Flashcards in Session 3 Deck (54):
Define Neural crest
A specialised population of cells that
originates within the neurectoderm
How do the Neural crest cells reach the area for Head & Neck development?
Begin at the lateral border of the neuroectoderm
Become displaced and enter the mesoderm
Migrate and contribute to Head & Neck
What are the major features of the face?
Palpebral fissues (Opening to the eye)
Philtrum (Small vertical groove above the upper lip)
Where do the Pharyngeal arches develop?
In the neck region around the Aortic arches
What does each Pharyngeal arch have?
Aortic arch artery
Mesenchyme filling (Will become cartilaginous bar)
What forms the facial skeleton?
Neural crest of 1st Pharyngeal arch
What forms the muscles of mastication?
Mesoderm of 1st Pharyngeal arch
What forms the muscles of facial expression?
Mesoderm of 2nd Pharyngeal arch (First prominence)
What is the facial primordia made of?
The 1st Pharyngeal arch (Paired and has 2 prominences)
Frontonasal prominence (Unpaired. Primordia of eyes)
Why is the Frontonasal prominence large?
Because it surrounds the ventro-lateral part of the forebrain
What drives development of the face?
Expansion of the cranial neural tube
What is the Stomatodeum?
An area of the embryonic head that contains the buccopharyngeal membrane(Avascular, will rupture to create the oral cavity opening)
What does the 1st Pharyngeal arch develop into?
What are the derivatives of the Frontonasal prominence?
Bridge of nose
What are the derivatives of the Maxillary prominence?
Lateral upper lip
Lateral upper jaw
What are the derivatives of the Mandibular prominence?
What is a placode?
A thickening of ectoderm which indicates it will go on to become a 'special senses'
Where do the nasal placodes appear?
On the frontonasal prominence. They then sink to become the nasal pits (With raised section around called prominence)
In what direction does the Maxillary prominence grow?
Medially. This pushes the nasal prominences closer together in the midline
What does the nasal prominences fuse with?
Each other in the midline
The Maxillary prominences
What does the Inter-maxillary segment give rise to?
The Primary palate
What are the components of the Inter-maxillary segment?
Labial component (Philtrum)
Upper jaw (4 incisors)
How is the Inter-maxillary segment created?
Fusion of the medial nasal prominences
What is the main part of the definitive palate made of?
The secondary palate
What is the secondary palate derived from?
Palatal shelves derived from the Maxillary prominence (2 made from the prominence)
How do the Palatal shelves grow?
Downwards into the oral cavity either side of the developing tongue (Which drops when the Mandible grows larger)
Palatal shelves then grow towards one another and fuse in the midline
Where does the nasal septum (vomer) fuse?
It develops as a midline, growns downwards and fuses with the palatal shelves
What is the dual origin of the lip and palate?
Intermaxillary segment (Philtrum and Primary palate)
Maxillary process (Fused palatal shelves, lateral part of lip)
What is the least severe version of a cleft lip disorder?
Lateral cleft lip
What is a Lateral cleft lip?
Failure of fusion of the medial nasal prominence and maxillary prominence (Can involve the Primary palate)
What is the most severe version of a cleft lip disorder?
A cleft lip and cleft palate
What is a Cleft lip and cleft palate?
Failure of fusion of the medial nasal prominence and maxillary prominence
Failure of the palatal shelves to meet in the midline
What are some of the signs of a Cleft lip and cleft palate?
Cannot feed properly
Issues with speech development
What does the Frontonasal prominence become?
Bridge of nose
Medial nasal prominence
Lateral nasal prominence
What does the Medial nasal prominence become?
Mid upper jaw
What does the Later nasal prominence become?
Sides of the nose
What does the Maxillary prominence become?
Lateral upper lip
Lateral upper jaw
What does the Mandibular prominence become?
(The prominence begins relatively small, but then enlarges a lot)
What is the primordia of the eyes?
Outpocketings of the forebrain on the side of the head (Optic vesicles)
How do the Optic vesicles develop?
They grow outwards and make contact with the overlying ectoderm. They then grow out towards the surface to make contact with the Optic placodes
What develops to make the lens of the eye?
What happens when the Optic vesicles meet the Optic placodes?
It invaginates and pinches off
What are the Retinas derived from?
Where are the eye primoridia originally placed?
At the side of the head
Why do the eye primordia move?
The facial prominences grow which causes the eye primordia to move to their position during life
What is the placode that aids auditory developed called?
The otic placode
What does the external auditory meatus develop from?
The 1st Pharyngeal cleft
What do the Auditory hillocks develop from?
The 1st Pharyngeal cleft. They go on to make the pinna of the ear from auricles
Where do the ears initially develop?
Side of the neck
How do the ears move to their normal position?
As the mandible grows the ears ascend to the side of the head and lie in line with the eyes
What is Fetal alcohol syndrome?
The neural crest cells and development of the brain are very sensitive to alcohol. Usually occurs in pregnancies that have a large alcohol intake
What are the signs of Fetal alcohol syndrome?
Low nasal bridge & short nose
Thin upper lip
Small eye openings
How does the inner ear develop?
Otic placodes invaginate to form Auditory vesicles.
Makes the Membranous Labyrinth which will go on to develop into the Cochlea and Semi lunar canal system