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Neuro Exam 1 - JLJ > Embryology of Pharyngeal Apparatus > Flashcards

Embryology of Pharyngeal Apparatus Flashcards

1
Q

What makes up the pharyngeal apparatus? What does it contribute to?

A

Pharyngeal arches, pouches, grooves (clefts), and membranes; contributes to formation of nasal cavities, mouth, larynx, pharynx, and neck

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2
Q

Describe the development of the pharyngeal arches

A

Develop early in 4th week as neural crest cells and migrate into future head and neck; 1st pair are called primordial jaws and appear lateral to developing pharynx; arches 2-4 appear as ridges on each side of the future head and neck regions; 5th and 6th are rudimentary and are not visible

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3
Q

What is the function of the pharyngeal arches?

A

Support lateral walls of the primordial pharynx and gives rise to prominences of tissue that contribute to craniofacial development

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4
Q

What does each pharyngeal arch consist of?

A

Core of mesoderm and mesenchyme; covered externally by ectoderm and internally by endoderm

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5
Q

In the pharyngeal arches, what does neural crest cell derived mesenchyme form?

A

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

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6
Q

In the pharyngeal arches, what does the paraxial mesoderm give rise to?

A

Populates each arch to form musculature

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7
Q

In the pharyngeal arches, what does the lateral plate mesoderm give rise to?

A

Angioblasts that differentiate into endothelium

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8
Q

In the pharyngeal arches, what does the prechordal plate mesoderm give rise to?

A

Extraocular musculature (i.e., orbicularis oculi)

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9
Q

What is the function of pharyngeal endoderm?

A

Plays essential role in regulating development of the arches

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10
Q

What does the cartilaginous rod of the pharyngeal arches form?

A

Skeletal elements

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11
Q

What does the muscular component of the pharyngeal arches give rise to?

A

Differentiates into muscles in the head and neck

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12
Q

Describe the arch artery

A

Arises from the truncus arteriosus of primordial heart; passes around the primordial pharynx to enter the dorsal aorta

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13
Q

Meckel’s cartilage is the name of the cartilage of what pharyngeal arch?

A

1

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14
Q

Riechert’s cartilage is the name of the cartilage of what pharyngeal arch?

A

2

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15
Q

The malleus and incus is formed from what?

A

Dorsal portion of meckel’s cartilage

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16
Q

The primordium of the mandible is formed from what?

A

Ventral parts of meckel’s cartilage

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17
Q

The stapes and styloid process of the temporal bone is formed from what?

A

Dorsal region of riechert’s cartilage

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18
Q

The lesser cornu/horn of the hyoid bone is formed from what?

A

Ossification of the ventral end of riechert’s cartilage

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19
Q

The 3rd arch cartilage ossifies and forms what?

A

Greater cornu of hyoid bone

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20
Q

The hypopharyngeal eminence gives rise to what?

A

Body of hyoid bone

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21
Q

What does the 4th arch cartilage give rise to? 6th?

A

4th: laryngeal cartilages including epiglottis (NCC derived)
6th: laryngeal cartilages, but the origin is uncertain

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22
Q

The first arch gives rise to what muscles?

A

Muscles of mastication (CN V)

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23
Q

The second arch gives rise to what muscles?

A

Stapedius and muscles of facial expression (CN VII)

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24
Q

The third arch gives rise to what muscles?

A

Stylopharyngeus (CN IX)

25
Q

The fourth arch gives rise to what muscles?

A

Cricothyroid, levator veli palatini, and constrictors of pharynx (CN X, specifically the superior laryngeal branch and its recurrent laryngeal branch)

26
Q

The sixth arch gives rise to what muscles?

A

Intrinsic muscles of the larynx (CN X)

27
Q

Arteries arising from the 1st-3rd aortic arch arteries are (asymmetrical/bilateral) and the 4th and 6th arch arteries are (asymmetrical/bilateral)

A

Bilateral; asymmetrical

28
Q

The endothelium of the head vasculature and aortic arch arteries arises from what embryonic layer?

A

Mesoderm

29
Q

Describe pharyngeal grooves

A

Located between pharyngeal arches; covered with ectoderm

30
Q

What is the first pharyngeal groove called?

A

External acoustic meatus

31
Q

Where would you find the 2-4 pharyngeal grooves?

A

Cervical sinus

32
Q

What is clinically significant about the 2nd pharyngeal groove?

A

Most common groove to have birth defects

33
Q

Describe the pharyngeal pouches

A

5 pairs, developing in a cranio-caudal sequence; found between the arches, starting inbetween the 1st and 2nd arch

34
Q

What are cervical cysts?

A

Remnants of cervical sinus and/or 2nd groove; persist and form slowly enlarging, painless, free-lying cyst in the neck, inferior to angle of the mandible

Can also come from accumulation of fluid and cellular debris derived from desquamation of epithelial linings

35
Q

Describe a cervical sinus anomaly

A

Failure of 2nd groove and cervical sinus to obliterate; detected due to discharge of mucus; typically associated bilaterally and commonly associated with auricular sinuses

36
Q

What is a cervical fistula?

A

Abnormal canal that opens into tonsillar sinus and externally in the side of the neck; persistence of parts of 2nd groove and pouch

37
Q

Describe pharyngeal membranes, including where they come from?

A

Form where pouch endoderm contacts ectoderm of pharyngeal grooves; quickly infiltrated by mesenchyme

38
Q

The tympanic membrane is formed from what?

A

1st pharyngeal membrane and intervening mesenchyme

39
Q

What does the 3rd pharyngeal pouch give rise to?

A

Dorsal portion differentiates into inferior parathyroid gland; ventral portions form the thymus

40
Q

What does the 4th pharyngeal pouch give rise to?

A

Dorsal portion differentiates into superior parathyroid glands; ultimobranchial body fuses with the thyroid gland and gives rise to the parafollicular cells

41
Q

What is the function of epithelial cords?

A

1) Grow into surrounding mesenchyme called thymic lobules
2) Become arranged around a central point to form thymic corpuscles
3) Form an epithelial reticulum for housing lymphocytes

42
Q

What does the thymic primordium develop from?

A

Pharyngeal arch 3 endoderm

43
Q

What is the first endocrine gland to develop?

A

Thyroid (about 24 dpf)

44
Q

Describe thyroid gland development

A

Forms from a median endodermal thickening in floor of primordial pharynx, descends in the neck with tongue growth and passes ventral to developing hyoid bone and laryngeal cartilages; connected to the tongue by a narrow tube called the thyroglossal duct

45
Q

What is 1st pharyngeal arch syndrome?

A

Abnormal development of the components of the 1st arch as a result of insufficient migration of NCC into the 1st arch during 4th week; results in malformation of eyes, ears, mandible, and palate

46
Q

What is Treacher-Collins syndrome?

A

Described by malar hypoplasia w/ down-slanting palpebral fissures, defects of lower eyelids, deformed external ears, and sometimes internal ears; autosomal dominant disorder via mutations in Treacher-Collins-Franceschetti syndrome 1 gene (TCOF1) leading to increased apoptosis of cranial NCC

47
Q

What is the Pierre Robin sequence?

A

Occurs de novo in most patients; associated with hypoplasia of the mandible, cleft palate, and defects of the eyes and ears; initiating defect is a small mandible resulting in posterior displacement of the tongue, which causes obstruction of full closure of palate, leading to bilateral cleft palate

48
Q

What is it called when you have an absence of a thyroid gland or one of its lobes?

A

Agenesis of thyroid gland (rare)

49
Q

What is it called when you have unilateral failure of formation of the thyroid gland?

A

Thyroid hemiagenesis (left lobe is more commonly absent and mutations in the receptor for thyroid stimulating hormone are likely involved)

50
Q

What is DiGeorge syndrome?

A

Agenesis of thymus and parathyroid glands as a result of breakdown in signaling from PA endoderm to NCC; presents as shortened philtrum of upper lip, low-set and notched ears, nasal clefts and thyroid hypoplasia; can also have cardiac abnormalities (defects in aortic arch and heart)

51
Q

Which of the following adult embryonic structures is not a derivative of the 2nd pharyngeal arch?

A. Masseter muscle, a muscle of mastication
B. Orbicularis oculi muscle, a muscle of facial expression
C. Reichert’s cartilage
D. Stapes
E. Lesser horn of the hyoid bone

A

A

52
Q

Which of the following adult embryonic structures is not a derivative of the 1st pharyngeal arch?

A. Mandible
B. Meckel's cartilage
C. Palatine tonsils
D. Maxilla
E. Malleus
A

C

53
Q

Which of the following adult structures is derived from the 1st pharyngeal arch?

A. Muscles of facial expression
B. Hyoid bone
C. Cricoid cartilage
D. Sphenomandibular ligament

A

D

54
Q

Which of the following nerves is not paired correctly with its associated pharyngeal arch?

A. Recurrent (inferior) laryngeal nerve - 6th pharyngeal arch
B. Superior laryngeal nerve - 4th pharyngeal arch
C. Facial nerve - 3rd pharyngeal arch
D. Trigeminal nerve - 1st pharyngeal arch

A

C

55
Q

Which of the following statements about the parathyroid glands is not correct?

A. The inferior parathyroids arise from the posterior portion of the 3rd pharyngeal pouch
B. The superior parathyroids arise from the anterior portion of the 3rd pharyngeal pouch
C. The paraythyroid glands are located on the posterior aspect of the thyroid gland
D. The parathyroid glands are derived from endoderm of the foregut

A

B

56
Q

Cervical cysts originate from epithelialized remnants of which of the following developmental regions?

A. Pharyngeal clefts
B. Pharyngeal pouches
C. Pharyngeal arches
D. Foramen cecum

A

A

57
Q

The palatine tonsils develop in association with which pharyngeal pouch?

A. 1st
B. 2nd
C. 3rd
D. 4th

A

B

58
Q

The foramen cecum is an adult remnant of which of the following structures?

A. Parotid gland
B. Inferior parathyroid glands
C. Superior parathyroid glands
D. Thyroid gland

A

D

59
Q

Which of the following pairs of structures is not matched correctly?

A. Innervation of intrinsic tongue muscles - CN XII
B. Sensory innervation to anterior 2/3s of the tongue - CN V
C. Innervation to the taste buds on posterior 1/3 of the tongue - CN IX
D. Sensory innervation to posterior 1/3 of tongue - CN X

A

D

Neuro Exam 1 - JLJ (17 decks)

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