Session 2 - Embryology of H&N Flashcards

1
Q

At what week do pharyngeal arches develop?

A

4

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2
Q

How many pharyngeal arches are there? What are they numbered?

A

1-6, 5 pharyngeal arches. Number 5 is obliterated.

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3
Q

What 3 structures does each pharyngeal arch have associated with it?

A

Artery, nerve, and cartilage bar

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4
Q

Describe the formation of the nerual tube

A
  • Notochord signals cause overlying ectoderm to thicken
  • Edges elevate out of plane of the disk and curl towards each other, creating the neural tube.
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5
Q

What part of the neural tube forms the brain?

A

anterior end

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6
Q

Name the 4 functional regions of the neural tube

A
  • Prosencephalon = forebrain
  • Mesencephalon = midbrain
  • Rhombencephalon = hindbrain
  • Spinal cord
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7
Q

How many cranial nerves are there? Which cranial nerves are derived in the forebrain?

A

12 cranial nerves

1 and 2 derived in forebrain

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8
Q

What is the facial skeleton derived from?

A

Frontonasal prominence and 1st PA

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9
Q

Where are the muscles of mastication derived from?

A

PA1

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10
Q

Where are the muscles of facial expression derived from?

A

PA2

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11
Q

What are the derivatives of PA1 and 2?

A

1 - Facial skeleton and muscles of mastication

2 - Muscles of facial expression

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12
Q

What are the derivatives of PA 3 and 6?

A

3 - stylopharyngeus

6 - Intrinsic muscles of the larynx

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13
Q

What are the derivates of PA4?

A

Cricothyroid, levator palatini, constrictors of the pharynx

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14
Q

What is the name of cranial nerve:

a) V
b) VII
c) IX
d) X - 4th PA
e) X - 6th PA

A

a) trigeminal
b) Facial
c) glossopharyngeal
d) superior laryngeal
e) recurrent laryngeal

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15
Q

What are the sensory and motor innervations of CN V?

A

Sensory - Skin of face, lining of nose and mouth

Motor - Muscles of mastication, muscles derived form mandibular process

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16
Q

What are the sensory and motor innervations of CN VII?

A

Sensory - Taste buds in Anterior 2/3 of tongue

Motor - Muscles of facial expression, muscles derived from PA2

17
Q

What are the sensory and motor innervations of CN IX?

A

Sensory - Posterior 1/3 of tongue

Motor - Stylopharyngeus muscle

18
Q

What are the sensory and motor innervations of CN X (PA4)?

A

Motor innervation - cricothyroid, constrictors of pharynx

19
Q

What are the sensory and motor innervations of CN X (PA6)?

A

Motor - Intrinsic muscles of the pharynx

20
Q

What are the cartilage bars derived from PA1, 2, 4, and 6?

A

PA 1 - Meckels

PA 2 - Reicherts

PA 4 and 6 - Cartilages of larynx

21
Q

What does the cartilage bar of PA1 develop into?

A
  • PhA1 divides into maxillary and mandibular prominences
  • Mandibular prominence develops the Meckel’s cartilage, composed of the Malleus and incus which provides a template for mandible formation via membranous ossification
22
Q

What does PA2 cartilage bar develop into?

A
  • Contributes to middle ear development via stapes
  • Forms the styloid process and hyoid bone
23
Q

What does the cartilage bar of the 4th and 6th PA devleop into?

A
  • Mesenchyme of 4th and 6th arch forms the epiglottis
  • Cartilage bars of 4th and 6th forms the thyroid, arytenoid, and cricoid cartilages
24
Q

What does the PA3 cartilage bar develop into?

A
  • Hyoid bone (great cornu and lower body)
25
Q

What are the arterial derivatives of PA 1-6?

A

1-3 - common, internal and external carotid arteries and branches

4 - Aortic arch and part of right subclavian

6 - pulmonary arteries

26
Q

Where does the aortic sac lie?

A

floor of the pharynx

27
Q

What are the pharyngheal pouches? How many pairs do we have?

A
  • Form on the endodermal side between the pharyngeal arches
  • These form the lateral ectodermal surface of the neck region
  • 4 pairs
28
Q

What does the 1st pharyngeal pouch become?

A

Eustachian tube and middle ear cavity

29
Q

What does the 2nd pharyngeal pouch become?

A

Crypts of palatine tonsil

30
Q

What does the 3rd pharyngeal pouch become?

A
  • Divides into dorsal and ventral
  • Dorsal part - inferior parathyroid
  • Ventral part - thymus
31
Q

What does the 4th pharyngeal pouch become?

A
  • Divides into dorsal and ventral part
  • Dorsal - Superior parathyroid
  • Ventral - Thyroid C cells
32
Q

From where are the ossicels of the middle ear derived?

A

Meckels and reicherts

33
Q

How many pharyngeal clefts are there and why?

A

Only 1st cleft remains as the 2nd arch grows down to cover the others.

34
Q

What could happen if the cervical sinus is not obliterated?

A

cysts or fistulae can occur anywhere along anterior border of SCM

35
Q
A