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BDS3 CDS Ortho > Facial Development > Flashcards

Facial Development Flashcards

1
Q

From what weeks does the embryonic phase of in-utero life occur ?

A

1-8 weeks - development of all limbs and organs including face occurs during this time.

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2
Q

From what weeks does the foetal phase of in-utero life occur ?

A

8 weeks to term - time of growth.

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3
Q

What percentage of miscarriages occur at embryo phase and foetal phase ?

A

10% embryo and 1% foetal.

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4
Q

What are the two layers of cells associated with a blastocyst ?

A

Ectoderm and endoderm.
(Mesoderm after ectoderm and endoderm begin to fold in on each other).

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5
Q

What are somites ?

A

Precursor populations of cells (appear as blocks) that give rise to important structures associated with the vertebrate body plan.

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6
Q

What does the neural tube form ?

A

Brain and spinal cord.

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7
Q

When does the neural tube form ?

A

4 weeks IU.

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8
Q

What condition occurs when the neural folds do not fuse bilaterally to form the neural tube ?

A

Spina bifida - can be detected on ultrasound scan.

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9
Q

A deficiency in what can lead to increase risk of spina bifida ?

A

Folate deficiency.

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10
Q

What condition occurs when the neural tube fails to develop into brain and spinal cord ?

A

Anencephaly - where cerebral hemispheres and cranial vault is absent and pregnancy will usually terminate naturally or child will pass away within hours of birth.

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11
Q

What are neural crest cells ?

A

Formed during the folding of neural plate, cells develop from ectoderm along the groove = neural crest cells (same as ectomesenchyme) and will undergo extensive migration in developing embryo and differentiate into different cell types.

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12
Q

What tissues do neural crest cells form ?

A

Contribute to branchial arch cartilage, bone, connective tissue and dental tissue - pulp, dentine, cementum and periodontal ligament.

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13
Q

What cell types do neural crest cells differentiate into ?

A

Spinal and autonomic ganglia, Schwann cells, adrenal medulla, meninges of the brain.

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14
Q

What are the two parts of first pharyngeal arch ?

A

Maxillary and mandibular processes.

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15
Q

How many pharyngeal arches are there ?

A

4.

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16
Q

At what stage and approximately what day do the maxilla and mandible begin to form IU ?

A

Stage 19 and 46th day.

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17
Q

When does formation of the face occur post fertilisation ?

A

During 8 weeks.
At weeks 5 to 7 - can see extension and fusion of facial processes.

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18
Q

What processes is the face formed by ?

A

Pronto-nasal process.
Rhombomeres 1 and 2.
First brachial (pharyngeal) arch.

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19
Q

What is the stomodeum ?

A

Depression between maxillary and mandibular processes of first pharyngeal arches - precursor to the mouth.

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20
Q

Why does a cleft lip/palate occur ?

A

Failure of fusion of the maxillary process of the first pharyngeal arch.
Upper lip and anterior part of palate fuse at different times and therefore can occur independently or together.

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21
Q

What does each pharyngeal arch contain ?

A

Artery, vein, nerve and block of muscle.

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22
Q

What nerve and block of muscle is related to the first pharyngeal arch ?

A

Trigeminal nerve and muscles of mastication.

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23
Q

What nerve and block of muscle is related to the second pharyngeal arch ?

A

Facial nerve and muscles of facial expression.

24
Q

What nerve and block of muscle is related to the third pharyngeal arch ?

A

Glossopharyngeal nerve and stylopharyngeus.

25
Q

What nerve and block of muscle is related to the fourth pharyngeal arch ?

A

Vagus nerve and cricothyroid muscle, levator veli palatini and the constrictor muscles of the pharynx.

26
Q

What are the two parts of the skull ?

A

Neurocranium - protective case round brain.
Viscerocranium - forms facial skeleton.

27
Q

What are the two types of ossification ?

A

Intramembranous and endochondral.

28
Q

What is endochondral ossification ?

A

Where there is no bone or cartilage precursor and calcified bone appears within endochondral layer.

29
Q

What is intramembranous ossification ?

A

Bone preceded by hyaline cartilage model (containing BV and nerves).

30
Q

What is different about the ossification of the maxilla and mandible ?

A

Bone develops adjacent to pre-existing cartilaginous skeletons i.e. nasal capsule (for maxilla) and Meckel’s cartilage (mandible).

31
Q

The base of the skull is formed by what type of ossification ?

A

Intramembranous (sphenoid bone, continued growth).

32
Q

What is Meckel’s cartilage ?

A

Forms in first pharyngeal arch - cartilage which acts as jaw support during early development and template for later forming jaw bones to form beside and ossicles of the ear.

33
Q

What is Reichert’s cartilage ?

A

Forms in second pharyngeal arch - cartilage which gives rise to styloid process, styloid ligament and hyoid bone.

34
Q

What are the 5 units which the mandible develops from ? What stimuli do they respond to ?

A

Condylar - forms articulation.
Angular - in response to lateral pterygoid and masseter muscle development.
Coronoid - forms in response to temporalis muscle development.
Alveolar - forms in response to tooth formation.
Body - forms in response to IAN.

35
Q

What are the 3 main sites of secondary cartilage formation ? And when do they disappear ?

A

Condylar - continues growth until 20 y/o.
Coronoid - disappears before birth.
Symphyseal - disappears just after birth.

36
Q

What is the definition of primary abnormality ? Examples ?

A

Defect in structure of organ or part of organ that can be traced back to anomaly in its development e.g. spina bifida, cleft lip.

37
Q

What are the two primary cartilages ?

A

Meckel’s cartilage and nasal process.

38
Q

What is the definition of secondary abnormality ? Examples ?

A

Interruption of normal development of organ that can be traced back to other influences e.g. teratogenic agents, infection (rubella), thalidomide, lithium, trauma, amniotic bands.

39
Q

What is the definition of deformation ?

A

Anomalies that occur due to outer mechanical effects on existing structures.

40
Q

What is the definition of agenesia ?

A

Absence of organ due to failed development during embryonic period.

41
Q

What is the definition of sequence ? Example ?

A

Single factor results in numerous secondary effects e.g. Pierre-Robin and cleft palate - baby has small mandible, tongue pushes against maxilla, palate doesn’t form properly and cleft palate occurs.

42
Q

What is the definition of syndrome ? Example ?

A

Group of anomalies that can be traced to common origin e.g. trisomy of chromosome 21 in Downs syndrome.

43
Q

What are 4 examples of facial syndrome which arise from early problems with facial development i.e. in the first 1-8 weeks ?

A

Cleft lip/palate.
Treacher Collins syndrome.
Foetal Alcohol syndrome.
Hemifacial microsomia.

44
Q

What are distinct facial features of foetal alcohol syndrome ?

A

Short palpebral fissures.
Low nasal bridge.
Microcephaly with small midface.
Micrognathia (small mandible).
Long upper lip with indistinct philtrum.
Mild intellectual disability.

45
Q

At what time does foetal alcohol syndrome often occur ?

A

Around day 17 - commonly mothers do not know they are pregnant at this point.

46
Q

What is hemifacial microsomia ?

A

Spectrum of multifactorial 3D progressive facial asymmetry.

47
Q

What causes hemifacial microsomia ? And when ?

A

Failure of neural crest migration to the front during fusion of two neural folds, occurring at day 19-28.

48
Q

What are the associated facial features of hemifacial microsomia ?

A

Unilateral mandibular hypoplasia.
Zygomatic hypoplasia.
High arched palate.
Malformed pinna.
Medical - normal intellect, deafness, cardiac and renal problems.

49
Q

What days IU does cleft lip occur between ?

A

28 to 38 days.

50
Q

What days IU does cleft palate occur between ?

A

42 to 55 days.

51
Q

What is the aetiological factors affecting cleft lip and palate ?

A

Genetic - monozygotic twins, syndromes, familial patterns, ethnic, more commonly left, sex ratio.
Environment - social deprivation, smoking, alcohol, anti-epileptics, multivitamins.

52
Q

What are the dental features of cleft lip and palate ?

A

Impacted teeth, crowding, hypodontia, supernumeraries, hypo plastic teeth, caries.

53
Q

What is achondroplasia ?

A

Problem with endochondrial ossification affecting long bones and base of skull.

54
Q

What are the facial features of achondroplasia ?

A

Shortened long bones.
Defects in base of skull.
Retrusive middle third of the face.
Frontal bossing.
Depressed nasal bridge and no nasal cartilage - prevents maxillary forward growth.

55
Q

What is Crouzon’s syndrome ?

A

Premature closure of cranial sutures (coronal and lambdoid) and requires surgical intervention i.e. distraction osteogenesis.

56
Q

What are the facial features of Crouzon’s syndrome ?

A

Proptosis of eyes (shallow orbits) and orbital dystopia.
Retrusion and vertical shortening of mid face.
Prominent nose.
Class III malocclusion - maxilla growth affected and mandible not.
Narrow spaced teeth.

BDS3 CDS Ortho (8 decks)

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