8/8/2019 Development of the Face- Alcantara
1/9
1
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)
8/8/2019 Development of the Face- Alcantara
2/9
2
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
8/8/2019 Development of the Face- Alcantara
3/9
3
- 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
8/8/2019 Development of the Face- Alcantara
4/9
4
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
8/8/2019 Development of the Face- Alcantara
5/9
5
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
8/8/2019 Development of the Face- Alcantara
6/9
6
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
8/8/2019 Development of the Face- Alcantara
7/9
7
- 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
8/8/2019 Development of the Face- Alcantara
8/9
8
- @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**
8/8/2019 Development of the Face- Alcantara
9/9
9