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ESA4 > Head and Neck Embryology > Flashcards

Head and Neck Embryology Flashcards

1
Q

What are the pharyngeal arches?

How many are there?

A

Mesenchyme proliferations in the lateral walls of the embryonic pharynx, each with an associated artery, vein nerve.

5, numbered 1 to 6 (no 5!)

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2
Q

What are the pharyngeal arches covered by?

A

ectoderm externally

endoderm internally

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3
Q

What are the embryological names for the forebrain, midbrain and hindbrain?

A

prosencephalon
mesencephalon
rhombencephalon

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4
Q

Which nerve is derived from the first pharyngeal arch?

What is its function?

A

Trigeminal CNV

sensory innervation. motor to muscles of mastication

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5
Q

Which nerve is derived from the second pharyngeal arch?

What is its function?

A

Facial CNVII

motor innervation to muscles of facial expression. special sensory to anterior 2/3rds of tongue

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6
Q

Which nerve is derived from the third pharyngeal arch?

What is its function?

A

Glossopharyngeal CNIX

motor to stylopharyngeus. general and special sensory to posterior 1/3rd of tongue

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7
Q

Which nerve is derived from the fourth and sixth pharyngeal arch?
What is its function?

A

Vagus Nerve CNX
4 = superior laryngeal nerve to cricothyroid and constrictors of pharynx
6 = recurrent laryngeal nerve to intrinsic pharynx muscles

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8
Q

Which cartilage bar is derived from the first pharyngeal arch?
What is its function?

A

Meckel’s cartilage
Forms the:
template for mandible which forms by membranous ossification
malleus and incus

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9
Q

Which cartilage bar is derived from the second pharyngeal arch?
What is its function?

A 
Reichert's
Forms the:
styloid process 
lesser cornu and upper body of the hyoid
stapes
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10
Q

What bone/s are derived from the third pharyngeal arch?

A

remainder of the hyoid bone

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11
Q

What cartilage/s are derived from the fourth/sixth pharyngeal arch?

A

thyroid
arytenoid
cricoid
epiglottis

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12
Q

Where are the pharyngeal pouches found?

A

The inner surface between the pharyngeal arches

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13
Q

What does the second pharyngeal pouch give rise to?

A

palatine tonsil

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14
Q

What do the third and fourth pharyngeal pouches give rise to?

A

They divide into ventral and dorsal compartments.
dorsal become the parathyroid gland
ventral 3rd becomes the thymus
ventral 4th become the c cells of the thyroid

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15
Q

Where are the pharyngeal clefts found?

A

The outer surface between the pharyngeal arches

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16
Q

What happens to the pharyngeal clefts?

A

the first pharyngeal cleft remains, forming the external auditory meatus
the second arch grows down to cover the third to sixth arches and grooves, creating the cervical sinus

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17
Q

What is a branchial cyst?

A

the cervical sinus persists along the border of the cricothyroid

18
Q

What type of mesenchyme is present in the pharyngeal arches?

What do they become?

A

some mesoderm, becoming muscle

most neural crest cells, becoming bone/cartilage

19
Q

What does the first pharyngeal pouch give rise to?

A

Eustachian tube

middle ear cavity

20
Q

What does the neural crest of the first pharyngeal arch give rise to?

A

facial skeleton

21
Q

What does the mesoderm of the second pharyngeal arch give rise to?

A

muscles of facial expression

22
Q

What does the mesoderm of the first pharyngeal arch give rise to?

A

muscles of mastication

23
Q

Which structures does the face develop from?

A

frontonasal prominence

1st pharyngeal arch

24
Q

Where does the oral fissure develop?

A

stomatodeum

buccopharyngeal membrane - no mesoderm!

25
Q

The first pharyngeal arch divides into the ….. during the formation of the face

A

maxillary prominence

mandibular prominence

26
Q

The FNP gives rise to

A

the bridge of the nose
the forehead
the philtrum

27
Q

The maxillary prominence gives rise to

A

cheeks
lateral upper lip
upper jaw

28
Q

The mandibular prominence gives rise to

A

lower jaw

lower lip

29
Q

Describe the development of the nose

A
  1. Nasal placodes appear in the FNP laterally
  2. sink to become nasal pits
  3. medial and lateral nasal prominences form either side of the pits
  4. the prominences are pushed closer together as the 5.maxillary prominences grow medially
  5. the medial nasal prominences fuse, creating the intermaxillary segment (gives rise to philtrum, 4 upper incisors, primary palate)
  6. the maxillary prominences then fuse with the medial nasal prominences
30
Q

How is the definitive palate formed?

A

the palatal shelves derived from the maxillary prominences grow vertically downwards into the oral cavity on either side of the tongue
the tongue’s position (because of the underdeveloped mandible) prevents fusion at this point
when the mandible grows large enough for the tongue to drop, the palatal shelves fuse in the midline
the nasal septum fuses with the palate in the midline

31
Q

Why is the lip and palate described as having a dual origin?

A

FNP = intermaxillary segment = primary palate

1st arch = maxillary prominences = secondary palate

32
Q

What causes lateral cleft lip?

A

failure of the medial nasal prominence and the maxillary prominence (primary palate) to fuse

33
Q

What causes cleft lip and palate?

A

failure of the medial nasal prominence and the maxillary prominence (primary palate) to fuse
combined with failure of the palatal shelves to meet in the midline

34
Q

What do organs of special sense develop from?

A

placodes

35
Q

Describe the development of the eyes

A

4th week = outpocketings of forebrain grow to make contact with overlying ectoderm = optic vesicles
optic placodes form => lens placode
optic vesicles make contact with the lens placode
the placode thickens, invaginates and pinches off forming the lens
the retina is derived from the forebrain

36
Q

How do the eyes move from the side of the head?

A

AS the facial prominences grow, they push the eyes to the front of the face
enables binocular vision

37
Q

Describe the development of the external ear

A

the 1st pharyngeal cleft gives the external auditory meatus

proliferations from the 1st and 2nd arches give the auricles

38
Q

Where do the external ears first form?

How do they move?

A

in the neck

the mandible’s growth forces the ears to ascend

39
Q

Describe the development of the inner ear

A

the otic placodes thicken and invaginate, forming the auditory vesicles.
the cochlea and semilunar system form

40
Q

Which parts of development is particularly sensitive to alcohol?

A

neural crest migration

development of the brain

41
Q

List some characteristics of fetal alcohol syndrome

A 
microencaphaly
low nasal bridge
small palpebral fissures
smooth filtrum
minor ear abnormalities

ESA4 (4 decks)

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