Microcephaly,Short palpebral fissures ,Short nose,Flat philtrum,Thin upper lip.

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.

What matters most is how you see yourself …

-enlow and hans

Color atlas of embryology –Ulrich drews

-Langman’s medical embryology –Sadler

--Human embryology –Inderbeer singh

--Cleft lip and craniofacial anomalies –Ann kummer

-World wide web

REFERENCES

Evolution & Development of Face

Health & Medicine

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