(15.2) Sense Organ - The Eyes Flashcards by Aeron Justine Aquino

develops as a neuroectodermal outgrowth of the embryonic prosencephalon that contacts surface ectoderm and is enveloped by induced mesodermal and neural crest mesenchyme.

eye (the organ for vision)

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The definitive 1. ? and its 2. ? are contained within an orbit that is only partly bony.

eye
adnexa

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Associated with the bulb of the eye what are the muscle that move eye

extraocular muscles

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What surround and cushion the eye

periorbital fascia and fat

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What protects the eye

eyelids and conjunctiva

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What keeps the eye’s surface moist, provides the first barrier to infection, and helps to nourish the cornea

lacrimal apparatus

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As a consequence of its dual origin, the eye has both what neural elements?

central and
peripheral neural elements.

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What nerve is a central nervous system structure with myelin
formed by oligodendroglial cells

optic nerve

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nerves of the 1. ? and 2. ? are peripheral nervous system structures with lemmocyte (Schwann cell) sheaths for myelin

extraocular muscles
iris

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What are the two tunics that surrounds the optic nerve are homologous to the meninges surrounding the brain and spinal cord

vascular and fibrous tunics

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What space of the optic nerve is continuous with the subarachnoid space of the brain and contains cerebrospinal fluid

intervaginal space

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intervaginal space of the optic nerve is continuous with the subarachnoid space of the brain and contains what fluid?

cerebrospinal fluid

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The eye includes the following:

• Orbit
• The eyeball or Globe
• Adnexa

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•deep bony cavity in the rostral surface of the skull
•it houses the globe and adnexa

ORBIT

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• Composed of very dense collagenous and elastic
tissue and fibrocytes

FIBROUS TUNIC

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These are the functions of what part of Globe(Eyeball)?
Functions:
– gives the eyes its shape and stiffness by resisting pressure of internal fluid
– protects internal vascular and light sensitive portions of the eye from environment
– refracts (bends) the light and conducts light to retina
– provide site for attachment of extraocular muscles

FIBROUS TUNIC

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– Opaque/white portion of the eye, approximately 75 % of the globes surface
– consists of a dense network of collagen and elastic fibers and their fibrocytes

sclera

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– Transparent/clear portion of the eye, approximately 25% of anterior segment of fibrous tunic
– avascular, nutrients arrive thru the capillary loops at the limbus
– innervation: long ciliary nerves enters the cornea at the limbus

cornea

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border where sclera and cornea meets

Limbus corneae

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• Lies internal to fibrous tunic
• Extremely vascular and heavily pigmented

VASCULAR TUNIC

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VASCULAR TUNIC referred to as?

“uvea”

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VASCULAR TUNIC Three regions:

• Choroid
• Ciliary body
• iris

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• Posterior part of vascular tunic, consists of dense meshwork of blood vessels

CHOROID

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Which part of vascular tunic are these functions?
Functions:
– provide nutrient and oxygen to retina
– limits light scatter
– improves vision in low-light situations

Choriod

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– structure adapted to increase light intensity under low-lighting situations – avascular region of choroid – contains rod shaped crystals that refract incoming light

Tapetum Lucidum

Tapetum Lucidum present in all domestic mammals except the?

pigs

• forms from thickening of choroid that is raised inward into posterior chamber of the eye • suspends the lens within the eyes • acts to change the thickness of the lens (accommodation)

CILIARY BODY

are smooth muscle bundles that originate on the sclera and attach to the base of the ciliary body

ciliary muscles

• Most anterior, smallest segment of vascular tunic • Thin, flat circular structure attached to ciliary body

IRIS

– responsible for eye coloration

Melanin granules

– is the only pigment present in the iris

Melanin

central opening in the iris; round in dogs; has set of smooth muscles

Pupil

• radially arranged; draws pupil open and admits more light; sympathetic

pupillary dilator

• circumferentially arranged; draws the pupil closed; parasympathetic

pupillary constrictor (sphincter)

– inner most layer of the eye

Retina

Retina – inner most layer; having 3 parts and a divisionary zone, what are those 3?

– Optic - visual – Ciliary – non-visual – Iridial - non-visual

– has the photoreceptor layer, in which are found the specialized neural receptor cells of the visual system, the rods and cones – largest part, relatively thick with 10 layers of cells; has pigment that gives the pupil black color – presence of light sensitive cells that are layer 9 out of 10 – optic disc, a “blind” spot because no photoreceptors are present, leaves the globe to become optic nerve – central area is the area of particularly acute vision

optic part (pars optica retinae)

– boundary between visual (optical) and non-visual (ciliary and iridial) parts of retina

ora serrata

– produces aqueous humor via active secretion

ciliary part (pars ciliaris retinae)

– bilayered epithelial layer – covering posterior surface of iris

iridial part (pars iridica retinae)

• solid yet soft, transparent, deformable structure situated in hyaloid fossa: a depression in the anterior surface of vitreous body • composed of elongate epithelial cells (lens fibers); fixed in position by a delicate suspensory apparatus, the zonula ciliaris • enveloped by elastic capsule; avascular in adult dogs

Lens

Which part of the eye brings images into focus on the retina?

Lens

A process by which ciliary processes zonules and ciliary muscles alter shape of the lens to change the distance at which objects are focused

Lens accommodation

What are the three chambers of the eye are distinguished in the interior of the eye:

• anterior • posterior • vitreous chamber

– the space bounded by the cornea anteriorly and the iris and anterior lens surface posteriorly

Anterior Chamber

– bounded anteriorly by the iris, posteriorly by the lens capsule and anterior face of the vitreous, and peripherally by the zonule and ciliary epithelium

Posterior Chamber

– approximately 80% of the volume of the globe

Vitreous Chamber

– a clear gel that fills the vitreous chamber – almost 98% water, other components are solid (eg. Protein) and fine fibers – normally acellular – tightly adheres to lens capsule, ciliary part of retina, and optic disc

Vitreous body

• mucous membrane that covers certain regions of the eye

CONJUNCTIVA

What conjunctiva lines inner surface of upper, lower and third eyelid

palpebral conjunctiva

Conjunctiva that covers the sclera

bulbar conjunctiva

point of reflection of palpebral and bulbar conjunctiva

conjunctival fornix

• mobile skin folds, upper and lower • closes over the corneal surface to protect the cornea, exclude light and spread essential tear film

EYELIDS (PALPEBRAE)

( upper or lower? )eyelid more mobile and larger

upper

in dog only the ( superior or inferior? )eyelid has eyelashes (cilia)

superior

Glands of the eyelids that are found in the follicles of the cilia(eye lashes)

sebaceous glands

What gland of the eylid are present in the free edges of both eyelids

tarsal glands

What ligament of the eyelid are poorly developed, anchors the lateral commisure to zygomatic arch

lateral palpebral ligament

What ligament of the eyelid are anchors medial commisure to frontal bone, serves as origin and insertion of orbicularis oculi muscle

medial palpebral ligament

• fold of tissue on ventromedial region of medial canthus • large and very mobile, capable of covering the entire cornea • when eye is open, it is withdrawn completely into the medial canthus

THIRD EYELID

– mixed seromucous gland that surrounds the base of the cartilage plate – tear film

Superficial gland of the 3rd eyelid

• responsible for production, dispersion and disposal of tears

LACRIMAL APPARATUS

Composition of Tear Film produced by tarsal glands

superficial oily layer

Composition of Tear Film produced by lacrimal gland and gland of the 3rd eyelid

middle aqueous layer

Composition of Tear Film produced by the goblet cells of the conjunctiva

deep mucous layer

What structure plays an essential role in maintaining the health of the eyes, keeps the cornea moist, washes away foreign bodies, facilitates gas and nutrient exchange in the avascular cornea, and contains antimicrobial substances to protect against infection?

Tear film

intraocular muscles (intrinsic or extrinsic?)

Instrinsic

extraocular muscles (instrinsic or extrinsic?)

Extrinsic

muscles of the eyelids (what muscle?)

palpebral muscles

INTRAOCULAR MUSCLES all smooth muscles lies entirely with-in the globe, what are the 3 muscles?

– ciliary muscles – pupillary dilator – pupillary constrictor

How many extraorbital muscles are there?

How many rectus muscles are there?

How many oblique muscles are there?

How many retractor muscles are there?

What extraocular muscle that rotate the globe upward?

dorsal rectus

What extraocular muscle that rotate the globe downward?

Ventral rectus

What extraocular muscle that rotate the globe medially?

Medial rectus

What extraocular muscle that rotate the globe laterally?

Lateral rectus

all extraocular muscles( except lateral recuts ) are innervated by what nerve?

oculomotor nerve

all are innervated by oculomotor nerve except lateral rectus which is innervated by nerve?

abducent nerve

What oblique rotate the dorsal surface of the globe medially

dorsal oblique

dorsal oblique rotate the dorsal surface of the globe medially, innervates by what nerve?

Trochlear nerve

What oblique rotate the dorsal surface of the globe laterally?

Ventral oblique

Ventral oblique rotate the dorsal surface of the globe laterally, innervated by what nerve?

Oculomotor nerve

withdraws the globe deeper into the orbit

retractor bulbi/oculi

retractor bulbi/oculi withdraws the globe deeper into the orbit, innervated by what nerve?

Abducent nerve

– move the eyelid to open or close the eye – adjust eyelid position in response to positional changes of the globe

Palpebral Muscles

– facial nerve – orbital part surrounds the bony orbit – palpebral part within the upper and lower eyelid

orbicularis oculi

– oculomotor nerve – primary muscle that act to raise the upper eyelid – ptosis ( drooping upper eyelid)

levator palpebrae superioris

– facial nerve – draws the lateral canthus caudally – assists in closure of the

retractor anguli oculi superioris

– depresses the lower lid assists in opening the eye – Innervated by buchal branches of facial nerve

palpebral part of the deep sphincter of the neck

– assists in holding the eyelids open – innervated by sympathetic fibers

superior and inferior tarsal muscles