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A&P > The Eye & Ear > Flashcards

The Eye & Ear Flashcards

1
Q

Where is the eye situated?

How is it protected?

What nerve is it supplied by?

A
  • Situated in the anterior part of the orbital cavity of the skull
  • Embedded in a pad of fat
  • Well protected from injury – only the anterior aspect is not surrounded by bone
  • Supplied by the 2nd cranial (optic) nerve
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2
Q

Label this image

A
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3
Q

Label this eye

A
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4
Q

What are the 3 layers of the eye?

A

Outer fibrous coat

  • Sclera
  • Cornea

Middle vascular coat

  • Choroid
  • Ciliary body
  • Iris

Inner nervous coat

•Retina

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5
Q

Label this image

A
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6
Q

Describe the sclera?

A

The sclera:

  • Opaque – ‘the white of the eye’
  • Posterior 5/6th of the outer coat
  • Continuous with the cornea anteriorly
  • Strong white fibrous tissue with a few scattered yellow elastic fibres
  • Poor blood supply
  • Smooth except where muscles attach
  • The optic nerve pierces the sclera posteriorly which extends along the nerve and is continuous with the dura mater of the skull
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7
Q

Describe the cornea?

A

The cornea:

  • Clear, transparent circular structure
  • Covers the anterior 1/6th of the eye
  • Slightly more convex than the sclera
  • Outer epithelial layer, the conjunctiva
  • Inner layer of modified connective tissue
  • Continuous at it’s margins with the sclera
  • Avascular
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8
Q

What is the choroid?

A

The choroid:

  • Thin pigmented vascular membrane
  • Dark brown in colour
  • Loosely attached to the sclera except where pierced by the optic nerve where the choroid is firmly attached to the sclera
  • Dense capillary network
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9
Q

What is the ciliary body?

A

The ciliary body

  • The choroid is continuous anteriorly with the ciliary body
  • Circular structure
  • Lies posterior to the junction of the cornea and sclera
  • Large numbers of smooth muscle fibres
  • The suspensory ligament of the lens is attached to its inner surface
  • The ciliary body is an intrinsic muscle – alters the convexity of the lens to focus light on the retina
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10
Q

What is the iris?

A

The iris

  • Thin pigmented membrane
  • Lies in the aqueous humour between the cornea and lens
  • Attached at its outer margins to the ciliary body
  • Intrinsic muscle containing circular and radial muscle fibres
  • Variations in the aperture of the iris occur with different environmental light intensities
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11
Q

What is the retina?

What are rods and cones?

What’s the macula?

What’s the fovea?

Explain the fovea?

A

The retina

  • Lines the choroid and extends anteriorly to the ciliary body
  • Delicate membrane containing nerve cells and fibres and specialised structures called rods and cones
  • Rods and cones are the light receptors of the eye
  • The macula is at the centre of the posterior part of the retina
  • In the centre of the macula is a small depression – the fovea
  • The fovea contains only cones and is the point of most accurate vision
  • Within the fovea, each cone is attached to one bipolar nerve cell whereas more peripherally a number of rods and cones are attached to a single nerve cell thereby decreasing visual acuity
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12
Q

Where is the optic disc?

What is the optic disc?

A
  • The optic disc is just medial to the macula
  • The optic disc is the region where the nerve fibres pass posteriorly to enter the optic nerve
  • The ophthalmic artery and vein also pass through the optic disc
  • The optic disc does not contain any rods or cones and is known as ‘the blind spot’
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13
Q

Label this image x3

A
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14
Q

What are rods and cones?

A
  • Photosensitive pigments
  • Convert light into nerve impulses

Rods

  • Black & white
  • More sensitive – can function in lower ambient light levels

Cones

  • Bright light
  • colour
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15
Q

What is the aqueous humour?

Where?

A

The Aqueous Humour

  • Clear watery fluid
  • Situated between the lens and the cornea
  • The anterior chamber is in front of the iris, the posterior chamber is behind the iris
  • Aqueous humour is secreted into the posterior chamber by capillaries in the ciliary body
  • Passes through the pupil into the anterior chamber where it drains into the ciliary veins
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16
Q

What is the lens of the eye?

A

The Lens

  • Biconvex transparent structure
  • Enclosed within a capsule
  • Suspended from the ciliary body by the suspensory ligament which is attached to the lens at its margins
  • The capsule and the lens are elastic
  • The shape of the lens is altered by contractions of the ciliary body
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17
Q

What is the vitreous humour?

A

The Vitreous Humour / Body

  • Jelly-like transparent substance
  • Fills the region of the eye that lies behind the lens
  • Helps maintain the shape of the eye
  • Helps maintain the position of the retina against the choroid
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18
Q

Label this image with:

Aqueous humour

Vitreous humour

Lens

A
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19
Q

Explain the extrinsic muscles of the eye?

A

The Extrinsic Muscles of the Eye

  • Responsible for the co-ordinated movements of the eye
  • Each eye has four ‘straight’ and two ‘oblique’ muscles
  • Arise from the bony walls of the orbit
  • Are attached to the sclera
  • Supplied by the oculomotor, trochlear and abducens cranial nerves
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20
Q

List the extrinsic eye muscles and what they do?

A

The Extrinsic Muscles of the Eye

  • Superior rectus – turns the eye upwards
  • Inferior rectus – turns the eye downwards
  • Medial rectus – turns the eye inwards
  • Lateral rectus – turns the eye outwards
  • Inferior oblique – turns the eye upwards and outwards
  • Superior oblique – turns the eye downwards and outwards
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21
Q

Label this image

A
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22
Q

What are the optic nerves?

Where do they pass?

A

The Optic Nerves

  • Formed on the posteromedial side of each eye where the nerve fibres pierce the optic disc
  • Leaves the orbital cavity through the optic foramen to enter the middle cranial fossa
  • The optic chiasma lies immediately anterior to the sella turcica

The optic nerves pass through the optic chiasma with the medial nerves crossing over

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23
Q

Label image

A
24
Q

What do the intrinsic muscles of the eye do?

A

Intrinsic muscles

  • Focus lens
  • Alter diameter of iris (controlling ambient light)
25
Q

What do the extrinsic muscles of the eye do?

A

Extrinsic muscles

•Global movement of the eye

26
Q

List the accessory organs of sight

A

The Accessory Organs of Sight

  1. •Eyebrows
  2. •Eyelids
  3. •Lacrimal apparatus
  4. •Extrinsic muscles of the eye
27
Q

What are eyebrows and what do they do?

A

Eyebrows

  • Hairs on the skin covering the supraorbital ridges of the frontal bone
  • Prevent sweat running into the eye
28
Q

What are eyelids and what do they do?

A

Eyelids

  • Form the anterior protection for the eye
  • Blink frequently
  • Corneal reflex – eyelids close instantly if an object approaches or touches the eye
  • The eyelashes have a protective function
  • Outer covering of skin
  • Contain areolar tissue and smooth muscle fibres which form the orbicularis oculi (sphincter muscle)
  • Lined by the conjunctiva
29
Q

What is the conjunctiva?

A

The Conjunctiva

  • Delicate mucous membrane
  • Forms the outer epithelial layer of the cornea and lines the eyelids
  • Referred to as the conjunctival sac, although only forms a closed sac when the eyelids are shut
30
Q

What is the lacrimal apparatus composed of?

A

The Lacrimal Apparatus

Composed of:

  • The lacrimal gland
  • The lacrimal ducts
  • The lacrimal canaliculi
  • The lacrimal sac
  • The nasolacrimal duct
31
Q

Where is the lacrimal gland?

What does it do?

A

The Lacrimal Gland

  • Lies in the orbital cavity in a recess in the lateral part of the roof just posterior to the supraorbital margin
  • Secretes ‘tears’ which pass down a number of small ducts into the upper outer angle of the conjuctival sac
  • The tears then pass across the anterior surface of the eye
  • Blinking helps move the tears over the eye
32
Q

What are the lacrimal canaliculi?

A

The Lacrimal Canaliculi

  • The lacrimal canaliculi are two small ducts which open at the medial aspect of the eye into each eyelid
  • The tears pass along these ducts to enter the lacrimal sac
33
Q

What are the lacrimal sac and duct?

A

The Lacrimal Sac & Duct

  • The lacrimal sac is a depression in the surface of the lacrimal bone
  • The nasolacrimal duct drains the tears from the lacrimal sac into the inferior meatus of the nose
  • The tears are continuously secreted by the lacrimal gland and moisten and clean the anterior surface of the eye
  • Crying is an emotional reaction whereby an excess of tears is produced which overflow the conjunctival sac
34
Q

Label this image with the lacrimal apparatus

A
35
Q

What is the ear?

Where?

Balance?

Cranial nerve?

A
  • Organ of hearing
  • Located mainly in the temporal bone
  • Closely associated with the ear are the semi-circular canals which have no auditory function but are involved in the maintenance of balance
  • The ear and the semi-circular canals are supplied by the vestibulocochlear (8th) cranial nerve
36
Q

Label the ear

A
37
Q

What are the 3 sections to the ear?

A
38
Q

What is the external ear composed of?

A

•The external ear – pinna and external auditory meatus, connects with the middle ear via the tympanic membrane

  • Pinna
  • External auditory meatus
  • Tympanic membrane
39
Q

Label the image

A
40
Q

What is the pinna?

A

The Pinna / Auricle

The pinna is attached to the side of the head

The upper portion is made of elastic fibrocartilage

The lower portion, the lobe, is composed of adipose and connective tissue

The pinna is covered with skin

41
Q

What is the EAM?

Length?

Makeup?

A

The External Auditory Meatus (EAM)

Slightly S shaped tube

Extends from the pinna to the tympanic membrane

About 4 cm long

Outer 1/3 is cartilaginous

Inner 2/3 has bony walls and lies within the temporal bone

Lined with skin which contains ceruminous glands (secrete wax)

42
Q

What is the tympanic membrane?

Shape?

Diameter?

3 coats?

A

Tympanic Membrane

Oval shaped membrane

Lies obliquely

Is about 9 – 10 mm across its greatest diameter

Three coats:

Outer stratified epithelial coat – continuous with epidermis of EAM

Middle fibrous coat

Inner cuboidal epithelial coat – continuous with lining of middle ear

43
Q

What is the middle ear?

A

The Middle Ear

  • Irregularly shaped cavity within the petrous portion of the temporal bone
  • Contains three small bones, the ossicles, which articulate and form a chain which transmits the vibrations of the tympanic membrane to the inner ear
  • Communicates with the pharynx through the auditory (Eustachian) tube
  • Lined by mucous membrane
44
Q

What are the 2 medial wall openings of the middle ear?

A

The medial wall has two openings:

  • The fenestra vestibuli (oval window) through which the middle ear communicates with the inner ear and is covered by the stapes
  • The fenestra cochlea (round window) through which the middle ear communicates with the cochlea and is covered by fibrous tissue
45
Q

What are the ossicles of the middle ear?

A

The Ossicles of the Middle Ear

  • Malleus, incus and stapes
  • Stretch across the middle ear from the tympanic membrane to the fenestra vestibuli
  • Malleus – hammer shaped, articulates with the incus
  • Incus – anvil shaped, connected to the roof of the middle ear by ligaments, articulates with the malleus and stapes
  • Stapes – stirrup shaped, articulates with the incus, base is connected to the fenestra vestibuli by a membrane
46
Q

Label this image

A
47
Q

What cranial nerve supplies the inner ear?

What two parts compose the inner ear?

A

Vestibular nerve and cochlear nerve are divisions of the eighth cranial nerve

The Inner Ear

Composed of two parts:

  • The bony labyrinth – a series of cavities lying within the petrous portion of the temporal bone
  • Filled with perilymph
  • Contains membranous labyrinth
  • The membranous labyrinth – a series of membranous sacs lying with the bony labyrinth
48
Q

What 3 parts compose the bony labyrinth of the inner ear?

A

The Bony Labyrinth

Composed of three parts:

The Vestibule

  • Communicates via the fenestra vestibuli with the middle ear
  • The cochlea and the semicircular canals open into the vestibule

The Cochlea

•Hearing

  • ‘Snail’s shell’
  • Lies anterior to the vestibule
  • Wide at it’s origin but gradually narrows
  • Communicates with the middle ear through the fenestra cochlea
  • Communicates with the vestibule

The Semicircular Canals

  • Three – superior, lateral and posterior
  • Communicate with the vestibule by five openings
  • Concerned with balance and the position of the head
49
Q

What is the vestibule of the inner ear?

A

The Vestibule

  • Communicates via the fenestra vestibuli with the middle ear
  • The cochlea and the semicircular canals open into the vestibule
50
Q

What is the cochlea of the inner ear?

A

The Cochlea

  • ‘Snail’s shell’
  • Lies anterior to the vestibule
  • Wide at it’s origin but gradually narrows
  • Communicates with the middle ear through the fenestra cochlea
  • Communicates with the vestibule

•Hearing

51
Q

What are the semicircular canals of the inner ear?

A

The Semicircular Canals

  • Three – superior, lateral and posterior
  • Communicate with the vestibule by five openings
  • Concerned with balance and the position of the head
52
Q

Label this image

A
53
Q

What is the membranous labyrinth?

What does it consist of?

A

The Membranous Labyrinth

•Lies within the bony labyrinth

Consists of two membranous sacs which lie within the vestibule:

  • The utricle
  • The saccule
54
Q

Explain the structure and function of the utricle and saccule of the membranous labyrinth?

A
  • The membranous labyrinth is filled with a fluid called endolymph
  • The utricle is the larger membranous sac
  • It extends into the semicircular canals, forming the semicircular ducts
  • The utricle communicates with the saccule
  • The utricle, saccule and semicircular ducts are lined with epithelial cells which possess fine processes called hair cells
  • Fibres from the 8th cranial nerve are interspersed between the hair cells
  • The cochlea duct arises from the saccule
  • It runs through the cochlea and divides the cochlea into an upper scala vestibuli and a lower scala tympani
  • The organ of Corti lines the cochlea duct, and is the organ of hearing
  • The organ of Corti is supplied by cochlear fibres of the vestibulocochlear nerve
55
Q

Explain the path of sound waves for hearing?

Frequency?

Amplitude?

A

Sound waves

  • Vibrations are transmitted through:
  • Tympanic membrane
  • The ossicles
  • The fenestra cochlea
  • Into cochlea duct causing wave motion in endolymph

Frequency

•positions

Amplitude

•Stimulates hair cells at different strength signal

56
Q

Explain how balance is achieved?

A

Changes in head position

  • Cause movement of perilymph and endolymph
  • Cause movement of hair cells

Resultant nerve impulses transmitted by vestibular nerve

Combined with input from eyes and receptors within joints and muscles

A&P (17 decks)

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