development of the face- alcantara

8/8/2019 Development of the Face- Alcantara

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Development of the Face

Lecture by: B.G. Alcantara, FPSA, FPCSMicroscopic Structural Human Biology, SY 2010-2011

FEU-NRMF Institute of Medicine

Developing Face

- represented by the FRONTONASAL REGION, and 1st

PHARYNGEAL(Brachial/ Visceral) ARCH

- FRONTONASAL PROMINENCE- composed of tissue that surrounds theforebrain

- At 5th week: STOMODEUM

Anlage/ Embryonic Origin Fate

Fronto-nasal Forehead, nasal bridge, medial/ lateralnasal prominences

Maxillary Process Cheeks, lateral portion of the upper lip

Mandibular Process Lower Lip

Development of the Tongue

@ 4th

week:

1st ARCH: ANTERIOR 2/3 of the Tongue; made up of:

a. 2 lateral lingual swellings

b. 1

st

medial swelling (tuberculum impar)

3rd ARCH: POSTERIOR 1/3 of the Tongue; made up of

a. 2nd

medial swelling (hypobrachial eminence/copula)

4th

ARCH: EPIGLOTTIS from the 3rd

medial swelling (post. part of the pharyngealarch)


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Development of the Nose

@ 5th week:

- OLFACTORY PLACODES line the NASAL PITS (Nasal Cavities)

- MEDIAL and LATERAL NASAL PROMINENCES from around the nasal pits

MEDIAL: Philtrum of upper lip

Crest and Tip of Nose

LATERAL: Alae of Nose

- Union of the medial and lateral nasal prominences with the maxillary is required for

the development of the upper lip

Development of the Palate

- The medial nasal processes- contribute to the tissues that will form the

anterior part of the palate, the PRIMARY PALATE

Medial Nasal Prominence

Lateral Nasal Prominence

Maxillary Prominence


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- Intermaxillary Segment: PRIMARY PALATE- Palatine Shelves: DEFINITIVE PALATE (6 th Week)

o positioned above the tongue to allow fusion in the midline

o change their contours such that they initially approximate each other

close to midpoint and fuse anteriorly and posteriorly from that point

o fusion of the palatine shelves with each other and with the nasalseptum separates the nasal cavities with the oral cavity

Development of Facial and Cranial Bones

- Neural crest cells from the majority of the facial and cranial skeleton;

however, mesodermal cells also contribute to the cranium

Medial Nasal Process

Primary Palate


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Development of the Eyes

FOUR EMBRYONAL ORIGIN OF THE EYENeuroectoderm - retina, posterior layer of the iris, optic nerve

Surface ectoderm - lens, corneal epithelium, bulbar and palpebral

conjunctivaMesoderm - fibrous, vascular coat

Neural crest cell - choroid, sclera, corneal endothelium

DAY 22: Optic Primordia- optic grooves (sulci) form as some of the cells in the eyesfields invaginate

DAY 27: Optic vesicles invaginates the optic cup

Optic Cup: Inner layer: Neuronal Layers

Outer layer: Pigment epithelium of the retina

Surrounding mesenchyme: choroid and sclera

Optic Stalk: Optic Nerve

The invaginating LENS PLACODE: forms the LENS VESICLE that pinches off the

surface ectoderm; invagination of the optic vesicle forms the bilayered OPTIC CUP

that remains connected to the forebrain via OPTIC STALK; LENS separate by the36

thday

Lens Vesicle

Optic Cup

Optic Stalk

Surface Ectoderm


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HYALOID VASCULATURE: surrounds the back of the lens; following the separationof the surface, the POSTERIOR LENS FIBERS elongate to obliterate the lens cavity

and the CORNEA begins to differentiate

ANTERIOR CHAMBER OF THE EYE: forms as a space and develops between the

lens and its closely associated IRIDOPUPILLARY MEMBRANE and the CORNEA

PUPILLARY MEMBRANE: should regress, but may persist after birth

CORNEA: consists of

a. OUTER EPITHELIAL LAYER- from surface ectoderm

b. INNER LAYERS- from neural crest cells

RETINA:

a. PIGMENTED LAYER: becomes relatively thinner as it develops

b. NEURAL LAYER: thickens; differentiates into distinct cell layers (rods and cones,

outer nuclear layer, inner nuclear layer, ganglion layer, optic nerve fibers, etc.)

- Folding of these layers results in the formation of the CILIARY PROCESSES

Cornea

Anterior Chamber

Iridopupillary

Membrane


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IRIS: forms from the outer rim of the OPTIC CUP

EYELIDS: begin to form at the end of embryonic period

- fuse at the beginning of the 2nd

trimester; reopen at the beginning of the 3rd

trimester

Development of the Ears

@ 3rd

Week :

Surface Ectoderm Otic Placode invaginates to become OTIC/ AUDITORYVESICLES (otocyst)

Ventral: Saccule, Cochlear duct, and Spiral Ganglion of CN VIII

Dorsal: Utricle, Semicircular Canals, Endolymphatic ducts and Vestibular Ganglion ofCN VIII

- Ectoderm: epithelium of the inner ear- Otic Pit: located dorsal to 2 nd pharyngeal cleft


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- Stato-/ Vestibulo- Acoustic Ganglion: begins to form between the otic vesicleand neural tube

Differentiation of the otic vesicle yields three major subdivisions of the inner ear

a. Endolymphatic Sac and Duct

b. Utricular Portion

c. Saccular Portion

- Outgrowth of saccule forms cochlear duct

@ 9th week: tall columnar, epithelial cells of growing cochlear duct Organ of Corti


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- @5th

week: EXTERNAL EAR forms from the tissues of 1st

and 2nd

PharyngealArches

- Initially, the developing external ears are more caudal than the lower jaw;growth of lower jaw places the external ear in a relatively higher and morevertical orientation

- @ 6th

week: six tissue elevations termed AURICULAR HILLOCKS become

apparent; three form from the 1 st arch, and three from the 2 nd arch

- Each hillock forms a distinctive portion of the definitive external earHillock #1- Tragus of the Ear

Hillock #6- Antiragus and part of Helix

**Lobule of ear is NOT derived from the hillocks**


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development of the face- alcantara

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