Development of the Head and Neck 1 Flashcards

1
Q

What does the fetal skull have, that the adult skull doesn’t?

A

Fontanelles

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2
Q

What are fontanelles?

A

Membranous areas of unfused skull

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3
Q

When will the fontanelles be closed?

A

Within the first 2 years of life

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4
Q

What is the function of fontanelles?

A
  • Flexibility allows passage through the birth canal
  • Allow for brain growth
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5
Q

What changes in the fontanelles can indicate pathology?

A
  • Sunken
  • Bulging
  • Enlarged
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6
Q

What do sunken fontanelles indicate?

A

Dehydration

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7
Q

What do bulging fontanelles indicate?

A

Increased intracranial pressure

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8
Q

When do enlarged fontanelles often occur?

A

In prematurity

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9
Q

What is the problem with enlarged fontanelles?

A

They can squash the brain, causing brain damage

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10
Q

When does the neural tube form?

A

Week 3

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11
Q

How is the neural tube formed?

A
  • The notocord is formed at gastrulation
  • The notocord sends signals causing the overlying ectoderm to thicken
  • Edges of the ectoderm elevate out of slipper-shaped neural plate, out of the plane of the disc
  • Edges curl towards one another, creating neural tube
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12
Q

What happens to the anterior end of the neural tube?

A

It begins to form the brain

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13
Q

Describe the anterior end of the neural tube when it’s beginning to form brain?

A

Initially in 3 vesicle stage, and vesicles quickly specialise

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14
Q

What do the vesicles of the neural tube specialise to form?

A
  • Prosencephalon - forebrain
  • Mesencephalon - midbrain
  • Rhombencephalon - hindbrain
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15
Q

What has happened to the embryo by the end of week 4?

A

It has folded

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16
Q

What helps to fold the embryo?

A

The growth of the neural tube

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17
Q

What does folding of the embryo create?

A

Primitive gut tube

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18
Q

Does the primitive gut tube include the primitive pharynx?

A

Yes

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19
Q

What is the primitive gut tube lined with?

A

Endoderm

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20
Q

Describe the head and neck region of the embryo early in week 4?

A
  • Face has no distinguishing external features
  • Head and neck represent half the length of the embryo
  • There is an open pore in the neural tube cranially and caudally, which is fusing from the middle upwards
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21
Q

Where does the pharynx extend in the adult?

A

From the base of the skull to the inferior border of the cricoid cartilage of the larynx

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22
Q

What are the divisions of the pharynx?

A
  • Nasal
  • Oral
  • Laryngeal
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23
Q

Where is the nasopharynx?

A

Superior to the soft palate

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24
Q

Where is the oropharynx?

A

Between the soft palate and the larynx

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25
Q

Where is the laryngopharynx?

A

Posterior to the larynx

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26
Q

What are the pharyngeal (or brachial) arches?

A

A system of mesenchymal proliferations in the neck region of the embryo

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27
Q

Where do the pharyngeal arches form?

A

In the lateral walls of the embryonic pharynx, towards the cranial end of the neural tube

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28
Q

What gives the bumps of the pharyngeal arches?

A

Lots of cell division and plastic mesenchyme production

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29
Q

What are the pharyngeal arches involved in?

A

Formation of the head and neck

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30
Q

What type of tissues do the pharyngeal arches give rise to?

A
  • Muscles
  • Cartilages
  • Nerves
  • Arteries
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31
Q

What systems of the body do the pharyngeal arches notably involve?

A
  • Brain
  • CVS
  • Special sensory organs
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32
Q

What is the pharyngeal apparatus very closely associated to?

A

Primitive heart and neural tube

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33
Q

When are the pharyngeal arches apparent from?

A

About 4 weeks in the developing embryo

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34
Q

What does each arch have?

Regarding its core

A

A large mesenchyme core

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35
Q

What migrates in to the mesenchyme core of the phayngeal arches?

A

Some neural crest cells

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36
Q

What are the pharyngeal arches covered in on either external surface?

A

Ectoderm

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37
Q

What is found between each arch on its external surface?

A

Pharyngeal groove, or cleft

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38
Q

What happens to the phayngeal groove?

A

They eventually disappear, except the first (between the first and second arches)

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39
Q

What does the first pharyngeal cleft become?

A

The external auditory meatus of the ear

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40
Q

What forms around the entrance to the external auditory meatus?

A

Swellings

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41
Q

What forms from the swellings of the entrance to the meatus?

A

The external ear (auricle)

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42
Q

How do the clefts disappear?

A

The second cleft grows down to cover the others, obliterating all the other clefts

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43
Q

What happens if the cervical sinus is not obliterated?

A

Cysts or fistulae can occur

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44
Q

Where can cysts or fistulae resulting from failure of obliteration of cervical sinus occur?

A

Anywhere along the anterior border of the sternocleidomastoid

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45
Q

What is the internal surface of the pharyngeal arch?

A

The part facing into the primitive gut tube

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46
Q

What is the internal surface of each pharyngeal arch covered by?

A

Endoderm

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47
Q

What is formed by the internal surface of the pharyngeal arch?

A

A similar pattern of grooves between each arch, known as pharyngeal pouches

48
Q

What arises from the pharyngeal pouches?

A
  • Parathyroid
  • Thymus
  • Tonsils
  • Middle ear
49
Q

What are the pharyngeal arches, grooves, and pouches collectively known as?

A

Pharyngeal apparatus

50
Q

How many pharyngeal arches are there?

A

5, numbered 1-6

The 5th arch doesn’t form in humans

51
Q

Which pharyngeal arch is biggest?

A

1st

52
Q

What happens to the size of the phayngeal arches?

A

They get progessively smaller from 1 to 6, so the 4th and 6th arch are not as readily visible as the others

53
Q

What is associated with each pharyngeal arch?

A
  • Cartilage bar
  • Nerve
  • Artery
54
Q

What is the cartilage bar of each pharyngeal arch dervied from?

A

Neural crest cells

55
Q

What will the cartilage bars subsequently become?

A

Skeletal elements of head and neck

56
Q

Which cartilaginous bar is largest?

A

Cartilage bar of 1st pharyngeal arch

57
Q

What does the cartilage bar of the first pharyngeal arch do?

A

Divides into maxillary and mandibular prominences

58
Q

What is the mandibular prominence known as?

A

Meckel’s cartilage

59
Q

What does Meckels cartilage give rise to?

A
  • Malleus
  • Incus
60
Q

How to the malleus and incus arise from the Meckel’s cartilage?

A

Remodelling

61
Q

What does the mandibular prominence provide?

A

Template for mandible

62
Q

How does the mandible form from the mandibular prominence?

A

Membranous ossification

63
Q

What is the cartilage bar of the 2nd arch known as?

A

Reichert’s

64
Q

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

A
  • Thyroid
  • Arytenoids
  • Cricoids
65
Q

What are the ossicles of the middle ear derived from?

A

Cartilage bar

66
Q

How many pairs of cranial nerves are there?

A

12

67
Q

What happens to the cranial nerves during development?

A

They loose their segemental arrangement

68
Q

How are the cranial nerves classified?

A

Based on their function and their embryological origin

69
Q

What are the classifications of cranial nerves?

A
  • Somatic efferent
  • Special sensory
  • Nerves of pharyngeal arches
70
Q

What parts of the neural tube are the cranial nerves derived from?

A

The mid- or hind-brain, except CN I and II

71
Q

What cranial nerves are associated with the pharyngeal arches?

A

V, VII, IX, and X

72
Q

Where do the cranial nerves associated with the pharyngeal arches arise from?

A

The lowest part of the brainstem

73
Q

What do the cranial nerves associated with the pharyngeal arches innervate?

A

They innervate the pharyngeal arch, and therefore the structural derivates of each pharyngeal arch is innervated by the particular cranial nerve associated with that arch

74
Q

What cranial nerve is associated with the first pharyngeal arch?

A

Trigeminal (V)

75
Q

What cranial nerve is associated with the second pharyngeal arch?

A

Facial (VII)

76
Q

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

A

Glossopharyngeal (IX)

77
Q

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

A

Vagus (X)

78
Q

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

A

Vagus (X)

79
Q

What cranial nerves have a relationship wtih the pharyngeal arch system?

A
  • CN XI (cranial accessory)
  • CN XII
80
Q

Where does the aortic sac lie?

A

On the floor of the pharynx

81
Q

What does each pharyngeal arch become associated with?

Regarding blood vessels

A

An aortic arch of blood vessels

82
Q

What does each aortic arch blood vessel run through?

A

The mesenchyme of its respective pharyngeal arch

83
Q

How does the arrangement of the aortic arch blood vessels initially appear?

A

Very organised

84
Q

What happens to the arrangement of the aortic arch blood vessels?

A

As the embryo develops, and structures start to derive from the pharyngeal arches, much of the order is lost

85
Q

What is the rearrangement of developing structures the reason for?

A

The recurrent laryngeal nerve of the vagus becomes looped under the arch of the aorta on the left side, and the subclavian artery on the right side

86
Q

What artery is derived from the first arch?

A

Common, external, and internal carotid arteries and branches

87
Q

What artery is derived from the second arch?

A

Common, external, and internal carotid arteries and branches

88
Q

What artery is derived from the third arch?

A

Common, external, and internal carotid arteries and branches

89
Q

What artery is derived from the forth arch?

A

Aortic arch (on left) and subclavian artery (on right)

90
Q

What artery is derived from the sixth arch?

A

Pulmonary arteries

91
Q

What are the muscular derivatives of the first arch?

A
  • Muscles of mastication
  • Mylohyoid
  • Anterior belly of digastric
  • Tensor tympani
  • Tensor veli palatine
92
Q

What are the muscular derivates of the second arch?

A
  • Muscles of facial expression
  • Stapedius
  • Stylohyoid
  • Posterior belly of digastric
93
Q

What are the muscular derivates of the third arch?

A

Stylopharyngeus (muscle of the pharynx)

94
Q

What are the muscular derivates of the fourth arch?

A
  • Cricothyroid
  • Levator palatine
  • Constrictors of pharynx
95
Q

What are the muscular derivates of the sixth arch?

A

Intrinsic muscles of the larynx

96
Q

What are the sensory derivatives of the first arch?

A

Main sensory supply to the face and nasopharynx

97
Q

What are the sensory derivatives of the 2nd arch?

A

Special sensory (taste) to anterior 2/3 of tongue

98
Q

What are the sensory derivates of the 3rd arch?

A

Sensory to posterior 1/3 of the tongue, and upper part of the pharynx

99
Q

What are the sensory derivatives of the 4th and 6th arches?

A

Sensory to linings of the lower pharynx and all larynx

100
Q

What are the skeletal derivative of the first arch?

A
  • Maxillae and zygomatic bones
  • Meckel’s cartilage
    • Malleus
    • Incus
  • Mandible
101
Q

What are the skeletal derivates of the second arch?

A

Reichert’s cartilage;

  • Hyoid
    • Lesser cornu
    • Upper body
  • Stapes
    • Part of middle ear
  • Styloid process
  • Stylohyoid ligament
102
Q

What are the skeletal derivatives of the 3rd and 4th arch?

A

Epiglottis

103
Q

What are the skeletal derivatives of the 4th and 6th arches?

A

Cartilages of larynx

104
Q

What does the facial skeleton arise from?

A

The frontonasal prominence and the first pharyngeal arch

105
Q

Why do the muscles of facial expression and the muscles of mastication have different cranial nerve innervation, despite being so topographically related?

A

Due to them being derived from different pharyngeal arches

106
Q

What are the muscles of mastication derived from?

A

The first pharyngeal arch

107
Q

What is the result of the muscles of mastication being derived from the first pharyngeal arch?

A

They are innervated by the facial nerve (CN VII)

108
Q

What is CN VII the nerve of?

A

The second arch

109
Q

What does CN VII pass through?

A

The stylomastoid foramen and parotid gland

110
Q

What happens in the second pharyngeal pounch?

A

There is epithelial proliferation, followed by migration in and colonisation by lymphoid precursors

111
Q

What happens to the 3rd and 4th pharyngeal pouches?

A

They divide into dorsal and ventral components

112
Q

What are the derivatives of the first pharyngeal pounch?

A
  • Pharyngotympanic (Eustachian) tube
  • Middle ear cavity
113
Q

What are the derivatives of the second phayngeal pouch?

A

Palatine tonsil

114
Q

What are the derivatives of the third pharyngeal pouch?

A
  • Inferior parathyroid (dorsal)
  • Thymus (dorsal and ventral)
115
Q

What are the derivatives of the 4th pharyngeal pouch?

A
  • Superior parathyroid
  • C cells of thyroid