BIOMED 3 Flashcards
Craniofacial development + cleft lip & palate
What has developed by 4-5 weeks?
Pharyngeal apparatus
- 1st arch is now called mandibular arch
- 2nd arch is now called hyoid arch
What are 6 external changes that form in weeks 4-5, contributing to craniofacial development?
Frontonasal process
Maxillary process (arches)
Nasal placodes
Nasal pits
Mouth
Tongue
What does the frontonasal process grow from?
Ectomesenchymal cells (cranial neural crest cells left on top from neurulation) that migrate to region & start to form new growth
Why is the frontonasal process an important outgrowth?
Forms structures of the face
Where does the maxillary process (/maxillary arch) start to grow from?
Posterior of mandibular arch
Starts lateral, will move more medially
Why is the maxillary process an important outgrowth?
Forming the palate + bones of the face
How are the nasal placodes and nasal pits formed?
In the frontonasal processes, ectomesenchyme cells form nasal placodes (blue)
Nasal placodes invaginate backwards + medially to form nasal pits (red)
How is the mouth formed?
Buccopharyngeal membrane breaks down (green)
How and when is the tongue formed?
In week 4… tongue buds arise from dif pharyngeal arches (I II III IV)
Fully formed by week 12
What are 4 external changes that form in weeks 5-7, contributing to craniofacial development?
Mandible
Eye placodes
Medial nasal processes fuse
Maxillary process continues to grow
How is the mandible (lower jaw) formed?
Mandibular arches fuse
How do the eye placodes form?
From ectoderm tissues, gives rise to main structures of the eye
What happens when the nasal pits move more medially, closer together?
Medial sides fuse to form tissue called the intermaxillary process (IMP)
What does the intermaxillary process form?
Primary nasal septum
Primary palate
Philtrum
What is the primary nasal septum?
Tissue that remains between the 2 fused medial nasal processes
How can a deviated septum affect speech?
Can affect breathing/resonance of voice
What is the primary palate?
Formed from same tissue as primary nasal septum (IMP) but extends horizontally + posteriorly
What does our palate today derive from?
Fusion of primary + secondary palates
What happens at 5.5 and 6 weeks when the maxillary process continues to grow?
Fuses with lateral nasal process to form nasolacrimal groove (light blue)
Fuses with medial nasal process (red)
Fuses with mandible below (dark blue)
What are 2 external changes that form in weeks 7-8, contributing to craniofacial development?
Philtrum
Fusion of maxillary + mandibular process
What is the filtrum?
Vertical line formed where the medial nasal processes + maxillary processes meet
How does cleft lip occur?
Incomplete fusion of one/both medial nasal processes + maxillary processes
(thus can be uni/bilateral)
What is the term for the incomplete fusion between the maxillary + mandibular processes?
Macrostomia
What is the term for the overcomplete fusion between the maxillary + mandibular processes?
Microstomia (small mouth)
What is the internal changes that forms in weeks 7-8, contributing to craniofacial development?
Secondary palate (main palate)
What is the secondary palate?
Roof of the mouth which separates the oral cavity from the nasal cavity
What are the 2 parts of the secondary palate?
Anterior 2/3 = hard palate, bone
Posterior 1/3 = soft palate, muscles with roles in breathing + swallowing
How is the secondary palate formed?
Outgrowth of maxilla bones: palatine processes /shelves (cartilage)
Horizontal plates of palatine bones move toward each other (posterior)
How did the secondary palate take a horizontal position above the tongue?
Initially, palatine processes deflected downwards by developing tongue
Mandible widens, allowing tongue to drop into floor of mouth
Palatine processes now have no restraint: shelves elevate
What fuses in regards to the secondary palate formation?
Palatine processes with…
- each other
- primary palate
- new secondary (bony) nasal septum
Maxillary tissue with mandibular tissue
How does cleft palate occur?
growth defect in palatal shelves
Delay in shelf elevation → failed fusion of lateral palatine processes / nasal septum / median palatine processes
What are 6 examples of cleft lips/palate?
What are the impacts of an incomplete left lip?
Little, but parents may choose to have surgery for psychological reasons
When is cleft lip/palate picked up?
In scans / first few days
How can cleft lip/palate impact newborns before surgery?
Harder to build pressure for feeding
Why does cleft lip have little impact on speech?
Repaired at 3-4m
Successful + easy surgery
Why do children with cleft lip + palate have higher risk of speech difficulties?
Can’t have palate repaired until 9-12m, as have to have lip repaired first (as easier + needed for feeding)
Do those with a bilateral cleft lip or a unilateral cleft lip have worse speech outcomes?
Bilateral
What is a submucous cleft palate?
Palate may looks unaffected
But, muscles that lift soft palate for speech are abnormal/defected
What are 4 signs of a submucous cleft palate?
Split uvula
Bony gap at back of hard palate
Midline of soft palate looks very thin / translucent
Nasal sounds
How many babies in the UK are born with a cleft lip and/or palate?
1 in 700
How many babies in the UK are born with a cleft palate only, and which gender does it occur more in?
1 in 2500 live births
Greater incidence in females
How many babies in the UK are born with a cleft lip and palate, and which gender does it occur more in?
1 in 800 live births
2:1 male to female ratio
Is there a known cause of clefts?
Largely unknown
Combination of genetic + environmental factors
Correlation, not causation
What are 4 contributory factors towards clefts?
Heavy smoking in early stages of pregnancy
Heavy alcohol consumption in early stages of pregnancy
Folic acid deficiency in early stages of pregnancy
10% born with cleft also have associated genetic syndrome
What are 4 genetic conditions linked to cleft?
Van Der Woude syndrome
Pierre Robin syndrome
Stickler’s syndrome
22q11 deletion syndrome
What are 4 impacts of cleft / palatal formation probelms?
Feeding + swallowing
Speech
Language
Social + emotional + educational attainment
What is velopharyngeal dysfunction (VPD) ?
Can occur after surgery
30% (potentially more)
Soft palate doesn’t completely close off the throat as it should during speech production
Palate too short / muscles weak
How does velopharyngeal dysfunction (VPD) affect speech/swallowing?
Hypernasal, as struggles to make pressure for certain sounds
Dysphagia: goes up nose, risk of aspiration
What is the impact of velopharyngeal dysfunction for people that speak other languages?
May sound more ‘normal’ if language uses more nasal sounds
What are the 2 main ways in which consonant production is affected by cleft?
Structural defect: child cannot avoid losing air through nasal cavity, weak + nasalised consonants (can use tongue, but sounds backed)
Active strategy/compensation to prevent oral-nasal, so changes place/manner of articulation, continues with learnt speech errors even when palate repaired
What are 4 common compensatory articulations (cleft speech characteristics)?
Glottal stops
Nasal fricatives
Pharyngeal fricatives
Velar stops
What are glottal stops (common compensatory articulation)?
Pop of air when vocal folds forced together
- release of air can make it sound like consonant omitted
What are nasal fricatives (common compensatory articulation)?
Stream of air directed through nasal cavity, not oral cavity
- sounds like talking through the nose
What are pharyngeal fricatives (common compensatory articulation)?
Base of tongue pressed against back of throat
- raspy ‘h’ (unintelligible)
What are velar stops (common compensatory articulation)?
Sounds made further back in mouth than intended
