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Anatomy #2- Head and Neck > Eye > Flashcards

Eye Flashcards

1
Q

Eyes

A
  • where you first see
  • required for survival in most species
  • look different in size, shape, colour between species and individuals
  • very similar in anatomy and function among mammals
  • use human directional anatomy (posterior, superior, inferior, anterior)
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2
Q

Predatory species

A
  • eyes set forward
  • overlapping fields of right and left view
  • large field of binocular vision
  • allows concentration on near objects and better perception of depth for hunting
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3
Q

Prey species

A
  • eyes are set more laterally
  • not much overlap between right and left fields of view
  • have a wide field of view
  • this allows awareness of surrounding
  • but at the cost of losing binocular vision
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4
Q

Eyeball

A

Globe or bulbus oculi

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5
Q

Adnexa

A

structures that protect and move the eyeball (fasciae, muscles, eyelids, conjunctiva, lacrimal apparatus)

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6
Q

Orbit

A

cavity containing the eyeball and most of the adnexa

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7
Q

Orbital cone

A

adnexal structures continue in a conical shape

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8
Q

Periorbita

A

the most external layer of orbital fascia
- connective tissue lining the orbit

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9
Q

orbital rim

A
  • dog, cat, pig- not fully bony, has orbital ligament that completes gap
  • fully bony in horse and ox
  • completely surrounded in higher primates
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10
Q

layers of eyeball

A
  • fibrous tunic
  • vascular tunic= uvea
  • nervous tunic= retina
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11
Q

fibrous tunic

A
  • external layer
  • made of dense collagenous tissue
  • gives form to and protects eye
  • only complete tunic
  • includes sclera and cornea
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12
Q

vascular tunic

A
  • also called uvea
  • middle layer
  • consists largely of smooth muscle and blood vessels
  • nourish and regulate lens shape and pupil size
  • includes choroid, ciliary body, and iris
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13
Q

Nervous tunic (retina)

A
  • most internal layer
  • largely made of nerves, extension of brain and connected by optic nerve (covered by meninges)
  • responsible for vision as it converts visual signs with nerve impulses
  • line the choroid are all the way to the pupil
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14
Q

Sclera

A
  • part of fibrous tunic
  • opaque posterior part of the fibrous tunic
  • generally white with blue/grey tinge
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15
Q

Cornea

A
  • rostral 1/4 of fibrous tunic and bulges out
  • made of special dense connective tissue arranged in lamellar form
  • avascular, fed by diffusion
  • interstitial fluid constantly pumped out to help transparency
  • lots of nerve endings to make it sensitive to touch (corneal reflex checked under anesthesia)
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16
Q

Choriod

A
  • part of vascular tunic
  • dense network of blood vessels within a heavily pigmented connective tissue
  • nourish the retina, responsible for “red eye” in pictures
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17
Q

Ciliary body

A
  • part of vascular tunic
  • suspends lens
  • regulates curvature of lens
  • production of aqueous humor
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18
Q

Iris

A
  • part of vascular tunic
  • suspended between cornea and lens
  • the only internal structure seen through cornea without instruments
  • adjusts the size of pupil
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19
Q

Layers of ciliary body

A
  1. Zonular fibers- attach to the equator of the lens to suspend it
  2. ciliary processes- radial ridges; anchor for zonular fibers
  3. ciliary muscle- attach ciliary processes to sclera; smooth muscle; used for accommodation to focus on near/far objects
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20
Q

Shape and colour of iris

A
  • A flat ring attached at periphery to the sclera
  • shape changes among species/individuals
  • colour of iris determines the colour of the eye (more melanin= more brown, albino= no melanin/appear red)
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21
Q

Iris controlling light

A
  • has pupil which is opening allowing light inside
  • has both sphincter and dilator muscles (dilators radial, sphincters= internal margin)
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22
Q

Different pupils appearance

A
  • Always appears black because fundus is dark
  • Cat= vertical slit when iris constricted, round when open

Dog= round
Ox, horse = oval

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23
Q

Iridic granules

A
  • also called corpora nigra
  • irregular outgrowth of posterior iris epithelium that contains coils of capillaries
  • can seen usually on upper pupil margin in ungulates
  • may provide shade from sun
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24
Q

Tapetum lucidum

A
  • causes eye shine in animals at night (not red eye)
  • a nocturnal adaptation to aid vision in dark
  • variously coloured light reflecting area (carnivores have crystal rods with tapetal cells arranged so light splits; herbivores use bricklight arrangement of collagen fibers)
25
Q

Layers of the nervous tunic

A
  1. outer pigmented retina
  2. inner neuroendothelial retina
26
Q

Outer pigmented retina

A
  • firmly attached to choroid
  • lacks pigment over tapetum lucidum
27
Q

inner neuroepithelial retina

A
  • photoreceptors (rods and cones) in caudal 2/3rds of fundus
  • phototransduction
28
Q

Are the layers of the nervous tunic attached?

A

2 layers are apposed but not firmly attached

  • the inner layer kept in place by vitreous humor
  • retinal detachment can occur and lasers can fuse back together
29
Q

Animals colour vision

A
  • all mammals have cones
  • few cones in nocturnal animals
  • old world higher primates are trichromatic (red, green, blue)
  • most mammals are dichromatic (have 2 cone pigments). Most domestic animals are red/green colour blind
  • rodents can sometimes see ultraviolet
  • likely birds, fish, and insects see more colour than we do
30
Q

Aqueous humor (part of ocular media)

A
  • clear fluid (electrolytes, glucose, aa, ascorbic acid)
  • nourish and waste removal for cornea and lens
  • maintain intraocular pressure
  • transmit and refract (bend) light
  • continuously produced and absorbed
    (produced by epithelial cells of ciliary body
  • absorbed in filtration (iridocorneal) angle by venous plexus at pectinate ligaments
31
Q

Location of aqueous humor

A

in anterior chamber (between cornea and iris) and in posterior chamber (between iris and lens)

32
Q

Vitrous humor of ocular media

A
  • forms 2-3rds of eye volume
  • gel like (water, collage, hyaluronic acid)
    encapsulated in vitreous body
  • maintain eye shape and position of retina
  • transmit and refract light
  • constant, not normally produced/absorbed
33
Q

Structure of lens

A
  • biconvex with nucleus surrounded by elastic fiber layers
  • enclosed in capsule and suspended by zonular fibers
  • avascular (fed by diffusion)
    dehydrated (60-75% water) to help clarity
  • transmit and refract light
34
Q

Lens ability to focus on far and near objects

A

Far: lens is stretched out at rest, so always focusing on far objects

Near: Parasympathetic causes ciliary muscles to contract (collectively act as a sphincter) which relieves tension on zonular fibers allowing lens to become rounder to focus on near objects

35
Q

Damage to lens

A
  • lens in old animals can become cloudy (cataracts)
  • less flexible (far-sighted)
36
Q

Ocular muscles

A
  • dorsal, ventral, lateral, medial recti muscles
  • dorsal and ventral oblique muscles
  • retractor bulbi muscle
37
Q

Dorsal, ventral, lateral, medial recti muscles

A
  • angle eye in respective direction
  • originate from apex of orbital cone, around optic canal
  • tendon inserted anterior to the vertical equator
38
Q

Dorsal and ventral oblique muscles

A
  • rotate eye, just to correct distortion due to recti muscles
  • Dorsal Oblique muscles originate from apex of orbital cone, deflected around the trochea (acting like a pulley). Tendon inserted near the vertical equator
  • vertical oblique muscle- attached to medial wall of orbit
39
Q

Retractor bulbi muscle

A
  • pull the eyeball back into the orbit
  • tendon inserted posterior to the vertical equator

Ox: form a complete circle around optic nerve
Dog: multiple single muscles
Humans: absent

40
Q

Eyelids (palpebrae)

A
  • upper lid more extensive and mobile (medial and lateral angles meet at palpebral fissue)
  • consist of skin, a musculofibrous layer and mucous membrane (palpebral conjunctiva)
  • skin is thin, delicate, and with tactile hair (cilia, eyelashes)
    Dog: cilia only on upper lid
    Cants: none
41
Q

Small ciliary and sebaceous glands of eyelid

A
  • associated with the roots of the cilia
  • inflammation of one such gland is called a stye (hordeolum)
42
Q

Musculofibrous layer of eyelid

A
  • formed by orbicularis oculi, orbital septum, aponeurosis of the levator muscle
  • orbicularis oculi lies directly under skin and closes eyelid
43
Q

Tarsus of eyelid

A
  • platelike fibrous continuation of orbital septum that stabilizes the edge of the lid
  • has a row of 20-40 small holes lining the lid edges that open a series of tarsal glands that secrete a fatty material
44
Q

Lacrimal puncta of eyelid

A

open near medial angle

  • part of the lacrimal system
45
Q

third eyelid

A
  • nictitating membrane= a conjunctival fold between lacrimal caruncle and eyeball
  • covered with conjunctiva on both sides and is invisible when the eye is closed
  • supported by T-shaped cartilage
46
Q

Retraction of third eyelid

A
  • retracted by smooth muscle and innervated by sympathetic fibers
  • it slides passively over eyeball when eye ball is retracted or pushed into orbit (cats can actively draw 3rd eyelid; can also be linked to neurological disorders if remain drawn)
  • seen in most domestic and wild animals
  • thought to provide protection
47
Q

Human 3rd eyelid remnant

A

Semilunar fold

48
Q

Subepithelial lymph nodes

A
  • seen on bulbar surface of eye
  • can become inflamed
49
Q

Palpebral conjunctiva

A

thin, transparent mucous membrane forming posterior of lid

reflected on base of lid and continues as bulbar conjunctiva

50
Q

What does a pale conjunctiva suggest?

A

anemia

51
Q

What is the potential space between lids and eyeball?

A

conjunctival sac with dorsal and ventral extremities called fornices

52
Q

Lacrimal fluid

A

Tears

  • keep conjunctiva clean and moist, supplies nutrients to the cornea
53
Q

Lacrimal gland proper

A
  • between eyeball and dorsolateral wall of orbit
  • duct opens in dorsal fornix
54
Q

Gland of 3rd eyelid

A

accessory lacrimal gland

  • Pigs and ox have additional deep 3rd eyelid lacrimal gland
55
Q

Lacrimal apparatus

A
  • lacrimal fluid is repelled by fatty secretion in tarsal glands
  • fluid will pool at medial lacrimal lake which is a shallow depression around lacrimal caruncle
  • fluid is drawn by capillary action via lacrimal puncta into lacrimal canaliculi and down into the lacrimal sac
  • duct system takes tears into nasolacrimal duct to open in nasal cavity/nostrils
56
Q

Blood supply of animal orbit

A

in domestic animals, mostly through external ophthalmic artery (a branch of maxillary artery). External ophthalmic artery will subdivide into 3 groups

57
Q

3 divisions of external ophthalmic artery

A
  1. supply eyeball, penetrate sclera to reach uvea and retina
    - short and long posterior cilliary arteries (retina), anterior ciliary arteries, greater arterial circle of iris)
  2. supply ocular muscles
  3. leave orbit to supply adjacent structures
    (lacrimal artery, supraorbital artery, malar artery, external ethmoidal artery)
58
Q

Nerve supply of the orbit

A

Total of 6 cranial nerves supply the orbit

  1. Optic (II)- sense of vision
  2. oculomotor (III)- somatic to most ocular muscles
  3. Trochlear (IV)- dorsal oblique
  4. Abducens (VI)- to lateral rectus and retractor bulbi
  5. Opthalmic (V1)- divides into lacrimal nerve, frontal nerve, nasociliary nerve)
  6. Zygomatic nerve- sensory to lower eyebeall and adjacent skin (also main nerve of ox)
  7. Auriculopalpebral (VII)- supply muscles of eyelids except the levator palpebrae superioris)

Autonomic sympathetic innervation dilates pupil , parasympathetic constricts pupil and accomodates lens for near focus

Anatomy #2- Head and Neck (6 decks)

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