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Neuroanatomy > Osteology Of The Base Of The Skull, The Orbit And The Ear > Flashcards

Osteology Of The Base Of The Skull, The Orbit And The Ear Flashcards

1
Q

Sutures

A

Fibrous joints between several individual bones in the base of skull

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2
Q

Cranial fossae

A

3 distinct depressions at the base of the skull from above

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3
Q

How many cranial fossae are there

A

3

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4
Q

What are the 3 cranial fossae

A

Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa

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5
Q

Cranial foramina

A

Small holes in the cranial fossa that allow the nerves, arteries and veins to pass in and out of the skull

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6
Q

Which lobes rest in the anterior cranial fossa

A

Frontal lobe

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7
Q

How many bones form the anterior cranial fossa

A

3- orbital part of the frontal bone
Cribriform plate and the crista galli of the ethmoid bone
Lesser wings of the sphenoid bone

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8
Q

What is the Foramen located in the anterior cranial fossa

A

Cribriform plate- transmits olfactory fibres that allow our sense of smell

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9
Q

Orbital part of the frontal bone

A

2 rounded elevations are the spherical cavities of the bony orbits (where the eyes are located)

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10
Q

Cribriform plate

A

Has many small holes for the passage of olfactory nerves

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11
Q

Crista galli

A

Vertical protrusion in the centre of the Cribriform plate

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12
Q

Lesser wings of the sphenoid bone

A

The sphenoid bone has smaller (lesser) superior wings, a body in its centre and larger (greater) inferior wings

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13
Q

How many bones for the middle cranial fossa

A

2- petrous and squamous parts of the temporal bone
Greater wing and body of the sphenoid bone

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14
Q

Number of Foramen in the middle cranial fossa

A

6

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15
Q

6 Foramen in middle cranial fossa

A

Optic canal
Superior orbital fissure
Foramen rotundum
Foramen ovale
Foramen lacerum
Foramen spinosum

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16
Q

Petrous part of the temporal bone

A

Very hard and bulbous inferior and medial part of the temporal bone
Inner and middle ear cavities located inside it

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17
Q

Where are the inner and middle ear cavities located

A

Inside the petrous part of the temporal bone

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18
Q

Squamous part of the temporal bone

A

Flat, lateral part of the bone

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19
Q

Sella turcica

A

Where the pituitary gland is located
Body of sphenoid bine

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20
Q

Body of the sphenoid bone

A

Includes a small rounded cavity - pituitary fossa
Also known as sella turcica- where pituitary gland is located

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21
Q

Optic canal

A

Transmits the optic nerve into the bony orbit

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22
Q

Superior orbital fissure

A

Transmits several nerves that provide motors innervation (oculomotor, trochlear and abducens nerves) and sensation (ophthalmic branch of trigeminal nerve) to the orbital region

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23
Q

Foramen rotundum

A

Transmits the maxillary branch of the trigeminal nerve

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24
Q

Foramen ovale

A

Transmits the mandibular branch of the trigeminal nerve

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25
Q

Foramen lacerum

A

The internal carotid artery exits the carotid canal through this Foramen to enter the skull

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26
Q

Foramen spinosum

A

Transmits the middle meningeal artery

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27
Q

Which parts of the brain rest in the posterior cranial fossa

A

Occipital lobes
Cerebellum
Brainstem

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28
Q

Which bones form the posterior cranial fossa

A

Occipital bone
Part of the petrous part of the temporal hone

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29
Q

Number of foramina in the posterior cranial fossa

A

4

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30
Q

4 foramina in posterior cranial fossa

A

Internal auditory meatus
Jugular Foramen
Hypoglossal canal
Foramen magnum

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31
Q

Internal auditory meatus

A

Transmit the vestibulocochlear and facial nerves into the inner ear cavity

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32
Q

Jugular Foramen

A

Transmits the Glossopharyngeal, vagus and accessory nerves and the internal jugular vein

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33
Q

Hypoglossal canal

A

Transmits the Hypoglossal nerve

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34
Q

Foramen magnum

A

Allows central nervous system fibres to leave the skull and become the spinal cord

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35
Q

Head injuries

A

A traumatic injury to the head may result in a fracture of the skull. If this occurs, there may be numerous consequences including:
• The brain itself could be directly damaged by the force.
• The fracture could extend through some of the foramina and damage the structures passing through them.
• The dura and arachnoid meninges may be damaged which could cause CSF to leak out. Clinically, this may be suspected if a clear liquid is seen to be leaking from the patient’s nose or ears after a head injury.
• Significant bleeding may occur from the fractured bone or due to damage to intracranial arteries, veins or dural venous sinuses.

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36
Q

Pterion

A

The pterion is an area of the skull often referred to as the ‘temple’ and it is located just lateral and posterior to the eyebrow. It is a shallow depression where four bones of the skull converge: the frontal, temporal, sphenoid and parietal bones. Because of this, it is considered to be the weakest part of the skull and prone to fracture if struck. Unfortunately, the middle meningeal artery lies immediately behind the pterion, therefore traumatic injuries to this area may cause an extradural haemorrhage.

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37
Q

Which artery lies immediately behind the pterion

A

Middle meningeal

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38
Q

Craniosynostosis

A

The sutures (joints between the bones) of the skull do not completely fuse until a child is around two years old. This allows the brain to increase in size as the child grows quickly in infancy. If certain sutures of the skull fuse together too early, as the brain continues to grow it will cause the skull to become misshapen and this is called craniosynostosis. The skull may be elongated in the longitudinal, transverse or oblique planes, depending on which sutures fuse before they are supposed to.

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39
Q

At what age do the sutures in the skull fuse

A

2 years old

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40
Q

Burr holes and craniotomies

A

If there is a build-up of pressure within the fixed confines of the skull, this must be relieved, or the brain will eventually be compressed which can lead to death. Common causes of a build of pressure in this way may include intracranial bleeding (such as an extradural haemorrhage) or a brain tumour. To relieve the pressure quickly, a small hole (about 10-15 mm diameter) can be drilled into the skull. This allows the brain to expand enough to relieve the pressure, or it can be used to directly drain the bleeding that’s causing the pressure build-up. To perform surgery on the brain, a larger hole may be needed. This is called a craniotomy, and a circular piece of the skull is removed. This may be replaced later, or a prosthetic implant may be used to close the craniotomy instead. 

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41
Q

Which 4 bones meet at the pterion

A

Frontal
Parietal
Temporal
Sphenoid

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42
Q

Shape of the bony orbits

A

Cones with a broad opening at the front, tempering to a narrow part at the back

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43
Q

Which bones form the bony orbits

A

Larger frontal, sphenoid, zygomatic and maxillary bones
Smaller ethmoid and lacrimal bones

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44
Q

Structures found in the orbits

A

Eye
Extraocular muscle
Nerves
Fat
Lacrimal gland

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45
Q

Number of foramina at back of bony orbit

A

3

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46
Q

3 foramina at back of bony orbit

A

Optic canal
Superior orbital fissure
Inferior orbital fissure

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47
Q

Lacrimal gland

A

Found in the superior lateral part of the orbit
Produces tears to lubricate the anterior surface of the eye

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48
Q

Number of extraocular muscles

A

7

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49
Q

LR6SO4

A

Lateral rectus- cranial nerve 6
Superior oblique - cranial nerve 4
Rest if the extraocular muscles- cranial nerve 3

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50
Q

Elevation

A

Look up

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51
Q

Depression

A

Look down

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52
Q

Adduction

A

Look medially

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53
Q

Abduction

A

Look laterally

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54
Q

Extorsion

A

To rotate the eye so the top of the eye rotates laterally

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55
Q

Intorsion

A

To rotate the eye so the top of the eye rotates medially

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56
Q

Conjugate eye movements

A

Eyes perform different movements to look to the same place
Eg to look left= left eye will abduct and right eye will adduct

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57
Q

7 extraocular muscles

A

Levator palpebrae superioris
Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Superior oblique
Inferior oblique

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58
Q

Nerve supply of Levator palpebrae superioris

A

Oculomotor nerve (CN III)

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59
Q

Nerve supply of superior rectus

A

Oculomotor nerve (CN III)

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60
Q

Nerve supply of inferior rectus

A

Oculomotor nerve (CN III)

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61
Q

Nerve supply of medial rectus

A

Oculomotor nerve (CN III)

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62
Q

Nerve supply of inferior oblique

A

Oculomotor nerve (CN III)

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63
Q

Nerve supply of lateral rectus

A

Abducens nerve (CN VI)

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64
Q

Nerve supply of superior oblique

A

Trochlear nerve (CN IV)

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65
Q

Action of the Levator palpebrae superioris

A

Elevate the superior eyelid

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66
Q

Action of the superior rectus

A

Elevate
Intort
Adduct

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67
Q

Action of the inferior rectus

A

Depress
Extort
Adduct

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68
Q

Action of the medial rectus

A

Adduct

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69
Q

Action of the lateral rectus

A

Abduct

70
Q

Action of the superior oblique

A

Intort
Depress
Abduct

71
Q

Action of the inferior oblique

A

Extort
Elevate
Abduct

72
Q

Findings if non-functional Levator palpebrae superioris

A

Ptosis (drooping eyelid)

73
Q

Findings if non-functional superior rectus

A

Unable to elevate

74
Q

Findings if non-functional inferior rectus

A

Unable to depress

75
Q

Findings if non-functional medial rectus

A

Unable to adduct

76
Q

Findings if non-functional inferior oblique

A

Unable to elevate if eye is adducted

77
Q

Findings if non-functional lateral rectus

A

Unable to abduct

78
Q

Findings if non-functional superior oblique

A

Unable to depress if eye is adducted

79
Q

Common tendinous ring (annulus of Zinn)

A

The four recti extraocular muscles originate at the back of the orbit on a fibrous ring

80
Q

Superior and inferior rectus

A

Main function: elevate or depress the eye
Secondary effects: intorsion, extorsion or adduction

81
Q

Trochlea

A

A fibrous sling which the superior oblique passes through located in the superior and medial corner of the orbit

82
Q

Action and location of the superior oblique

A

Originates at the back of the eye
Passes through the trochlea
Inserts onto the top of the eye
Intorsion as pulls the top of the eye medially causing it to rotate

83
Q

What help maintains steady vision when looking up or down

A

Oblique muscles are able to Intort and extort to counter the secondary effects of extorsion and Intorsion caused by the inferior and superior recti muscles

84
Q

Accommodation

A

The eye must be able to focus light to varying amounts depending on how far away the object is that is being visualised

85
Q

Mechanism of accommodation

A

The eye adjusts the thickness of the lens
Thicker lens= greater refraction of light —> near objects
Thinner lens= less refraction of light —> far away objects

86
Q

Thinner lens

A

Less refraction of light
Far away objects

87
Q

Thicker lens

A

More refraction of light
Near objects

88
Q

Which muscles are responsible for adjusting the thickness of the lens

A

Ciliary muscles

89
Q

Which nerve innervates the ciliary muscles

A

Parasympathetic fibres of the oculomotor nerve (CN III)

90
Q

Which nerve innervates the constrictor pupillae

A

Parasympathetic fibres of the oculomotor nerve (CN III)

91
Q

How is the retina protected from over exposure to light

A

Constrictor pupillae in iris constricts = circular muscle

92
Q

Which nerves innervate the dilator pupillae

A

Sympathetic fibres that originate from the sympathetic chain and enter the skull alongside the internal carotid artery

93
Q

How is the iris dilated when it is dark

A

Dilator pupillae will dilate - radial muscle

94
Q

Pupillary light reflex

A

Responsible for automatically adjusting the amount of light entering the eye

95
Q

Afferent nerve of pupillary light reflex

A

Optic nerve - carries information about amount of light detected on retina to the midbrain

96
Q

Synapse between the afferent and efferent nerves of the pupillary light reflex

A

Edinger-Westphal nucleus in midbrain

97
Q

Efferent nerve of the pupillary light reflex

A

Oculomotor nerve - initiates constriction of the constrictor pupillae

98
Q

Direct pupillary response

A

Constriction of pupil with light shone directly into it

99
Q

Consensual pupillary response

A

Constriction of the pupil with light not shone into it

100
Q

Causes of consensual pupillary response

A

Connection between the left and right Edinger-Westphal nuclei

101
Q

Function of lacrimal gland

A

Produces tears to lubricate and moisten the surface of the eye

102
Q

Location of the lacrimal gland

A

Superior and lateral corner of the orbit

103
Q

Location of lacrimal ducts

A

Inferior and medial corner of the orbit

104
Q

Pathway of tears

A

Secreted by lacrimal gland
Flow across the eye into lacrimal ducts
Drain into nasal cavity via nasolacrimal duct

105
Q

What drains tears into the nasal cavity

A

Nasolacrimal duct

106
Q

Which nerve innervates the lacrimal gland

A

Parasympathetic fibres of the facial nerve (CN VII)

107
Q

Orbital wall fractures

A

Direct traumatic blows to the eye (as may be sustained during a fist fight) may fracture the walls of the orbit. These are known as ‘blow out’ fractures and a fracture of the inferior orbital wall is most common. The inferior rectus muscle can become trapped inside the fracture, tethering the eye in position and patients will be unable to look up.

108
Q

Cataracts

A

A cataract is a common ocular condition characterised by clouding of the lens that is responsible for focusing light onto the retina. Cataracts develop slowly and painlessly, and whilst they cannot be prevented, they are relatively easily treated surgically, by removing the affected lens and replacing it with a new and clear intraocular lens.
 

109
Q

Oculomotor nerve palsy

A

If the oculomotor nerve is not functioning on one side, it produces a very characteristic set of findings on clinical examination. The affected eye will rest in a ‘down-and-out’ position (depressed and abducted). This is because the lateral rectus and superior oblique muscles are unopposed so pull the eye into that position at rest. The affected eye’s pupil will also be dilated due to loss of parasympathetic nerve supply to the constrictor pupillae, leaving dilator pupillae unopposed. Finally, due to the loss of motor nerve supply to levator palpebrae superioris, the eyelid will droop. This is known as ptosis. Additionally, on asking the patient to look left and right, the affected side will be unable to adduct.

110
Q

Abducens nerve palsy

A

If the abducens nerve is not functioning on one side, the affected eye will be unable to abduct as the lateral rectus muscle is no longer working. The lateral rectus muscle may be overpowered by the medial rectus, which is still functional, to pull the eye medially at rest causing strabismus (sometime referred to as a ‘squint’).

111
Q

How do clinicians test the function of the trochlear nerve

A

To isolate the superior oblique muscle and ensure the patient is moving their eye in such a way that only the superior oblique can perform that movement, a clinician observes if the patient can depress an adducted eye. Whilst adducted, the inferior rectus, which is normally responsible for depression, is kinked in such a way that it is rendered weak and unable to depress the eye. Because of the orientation of the fibres of the superior oblique and where it attaches to the top of the eye, it becomes a powerful depressor of the eye in the adducted position.

112
Q

Testing eye movements

A

The do this, a clinician may ask the patient to follow their finger as they draw the shape of the letter ‘H’ in front of the patient. The clinician observes the patient’s eyes to ensure they are moving together and asks the patient if they are experiencing any diplopia (double vision).

The four recti muscles are relatively straightforward to test as they are functioning if the eyes can elevate, depress, abduct and adduct.

113
Q

Effect of opiates on pupillary response

A

Cause pupillary constriction in higher doses

114
Q

Effect of sympathomimetics on pupillary response

A

Pupillary dilation

115
Q

Examples of opiates

A

Morphine
Heroine (diamorphine)

116
Q

Examples of sympathomimetics

A

Ecstasy (MDMA)
Cocaine

117
Q

Head injuries and pupillary response

A

If a patient suffers a significant head injury and has bleeding inside the skull (for example, an extradural haemorrhage), intracranial pressure will rise. This may lead to compression of the oculomotor nerve on one or both sides. If compressed, the oculomotor nerve may be unable to function properly and an early sign of this is dilation of the ipsilateral pupil. This is another reason why clinicians often check the size of a patient’s pupils during clinical examination of unconscious patients. A fixed and dilated pupil is a concerning sign.

118
Q

Most external part of the ear

A

Pinna

119
Q

What makes up the outer ear

A

Pinna, ear canal and tympanic membrane

120
Q

Pinna

A

Shaped to gather sound waves and direct them into the ear canal

121
Q

Ear canal

A

Directs sound waves towards the tympanic membrane

122
Q

Tympanic membrane

A

Vibrates and transmits sound waves deeper into the ear towards the cochlea

123
Q

What does the middle ear cavity contain

A

The ossicles
Eustachian tube
Tensor tympani muscle
Stapedius muscle

124
Q

Ossicles

A

3 of the smallest bones in the body
They carry the sound waves to the oval window which conveys it into the cochlea

125
Q

3 ossicles

A

Malleus
Incus
Stapes

126
Q

Malleus locatiom

A

First ossicle resting against the tympanic membrane

127
Q

Malleus

A

Shaped like a hammer
‘Handle’ connects to tympanic membrane
‘Head’ connects to incus

128
Q

Location of incus

A

Second ossicle

129
Q

Which ossicle can be seen during otoscopy

A

Malleus

130
Q

Stapes location

A

Third ossicle

131
Q

Stapes function

A

Receives sound wave vibrations from the incus and transmits them onto the oval window which marks the boundary between the middle and inner ear cavity

132
Q

Oval window

A

Marks boundary between the middle and inner ear cavity

133
Q

Location of the superior opening of the Eustachian tube

A

Superior opening of the auditory tube in the middle ear cavity

134
Q

Location of inferior opening of the auditory tube

A

Posterior and inferior part of the nasal cavity

135
Q

Function of the Eustachian tube

A

Maintains equal air pressure on both sides of the tympanic membrane by providing a connection of airflow between the external environment and middle ear cavity via the nasal cavity

136
Q

Tensor tympani muscle

A

Inserts on the malleus and when it contracts, increases tension in the tympanic membrane (reducing how much it can vibrate)

137
Q

Innervation of the tensor tympani muscle

A

Mandibular branch of the trigeminal nerve (CN V)

138
Q

Stapedius muscle

A

Inserts in the stapes and when it contracts, dampens the vibrations of the stapes

139
Q

Innervation of the Stapedius muscle

A

Facial nerve (CN VII)

140
Q

What does the inner ear cavity include

A

Bony labyrinth
Cochlea
Vestibular system

141
Q

Bony labyrinth

A

A network of small bony passages within the petrous part of the temporal bone of the skull

142
Q

Which 2 main organs does the bony labyrinth contain

A

Cochlea
Vestibular system

143
Q

Cochlea

A

As sound waves and vibrations travel through fluid in the cochlea, they are converted into electrical impulses which are passed via the cochlear nerve to the auditory cortex - allowing us to perceive sound

144
Q

Round window

A

Located near to the oval window and bulges in and out to allow the fluid in the cochlea to move

145
Q

Vestibular system consists of

A

Semicircular canals
Utricle
Saccule

146
Q

Vestibular system

A

Contains fluid, which flows when we move our head
Movement detected by specialised cells that cause them to produce electrical impulses
Passed along vestibular nerve towards parts of the brain eg cerebellum, thalamus, certain cranial nerve nuclei

147
Q

Number of semicircular canals in vestibular system

A

3

148
Q

Number of semicircular canals in the vestibular system

A

3

149
Q

Function of semicircular canals

A

Perceive mivement

150
Q

Arrangement of semicircular canals

A

3 positioned perpendicular to each other in three dimensions

151
Q

Function of utricle and saccule

A

Perceive linear acceleration

152
Q

Which nerve carries impulses from the cochlea and vestibular system

A

Vestibulocochlear nerve (CN VIII)

153
Q

Where does the vestibulocochlear nerve pass through

A

The internal auditory meatus towards the nuclei in the pons

154
Q

Oculocephalic reflex

A

Maintain a fixed gaze whilst moving our head due to connection between the vestibulocochlear nerve and oculomotor, trochlear and abducens nerves

155
Q

Vertigo

A

Vertigo is the symptom of being able to perceive movement when there is none. This is commonly perceived and recreated if you spin around several times and then stop suddenly. The perception of the world continuing to spin around you, or the floor moving unevenly beneath you, is vertigo. There are various causes of vertigo, but a common presentation to clinical practice is a disorder of the vestibular system. Inflammation, infections, endo/perilymph disorders or cancers of the vestibular system or nerves may cause vertigo.

156
Q

Vestibular Schwannoma

A

Also known as an acoustic neuroma, this is a benign tumour of the Schwann cells surrounding the vestibulocochlear nerve. As it grows, it gradually leads to symptoms of unilateral hearing loss, tinnitus, a feeling of fullness in the ear and vertigo. If it grows large enough, it will start to compress the other cranial nerves that leave the brainstem around the same position. This position is known as the cerebellopontine angle, and other cranial nerves leaving the brainstem here are the trigeminal (CN V) and facial (CN VII) nerves.

157
Q

Otitis media

A

Otitis media is the term for inflammation within the middle ear cavity. It is most often caused by a simple viral infection and is particularly common in young children. When a patient is suffering from an upper respiratory tract infection, the inflammation can spread throughout the upper respiratory tract from the nose and pharynx to the middle ear cavity via the auditory tube. This can lead to accumulation of inflammatory fluid and pus in the middle ear cavity, impairing conduction of sound waves along the ossicles.

The auditory tube is relatively narrow in young children and therefore less effective at draining the middle ear cavity. Because of this, a build of pus behind the tympanic membrane can increase pressure significantly which can be painful. If the inflammation continues, the tympanic membrane may rupture due to the pressure. This may relieve the pain and allow drainage of the pus. The tympanic membrane will usually later heal on its own. However, more serious cases of otitis media can spread deeper into the ear and cause inflammation of the cochlea or vestibular system, mastoid process of the temporal bone or the meninges.

158
Q

What happens when our ears pop

A

pressure can be felt when descending in an aeroplane from a significant height, or when diving underwater. As you descend deeper, air (or water) pressure outside the tympanic membrane increases and causes the membrane to bulge inwards. To counter this, air is allowed to pass up through the auditory tube to increase air pressure on the inside of the tympanic membrane. Sometimes, if the pressure correction occurs suddenly, you can feel a ‘pop’ in your ear.

159
Q
  1. List the cranial nerves which pass through the following foramina:
    a. Superior orbital fissure
A

Oculomotor (III)
Trochlear (IV)
Ophthalmic (V1)
Abducens (VI)

160
Q
  1. List the cranial nerves which pass through the following foramina:
    b. Jugular foramen
A

Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)

161
Q
  1. List the cranial nerves which pass through the following foramina:
    c. Internal acoustic meatus
A

Facial (VII)
Vestibulocochlear (VIII)

162
Q
  1. Within which bone is the sella turcica situated?
A

Sphenoid bone

163
Q

What structure is found within the sella turcica?

A

Pituitary gland

164
Q
  1. Which four bones unite to form the pterion?
A

Parietal bone
Squamous part of temporal bone
Greater wing of sphenoid bone
Frontal bone

165
Q

Which artery is located immediately deep to the pterion? Which kind of intracranial haemorrhage may be caused by a disruption of this artery?

A

Middle meningeal artery
Extradural haemorrhage

166
Q
  1. Interruption to which nerve(s) would cause miosis (constricted pupil), ptosis and a lack of sweating on the affected side of the face?
A

Ascending sympathetic fibres in the sympathetic trunk - Horner’s syndrome

167
Q
  1. How could you test the function of the trochlear nerve? What exactly would you ask your patient to do to achieve this?
A

Ask the patient to look down and to the opposite side if the eye that you’re testing i.e., if testing the left eye, ask the patient to look down and to the right
This ensures the eye is adducted and depressed
The superior oblique muscle is the only muscle able to fully depress an adducted eye

168
Q
  1. A fracture of the roof of the maxillary sinus would mean which wall of the orbit is fractured? Which extraocular muscle may be impinged in this fracture? How would this appear on examination?
A

Inferior wall of the orbit
Inferior rectus muscle
Patient would be unable to look upwards

169
Q
  1. What is the order of the ossicles from tympanic membrane to oval window?
A

Malleus
Incus
Stapes

170
Q
  1. What happens when we feel our ears ‘pop’?
A

Equalisation of pressure in either side of the tympanic membrane

171
Q

Where are the middle and inner ear cavities located

A

Petrous part of the temporal bone

172
Q

Which nerve travels through the middle ear cavity and branches to supply the tongue

A

Facial nerve

Neuroanatomy (8 decks)

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