Development Of The Nose And Face Flashcards
Where do neural crest cells originate from and where do they migrate to?
From within the neuroectoderm which has differentiated from ectoderm under the influence of the neural tube.
How is the neural crest formed?
Cells of the lateral border of the neuroectoderm become displaced and enter the mesoderm. They migrate and contribute to a variety of head and neck structures which happens as the neural tube fuses this is how the neural crest develops.
What are the major features of the face?
Palpebral fissures
Oral fissures
Nares
Philtum
Where is the facial skeleton derived from?
Neural crest of the first pharyngeal arch
Where are the muscles of mastication derived from?
Mesoderm of the first pharyngeal arch
Where are the muscles of facial expression derived from?
Second pharyngeal arch
Where are the facial primordia derived from?
The first pharyngeal arch
What does the frontonasal prominence surround and what is found on it?
The ventrolateral part of the forebrain
Primordia of the eyes
How does the nose develop in the first stages?
Nasal placodes appear on FNP which sink to become nasal pits
Medial and lateral prominences form on either side of the pits
Rupturing of the buccopharyngeal membrane causes opening into cranial parts of the primitive gut tube
How does the nose fuse?
Maxillary prominences grow medially, pushing the nasal prominences closer together in the midline.
Maxillary prominences fuse with the medial nasal prominences and medial prominences fuse in the midline
What does fusion of the medial nasal prominences create?
The intermaxillary segment
What are the components of the intermaxillary segment?
Labial component - philtrum
Upper jaw - 4 incisors
Palate - primary palate
What makes up the main part of the definitive palate?
The secondary palate
What is the secondary palate derived from?
Palatal shelves which are derived from the maxillary prominences
What separates the nose from the mouth?
The secondary palate
How does the secondary palate develop?
The maxillary prominence gives rise to two palatal shelves
They grow vertically downwards into the oral cavity on each side of the developing tongue
The mandible grows large enough to expand the oral cavity and allow the tongue to drop
Palatal shelves then grow towards eachother and fuse in the midline on roof of mouth
How does the nasal septum develop?
As a midline down-growth to ultimately fuse with the palatal shelves
What is a lateral cleft lip?
Failure of fusion of the medial nasal prominence and maxillary prominence
What is a cleft lip and cleft palate?
Combined with failure of the palatal shelves to meet in the midline
What happens to the frontonasal prominence?
Becomes the forehead, bridge of nose, medial and lateral nasal prominences
What happens to the medial nasal prominence?
Philtrum
Primary palate
Mid upper jaw
What does the lateral nasal prominence become?
Sides of the nose
What does the maxillary prominence become?
Cheeks
Lateral upper lip
Secondary palate
Lateral upper jaw
What does the mandibular prominence become?
Lower jaw and lip
In which week does development of the eyes begin?
Fourth week
How do the eyes develop?
Outpocketings of the forebrain grow out to make contact with overlying ectoderm
Optic placodes will develop into the lens of the eye
Optic vesicles grow out towards the surface to make contact with the lens placodes
Lens placode invaginates and pinches off
Where is the retina derived from?
Diencephalon (forebrain)
What is the positioning of the eye primordia?
Positioned on the side of the head
As facial prominences grow, the eyes move to the front of the face giving binocular vision
Where does the external auditory meatus develop from?
First pharyngeal cleft
What do the auricles of the ear develop from?
First and second pharyngeal arches surrounding the meatus
What is the positioning of the external ears?
Develop initially in the neck
As mandible grows, the ears ascend to the side of the head to lie in line with the eyes
What are all common chromosomal abnormalities associated with?
External ear anomalies
Where is the inner ear derived from?
Otic placodes
How does the inner ear develop?
Otic placodes invaginate into the auditory vesicles
Have a membranous labyrinth made up of a cochlea and semi-lunar canal system
What is fetal alcohol syndrome?
Neural crest cell migration and development of the brain are known to be extremely sensitive to alcohol
What is the incidence of fetal alcohol syndrome and alcohol-related neuro-developmental disorder (ARND)?
1/100 births
Which placodes does vision, smell, hearing and balance come from?
Vision - optic placode
Smell - nasal placode
Hearing and balance - otic placode
What is development of the face driven by?
Expansion of the cranial neural tube forming a large frontonasal prominence
