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Neuro Block 4 - KJ > Embryology of Head & Neck > Flashcards

Embryology of Head & Neck Flashcards

1
Q

Define Pharyngeal (brachial) apparatus:

A
  • Surrounds developing foregut
  • Source of mesenchymal tissue that will form the head & neck, face, palate & nasal cavity structures
  • Target for migrating neural crest cells that differentiate into skeletal, muscular and neural structures
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2
Q

What are the parts of the pharyngeal apparatus?

A
  • Arches
  • Clefts
  • Pouches
  • Membranes
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3
Q

What are the pharyngeal arches?

A

Bars of mesenchyme covered with ectoderm externally and endoderm internally. Form around the developing gut tube (pharynx)

  • Contribute to viscerocranium
  • Five pairs
  • Lateral plate mesoderm forms initial shape of pharyngeal arches
  • Branch of aorta associated with each arch
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4
Q

What is present by weeks 4-5?

A

Primordial of head, neck, face, palate & nasal cavity

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5
Q

What are the pharyngeal clefts (grooves)?

A
  • Four pairs
  • Surface ectoderm - lined invaginations
  • Form between the pharyngeal arches (depressions between the arches)
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6
Q

What are the pharyngeal pouches?

A
  • EPITHELIAL
  • Develop in cranial to caudal direction
  • Four pairs
  • Endoderm - lined pouches along the lateral walls of the pharyngeal gut
  • Located opposite the pharyngeal clefts
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7
Q

What are the pharyngeal membranes?

A
  • Separate the ‘pouches’ from the ‘clefts’
  • Consist of ectoderm (externally), endoderm (internally) and mesenchyme in between
  • Membranes do NOT break down in humans, so clefts and pouches do not communicate! [no gills]
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8
Q

What are the five facial prominences?

A
  • 1 Frontonasal prominence
  • 2 Maxillary prominences (first pharyngeal arch mesenchyme)
  • 2 Mandibular prominences (first pharyngeal arch mesenchyme)
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9
Q

What cell types migrate into the arches as they are forming?

A
  • Mesoderm from Somites & Somitomeres
  • Neural Crest
  • Nerves
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10
Q

Where does mesoderm from somites and somitomeres go?

A

Migrate into the arches

  • Eye muscle precursors from occipital somites
  • Forms most of skeletal muscle in head & parts of skull
  • Tongue precursors from occipital somites
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11
Q

What do neural crest cells that migrate to the pharyngeal arches form?

A

-Skeletal elements of the head & parts of the PNS

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12
Q

What pharyngeal membrane do you need to know about?

A

1st Membrane!

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13
Q

What structure develops from the 1st pharyngeal membrane?

A

Tympanic Membrane (only membrane to persist - has 3 layers: endoderm, mesoderm, ectoderm)

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14
Q

How many pharyngeal clefts are there?

A

4!

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15
Q

What develops from the first pharyngeal cleft?

A

External auditory meatus (epithelial lining)

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16
Q

What develops from the second, third and fourth pharyngeal cleft?

A

Cervical Sinus

  • Normally disappears
  • Lateral cervical (branchial) cyst or fistula when it persists
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17
Q

What develops from the first pharyngeal pouch?

A

Tubotympanic recess —> becomes:

  • Auditory tube (epithelial lining)
  • Tympanic or middle ear cavity (epithelial lining)
  • Mastoid air cells
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18
Q

What develops from the second pharyngeal pouch?

A

-Palatine tonsils

epithelial component

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19
Q

What develops from the third pharyngeal pouch?

A
  • Thymus (ventral)

- Inferior Parathyroid Glands (dorsal)

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20
Q

What develops from the fourth pharyngeal pouch?

A
  • Superior parathyroid glands (dorsal)

- Ultimobranchial bodies (ventral) -AKA parafollicular cells of thyroid

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21
Q

What are the pharyngeal arches?

A

First, Second, Third, Fourth and Sixth

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22
Q

What nerve innervates each of the 5 arches?

A

1st - Trigeminal Nerve (V3)
2nd - Facial Nerve (CN VII)
3rd - Glossopharyngeal Nerve (CN IX)
4th - Vagus Nerve (CN X) - Superior Laryngeal
6th - Vagus Nerve (CN X) - Recurrent Laryngeal

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23
Q

What skeletal parts arise from the first pharyngeal arch?

A 
Maxillary prominence (upper jaw):
-Maxilla
-Zygomatic
-Squamous part of temporal bone
(intramembranous ossification)
Mandibular prominence (lower jaw):
-Malleus -Incus (endochondral ossification)
-Anterior Ligament of Malleus
-Spin of Sphenoid
-Sphenomandibular ligament
(all from Meckel's Cartilage)
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24
Q

What cartilage does the first arch skeleton develop from?

A

Meckel’s Cartilage

25
Q

What muscles derives from the first pharyngeal arch?

A

“Tense, tense, chew, chew”

  • Muscles of mastication (temporals, masseter)
  • Mylohyoid
  • Anterior belly of digastric
  • Tensor tympani
  • Tensor Veli Palatini
26
Q

What skeletal components are from the 2nd pharyngeal arch?

A

-Stapes -Styloid process
-Stylohyoid Ligament
-Lesser cornu
-Upper body of hyoid bone
[All from Reichert’s cartilage]

27
Q

What muscle components are from the 2nd pharyngeal arch?

A
  • Muscles of facial expression
  • Posterior belly of the digastric
  • Stylohyoid
  • Stapedius
28
Q

What skeletal components are from the 3rd pharyngeal arch?

A
  • Lower body of the hyoid bone

- Greater Cornu

29
Q

What muscle is derived from the 3rd pharyngeal arch?

A

-Stylopharyngeus

30
Q

What skeletal components are derived from the fourth and sixth arch?

A

Thyroid Cartilage

Cricoid Cartilage

31
Q

What muscles are derived from the 4th pharyngeal arch?

A
  • Muscles of soft palate (except tensor veil palatini)
  • Muscles of pharynx (except stylopharyngeus)
  • Cricothyroid
  • Cricopharyngeus
32
Q

What muscles are derived from the 6th pharyngeal arch?

A
  • Intrinsic muscle of larynx (except cricothyroid)

- Striated (upper) muscle of esophagus

33
Q

What innervates the palatoglossal muscle? Motor or sensory?

A

Palatoglossus (Vagus Nerve, CN X) - Motor

34
Q

What does motor innervation for almost all tongue muscles?

A

Hypoglossal Nerve (CN XII)

35
Q

What provides general sensory information to the 4th arch/middle back of tongue?

A

Internal Laryngeal Nerve (CN X)

36
Q

What provides general and special sensory information to the 3rd arch (back 1/3 of tongue & vallate papillae)?

A

Glossopharyngeal Nerve (CN IX)

37
Q

What supplies general sensory information to the anterior 2/3 of the tongue?

A

Lingual Nerve (V3)

38
Q

What supplies special sensory information to the anterior 2/3 of the tongue?

A

Chorda tympani (CN VII) -taste afferents

39
Q

What supplies general & special visceral sensory information (GI, heart, etc.) from the epiglottis?

A

Vagus Nerve (CN X)

40
Q

What part of the tongue develops from 1st arch mesenchyme?

A

Anterior 2/3 of tongue (oral part)

-From median tongue bud and two distal tongue buds (these overgrow and fuse)

41
Q

What part of the tongue develops from 2nd arch mesenchyme?

A

Copula

-3rd arch overgrows 2nd arch, so arch 2 doesn’t contribute to tongue mucosa

42
Q

What part of the tongue develops from 3rd arch mesenchyme?

A

Posterior 1/3 (root of pharyngeal part)

-Hypobranchial eminence

43
Q

What part of the tongue develops from 4th arch mesenchyme?

A
  • Hypobranchial eminence
  • Epiglottis
  • Extreme posterior tongue
44
Q

What do myoblasts become?

A

Most tongue muscles are derived from them (they migrate with hypoglossal nerve from occipital myotomes)

45
Q

What is the terminal sulcus?

A

Boundary between anterior 2/3 and posterior 1/3 of tongue

-Former position of buccopharyngeal membrane

46
Q

Where can you have stenosis or atresia (narrowed/closed off)?

A
  • Ear Canal
  • Nasal Passage
  • Larynx
  • Esophagus
  • Trachea
47
Q

Where can you have clefts?

A
  • Ear pit
  • Nasal masses
  • Face
  • Lip
  • Palate
  • Larynx
  • Tracheal-Esophageal
48
Q

What are some vestigial structures that were supposed to be obliterated but persisted?

A
  • Thyroglossal duct

- Branchial cleft

49
Q

What is caused by a deficiency of neural crest cells migrating into the first pharyngeal arch?

A

Treacher Collns Syndrome & Pierre Robin Syndrome

50
Q

What are the symptoms and cause of Treacher Collins Syndrome?

A
  • Mandibulofacial dysostosis
  • Abnormal development of structures derived from the first arch
  • Hypoplasia of upper & lower jaw; external & middle ear deformities, palate & eyelid defects
  • Conductive hearing loss
  • Autosomal dominant and/or teratogenic cause
51
Q

What can the face look like for a child with Treacher Collins?

A
  • Eyelid Malformation
  • Hypoplastic Cheek and Jaw
  • External Ear malformation and low-set
  • “Fishmouth” appearance
52
Q

What is Pierre Robin Syndrome?

A
  • Deficiency of neural crest cells migrating into the arch
  • Abnormal development of structures derived from the first arch
  • Micrognathia + large, posteriorly placed tongue ->airway obstruction (glossoptosis)
  • U-shaped cleft palate problems
53
Q

What causes Pierre Robin Syndrome?

A

Genetic and/or environmental etiology

54
Q

What can be used in severe cases of Pierre Robin syndrome?

A
  • Distraction osteogenesis (pulling mandible apart to induce bone growth) (mandibular lengthening) is employed
  • May need tracheostomy to maintain airway while mandibular lengthening is occurring
  • 1/8,500 births
55
Q

What is the function of the inferior and superior parathyroid glands?

A

Increase blood Ca2+

56
Q

What is the function of the Ultimobranchial bodies?

A

Decrease blood Ca2+ (Calcitonin)

57
Q

What is DiGeorge Syndrome?

A
  • Genetic and/or environmental causes (micro deletion of Chr. 22q11.2)
  • No thymus or parathyroids (diminished immunity, hypocalcemia)
  • Failure of neural crest migration into arches –> 3rd & 4th pouch failure & hypoplasia of 1st arch (cleft palate, low set ears, poor feeding, delayed speech)
  • Heart defects, poor circulation, poor muscle tone
58
Q

What are the “CATCH-22” Symptoms of DiGeorge Syndrome?

A 
Cardiac Abnormalities
Abnormal facies
Thymic aplasia
Cleft palate
Hypocalcemia
22 - deletion/abnormality of chromosome 22
59
Q

What happens when the cervical sinus (from the 2nd, 3rd & 4th clefts) persists?

A

It is called a lateral cervical (branchial) cyst or fistula

Neuro Block 4 - KJ (12 decks)

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