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NeuroEndo Test 1 > Embryology of the Pharyngeal Apparatus > Flashcards

Embryology of the Pharyngeal Apparatus Flashcards

1
Q

When do the pharyngeal arches develop? What are they derived from?

A

4th week

Neural crest

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2
Q

How are the pharyngeal arches organized (layer wise)?

A

Arch is lined externally by ectoderm and internally by endoderm
Core is initially mesenchyme from Neural Crest but then true mesoderm migrates in

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3
Q

What is the role of NCC-derived mesenchyme in the pharyngeal arch?

A

form all connective tissue in the head (including dermis)

smooth muscle of vasculature

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4
Q

What is the role of paraxial mesoderm in the pharyngeal arch?

A

populate each arch to from PA musculature

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5
Q

What is the role of lateral plate mesoderm in the pharyngeal arch?

A

angioblast which differentiate into endothelium to line the blood vessels in the face

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6
Q

What is the role of prechordal plate mesoderm in pharyngeal arches?

A

extraocular musculature (orbicularis oculi)

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7
Q

What kind of cartilage is found in PA1? What is its role in development?

A

Meckel’s cartilage

Dorsal portion forms malleus and incus

Ventral= primordium of mandible

Placeholder of lower jaw –> forms mandible (laterally) via inter-membrane ossification

Perichondrium –> anterior ligament of malleus and sphenomandibular ligament

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8
Q

What kind of cartilage is in PA2? What does the dorsal and ventral regions become?

A

Riechert’s cartilage

Dorsal= stapes and styloid process of temporal bone
Ventral= ossifies (intermembraneous) and forms lesser cornu aka horn of hyoid
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9
Q

What is the role of third arch cartilage?

A

Forms greater cornu of hyoid via cartilaginous ossification

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10
Q

Where is the body of hyoid formed from?

A

PA 3 and 4

formed by prominence in embryonic pharynx aka hypopharyngeal eminence

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11
Q

What do the 4th and 6th arch cartilages contribute to?

A

Laryngeal cartilage

- specifically 4th is NCC derived and includes the epiglottis

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12
Q

Where are the muscular components of the PAs derived from?

A

Paraxial mesoderm and prechordal plate

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13
Q

What muscle(s) come from the first arch?

A

Muscle of mastication (CN V) #chewonthat

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14
Q

What muscle(s) come from the second arch?

A

Stapedius m. and muscles of fascial expression (CN VII) #smileandsaycheese

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15
Q

What muscle(s) come from the third arch?

A

Stylopharyngeus (CN IX) #elevateanddialte

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16
Q

What muscle(s) come from the fourth arch?

A 
Circothyroid
Levatator veli palatini
Constrictors of the pharynx 
CN X
#pushitpushitrealgood
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17
Q

What muscle(s) come from the sixth arch?

A 
Intrinsic muscles of the larynx (CN X)
#soundoff
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18
Q

What nerve supplies PA1?

A

The trigeminal nerve: just V2 and V3

  • principal sensory nerve of head and neck
  • motor nerve for muscles of mastication
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19
Q

What nerve supplies PA2?

A

Facial nerve (CN VII) muscles of fascial expression

20
Q

What nerve supples PA3?

A

Glossopharyngeal (CN IX)

Stylopharyngeus m.

21
Q

What nerve supplies PA4?

A

superior laryngeal branch of Vagus N. (CN X) and its recurrent laryngeal branch

22
Q

What nerve supplies PA6?

A

Recurrent (inferior) laryngeal of the Vagus N. (CN X)

23
Q

Where do the arch arteries come from?

A

The aortic sac which is a basket like structure arising from the dorsal aorta
- remodeled into great arteries of the thorax, head and neck

24
Q

Where are pharyngeal grooves located? What are they covered with?

A

Externally, between pharyngeal arches

Ectoderm

25
Q

Where does the first groove lie?

A

External acoustic metaus

26
Q

What do grooves 2-4 lie in?

A

the cervical sinus which closes off during development

27
Q

Where are pharyngeal pouches? What are they derived from?

A

Lines pharynx internally

Pharyngeal endoderm

28
Q

How do cervical cysts arise? What are the symptoms?

A

Remnants of cervical sinus and/or 2nd groove

Slow enlarging painless cyst in neck inferior to angle of mandible\, filled with fluid and cellular debris from desquamation of their epithelial lining

29
Q

How do cervical sinus anomalies arise? What are the symptoms?

A

Failure of 2nd PA groove and cervical sinus to obliterate
Discharge of mucus
Normally bilateral and associated with auricular sinuses

30
Q

How do cervical fistulas arise? What are the symptoms?

A

Abnormal canal that opens into the tonsillar sinus due to persistence of parts of 2nd groove and pouch

31
Q

What are pharyngeal membranes?

A

Where pouch endoderm comes into contact with groove ectoderm
- quickly infiltrated by mesenchyme

32
Q

What does the 1st pharyngeal membrane form?

A

Tympanic mebrane

33
Q

What does the endoderm of the 1st pouch form?

A

Expands into tubotympanic recess –> Tympanic cavity and mastoid antrum

Elongates to form pharyngotympanic tube

Contacts 1st groove contributing to tympanic membrane

34
Q

What does the 2nd pouch form?

A

Tonsillar sinus
Endoderm proliferate and forms tonsillar epithelium
Mesenchyme become lymphoid nodules of palatine tonsil

TONSILS

35
Q

What does the 3rd pouch form?

A 
Dorsal= inferior parathyroid
Ventral= thymus

Caudally migrates aka pulls structures down

36
Q

What does the 4th pouch form?

A

Dorsal= superior parathyroid glands

Ultimobranchial body fuses with thyroid gland and gives rise to parafollicular cells

37
Q

Where are epithelial cords derived from? What are their 3 functions?

A

PA3 endoderm which form the thymic primordium

  1. grow into surrounding mesenchyme –> thymic lobules
  2. Become arranged around a central point –> thymic corpuscles
  3. Form epithelial reticulum for housing lymphocytes
38
Q

Where is the thyroid gland derived from?

A

NOT ARCH DERIVATIVE

Comes from developing floor of the pharynx: median endodermal thickening

Descends in neck with tongue growth and passes ventral to developing hyoid and laryngeal cartilage, connected by thyroglossal duct
- only gland moving

39
Q

What is first arch syndrome (generally)?

A

Insufficient migration of NCC into the 1st arch during the 4th week

40
Q

What is Treacher-Collins syndrome?

A

type of first arch syndrome

Autosomal dominant, mutation in TCOF1 which is involved in ribosome biogenesis
- truncation leads to increased apoptosis of cranial NCC

Malar hypoplasia down slanting palperbal fissures, deformed external ear, defects of lower eyelid

41
Q

What is Pierre Robin syndrome?

A

First arch syndrome, Occurs de novo

hypoplasia

Initiating defect= small mandible –> posterior displacement of tongue –> obstruction of closure of the palate –> bilateral cleft palate
- difficulties feeding

42
Q

What is agenesis of thyroid gland?

A

Complete absence of a thyroid gland or one of its lobes

43
Q

What is thyroid hemiagenesis?

A

Unilateral failure of formation

Left lobe more commonly absent

44
Q

What is DiGeorge Syndrome?

A

Breakdown of signlaing from PA enoderm to NCC –> agenesis of thymus and parathyroid glands

CONGENITAL HYPOPARATYROIDISM

Cardiac abnormalities
Nasal clefts, thyroid hyperplasia
Shortened philtrum of upper lip, low set and notched ears

45
Q

What is the foramen cecum a remanent of?

A

Thyroid gland

Little bump on tongue

NeuroEndo Test 1 (14 decks)

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