Development of the Face Flashcards
When does the facial primordia appear?
Early in the 4th week
What does the facial primordia appear around?
The large primordial stomodeom
Facial development depends on what 2 organizing centers?
Depends upon the inductive influence of: Prosencephalic - forebrain Rhombencephalic - hindbrain
The prosencephalic organizing center is derived from?
Prechordal mesoderm that migrates from the primitive streak
The prosencephalic center is located where?
Rostral to the notochord and ventral to the prosencephalon or forebrain.
The rhombencephalic organizing center is what to the rhombencephalon (hindbrain)?
Ventral
Prosencephalic
Forebrain
Rhombencephalic
Hindbrain
Mesencephalic
Midbrain
5 facial primordia (prominences) around the stomodeum
Single frontonasal prominence Paired maxillary prominence Paired mandibular prominences
The paired facial prominences are derivatives of what?
First paired of pharyngeal arches
The prominences are produced mainly by the proliferation of what?
Neural crest cells
Where do neural crest cells migrate from?
The lower mesencephalon and upper rhombencephalon
When do the neural crest cells migrate and create the prominences?
During the 4th week
Neural crest cells in the facial & oral regions are the major source of what?
Connective tissue components including cartilage, bone, and ligaments
The FNP surrounds what?
The ventrolateral part of the forebrain
FNP
Frontonasal prominence
The forebrain gives rise to what that forms the eyes
Optic Vesicles
The frontal part of the FNP forms what?
The forehead
The nasal part of the FNP forms what?
The rostral boundary of the stomodeum, primordial mouth and mose
The paired maxillary prominences form what?
The lateral boundaries of the stomdeum
The paired mandibular prominences constitute what?
The caudal boundary of the primitive mouth
Facial development occurs mainly between when?
4th & 8th weeks
When does the face have an unquestionable human apperance
By the end of the embryonic period (8th week)
Facial proportions develop when?
During the fetal period
What parts of the face form first?
The lower jaw and lower lip
What forms the lower jaw and lip and in what plane?
Merging of the medial ends of the manibular prominences in the median plane
By the end of the 4th week what develops on the inferolateral parts of the FNP.
Nasal placodes - Bilateral oval thickenings of the surface ectoderm
What is nasal placodes?
The primordia of the nose and nasal cavities
Placodes are initially what shape?
Convex
Later placodes are changed in each placode how?
Stretched to produce a flat depression
Mesenchyme in the margins of the placodes proliferates producing what?
Horseshoe shaped elevations - the medial and lateral nasal prominences
The nasal placodes lie in depressions as a result of what?
Proliferating of mesenchyme in the margins of the placodes
Depressions of the nasal placodes are what?
Nasal pits
Nasal pits are the primordial of what?
The anterior nares (nostrils) and nasal cavities
Proliferation of mesenchyme in the maxillary prominences causes what?
Causes the prominences to enlarge and grow medially toward each other and the nasal prominences
The medial migration of the maxillary prominences moves what?
The medial nasal prominences toward the median plane and each other
Each lateral nasal prominence is separated from the maxillary prominence by what?
A cleft called the nasolacrimal groove
The eyes are derived from four sources
- neuroectoderm of forebrain 2. Surface ectoderm of head 3. Mesoderm between above layers 4. Neural crest cells
The neuroectoderm of the forebrain differentiates into what?
The retina Posterior layers of the iris The optic nerve
The surface ectoderm of the head forms what?
The lens of the eye and The corneal epithelium
The mesoderm between the neuroectoderm and surface ectoderm gives rise to what?
Fibrous and vascular coats of the eye
Mesenchymal cells are derived from what?
Mesoderm
Neural crest cells migrate into what?
The mesenchyme from the neural crest
Neural crest cells that migrate into the mesenchyme from the neural crest differentiate into what?
The choroid, Sclera, and corneal endothlium
The first indication of the eye is what?
Optic groove
Optic groove forms when?
Beginning of the 4th week
The groove deepens to form what?
A hollow optic vesicle that projects from the forebrain
The optic vesicles contact what?
The surface ectoderm
The optic vesicles induces development of what?
Lens placode - the primordial lens
Invaginates
Enclose, sheathe / to fold in so that an outer becomes an inner surface
The lens placode invaginates to form what?
The lens pit and lens vesicles
The optic vesicle invaginates to form what?
An optic cup
The retina forms from what?
The 2 layers of the optic cup
What is Coloboma?
A defect in the inferior sector of the iris or a notch in the pupillary margin
Coloboma gives the pupil what kind of appearance?
A keyhole appearance
Coloboma may be limited to what or may extend where?
The iris Extend deeper and involve the ciliary body and retina
A typical coloboma results from what?
The failure of closure of the retinal fissure
A typical coloboma results when?
During the 6th week
Coloboma defect may be?
Genetically determined or caused by environmental factors
A simple coloboma of the iris is frequently what?
Hereditary
A simple coloboma is transmitted by?
An autosomal dominant characteristic
The iris in congenital aniridia is what?
Almost completely absence
Congenital aniridia results from what?
An arrest of development at the rim of the optic cup
When does congenital aniridia occur?
During the 8th week
Congenital aniridia may be associated with what?
Glaucoma and other eye abnormalities
Aniridia may be what?
Familial, the transmission being dominant or sporadic
Aniridia is the result of what mutation?
Mutation of the Pax6 gene
Congential Glaucoma is what?
Abnormal elevation of intraocular pressure in newborns
Congenital glaucoma results from what?
Abnormal development of the drainage mechanism of the aqueous humor during the fetal period
Intraocular tension rises because of what?
An imbalance between the production of aqueous humor and its outflow
What is aqueous humor?
a transparent, gelatinous fluid similar to plasma, but containing low-protein concentrations
The imbalance between the production of aqueous humor and its outflow may be a result from what?
Abnormal development of the scleral venous sinus
Congenital glaucoma is genetically heterogeneous but the condition may result from what?
A rubella infection during early pregnancy
What color is the lens with congenital cataracts?
Opaque and frequently appears grayish-white.
What results from congenital cataracts?
Blindness
Many lens opacities (opaque) are what?
Inherited. Dominant transmission being more common than recessive or sex linked transmission
Some congenital cataracts are caused by what?
By teratogenic (Of, relating to, or causing malformations of an embryo or fetus) particularly the rubella virus, that affect early development of the lenses
The lenses are vulnerable to rubella virus when?
Between the 4th and 7th weeks when primary lens fibers are forming
Cataract and other ocular abnormalities caused by the rubella virus could be completely prevented if what?
If immunity to rubella were conferred on all women of reproductive age
Physical agents such as what can also damage the lens and produce cataracts?
Radiation
Another cause of cataract is what?
An enzymatic deficiency - congenital galactosemia
Congenital cataracts appear when?
As early as the second week after birth
How does the enzyme deficiency cause the cataract formation?
Large amounts of galactose from milk accumulate in the infant’s blood and tissues, causing injury to the lens
Congenital detachment of the retina occurs when?
When the inner and outer layers of the optic cup fail to fuse during the fetal period to form the retina and obliterate the intraretinal space
A detached retina may follow what?
A blow to the eyeball
What is a result of a detached retina?
Fluid accumulates between the layers and vision is impaired
Cyclopia is caused by?
A failure of the embryonic prosencephalon to properly divide the orbits of the eye into 2 cavities
Cyclopia is also called?
Synophthalmia
What is cyclopean?
A very rare anomaly where the eyes are partially or completely fused forming a single median eye enclosed in a single orbit
The cranial neural tube develops into what?
The brain
The brain develops from what?
Three primary brain vesicles formed by the fusion of the neural folds in the cranial region and closure of the rostral neuropore
The 3 primary brain vesicles form what?
- Forebrain (prosencephalon) 2. Midbrain (mesencephalon) 3. Hindbrain (rhombenccphalon)
Just for reference
Front view
Reference
Reference
What anomaly is this?
Congenital Aniridia
What is this anomaly?
Glaucoma
What is this?
Congenital glaucoma - Rubella virus
What is this?
Cataracts
What is this?
Cataracts
What is this?
Coloboma of Iris
What is this?
Synophthalmia or Cyclopia
