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NE Exam 1 > Embryology: Derivatives of Pharyngeal Apparatus > Flashcards

Embryology: Derivatives of Pharyngeal Apparatus Flashcards

1
Q

When do the PAs start developing?

A

4th week when neural crest cells migrate into the future head and neck

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2
Q

1st pair of arches, the ___ ___, appear lateral to the developing pharynx

A

Primordial jaws

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3
Q

What arches are rudimentary and not visible on the surface of the embryo the 4th week?

A

5th/6th arches – eventually disappear completely

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4
Q

Neural Crest Cells migrate from ___ (Prosencephalon), ___ (Mesencephalon), and ____ (Rhombencephalon) during the 4th week.

A
  • Forebrain
  • Midbrain
  • Hindbrain
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5
Q

NCC from forebrain and midbrain form the ___ ___

A

Frontal Process (FNP)

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6
Q

NCC from the midbrain and hindbrain form the (1) ___ and the (2) ____

A

(1) Maxillary (MXP)
(2) Mandibular

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7
Q

What would happen if NCC from midbrain and hindbrain didn’t separate into Maxillary and Mandible?

A

You wouldn’t have a jaw

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8
Q

Each PA consists of a core of ___ and ____, covered externally by ___ and internally by ___

A
  • Mesoderm and Mesenchyme
  • Ectoderm
  • Endoderm
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9
Q

Mesenchyme

A

Embryonic connective tissue derived from migratory NCC

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10
Q

Head Mesoderm

A

Mesoderm arising from Paraxial Mesoderm

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11
Q

Once formed, the PA:
(1)
(2)

A

(1) support the lateral walls of the Primitive Pharynx
(2) give rise to facial prominences that contribute to craniofacial development

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12
Q

Pharyngeal ___ plays an essential role in regulating the development of the arches.

A

Endoderm

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13
Q

What are the 4 PA components?

A

(1) NCC-Derived Mesenchyme
(2) Paraxial Mesoderm
(3) Lateral Plate Mesoderm
(4) Prechordal Plate Mesoderm

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14
Q

What does NCC-Derived Mesenchyme form?

A

All connective tissue in the head, including the dermis and smooth muscle

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15
Q

What does the Paraxial Mesoderm form?

A

It populates each arch to from PA musculature (the muscles that arise from each arch)

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16
Q

What does the Lateral Plate Mesoderm form?

A

Angioblasts that differentiate into endothelium (blood vessel formation)

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17
Q

What does the Prechordal Plate Mesoderm form?

A

Extraocular musculature (the muscles that move your eyes)

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18
Q

What 4 main elements do PAs house?

A

(1) Cartilaginous Rod: forms skeletal elements
(2) Muscular Component: forms muscles of the head/head
(3) Cranial Nerves: with sensory and/or motor components
(4) Arch Artery: form vasculature of the head/neck

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19
Q

What will the first arch cartilage form?

A
  • Malleus and Incus
  • Perichondrium -> anterior ligament of malleus and sphenomandibular ligament
  • Meckel’s Cartilage -> primordium of mandible (bone forms lateral to this cartilage, which eventually disintegrates)
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20
Q

What is cartilage of the 2nd PA called?

A

Riechert’s Cartilage

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21
Q

What does the Second Arch Cartilage (Riechert’s cartilage) form?

A
  • Contributes to stapes and styloid process of temporal bone; remainder disintegrates
  • Perichondrium -> Stylohyloid Ligament
  • Lesser cornu/horn and upper body of Hyoid Bone
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22
Q

What does the Third Arch Cartilage form?

A
  • Greater cornu/horn and lower body of Hyoid Bone
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23
Q

What does the Fourth Arch Cartilage form?

A

Thyroid and Epiglottal cartilages (Epiglottis doesn’t form until 5th month)

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24
Q

When does the Epiglottis form?

A

Later in the 5th month

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25
Q

What does the Sixth Arch Cartilage form?

A
  • Remaining Laryngeal cartilages (cuneiform, corniculate, arytenoid and cricoid cartilage)

(Uncertain if this cartilage originates from NCCs or mesoderm)

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26
Q

Most muscular components of the arches form from what type of mesoderm?

A

Paraxial

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27
Q

What muscles does the First Arch form?

A

ChewOnThat

  • Muscles of mastication (Temporalis, Masseter, Pterygoids, Mylohyoid, Anterior Belly of Digastric, Tensor Veli Palatini, Tensor Tympani)
  • Muscles are innervated by the Mandibular division of the Trigeminal N (CN V)
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28
Q

What muscles does the Second Arch form?

A

SmileAndSayCheese

  • Muscles of facial expression (Buccinator, Auricular muscles, Occipitofrontalis, Posterior Belly of Digastric, Stylohyoid, Stapedius, Platysma)
  • Muscles are innervated by the Facial N (CN VII)
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29
Q

What muscles does the Third Arch form?

A

ElevateAndDilate

  • Stylopharyngeus
  • Muscle is innervated by Glossopharyngeal N (CN IX)
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30
Q

What muscles does the Fourth Arch form?

A

PushItPushItRealGood

  • Muscles: Pharyngeal constrictors, cricothyroid, Levator Veli Palatini
  • Muscles are innervated by the Superior Laryngeal branch of the Vagus N (CN X)
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31
Q

What muscles does the Sixth Arch form?

A

SoundOff

  • Muscles: Intrinsic Laryngeal Muscles (Cricoarytenoids, Thyroarytenoid)
  • Muscles innervated by the Recurrent Laryngeal branch of Vagus N (CN X)
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32
Q

Extraocular muscles arise from the ___ ___

A

Prechordal Plate
- Levator Palpebrae Superioris, Superior/Medial/Inferior Recti, & Inferior Oblique all innervated by Oculomotor N (CN III)
- Superior Oblique innervated by Trochlear N (CN IV)
- Lateral Rectus innervated by Abducens N (CN VI)

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33
Q

Tongue musculature arises from ___ ___

A

Occipital Myotomes
(Muscles: Extrinsic and Intrinsic Lingual muscles except Palatoglossus; innervated by Hypoglossal N)

34
Q

What nerve supplies the First PA?

A

Trigeminal N (CN V)
- Principal sensory nerve of the head and neck (V2: Maxillary Division)
- Motor nerve for the muscles of mastication (V3: Mandibular Division)

35
Q

What nerve supplies the Second PA?

A

Facial N (CN VII)

36
Q

What nerve supplies the Third PA?

A

Glossopharyngeal N (CN IX)

37
Q

What nerve supplies the Fourth PA?

A

Superior Laryngeal Branch of Vagus N (CN X)

38
Q

What nerve supplies the Sixth PA?

A

Recurrent Laryngeal Branch of Vagus N

39
Q

Endothelium of the head vasculature and aortic arch arteries arise from what mesoderm?

A

Lateral Plate Mesoderm

40
Q

Aortic Arch Arteries

A

Basket-like structure that initially consists of 5 pairs of arteries arising from the Aortic Sac

41
Q

Arteries arising from which aortic arches are bilateral?

A

Arteries arising from 1st-3rd Aortic Arch Arteries are bilateral

42
Q

Arteries arising from which aortic arches are asymmetrical?

A

4th and 6th

43
Q

Aortic Arch Arteries can contribute to ____ ___ when they do not form as expected

A

Cardiovascular Anomalies

44
Q

First Arch Syndrome

A
  • Abnormal development of the components of the first arch
  • Leads to malformations of the eyes, ears, mandible and palate
45
Q

What is First Arch Syndrome a result of?

A

Insufficient migration (likely due to early apoptosis) of NCC into the 1st arch during the 4th week

46
Q

Treacher-Collins Syndrome (Mandibulofacial Dysostosis)

A
  • Malar Hypoplasis with down-slanting palpebral fissures, defects of lower eyelids, deformed external ears and sometimes middle and internal ears
  • Autosomal dominant disorder
47
Q

Treacher-Collins Syndrome is a result of what gene mutation?

A

Treacher-Collins Franceschetti Syndrome 1 Gene (TCOF1)
- encodes for the protein TREACLE which is involved in ribosome biogenesis
- truncated in TCS leading to increased apoptosis of cranial NCC

48
Q

Pierre Robin Sequence

A
  • Typically occurs de novo in most patients
  • Associated with hypoplasia of the mandible, cleft palate, and defects of the eyes & ears
49
Q

What is the initiating defect of Pierre Robin Sequence? What does this defect lead to?

A

Small mandible (micrognathia) -> posterior displacement of tongue -> obstruction of full closure of the palate -> bilateral cleft palate

50
Q

Where are Pharyngeal Grooves located? What are they covered with?

A
  • Located externally between Pharyngeal Arches
  • Covered with Ectoderm
51
Q

Where are Pharyngeal Pouches located? What are they covered with?

A
  • Located internally as part of the pharynx
  • Covered with Endoderm
52
Q

First pair of Pharyngeal Grooves and Pouches are located between the __ and __ arches with ___ ___ located between them

A
  • 1st and 2nd
  • Pharyngeal Membranes
53
Q

What does the First Pharyngeal Groove form?

A

External Acoustic Meatus

54
Q

Pharyngeal Grooves 2-4 lie in the ___ ___ which is eventually obliterated by PA tissue closure of 2, 3 and 4

A

Cervical Sinus (called a sinus because still open)

55
Q

Birth defects of what groove are most common?

A

2nd Pharyngeal Groove (occurs when cervical sinus doesn’t close)

56
Q

The First Pharyngeal Pouch expands into what? What does this become?

A

Tubotympanic Recess -> Tympanic Cavity & Mastoid Antrum

57
Q

What does the First Pharyngeal Pouch elongate to form?

A

Pharyngotympanic Tube

58
Q

Endoderm from the First Pharyngeal Pouch contacts the First Pharyngeal Groove (contact of these two results in formation of the 1st Membrane) which contributes to:

A

Tympanic Membrane

59
Q

1st Membrane + Intervening Mesenchyme (from middle of PA) forms:

A

Tympanic Membrane

60
Q

Portion of the 2nd Pouch forms the:

A

Tonsillar Sinus

61
Q

Endoderm from the 2nd Pouch forms the:

A

Tonsillar Epithelium

62
Q

Mesenchyme from the 2nd Pouch forms the:

A

Lymphoid Nodules (that give rise to the Palatine Tonsil)

63
Q

Dorsal portion of the 3rd Pouch differentiates into:

A

Inferior Parathyroid Gland

64
Q

Ventral portion of the 3rd Pouch differentiates into:

A

Thymus

65
Q

The Inferior Parathyroid Glands and Thymus migrate ___

A

Caudally
(due to the growth of the brain and cardiac regions)

66
Q

Dorsal portion of the 4th Pouch differentiates into:

A

Superior Parathyroid Glands

67
Q

Ventral portion of the 4th Pouch gives rise to the:

A

Ultimobranchial Body

68
Q

What does the Ultimobranchial Body fuse with? What does it form?

A

Fuses with the Thyroid Gland and gives rise to Parafollicular Cells

69
Q

Branchial Anomalies: External Cervical Sinus

A
  • Failure of 2nd groove and cervical sinus to obliterate/combine
  • Typically external; internal is rare
  • Detected due to discharge of mucus (b/c lined with epithelium)
  • Commonly associated with auricular sinuses (near Tragus of ear)
70
Q

Branchial Anomalies: Internal Cervical Sinus

A
  • Persistence of 2nd Pouch
  • Rare
  • Open into tonsillar sinus or near Palatopharyngeal Arch
  • Also can be detected due to discharge of mucus (b/c lined with epithelium)
71
Q

Branchial Anomalies: Cervical Cysts

A
  • Remnants of cervical sinus and/or 2nd Groove; outer surface of cyst is encapsulated in cyst
  • Slowly enlarging, painless, free-lying cyst in the neck, inferior to angle of mandible
  • Over time can accumulate fluid and cellular debris (can causing bulging, problems swallowing, infection)
72
Q

Branchial is same thing as Pharyngeal

A
73
Q

Branchial Anomalies: Cervical Fistula

A
  • Canal that opens into Tonsilar Sinus and external side of neck (essentially an opening in the skin of the neck that has a canal with an internal opening into the tonsillar sinus where the palatine tonsil is located)
  • Persistence of parts of cervical sinus and tonsillar sinus (2nd pouch)
  • Ascends through subcutaneous tissue and Platysma to reach carotid sheath; passes between carotids and opens into tonsillar sinus
  • Would allow for leakage of food and liquids; prone to infections
74
Q

When does Thyroid Gland start developing?

A

24 days after fertilization
(first endocrine gland to develop!)

75
Q

What does the Thyroid Gland form from?

A

Endodermal thickening in the floor of the Primordial Pharynx

76
Q

Thyroid Gland Development

A

(1) Endodermal thickening in floor of Primordial Pharynx -> Thyroid Primordium
(2) Descends in the neck (through the Foramen Cecum) as the tongue grows -> moves ventral to hyoid bone an dlaryngeal cartilages
(3) Once in new position, it is still connected to the tongue by a narrow tube called the Thyroglossal Duct
(4) Promordium is hollow but eventually becomes a solid cellular mass, that divides into right/left lobes conneccted by the isthmus
(5) Definitive shape by 7 weeks and thyroglossal duct with degenerate

77
Q

Thyroid Gland Development Anomalies: Ectopic Thyroid Tissue

A
  • If this anomaly occurs, the extra thyroid tissue is often in accessory, lingual or cervical regions
  • Extra tissue forms along the course of the duct
78
Q

Example of a Thyroid Gland Development Anomaly

A

Sublingual Thyroid Gland forms but does not descend in the neck, just sits below the tongue

79
Q

Thyroid Gland Development Anomalies: Thyroglossal Duct Cyst

A
  • Forms in tongue or anterior neck
  • Critical to distinguish from ectopic thyroid prior to surgical removal
  • Results from persistent Thyroglossal Duct
  • Can cause problems swallowing
80
Q

Congenital Anomalies of Thyroid Gland: Agenesis

A

Absence of a thyroid gland or one of its lobes (rare)

81
Q

Congenital Anomalies of Thyroid Gland: Thyroid Hemiagenesis

A
  • Unilateral failure of formation
  • Left lobe more commonly absent
  • Mutations in the receptor for the thyroid-stimulating hormone are likely involved
82
Q

DiGeorge Syndrome

A
  • Breakdown of signaling from PA endoderm to NCC
  • Often caused by chromosomal deletion which impairs signaling from endodermal lining in the pouches – w/o signaling then NCC doesn’t know what to do
  • Associated signs/sxs: agenesis of thymus and parathyroid glands, congenital hypoparathyroidism, shortened philtrum of upper lip and low-set and notched ears, nasal clefts, thyroid hypoplasia, cardiac abnormalities (defects in aortic arch and heart)

NE Exam 1 (14 decks)

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