Week 7 lesson 49a- Eye anatomy

What is the main function of the pupil in an animals eye?

It controls light entering the eye

What is the term used to describe the region which contains the eye, the extraocular muscles, nerves, and blood vessels?

Orbit

What is formed by the maxillary, lacrimal, zygomatic, frontal, temporal, palatine, sphenoid bones?

The boney orbit

What does an open bony orbit mean?

Incomplete dorsolaterally

What ligament extends from zygomatic process of frontal bone to frontal process of zygomatic and is palpable?

Orbital ligamen

In which species do they have an open boney orbit?

Dogs, cats, and pigs

What does a closed bony orbit mean?

Complete orbit

Which species have a closed bony orbit?

Horse, cow, sheep

What are the advantages of having an open bony orbit?

Facilitates wide opening of the jaw (to catch prey)

What is the advantage of a closed bony orbit?

Protection for fighting

What are the three basic layers of the eye?

1. Fibrous layer

2. Vascular layer

3. Neural layer

What structures make up the fibrous layer?

Cornea and sclera

What structures make up the vascular layer?

(Uveal tract)

1. iris

2. ciliary body

3. choroid

What structure makes up the neural layer?

Retina

What structures make up the internal optical media?

Aqueous humor

Lens

Vitreous humor

What solution is contained in the anterior and posterior chamber?

Aqueous humor

What solution is contained in the vitreal chamber?

Vitreous humor

What is the outer layer of the eye?

Sclera

What structure is transparent, protective outer layer of the eye?

Cornea

What is the thin membrane that runs to the edge of the cornea and covers the inside of the eyelids?

Conjunctiva

What are the two types of conjunctiva?

Palpebral conjunctiva

Bulbar conjunctiva

What conjunctiva forms the lining of the inside of the eyelids?

Palpebral conjunctiva

What conjunctiva is covering the anterior globe or episclera and the conjunctiva covering the nictitating membrane?

Bulbar conjunctiva

The size and shape of what structure vary among domestic species, but in all cases it consists of: Superficial epithelium and basement membrane, Large and relatively acellular stroma, deeper Descemet’s membrane, and deeper single-layer endothelium?

Cornea

What structure maintians a strong barrier between the eye and the environement, it is also transparent medium to permit passage of light and images into the posterior segment?

Cornea

What structure in the vacular middle layer of the eye controls pupil size and amount of light into the eye by using constrictor and dilator muscles?

Iris

What structure in the vascular middle layer of the eye suspends lens and controls lens shape?

Ciliary body

What structure of the vascular middle layer of the eye is the nutrution of retina and contains the tapetum?

Choroid

What is the tapetum?

Light refection to increase sensitivity to light

What structure provides most of the eye with color, as well as th epupil to regulate the amount of light that enters the eye and posterior segment?

Iris

What structure shape varies widely among animals specie, including circle, vertical slit, horizontal oval, square?

Pupil

What process provides most of the aqueous humor to nourish the anterior segment and remove its metabolic wastes.

Ciliary body process

What structure also accommodated and regulates the lens curvature?

Ciliary body musculature

The ciliary body continues posteriorly as what?

Choroid

Where is the aqueous humor produced?

Ciliary body

What structure optically clear and avascular, consists of the anterior lens caspule, anterior cortex, nucleus, posterior cortex, posterior lens capsule?

Lens

What is formed early in the development of the eye and insulate the lens protein from the later developing immune system?

Lens

What condition affects the transparency of the lens?

Cataracts

What sits behind the iris, changes its shape to focus light onto the retina?

Lens

How do the ciliary muscles respond to cause the lens to become thicker allowing the lens to focus on nearby objects?

Contract

How does the ciliary muscles respond to cause the lens to become thinner allowing to focus on distant objects?

Relax

What is a clear gel-like substance that fills the space between the lens and the retina?

Vitreous humor

What substance is composed of approximately 98-99% water with traces, with trace amounts of hyaluronic acid, glucose, anions, cations, ions, and collagen?

Vitreous humor

What is the primary function of Vitreous humor?

Keep retina in place against the back wall of the eye

The posterior segment of the eye from superficial to deep consists of which structures?

1. Posterior sclera

2. Chorid

3. Tapetum lucidum

What structure contains pigment cells, blood vessels to support the high metabolic needs of the retina?

Choroid

What structer is used to enhance vision in dim light. A reflective layer that magnifies incoming light

What is the tapetum lucidum called in carnivores?

Tapetum cellulosum

What is the tapetum lucidum called in herbivores?

Tapetum fibrosum

The ocular fundus consist of what structures?

• Tapetal fundus

• nontapetal fundus

• retinal vasculature

• optic disc

What part of a dogs eye is responsible for controlling the amount of light that enters?

iris

What structure in the retina are used for collecting dim light, sot hey have better night vision?

Rods

What structure in the retina are responsible for color vision?

Cones

Dogs cannot differentiate colors as well because they have __________ but are not completely colorblind?

Fewer cones

What reflective layer of the eye provides a characteristic blue or greenish gloss to dogs eyes when light shines into them at night?

Tapetum lucidum

What structure of the eye converts images and transmits electrical impulse to the brain, and contains cells that sense light (photoreceptors)?

Retina

What structure is the most sensitive area of the retina in dogs, this structure contains thousands of tightly packed photoreceptors

Each photoreceptor in the retina is attached to a nerve fiber that bundle together to form what?

optic nerve

How do the photoreceptors carry the information to the brain?

Photoreceptors convert the image into electrical impulses, which are carried to the brain by the optic nerve

What is the structure where the retinal ganglion axons leave the eye through a weak and fenestrated scleral lamina cribosa to synapse in the lateral geniculate body or middle brain,or midbrian and rostral colliculi?

optic disc

What species lack a tapetal fundus?

Pigs and rabbits

In birds what structure is a highly vascularied and pigmented organ located at the internal ventral-posterior wall of the eyebally covering the optic nerve and is oriented dorso-nasal to ventro-temporal with anterior projection into the vetreous chamber?

Pecten oculi

What structure in the birds eye has a function that is under debate?

Pecten oculi

What extra ocular muscle is innervated by the oculomotor nerve and has the function of elevating the globe?

Dorsal rectus

What extra ocular muscle is innervated by the oculomotor nerve and has the function of depressing the globe?

Ventral rectus

What extra ocular muscle is innervated by the oculomotor nerve and has the function of turns the globe nasally?

Medial rectus

What extra ocular muscle is innervated by the abducens nerve and has the function of turning the globe temporally?

Lateral rectus

What extra ocular muscle is innervated by the trochlear nerve and has the function of intorts the globe?

Dorsal oblique

What extra ocular muscle is innervated by the oculomotor nerve and has the function of extorts the globe?

Ventral oblique

What extra ocular muscle is innervated by the abducens nerve and has the function of retracts the globe?

Retractor bulbi

What structure of the eye is a additional whitish pin eyelid and extends across the yee when needed to protect the eyeball from scratches?

Nictitating memebrane (third eyelid)

Tears are comprised of water, oil, and mucous. What glands in the eye make each of these components?

Lacrimal gland: Located in the dorsal edge of eye and produce the water portion

Mucus glands: In the conjunctiva and produce the mucus portion

Meibomian gland: with in the eyelids and create the oil portion

What duct allows tears to drain from each eye into the nose. Each of these ducts has opening at the edge of the upper and lower eyelids near the nose?

Nasolacrimal ducts

What are the opening at the opening at the edge of the upper and lower eyelids near the nose called?

Lacrimal puncta

Explain the process of tear production and drainage.

Tears produced by lacrimal gland/superficial tear gland of the third eyelid → Tears drain from eye via the two nacolacrimal puncta → Into the two nasal canaliculi which connect at the lacrimal sac → then it drains into the nasolacrimal duct → empties into the nasal cavity via the nasal punctum

Describe what a positive Jones test indicates?

If fluorescein stain is visible int he nostrils after the cornea is stained then the nasolacrimal system is functioning.

What are the three layers of the tear film?

1. Lipid layer

2. Aqueous layer

3. Mucus layer

What is the function of the lipid layer of the tear film?

Most superficial layer and is used to stabilize and reduce evaporation

What gland produces the lipid layer of the tear film?

Meibomian glands

What is the function of the aqueous layer of the tear film?

Middle layer and is used as nutrition and removal of waste

What glands produce the aqueous layer of the tear film?

Third eyelid gland and lacrimal gland

What is the function of the mucus layer of the tear film?

Inner layer and is used for immunoregulatory function by secreting IgA.

What glands produce the mucus layer of the tear film?

Conjunctiva goblet cells

Why is it important that tears are made of water, oil, and mucus instead of just water?

It creates a more protective tear that is slower to evaporate

Lesion to what salivary gland can be misinterpreted into eye problems because inflammation can push up on the eye, especially in carnivores?

zygomatic gland