Craniofacial development Flashcards

1
Q

What are the pharyngeal arches?

A

Outpouchings on left and right side of the pharynx

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2
Q

How are pharyngeal arches separated on the ectoderm?

A

by the pharyngeal clefts - external

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3
Q

How are pharyngeal arches separated on the endoderm?

A

by the pharyngeal pouches (internal)

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4
Q

How are the pharyngeal arches named?

A

I, II, III, IV, VI - arch V does not develop

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5
Q

What does each pharyngeal arch contain?

A
  1. cartialge
  2. artery
  3. mesoderm (for muscle)
  4. specific cranial nerve
  5. skeletal component derived from ectomesenchyme
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6
Q

Which cranial nerve innervates pharyngeal arch I?

A

trigeminal nerve - CNV

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7
Q

Which cranial nerve innervates pharyngeal arch II?

A

facial nerve - CNVII

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8
Q

Which cranial nerve innervates pharyngeal arch III?

A

Glossopharyngeal nerve -CNIX

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9
Q

Which cranial nerve innervates pharyngeal arch IV?

A

vagus nerve (CNX)

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10
Q

Which cranial nerve innervates pharyngeal arch VI?

A

vagus nerve (CNX)

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11
Q

What muscles are formed from pharyngeal arch I?

A
  1. muscles of mastication (temporalis, masseter)
  2. myelohyoid for swallowing and speaking
  3. muscle stabilising the hyoid bone while swallowing (anterior belly of digastric muscle)
  4. tensor veli platini
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12
Q

What muscles are formed from pharyngeal arch II?

A
  1. muscles of facial expression
  2. stylohyoid
  3. posterior belly of digastric muscle (stabilises hyoid bone)
  4. stapedius
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13
Q

What muscles are formed from pharyngeal arch III?

A

Stylopharyngeus (stabilises pharynx in swallow)

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14
Q

What muscles are formed from pharyngeal arch IV?

A
  1. pharyngeal constrictors
  2. soft palate
  3. levator veli palatini (elevates soft palate in swallow)
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15
Q

What muscles are formed from pharyngeal arch VI?

A

Intrinsic muscles of larynx - move vocal cords to produce speech sounds

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16
Q

What are the skeletal derivatives of pharyngeal arch I?

A
  1. Meckel’s cartilage
  2. ear cartilage
  3. malleus
  4. incus
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17
Q

What are the skeletal derivatives of pharyngeal arch II?

A
  1. stapes
  2. styloid process
  3. part of hyoid bone
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18
Q

What are the skeletal derivatives of pharyngeal arch III?

A

hyoid bone

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19
Q

What are the skeletal derivatives of pharyngeal arch IV?

A
  1. laryngeal arches
  2. epiglottis
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20
Q

What does the first pharyngeal cleft form?

A

External ear

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21
Q

What happens to the pharyngeal clefts?

A

I - grows into outer ear
All others grow over

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22
Q

What does pharyngeal pouch I form?

A

Ear cavity and auditory tube

23
Q

What does pharyngeal pouch II form?

A

The palatine tonsil

24
Q

What does pharyngeal pouch III form?

A

Inferior parathyoid gland and thymus

25
Q

What does pharyngeal pouch IV form?

A

superior parathyroid gland

26
Q

What forms the mandibular arch?

A

pharyngeal arch I

27
Q

What forms the hyoid arch?

A

pharyngeal arch II

28
Q

Where does the maxixiallry process come from?

A

Branches from the mandibular arch to above it

29
Q

When does the tongue begin development?

A

In the 4th week

30
Q

Where do the tongue muscles develop from?

A

mesoderm cells further back in spinal cord, not form pharyngeal area

31
Q

What part of the tongue is formed by pharyngeal arch I?

A

mucosa of anterior 2/3 tongue from lateral lingual swellings

32
Q

What part of the tongue is formed by pharyngeal arch II?

A

taste buds on anterioe 2/3

33
Q

What part of the tongue is formed by pharyngeal arch III?

A

mucosa and tastebuds of posterior 1/3

34
Q

Which arch do the majority of defects affect?

A

1

35
Q

What can pharyngeal arch defects affect?

A
  1. underdeveloped mandible
  2. absent or reduced malleus or incus
  3. malformed external ears
36
Q

What happens at 4 weeks in relation to facial development?

A
  1. pharyngeal arches have developed
  2. mouth is a slit between frontonasal processes and mandibular processes
  3. nose and nasal cavities will form from nasal pits
37
Q

Where does the frontonasal process arise from?

A

grows from ectomesenchymal cells that migrate to the region and begin to form new growth

38
Q

Where do the nasal placodes arise from?

A

in the frontal nasal process due to the growth of ectomesenchyme cells

39
Q

What will the nasal placodes eventually form?

A

olfactory epithelium in the roof of the nasal cavity

40
Q

How is the intermaxillary process formed?

A

from fusion of the medial sides of the nasal pits (the primary nasal septum)

41
Q

What will the intermaxillary process form?

A
  1. primary nasal septum
  2. primary palate
  3. philtrum
42
Q

How is the primary palate formed?

A

Same tissue as the primary septum (intermaxillary process) extends out horizontally and posteriorly

43
Q

How is the primitive nasal cavity separated?

A

by the primary nasal septum which extends horizontally at its inferior border as the primary palate

44
Q

How is the philtrum formed?

A

from the intermaxillary tissue which fuses on both sides of the maxillary process

45
Q

How is the maxillary process formed?

A

New tissue grows dorsally from the mandibular arch

46
Q

What will the maxillary process form?

A

the cheeks and secondary palate

47
Q

What do the maxillary processes fuse with ?

A
  1. the mandible below
  2. fuse with lateral nasal processes
  3. fuse with medial nasal processes and intermaxillary tissue to form philtrum
48
Q

What is macrostomia?

A

incomplete fusion between maxillary and mandibular processes

49
Q

What is the secondary palate?

A
  1. the roof of the mouth which separates the oral cavity from the nasal cavity
  2. anterior 2/3 is bone (hard palate)
  3. posterior 1/3 is several soft muscles with roles in breathing and swallowing (soft palate)
50
Q

What is the hard palate formed from?

A

from outgrowths of the maxilla called the palatine processes and the horizontal plates of the palatine bones

51
Q

What happens to the palate at 7-8 weeks?

A
  1. tongue forms in floor of mouth and fills the oro-nasal space
  2. palatine processes are therefore deflected down towards the tongue
52
Q

What happens to the palate at 8 weeks?

A
  1. developing brain acquires a cervical flecture which lifts the head away from the cardiac bulge
  2. mandible widens allowing tongue to drop to floor of mouth
  3. palatine shelves elevate into horizontal position above tongue
53
Q

What happens to the palate at week 10?

A
  1. all processes have grown to the point where they make contact and fuse
  2. palatine processes fuse with each other, primary palate, and nasal septum