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MD4001 Week 3 > 8. Anatomy of special sense organs > Flashcards

8. Anatomy of special sense organs Flashcards

1
Q

Location of the olfactory tract and bulb?

A

Inferior surface of the frontal lobe

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2
Q

Reasons for acoustic meatus narrowing?

A

Acoustic neuroma

Also… due to mastoiditis and Paget’s disease

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3
Q

Tumours in the internal acoustic meatus & at the cerebellopontine angle will impinge upon…

A

Tumours in the internal acoustic meatus & at the cerebellopontine angle will impinge upon CNVII & VIII giving ipsilateral facial signs (possibly extending to include CN V)

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4
Q

Course of CN I on the base of skull?

A

Arise from olfactory bulb and pass through the cribriform plate of the ethmoid bone.
Then within the superior aspect of the nasal cavity.

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5
Q

Course of CN II on the base of skull?

A

CN II surrounded by a sleeve of meninges & CSF passes through the optic canal with the ophthalmic branch of the internal carotid artery to reach the orbit

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6
Q

What are the 2 nuclei of the CN VIII?

A

Vestibular and cochlear nucleus

Hence the name “vestibulocochlear nerve”

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7
Q

Potential structures affecting in a cranial base fracture?

A 
Ear
Eye
Nose
Petrous temporal bone
Orbit
Cribriform plate
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8
Q

Which bone prevents posterior dislocation of the mandible?

A

The tympanic plate of the temporal bone

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9
Q

What are the external, middle and internal structures of the ear?

A

External:

  • Auricle
  • External acoustic meatus of cartilage and bone (leads sound eaves to the tympanic membrane)

Middle:

  • Ossicles (which mechanically transmit sound, connected to pharynx by the auditory tube)
  • Tympanic membrane

Internal:

  • Semi-circular canals (detect motion)
  • Cochlea (detect hearing, converts mechanical signals to electrical. Innervated by CN VIII)
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10
Q

Stylomastoid foramen through which CN ____ emerges

A

Stylomastoid foramen through which CN VII emerges

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11
Q

Where does the vestibulocochlear apparatus lie within?

A

Petrous temporal bone

The bony semicircular canals, particularly the anterior, cause slight elevations on the bone surface in the middle cranial fossa

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12
Q

Role of the auricle?

A

elastic cartilage for support & ‘catching’ the sound & funnelling it into the external acoustic meatus

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13
Q

Composition of external acoustic meatus?

A

Lateral 1/3 = Cartilaginous
Medial 2/3 = bony

Lined by skin, with hairs, containing ceruminous glands (modified sweat glands) that secrete ear wax

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14
Q

How and why is the external acoustic meatus?

A

Slightly sinuous course so should be straightened for examination of the tympanic membrane by pulling the ear superiorly, posteriorly & slightly laterally

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15
Q

The internal surface of the tympanic membrane and middle ear are supplied by…

A

the CN IX

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16
Q

What holds the tympanic membrane in place?

A

Held within the temporal bone by a fibrocartilaginous ring

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17
Q

Name the 3 ossicles found in the tympanic cavity?

A
  1. Stapes
  2. Incus
  3. Malleus (attached to the tympanic membrane)
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18
Q

Difference between round and oval window of the cochlea in the inner ear?

A

The round window acts as a pressure release. Covered by a secondary tympanic membrane

The oval window is covered by the base of the stapes ossicle bones, hence it converts mechanical impulses to electrical signals

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19
Q

Which muscles prevent excess movement of the ossicles?

A

Tensor tympani and stapedius

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20
Q

Innervation and attachment of tensor tympani?

A

Innervation: CN V3 via nerve to medial pterygoid muscle

Attachment: From canal of petrous temporal bone above the auditory tube –> handle of malleus ossicle

Role to prevent excess movement of the malleus

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21
Q

Innervation and attachment of stapedius?

A

Innervation: CN VII

Attachment: Arises within the pyramidal eminence –> neck of the stapes

Role to prevent excess movement of the malleus.
Loss of function causes hyperacusis

22
Q

Other names for auditory tube?

A

Eustachian

Pharyngotympanic

23
Q

At which point does the auditory canal become cartilaginous?

A

Initially bone, becomes cartilaginous between the petrious temporal bone and the greater wing of the sphenoid

24
Q

Why does swelling of the tubal tobsil cause otitis media?

A

It can block the auditory tube

25
Q

middle ear extending posteriorly via the epitympanic recess & aditus into ….

A

the mastoid antrum & air cells

26
Q

How to middle ear infections arise? What is the associated risk?

A

Infections in the middle ear are common & often caused by obstruction to the auditory tube
Chronic infections may damage the ossicles causing conductive deafness & these may even spread to the mastoid air cells or beyond

27
Q

Why is there a risk of infection spread between the middle ear and middle cranial fossa?

A

The roof of bone is very thin and weak

28
Q

Bony labyrinth..
Where?
Consists of?
Contains

A

Is the rigid, bony outer wall of the inner ear in the temporal bone.

It consists of three parts:
the vestibule, semicircular canals, and cochlea.

Membranous labyrinth
Perilymph
Endolymph

(In the inner ear)

29
Q

Role of the cochlear and vestibular aqueducts?

A

Cochlear & vestibular aqueducts allow the membranous labyrinth to connect with the subarachnoid space for reabsorption of peri & endolymph

30
Q

Innervation fo the semicircular canals, utricles and saccule of the labyrinth?

A

From the vestibular part of CN VIII

Leaves these structures to form a ganglia in the internal acoustic meatus

31
Q

Clinical signs that the balance has been disturbed?

A

Ataxia
Vertigo
Nausea
Nystagmus

32
Q

What is the cochlea’s innervation?

A

The cochlear part of CN VIII is derived from the organ of Corti in the cochlea & lies in the internal acoustic meatus with the vestibular part of CN VIII & CN VII

33
Q

What separates the anterior and posterior chambers of he eye?

A

The iris but communicate via the pupil

Contain the aqueous humour

34
Q

What forms the outer fibrous layer of the eye?

A

Sclere (replaced by cornea anteriorly)
(Below it is the vascular choird layer
Most inner is the retina)

35
Q

Choroid continues as the ciliary body which forms a complete…..

A

Choroid continues as the ciliary body which forms a complete supportive ring around the lens & iris

36
Q

When ciliaris contracted, what happens to the lens?

A

When ciliaris muscle (in the ciliary body) contracts (parasympathetic, CN III, Edinger-Westphal nucleus) the ring shrinks, the suspensory ligaments relax, & the lens becomes rounded (accommodation for close vision)

37
Q

The iris contains both the sphincter (__________, CN III, Edinger-Westphal nucleus) & _____ (sympathetic) pupillae

A

The iris contains both the sphincter (parasympathetic, CN III, Edinger-Westphal nucleus) & dilator (sympathetic) pupillae

38
Q

Production and reabsorption of aqueous humour?

A

Aqueous humour is secreted by the ciliary body & reabsorbed by the scleral venous sinus (canal of Schlemm)

39
Q

Cause of glaucoma?

A

Glaucoma results from excess pressure; drugs that constrict the pupil may ‘pull’ the venous sinus open & help

40
Q

What is the role of ciliary muscles in lens accommodation?

A

Ciliary muscle relaxation –> zonular fibers under tension –> Lens is stretchde thin to refract light from distance

PS stimulation to ciliary muscles leads to contract–> Zonule fibers relax –> Internal tension and lack of stretching cause lens to become more spherical. Now able to refracted light to near vision

41
Q

Dilator pupillae under ________ control

Sphincter pupillae under _________ control

A

Dilator pupillae under sympathetic control

Sphincter pupillae under parasympathetic control

42
Q

What structures are present at the optic disk? Why is called the blindspot?

A

• ‘Entry’ of optic nerve & central retinal vein with artery
which is an end/terminal artery with obstruction
causing blindness
• Devoid of photoreceptors & often referred to as the
‘blind spot’

43
Q

Clinical macula = anatomical ______ centralis

A

Clinical macula = anatomical fovea centralis

I.e. region of greatest visual sensitivity

44
Q

Rods sensitive to ____ light and ____ colour

A

Rods sensitive to dim light and no colour

45
Q

Cones sensitive to ____ light and ____

A

Rods sensitive to bright light and colour

46
Q

inferior and posterio relation relation of optic chiasm?

A

The pituitary gland.

Pituitary tumour = tunnel vision

47
Q

Optic nerves —-> optic chiasm —> optic ___ –> _______ bodies of the thalamus –> occipital lobe of ____

A

Optic nerves —-> optic chiasm —> optic tracts –> geniculate bodies of the thalamus –> occipital lobe of cortex

48
Q

The right visual field passes to the left optic TRACT & left occipital lobe & vice versa!

A

The right visual field passes to the left optic TRACT & left occipital lobe & vice versa!

49
Q

Where is the lesion/problem:

  1. Left homoymous hemianopia?
  2. Blind in right eye
  3. Bitemporal hemianopia
A
  1. Right optic tract
  2. Right optic nerve
  3. At optic chiasm
50
Q

Clinical consequences of Horner’s syndrome?

A

Injury to symp trink –> loss of symp supply to:

  • Pupil dilator
  • Smooth muscle of levator palpebrae superioris
  • Sweat glands
  • Blood vessels

Soooo…. presents with:

  • Miosis (constriction)
  • Ptosis (droopy eye)
  • Anhydrosis
  • Flushed face
51
Q

Injury to the oculomotor nerve (CN III) will remove the _________ pupil constriction leading to a dilated pupil with ptosis (complete loss of levator palpebrae _______) & the eye is ______ downwards & outwards (______ oblique & lateral rectus)

A

Injury to the oculomotor nerve (CN III) will remove the parasympathetic pupil constriction leading to a dilated pupil with ptosis (complete loss of levator palpebrae superioris) & the eye is turned downwards & outwards (superior oblique & lateral rectus)

MD4001 Week 3 (12 decks)

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