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ENT SM > Embryology > Flashcards

Embryology Flashcards

1
Q

What kind of structures are the pharyngeal arches

A

Solid structures

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2
Q

In what organisms do pharyngeal arches develop

A

In all vertebrates

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3
Q

When do the arches develop

A

Weeks 4 and 5

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4
Q

What are pharyngeal arches also known as

A

Branchial arches

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5
Q

What are the numbers of the arches in humans

A

1,2,3,4,6

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6
Q

What are the pharyngeal arches derived from?

A

All 3 germ layers - mesoderm, ectoderm and endoderm

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7
Q

What is the core of the mesenchyme derived from

A

Paraxial and lateral plate mesoderm

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8
Q

What does the paraxial and lateral plate mesoderm form

A

Musculature of the face and neck

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9
Q

What do the neural crest cells form

A

The skeletal components of the face

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10
Q

What is the name for the external indentations between one arch and the next

A

Cleft

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11
Q

What is the name for the internal indentations between one arch and the next

A

Pouch

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12
Q

What are the clefts lined with

A

Ectoderm

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13
Q

What are the pouches lined with

A

Endoderm

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14
Q

Why is the migration pathways of the neural crest important

A

They provide a pathway for the axons of the cranial nerves to follow

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15
Q

Cranial nerve 7 (facial) follows what arch

A

2

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16
Q

Cranial nerve 5 (trigeminal) follows what arch

A

1

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17
Q

Cranial nerve 9 (glossopharyngeal) follows what arch

A

3

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18
Q

Cranial nerve 10 (vagus) follows what arch

A

4 and 6

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19
Q

What nerve follows arch 4

A

superior laryngeal branch of the vagus nerve

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20
Q

What nerve follows arch 5

A

Recurrent laryngeal branch of the vagus nerve

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21
Q

What are the 2 main skeletal components of the first arch

A

Maxillary process (dorsal portion) and the mandibular process (ventral portion)

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22
Q

What is Meckel’s cartilage

A

An embryonic cartilage that is associated with the mandibular process but does not form bone

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23
Q

What does the maxillary process of the 1st arch contain

A

Maxilla, zygomatic and part of the temporal bone

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24
Q

What does the mandibular arch contain

A

Meckel’s cartilage –> incus, malleus and mandible

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25
Q

What muscles form form arch 1

A

Muscles of mastication, anterior belly of digastric mylohyoid, tensor tympani and tensor palatini

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26
Q

What nerve supplies the muscles from arch 1

A

V3

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27
Q

What sensory nerves supply what parts of the skin of the face that come from arch 1

A

V1 (ophthalmic)
V2 (maxillary)
V3 (mandibular)

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28
Q

What does the myohyloid muscle do

A

Forms the floor of the mouth

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29
Q

What are the muscles supplied by

A

The 3rd branch of the trigeminal nerve

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30
Q

What does the 2nd arch form

A

Skeletal components

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31
Q

What are the skeletal components of arch 2

A 
Stapes
styloid process of the temporal bone 
stylohyoid ligament 
Lesser horn 
Upper part of body of hyoid
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32
Q

What are the muscles that form form arch 2

A

Muscles of facial expression
stapedius
stylohyoid
posterior belly of digastric and auricular muscles

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33
Q

What nerve supplies the muscles from arch 2

A

The facial nerve (7)

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34
Q

Describe the auricular muscles in humans

A

Extremely rudimentary but in other species they are better developed (dogs perk their ears up whereas humans can barely move their ears)

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35
Q

What forms from the 3rd arch

A

Greater horn and lower part of body of hyoid

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36
Q

What is the only muscle formed from arch 3

A

Stylopharyngeus muscle

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37
Q

What nerve supplies the stylopharyngess muscle

A

Glossopharyngeal nerve

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38
Q

What is formed from the 4th and 6th arches

A

Laryngeal cartilages

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39
Q

What are the muscles formed from arch 4

A

Cricothyroid
Levator palatini
Pharyngeal constrictors

40
Q

What nerve supplies the muscles from arch 4

A

Superior larygneal nerve of vagus nerve (X)

41
Q

What are the muscles formed in arch 6

A

Intrinsic larygenal muscle

42
Q

What are all the muscles and cartilages from arch 6 supplied by

A

The recurrent laryngeal nerve

43
Q

What is formed from the 1st pouch

A

Middle ear
Eustachian tube
contributes to the Tympanic membrane

44
Q

What is formed in the 2nd pouch

A

Palatine tonsil

45
Q

What does the middle ear do during development

A

Engulfs the bony structures formed in the 1st arch

46
Q

How does the palatine tonsil form

A

The endoderm of the 2nd pouch will proliferate and give rise to it

47
Q

What structures are formed in the 3rd pouch

A

Inferior parathyroid gland

Thymus

48
Q

What structures are formed in the 4th pouch

A

Superior parathyroid gland

Ultimobranchial body

49
Q

Why is the thymus so important

A

T cells mature in here

50
Q

What is the ultimobranchial body

A

A fancy name for the structure that give cells that populate the thyroid i.e. C cells

51
Q

what does the foramen caecum make

A

the point of proliferation. It migrates down to the thyroid

52
Q

what is the first thing to become associated with the foramen caecum

A

the structures from the 4th pouch

53
Q

How does the anterior parathyroid move down?

A

The thymus is in the anterior mesosynum and starts to migrate away and as it does it pulls the anterior parathyroid down and onto the posterior surface

54
Q

What happens to the 2nd, 3rd and 4th clefts

A

They ultimately will be lost - they lose contact with outside and form the cervical sinus
The ectoderm will overgrow the structures.

55
Q

What is eventually formed form the 1st cleft

A

The external auditory meatus

56
Q

What are the 3 components of the ear

A

Inner
Middle
External

57
Q

What do the Otic places give rise to

A

The inner ear which divides into 2 components:

semicircular canals and also the organ of corti

58
Q

Describe the appearance of the Otic Placode

A

Very pronounced indentation

59
Q

What makes up the Otic Placode

A

A thickening of the ectoderm will begin to invaginate on either side of the embryo

60
Q

What gives rise to the inner ear

A

Otic Vesicles

61
Q

Describe the process in which a otic placed becomes and otic vesicle

A

The ectoderm will pull in from either side of the invagination to form a pit which will then completely separate off and form a vesicle

62
Q

What do the Utricular portion and saccular portion of the otic vesicle eventually connect via

A

A thin duct

63
Q

What does the saccular portion give us

A

The cochlea

64
Q

What does the Utricular portion give us

A

The semicircular canals

65
Q

At what stage do the semicircular canals develop

A

Week 6

66
Q

What are the semicircular canals filled with

A

Fluid

67
Q

How will the 3 semicircular canals all connect eventually

A

Into the utricle

68
Q

How do the 3 canals lie in relation to each other?

Why is this important?

A

90 degrees to one another

This is an organ of balance - having these 3 planes allows the semicircular canals to sense movement in all directions

69
Q

What is the name for the dilated end of the semicircular canals

A

Crus Ampullare

70
Q

What is the name for the non-dilated end of the semicircular canals

A

Nonampullare

71
Q

What do the swollen ends of the semicircular canal do

A

They sense movement of fluid within the canal and respond to this by feeding information back to the brain which then alters us to keep us balanced

72
Q

Describe how and when the cochlear duct grows

A

In a spiral (2.5 turns) between weeks 6-8

73
Q

What does the surrounding mesenchyme of the cochlear duct become

A

Cartilaginous

74
Q

What is the cochlear duct surrounded by

A

A basement membrane which grows a cartilaginous shell

75
Q

What is the function of the bony strut

A

It provides support for the cochlear duct

76
Q

Why is the modiolus an important structure

A

In terms of providing innervation into the cochlear duct

77
Q

Describe the function of the vestibuli

A

It is in contact with the cochlear duct and will become the vestibular membrane

78
Q

Describe the pathway of sound in terms of the scala vestibule and scala tympani

A

The sound wave will travel down the scala vestibule and once it reaches the tip of the scala vestibule, there is a communication where the sound waves will tavel back through the scala tympani

79
Q

What innervated the inner hair cells

A

Auditory nerve fibres

80
Q

What nerve sends information about sound back to the brain

A

The cochlear nerve

81
Q

Where do the ossicles of the middle ear come from

A

The pharyngeal arches

82
Q

What forms the cavity of the middle ear

A

The ossicles

83
Q

What happens when the mesenchyme surrounding the auditory ossicles breaks down

A

The bones will expand to fill the space left behind

84
Q

What develops to help stabilise the bones of the inner ear

A

Ligaments

85
Q

How is the meatal plug formed

A

The epithelial cells rapidly proliferate to form the Meatal plug which then remains in place until the 7th month of development before then breaking down

86
Q

How many mesenchymal proliferation are there?

A

6

87
Q

Where do the mesenchymal proliferations come from

A

3 from arch 1 and 3 from arch 2

88
Q

What fuses to form definitive Auricle

A

Hillocks

89
Q

Where are the external ears initially formed

A

In the lower neck

90
Q

How do the external ears ascend

A

Due to the development of the mandible

91
Q

Name 4 abnormalities of the external ear

A

Microtia (anotia)
Microtia
Preauricular pit
Preauricular appendages

92
Q

What is anti

A

No structures of the external ear can be seen

93
Q

What is Microtia

A

relatively small ear

94
Q

What is Periauricular appendiages

A

Additional appendages

95
Q

What is Preauricular pit

A

Small indentation

ENT SM (19 decks)

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