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Head, neck and introduction to neuroanatomy > Session 5 > Flashcards

Session 5 Flashcards

1
Q

Describe the embryo at 4 weeks

A
  • No face yet discernible
  • Head and neck take up almost half of body
  • Structure of embryonic head is becoming increasingly complex, but follows a familiar segmental pattern
  • Each segment contains structures from various systems
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2
Q

Describe the ectoderm of the pharyngeal arches

A
  • Forms lining of GI and respiratory tracts
  • Forms glands
  • Covers superficial surface of arch
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3
Q

Describe the cartilage bar of the pharyngeal arches

A
  • Mesodermal
  • Supports the arch (similar to ribs)
  • Has associated muscles (like intercostal muscle)
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4
Q

Describe the cranial nerves of the pharyngeal arches

A
  • Come off from neural tube
  • Each arch has a different nerve
  • Motor to muscles associated with cartilage bars
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5
Q

Describe the arteries of the pharyngeal arches

A
  • Mesodermal
  • One of the aortic arches
  • Branches individually feed each pharyngeal arch with blood
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6
Q

Describe the endoderm of the pharyngeal arches

A
  • Contributes to pharynx
  • Forms GI and respiratory endothelium
  • Forms endocrine glands
  • Covers deep aspect of arch
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7
Q

Give the derivatives for the 1st pharyngeal arch

A
  • Trigeminal nerve (V)
  • Aortic arch 1
  • Gives muscles of mastication
  • Gives mandible, malleus and incus
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8
Q

Give the derivatives of the 2nd pharyngeal arch

A
  • Facial nerve (VII)
  • Aortic arch 2
  • Gives muscles of facial expression
  • Gives stapes and superior part of hyoid bone
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9
Q

Give the derivatives of the 3rd pharyngeal arch?

A
  • Glossopharyngeal nerve (IX)
  • Aortic arch 3
  • Stylopharyngeus muscle
  • Inferior part of hyoid bone
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10
Q

Give the derivatives of the 4th and 6th pharyngeal arches

A
  • Vagus nerve (X)
  • Aortic arches 4 and 6
  • Pharyngeal and laryngeal muscles
  • Laryngeal cartilages
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11
Q

What are the pharyngeal clefts and pouches?

A
  • Pharyngeal arch has adjacent swellings
  • Between adjacent swellings there are depressions of ectoderm and endoderm
  • Pouches = evaginations of endoderm
  • Clefts = invaginations of ectoderm
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12
Q

How many pharyngeal pouches are there?

A
  • 4
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13
Q

What structures are given by the first pharyngeal pouch?

A
  • Eustachian tube
  • First pharyngeal cleft becomes external acoustic meatus
  • Thin membrane between first pouch and first cleft forms tympanic membrane
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14
Q

How many pharyngeal clefts are there?

A
  • Just 1
  • Downwards growth of 2nd aortic arch obliterates the others
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15
Q

What structures are formed from the 2nd, 3rd and 4th pharyngeal pouches?

A
  • 2nd pouch forms palatine tonsil
  • 3rd and 4th pouches form thymus and parathyroid tissue
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16
Q

What is the difference between a branchial cyst, sinus and fistula?

A
  • Cyst is enclosed
  • Sinus communicates with skin
  • Fistula connects skin with pharynx
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17
Q

What causes branchial cysts, sinuses and fistulas?

A
  • Obliteration of clefts 2, 3 and 4 can be disordered and 2nd arch grows down
  • Obliteration is incomplete
  • Presents with lump in neck
  • Branchial cysts sit anterior to sternocleidomastoid
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18
Q

Outline the development of the nose

A
  • Frontonasal processes give rise to anterior parts of forehead and nose
  • Nasal placodes invaginate to form nasal pits
  • Nasal pits become nostrils
  • Medial nasal process and lateral nasal process move medially to form bridge of nose in the midline
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19
Q

Outline the development of the mandible and maxilla

A
  • Mandibular processes of first pharyngeal arch fuse in the midline to form mandible
  • Maxillary processes visible just above 1st pharyngeal arch move towards midline to form maxilla
  • Maxillary processes also fuse with medial nasal processes resulting in formation of nose and philtrum of upper lip
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20
Q

Outline the development of the mouth

A
  • Buccopharyngeal membrane disappears by apoptosis to form stomodeum which connects directly with embryonic pharynx
  • Stomodeum = primitive mouth
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21
Q

Outline how the ear develops

A
  • External ear ascends until it sits at the same level as the nose
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22
Q

How does the palate develop?

A
  • Palatal shelves grow medially and fuse in midline
  • Tongue must drop down to allow fusion to happen
  • Nasal septum grows down and fuses with palate
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23
Q

What palatal abnormalities can occur?

A
  • Small defect (hole) in palate due failure of palatal shelves to fuse in midline
  • Failure of fusion of frontal nasal process with maxillary process - leads to cleft lip
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24
Q

What are the auricular hillocks?

A
  • Surround 1st pharyngeal cleft
  • Should ascend and become external ear
  • This process involves neural crest cells
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25
Q

How does alcohol affect foetal development?

A
  • Ingestion of toxins during early stages of development causes cellular migration to become disordered
  • Leads to foetal alcohol syndrome
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26
Q

What is the appearance of someone with foetal alcohol syndrome?

A
  • Low-set ears
  • Small head
  • Low nasal bridge
  • Underdeveloped jaw
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27
Q

Outline how the tongue develops

A
  • Anterior 2/3 develops from first arch
  • Posterior 3rd develops from 2nd and 3rd arches
  • Muscles arise from somites at level of hypoglossal nerve
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28
Q

What is the innervation of the tongue?

A
  • Anterior 2/3 gets general sensation from trigeminal nerve and taste from facial nerve
  • Posterior 1/3 gets general sensation and taste from glossopharyngeal nerve
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29
Q

How does the thyroid gland develop?

A
  • Thyroid develops in foramen caecum of tongue
    -Thyroid diverticulum grows downwards and takes cells with it to the embryonic neck
  • Thyroglossal duct breaks down
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30
Q

What happens if the thyroglossal duct doesn’t break down?

A
  • Cysts and fistula are present at the foramen caecum
  • Ectopic thyroid tissue can sometimes be found anywhere along the path of descent
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31
Q

What fibres are found in the trigeminal nerve?

A
  • General sensory
  • Motor
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32
Q

From where does the trigeminal nerve arise?

A
  • Pons
33
Q

What are the target tissues of the trigeminal nerve?

A
  • Skin and tissues of face, portion of scalp, and deep facial structures
  • Anterior 2/3 of tongue (general sensation only, not taste) via branch of Vc
  • Muscles of mastication via branches of Vc
34
Q

How do we clinically examine the trigeminal nerve?

A
  • Light touch of Va, Vb and Vc dermatomes
  • Muscles of mastication action
  • Corneal reflex
35
Q

What presentation would you see in a patient with a trigeminal nerve lesion?

A
  • Sensory deficits within dermatomal regions on affected side
  • Weakness in muscles of mastication if Vc involved
  • Absent corneal reflex (Va is sensory part of reflex)
36
Q

Which virus can cause a trigeminal nerve lesion?

A
  • Herpes zoster virus
  • Causes ophthalmic shingles
  • Virus reactivated in trigeminal ganglion
  • Can affect cornea and conjunctiva
37
Q

What are the causes of trigeminal nerve lesions?

A
  • Trigeminal herpes zoster
  • Trigeminal neuralgia (compression from an aberrant blood vessel)
  • Orbital and mandibular fractures
  • Posterior cranial fossa tumours
38
Q

Outline the route taken by the trigeminal nerve

A
  • After it exits pons, trigeminal splits into 3 divisions
  • Va (ophthalmic) passes through cavernous sinus and into superior orbital fissue
  • Vb (maxillary) passes through cavernous sinus and foramen rotundum
  • Vc (mandibular) passes into foramen ovale to exit intracranial cavity
  • All branches then divide into other branches
39
Q

What are the key sensory divisions of Va?

A
  • Frontal nerve - gives rise to supraorbital and supratrochlear nerve of forehead
  • Nasociliary nerve - supplies sensory to eye and skin over nose
40
Q

What are the key sensory divisions of Vb?

A
  • Infra-orbital nerve
  • Superior alveolar nerves - supplies upper teeth and gums
41
Q

What are the key sensory divisions of Vc?

A
  • Auriculotemporal nerve - sensory to side of scalp, part of external ear and TMJ
  • Lingual nerve - general sensation from anterior 2/3 of tongue
  • Inferior alveolar nerve - supplies lower teeth and gums
  • Mental nerve
42
Q

What is Hutchinson’s sign?

A
  • If vesicles are present over the tip of the nose in ophthalmic shingles, there is increased risk that eyes will be affected
43
Q

What injury can involve the infraorbital nerve?

A
  • Orbital fractures
  • Can also include superior alveolar nerve
  • Pt will present with deficit in sensory information in lower eyelid and part of cheek
44
Q

What information does the mental nerve carry?

A
  • Sensation from lower lip and chin and incisors on lower mandible
45
Q

Where does nerve Vc branch to give the nerves supplying the muscles of mastication?

A
  • Infratemporal fossa
46
Q

Outline the route taken by the mental nerve

A
  • Enters mandibular canal
  • Then becomes inferior alveolar nerve running within bone of mandible
  • Makes it vulnerable in mandibular fractures
  • Pt will present with sesnory loss over lower lip or chin
47
Q

What fibres are found within the facial nerve?

A
  • Motor
  • Special sensory (taste)
  • Parasympathetic
48
Q

What are the target tissues of the facial nerve?

A
  • Motor to muscles of facial expression and nerve to stapedius
  • Special sensory to anterior 2/3 of tongue
  • Parasympathetic to glands (lacrimal. nasal and salivary)
49
Q

What do we examine when we suspect a facial nerve lesion?

A
  • Muscles of facial expression
  • Will see unilateral facial droop including forehead
  • Pt may report symptoms due to absence of other facial nerve functions e.g. altered taste
50
Q

What can cause facial nerve lesions once it has left the brainstem?

A
  • Lesions in/ around internal acoustic meatus
  • Posterior cranial fossa tumours
  • Basal skull fracture involving petrous bone
  • Middle ear disease
  • Inflammation in facial canal causing facial nerve palsy e.g. Bell’s Palsy, Ramsay Hunt syndrome
  • Parotid disease
51
Q

Outline the route taken by the facial nerve

A
  • Passes through internal acoustic meatus
  • Moves into petrous bone where it gives off 3 branches
  • Rest of nerve continues through facial canal
  • Close relationship with middle ear
  • Emerges via stylomastoid foramen through base of skull
  • Passes through parotid gland
  • Gives of several extracranial branches that supply muscles of facial expression
52
Q

Which branches does the facial nerve give off at the petrous bone?

A
  • Nerve to stapedius - innervates muscle that dampens vibration of stapes
  • Greater petrosal nerve - carries parasympathetic fibres to lacrimal and nasal mucosal glands
  • Chorda tympani - taste from anterior 2/3 of tongue, carries parasympathetic fibres to salivary glands (except parotid)
53
Q

How do we tell the difference between facial droop involving the facial nerve and facial droop due to a stroke?

A
  • Facial nerve lesion causes ipsilateral droop involving entire half of face
  • Stroke patients can still close eyelid and their forehead is spared
54
Q

Why is the forehead spared in a stroke?

A
  • If you have a stroke, it affects the connection between the brain and the facial nerve
  • It affects the facial nerve before it exits the brainstem
  • The primary motor cortex with dominant control is found in the side of the brain affected by stroke
  • The facial nerve has back-up from the primary motor cortex on the other side of the brain
  • This back-up only helps the upper half of the face
55
Q

Why is the forehead affected in a facial nerve lesion?

A
  • Injury involves facial nerve anywhere after it exits the brainstem and along its route to target tissue
  • No backup
56
Q

What fibres are found in the vestibulocochlear nerve?

A
  • Special sensory
57
Q

From where does the vestibulocochlear nerve arise?

A
  • Pons
58
Q

What are the target tissues of the vestibulocochlear nerve?

A
  • Cochlea - hearing
  • Semi-circular canals - balance
59
Q

How do we examine the vestibulocochlear nerve?

A
  • Gross bedside hearing tests
  • Tuning fork testing
  • Patients can present with hearing loss, vertigo and tinnitus
60
Q

What can cause vestibulocochlear lesions?

A
  • Vestibular schwannoma or other posterior cranial fossa tumours
  • Occlusion of labyrinthine artery (supplies the nerve)
  • Base skull fracture involving petrous bone
  • Brainstem lesion of pons (very very rare)
61
Q

What is a vestibular schwannoma?

A
  • Benign tumour involving Schwann cells associated with vestibulocochlear nerve
  • Slow growing
  • Usually unilateral
62
Q

What are the symptoms and signs of a vestibular schwannoma?

A
  • Unilateral hearing loss
  • Tinnitus
  • Vertigo
  • Numbness, pain or weakness down one half of the face
63
Q

What are the similarities between the glossopharyngeal and vagus nerves?

A
  • Arise from medulla
  • Run through posterior cranial fossa
  • Exit through jugular foramen
  • Both carry parasympathetic fibres
  • Enter into carotid sheath
  • Close relationship with ECA and ICA
  • Glossopharyngeal nerve leaves sheath superiorly
64
Q

What are the targets of the glossopharyngeal nerve?

A
  • Mainly sensory to oropharynx, tonsils, middle ear cavity
  • Sensory and special sensory to posterior 1/3 of tongue
  • 1 swallowing muscle
  • Parasympathetic to parotid gland
  • Afferents from carotid sinus and body
65
Q

What are the targets of the vagus nerve?

A
  • Motor and sensory
  • Muscles of larynx and pharynx including soft palate
  • Sensory to larynx and laryngopharynx
  • Parasympathetic to many tissues
66
Q

How will patients present with a lesion of the glossopharyngeal nerve or vagus nerve?

A
  • Difficulty with swallowing
  • Weak cough (vagus nerve only)
  • Difficulties with speech or changes in voice (vagus nerve only)
67
Q

How do we examine patients with a suspected glossopharyngeal/vagus nerve lesion?

A
  • Speech, swallow, cough
  • Soft palate movement and uvula position (vagus nerve)
  • Can also test gag reflex though not commonly done
68
Q

What can cause lesions of the glossopharyngeal/vagus nerve?

A
  • RLN branch of vagus nerve vulnerable in thyroid pathology or surgery and superior thorax/mediastinal pathology
  • Pathology or surgery involving carotid sheath structures
  • Posterior cranial fossa tumours
  • Base of skull fractures
  • Brainstem lesions e.g. infarct
69
Q

What are the key branches of the vagus nerve in the neck?

A
  • Right recurrent laryngeal nerve
  • Left recurrent laryngeal nerve
70
Q

What are the similarities between the accessory and hypoglossal nerves?

A
  • Arise from medulla
  • Run through posterior cranial fossa
  • Enter into carotid sheath and leave superiorly
  • Hypoglossal exits and travels towards tongue
  • Accessory exits and travels towards posterior triangle
  • Both nerves are motor
71
Q

What is the target of the hypoglossal nerve?

A
  • Muscles of tongue
72
Q

How do we examine the hypoglossal nerve?

A
  • Tongue movements and protrusion
73
Q

What can cause lesions to the hypoglossal nerve?

A
  • Surgery/pathology in proximity to or involving contents of upper carotid sheath and internal/external carotid arteries
  • Posterior cranial fossa tumours
  • Brainstem (medullary) lesions involving hypoglossal nucleus
74
Q

What happens to the tongue when one of the hypoglossal nerves is injured?

A
  • It deviates towards the wounded side
75
Q

What are the targets of the spinal accessory nerve?

A
  • Sternocleidomastoid
  • Trapezius
76
Q

How do we examine the spinal accessory nerve?

A
  • Turn head (tests actions of SCM)
  • Shrug shoulders (tests action of trapezius)
77
Q

What can cause spinal accessory nerve injury?

A
  • Injuries, surgery or pathology involving posterior triangle
  • Posterior cranial fossa tumours
  • Base of skull fractures
  • Brainstem (medullary lesions) e.g. infarct
78
Q

Where does the spinal accessory nerve run?

A
  • Emerges deep to posterior border of SCM to enter posterior triangle
  • Runs superficially in posterior triangle to reach trapezius

Head, neck and introduction to neuroanatomy (11 decks)

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