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ENT Patrick Stenhouse > Embryology - Pharyngeal Arches and Ear > Flashcards

Embryology - Pharyngeal Arches and Ear Flashcards

1
Q

What do the pharyngeal arches give rise to?

A

Facial and neck structures

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2
Q

At which day does arch 1 geneally develop by?

A

22

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3
Q

How many arches are there?

A

5

(1,2,3,4 and 6 - 5 degenerates)

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4
Q

Each pharyngeal arch consists of which 4 parts?

A
  1. Core of mesenchyme (from paraxial/lateral plate of mesoderm)
  2. Neural crest cells
  3. Cranial nerve component
  4. Artery
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5
Q

What does the core of mesenchyme within the pharyngeal arches go on to develop into?

A

Musculature of face and neck

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6
Q

Neural crest cells within the pharyngeal arches go on to form what?

A

Skeletal components of the face

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7
Q

How are the pharyngeal pouches separated?

A

Pharyngeal clefts

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8
Q

What lines the pharyngeal arches?

A

Externally - Ectoderm

Internally - Endoderm

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9
Q

Which cranial nerve is associated with the first pharyngeal arch?

A

Trigeminal nerve

(Maxillary and mandibular divisions)

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10
Q

Which cranial nerve is associated with the 2nd pharyngeal arch?

A

Facial nerve

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11
Q

Which cranial nerve is associated with the 3rd pharyngeal arch?

A

Glossopharyngeal

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12
Q

Which cranial nerve is associated with the 4th pharyngeal arch?

A

Superior laryngeal branch of vagus

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13
Q

Which cranial nerve is associated with the 6th pharyngeal arch?

A

Recurrent laryngeal nerve of vagus nerve

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14
Q

Which two portions can the 1st pharyngeal arch be split?

A
  1. Dorsal (maxillary process)
  2. Ventral (mandibular process)
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15
Q

Which skeletal components will develop within the dorsal portion of the 1st pharyngeal arch?

A
  1. Maxilla
  2. Zygomatic process and part of temporal bone
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16
Q

Which skeletal components will develop within the ventral portion of the 1st pharyngeal arch?

A

Meckel’s cartilage

(Incus, malleus and mandible develop)

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17
Q

Which muscles will develop within the 1st pharyngeal arch?

A
  1. Muscles of mastication
  2. Anterior belly of digastric
  3. Mylohyoid
  4. Tensor tympani
  5. Tensor palatini
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18
Q

The muscles which develop within the 1st pharyngeal arch are all innervated by which cranial nerve?

A

CN V3

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19
Q

Which muscle forms the floor of the mouth?

A

Mylohyoid

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20
Q

Which skeletal components arise from the 2nd pharyngeal arch?

A
  1. Stapes
  2. Styloid process of temporal bone and stylohyoid ligament
  3. Lesser horn and upper part of hyoid bone body
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21
Q

Which muscles will arise from pharyngeal arch 2?

A
  1. Muscles of facial expression
  2. Stapedius
  3. Stylohyoid
  4. Posterior belly of digastric
  5. Auricular muscles
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22
Q

The muscles which are dervived from the 2nd pharyngeal arch are all supplied by which cranial nerve?

A

CN VII

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23
Q

Which muscle(s) are dervived from the 3rd pharyngeal arch?

A

Stylopharyngeus

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24
Q

The muscle(s) derived from the 3rd pharyngeal arch are innervated by which cranial nerve?

A

CN IX

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25
Q

Which bony aspects are derived from the 3rd pharyngeal arch?

A

Greater horn and lower part of body of hyoid

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26
Q

What two main types of tissue do the 4th and 6th pharyngeal arches contribute?

A
  1. Cartilage
  2. Musculature
27
Q

Which pharyngeal arches contribute to the laryngeal cartilages?

A

4 and 6

28
Q

Which muscles does the 4th pharyngeal arch contribute?

A
  1. Cricothyroid constrictor
  2. Levator palatini constrictor
  3. Pharyngeal constrictor
29
Q

Which muscle(s) are provided by the 6th pharyngeal arch?

A

Intrinsic laryngeal muscle

30
Q

What does the first pharyngeal cleft give rise to?

A

External auditory meatus

31
Q

What do the 2nd to 4th pharyngeal clefts give rise to?

A

Cervical sinus

(this degenerates)

32
Q

What are the pharyngeal pouches?

A

Invaginations of the internal endoderm which lines the pharyngeal pouches

33
Q

What does the first pharyngeal pouch go on to become?

A
  1. Middle ear
  2. Eustachian tube
  3. Tympanic membrane
34
Q

What does the 2nd pharyngeal pouch go on the develop?

A

Palatine tonsil

35
Q

What does the 3rd pharyngeal pouch go on to develop?

A
  1. Inferior parathyroid gland
  2. Thymus
36
Q

What does the 4th pharyngeal pouch go on to develop?

A

Superior parathyroid gland

Ultimobranchial body (contributes C cells of the thymus)

37
Q

What does the thyroid gland develop from?

A

Foramen caecum of tongue

38
Q

How does the inferior parathyroid glands eventually become inferior to the superior ones when they are initially more cranial?

A

Inferior parathyroid glands are produced in the 3rd pharyngeal pouch

The thymus gland migrates down into the chest and drags the inferior parathyroid glands inferior to the superior ones

They then detach and migrate into the thyroid gland

39
Q

What are the otic placodes?

A

Thickenings of the external ectoderm

Go on to become the ear and auditory system

40
Q

How many otic placodes are present?

A

2

(one for each ear)

41
Q

What do the otic vesicles firstly transition to become?

A

Otic pits and then otic vesicles

(they invaginate)

42
Q

Which embrylogical structure gives rise to the inner ear?

A

Otic vesicles

(sensory cells of inner ear also develop here)

43
Q

How many parts are the otic vesicles comprised of?

A

3

44
Q

What are the names of the 3 parts which make up the optic vesicle?

A
  1. Endolymphatic sac and duct
  2. Utricular portion
  3. Saccular portion
45
Q

What does the utricular portion of the otic vesicles go on to develop into?

A

Semicircular canals

46
Q

What does the saccular portion of the otic vesicles go on to develop into?

A

Cochlea

47
Q

During week 6, how do the utricular part of the otic vesicles change?

A
  1. They become flattened outpocketings
  2. The central part of the walls then appose each other and break down
48
Q

What is the name given to the dilated end of each of the semicircular canals?

A

Crus ampullare

(there are three of these)

49
Q

What is the name given to the non-dilated end of each of the semicircular canals?

A

Crus non-ampullare

(there are two of these)

50
Q

Why is there 3 crus ampullare and only 2 crus non-ampullare?

A

Two crus non-ampullare fuse

51
Q

What is found within the crus ampullae?

A

Crista ampullaris

Composed of:

  1. Sensory cells for balance
  2. Vestibular fibres of VIII
52
Q

In which timeframe does the cochlear duct grow in a spiral?

A

Weeks 6-8

53
Q

What tissue type surrounds the cochlear duct and what happens to this tissue at around the week 6-8 period?

A

Mesenchyme tissue

It becomes cartilaginous

54
Q

What does the developing cartilaginous tissue around the cochlear duct at weeks 6-8 eventually become?

A

Temporal bone

55
Q

Which structure houses the cochlear fibres of CN VIII?

A

Modiolus

56
Q

Which structure houses the cells of hearing?

A

Basilar membrane

(at organ of corti)

57
Q

What is the organ of Corti?

A

Sensitivie element in the inner ear

It is situated on the basilar membrane in one of the three compartments of the Cochlea

It contains four rows of hair cells which protrude from its surface

58
Q

Which structure overlies the hair cells of the organ of Corti?

A

Tectorial membrane

59
Q

What is special about the inner hair cells in the organ of Corti?

A

They have cilia on their surface which makes contact with the tectorial membrane

60
Q

As the middle ear cavity develops, which tissue breaks down allowing what to form?

A

Mesenchyme breaks down

Tympanic cavity forms (from originally being a expansion of the first pharyngeal pouch)

61
Q

What is they tympanic membrane formed from?

A
  1. Wall of first pharyngeal pouch
  2. Wall of first pharyngeal cleft
62
Q

The auricle forms from which structures?

A

1st and 2nd pharyngeal arches

Each arch provides 3 auricular hillocks

63
Q

What are auricular hillocks

A

Small proliferations of cells which surround the external acoustic meatus and form the auricle

ENT Patrick Stenhouse (27 decks)

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