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Anatomy 2 > Eye 1 > Flashcards

Eye 1 Flashcards

1
Q

what % of sensory receptors in the human body are located in the eyes

A

over 50%

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2
Q

Name the 3 main components of the eye

A

bony orbit
accessory structures
eyeball itself

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3
Q

Describe the bony orbit

A

the eyeball is a sphere - 2.5cm in diameter, suspended within a cavity in the skull = bony orbit - by muscles controlling its movements, consists of a roof, floor and medial & lateral walls (superior orbital wall, medial orbital wall, inferior orbital wall, lateral orbital wall, apex region)

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4
Q

Describe the role of periorbital fat

A

partially cushions eyeball, thick layer, protects it during movement

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5
Q

Name 5 accessory structures of the eye

A 
eyelid
eyelashes
eyebrows
lacrimal apparactus
extrinsic eye muscles
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6
Q

Describe the roles of the Eyelids

A

upper and lower eyelids (Palpebrae), shade the eyes during sleep, protect the eyes from excessive light and foreign objects, spread lubricating secretions over the eyeballs

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7
Q

Describe the tarsal plate within the eyelids

A

a thick fold of connective tissue within the eyelid that gives its form and support, embedded n each tarsal plate are rows of sebaceous glands known as tarsal or Meibomian glands - secrete a fluid that helps keep the eyelids from adhering to each other

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8
Q

Describe the conjunctiva of the eyelids

A

a thin, protective mucous membrane, lines the inner aspect of the eyelids and the surface of the eyeball, it covers the sclera but not the cornea

over the sclera the conjunctiva is vascular

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9
Q

Describe the role of eyelashes

A

protect the eye from debris

sebaceous ciliary glands at the base of the hair follicles release a lubricating fluid onto the lashes

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10
Q

Describe the role of the eyebrows

A 
help protect the eyeballs from 
foreign objects
perspiration
direct rays of the sun
provide facial expression
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11
Q

Describe the lacrimal apparatus

A

the lacrimal glands produce and secrete about 1ml of lacrimal fluid (tears) per day, the tears drain into the lacrimal ducts and out onto the surface of the conjunctiva of the upper lid, the tears then pass medially over the anterior surface of the eyeball, the tears then enter 2 small openings called lacrimal puncta, from the puncta the tears pass into the lacrimal canals which lead into the lacrimal sac and then into the nasolacrimal duct

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12
Q

Describe which lacrimal fluid contains

A

salts, some mucus and lysozyme - a protective bactericidal enzyme

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13
Q

What is the function of tears

A

to protect, clean, lubricate and moisten the conjunctiva and corneal epithelium

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14
Q

Describe the extrinsic eye muscles

A

extend from the walls of the bony orbit to the sclera of the eye, surrounded in the orbit by a significant quantity of orbital fat, capable of moving the eye in almost any direction

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15
Q

Name the 6 extrinsic eye muscles that move each eye

A 
superior rectus muscle
inferior rectus muscle
lateral rectus muscle
medial rectus muscle
superior oblique rectus muscle
inferior oblique rectus muscle
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16
Q

Which cranial nerves are the extrinsic eye muscles supplied by

A

Oculomotor (III) - supplies the superior, medial, inferior and inferior oblique rectus muscles
Trochlear (IV) - supplies the superior oblique rectus muscle
Abudcens (VI) - supplies the lateral rectus muscle

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17
Q

Name the 3 layers of the eyeball

A

Fibrous tunic - superficial layer
Vascular tunic - middle layer
Retina - inner layer

18
Q

Describe the cornea of the eyeball

A

a transparent coat that covers the coloured iris, its curved and so helps focus light onto the retina

19
Q

Describe the sclera of the eyeball

A

‘white of the eye’, covers entire eyeball except the cornea, gives shape to the eyeball, makes it more rigid, protect its inner parts, serves as a site of attachment for the extrinsic eye muscles

20
Q

Desciribe the fibrous tunic layer of the eyeball

A

consists of the anterior cornea and posterior sclera

21
Q

Describe the vascular tunic or uvea layer of the eyeball

A

composed of 3 parts
Choroid
Ciliary Body
Iris

22
Q

Describe the choroid

A

lines most of the internal surface of the sclera, produces the pigment melanin - absorbs stray light rays, preventing reflection and scattering of light within the eyeball - ensures image cast on retina remains sharp and clear

23
Q

Describe the anterior portion of the vascular tunic eyeball

A

the choroid becomes the ciliary body - contains the ciliary muscle, suspensory ligaments (zonules) extends from the ciliary body and attach to the lens
contraction or relaxation of the ciliary muscle changes the tightness of the suspensory ligaments which alters the shape of the lens, adapting it for near or far vision

24
Q

Describe what happens for near vision

A

ciliary muscles contract and the central lens thickness increases to increase its power

25
Q

Describe the iris within the vascular tunic layer of the eyeball

A

coloured portion of the eyeball, suspended between the cornea and the lens, attached at its outer margin to the ciliary suspensory ligaments (zonules), iris consists of muscle fibres which function to regulate the amount of light entering the eyeball through the pupil in response to light levels

26
Q

Describe what happens in bright/dim light

A

bright light causes a decrease in the size of the pupil (constriction)
dim light causes an increase in the pupil’s size (dilation)

27
Q

What determines eye colour

A

the amount of melanin in the iris

28
Q

Describe the Retina

A

lines the posterior 3/4 of the eyeball, and is the beginning of the visual pathway, consists of a pigmented layer and a neural layer
the melanin in the pigmented layer helps absorb stray light rays
neural (sensory) layer processes visual data before sending it as a nerve impulse to the occipital lobe of the brain via the optic nerve

29
Q

Describe the neural layer of the retina

A

contains neutrons called photoreceptors - specialised cells that begin the process of converting light rays to nerve impulses
2 types = rods and cones

30
Q

Each retina has how many rods/cones

A

6 million cones and 120 million rods

31
Q

Explain the difference between rods and cones

A

rods allow us to see in dim light - don’t provide colour vision therefore in dim light we can only see black, white, shades of grey between
brighter light stimulates cones which do produce colour vision

32
Q

Describe how the retina can be viewed

A

with an ophthalmoscope, shines light into the eye through the pupil providing a magnified image of the retina and its blood vessels as well as the optic (II) nerve
surface of the retina is the only place in the body where blood vessels can be seen directly and are examine for pathological changes

33
Q

Where does the optic (II) nerve exit the eyeball and what is also visible in an image of a retina

A

optic (II) nerve exits at the site of the optic disc

also visible are the macula lutea and fovea centralis

34
Q

Describe the optic disc

A

also called the blind spot, contains no rods or cones so can’t see an image striking the blind spot

35
Q

Describe the macula lutea

A

is in the exact centre of the posterior portion of the retina

36
Q

Describe the fovea centralis

A

a small depression in the macula lutea, no rods present only cones, area of highest visual acuity or resolution (sharpness of vision)

37
Q

Describe the lens

A

normally transparent and lacks blood vessels, helps focus images on the retina for clear vision, divides the interior of the eyeball into 2 cavities = anterior cavity and vitreous chamber

38
Q

Describe the anterior cavity formed by the lens

A

consists of 2 chambers = anterior and posterior chambers, both filled with a transparent watery fluid known as aqueous humor - its function is to nourish the lens and corns and is completely replaced about every 90 minutes

39
Q

Describe the posterior vitreous chamber formed by the lens

A

contains a transparent jellylike substance called the vitreous body, holds the retina flush against the choroid, giving the retina an even surface for the reception of clear images, doesn’t ungergo constant replacement, consists mostly of water, also contains phagocytic cells that remove debris, keeping this part clear for unobstructed vision

40
Q

Describe intraocular pressure within the eyeball

A

produced mainly by the aqueous humor and partly by the vitreous body, maintains the shape of the eyeball and prevents it from collapsing

puncture wounds to the eyeball may cause loss of aqueous humor and the vitreous body causing a decrease in intraocular pressure, a detached retina and in some cases blindess

Anatomy 2 (18 decks)

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