Special Senses, Ch 15 Flashcards
Two thin folds that cover the anterior part of the orbit. Prevents foreign objects from entering the eye and distributes tears across the surface during blinking.
Eyelids
Palpaebrae
Each eyelid is stiffened by this piece of dense regular collagenous ct. Modified sebaceous glands are located within these, secreting oil to prevent the eyelids from sticking together.
Tarsal plate
Tarsal glands
The upper and lower eyelids meet at the edges of the orbit at what areas?
This fleshy structure is found in one area, contains sebaceous glands that secrete a whitish lubricating substance.
Medial and lateral commissures, also
Medial and lateral canthi
Lacrimal caruncle
A thin epithelial membrane that lines the posterior surface of the eyelids as this. Then turns back on itself as this to cover the anterior surface of the white part of the eye. Translucent, which permits the observation of blood vessels beneath it.
Conjunctiva
Posterior is palpebral, anterior is bulbar
Conjunctivitis, pink eye, viral or bacterial
Produces tears and drains them from the eye. Part of it is this gland, in the superolateral region of the orbit, just posterior to the conjunctiva. When stimulated by ANS, ducts release tears and mucus into the conjunctival sac to lubricate and wash away dust and debris.
Lacrimal apparatus
Lacrimal gland
Tears that have been swept across the eye first enter these tiny holes in the medial edge of each eyelid. They are continuous with these small ducts that empty into this sac. The sac is located in a small depression in the lacrimal bone and drains into a duct.
Lacrimal puncta
Lacrimal canaliculi
Lacrimal sac
The lacrimal sac drains into this duct, which travels through the lacrimal and maxillary bones to reach the inferior nasal meatus, just inferior to the inferior concha.
Nasolacrimal duct
Six skeletal muscles that have their origins on the walls of the orbit and insert into the outer layers of each eyeball. Produce very small, precise movements, so they are along the most highly innervated skeletal muscles in the body. Innervated by oculomotor (III), trochlear (IV), abducens (VI).
Superior, inferior, lateral, medial rectus
Superior oblique
Inferior oblique
Extrinsic muscles of the eye that extend from a common tendinous ring on the posterior wall of the orbit to their respective insertions on the eyeball.
Superior, inferior, lateral, medial rectus muscles
Extrinsic eye muscle that travels from the posterior orbit along the medial wall and through a fibrous loop before inserting on the superolateral part of the eyeball.
Superior oblique muscle
Trochlea
Extrinsic eye muscle that sweeps from the medial floor of the orbit to insert on the inferolateral part of the eyeball.
Inferior oblique muscle
What are the accessory structures of the eye?
Eyelids Eyebrows Eyelashes Conjunctiva Lacrimal apparatus Extrinsic eye muscles
If the eyes cannot move together, they send slightly different images to the brain, which is interpreted as blurred or double vision, called this. If present as birth, it’s known as what?
Diplopia
Strabismus, lazy eye
The outermost layer of the eyeball
The middle layer
The innermost layer
Fibrous layer
Vascular layer
Neural layer/retina
The white part of the eye, part of the fibrous tunic. 5/6ths of th eyeball. Numerous collagen fibers allow it to resist deformation from internal and external forces, maintaining its shape. The fibers arrange irregularly, making it opaque.
Sclera
Part of the fibrous tunic, but is translucent, allowing it to admitting and focusing light. This is because of the orderly parallel arrangement of collagen fibers, relative lack of water in the tissue, and absence of blood vessels. Avascular, getting O from fluid behind it as well as air. Many pain receptors, few touch.
Cornea
The most extensive component of the vascular layer, containing many capillaries as well as a pigment to reduce the scattering of light.
Choroid
Part of the vascular tunic, the choroid is continuous with this, which contains a ring of smooth muscle that surrounds the lens. Fine threads connect it to the lens. Contraction and relaxation of the smooth muscle changes the shape of the lens to focus light on the retina.
Ciliary body
Suspensory ligaments
The colored portion of the vascular layer just anterior to the ciliary body. Color is determined by the amount of melanin. Surrounds this circle, which is the opening through which light enters the eye.
Iris
Pupil
The iris contains these two muscles that protect the eye and improve vision by controlling how light enters. The first contracts following parasympathetic stimulation and constricts the pupil. The other contracts following sympathetic, with fibers in a radiating pattern that causes it to enlarge the pupil.
Pupillary sphincter
Pupillary dilator
In the retina, what are the two layers? What is the boundary between the anterior retina and the posterior edge of the ciliary body known as? Serrated line.
Superficial layer that is a thin, pigmented epithelium that reduces scattering of light and nourishes the photoreceptors.
Deep layer that contains photoreceptors and the cells that give rise to the optic nerve.
Ora serrata
An area in the retina that contains high density of photoreceptors relative to the rest of the retina. It allows for extremely detailed vision, enabling focus on a particular object. Located in the center of a yellowish region which also has a lot of the receptors.
Fovea centralis
Macula lutea
Area of the retina where the axons of the optic nerve gather, without any photoreceptors. Therefore it doesn’t capture an image and is a blind spot.
Optic disc
How are the retina’s epithelium and photoreceptors nourished?
How are the deeper structures supplied?
Blood vessels in the choroid.
Branches of the retinal artery, which enters the eye through the optic nerve.
The blood vessels are visible through the pupil.
A slightly flattened sphere located posterior to the iris and pupil that focuses light on the retina from objects near the eye. Surrounded by the ciliary body and connected to it by suspensory ligaments. Contains cells known as ____ fibers that lack nuclei and are tightly packed to make them transparent.
Lens
Maintains shape through elastic fibers found in its capsule.
The large posterior cavity of the eyeball is filled with this gelatinous material, which presses the retina against the choroid and helps maintain shape. Mostly water and collagen, very few cells. Hyaloid canal passes through from the lens to the optic nerve.
Vitreous humor
The anterior cavity of the eyeball consists of two smaller cavities, one between the lens and iris, and one between the iris and cornea. These are filled with this, secreted by the ciliary body. Flows from the back through the pupil to the front, and then into a blood vessel that circles the anterior edge of the iris.
Posterior chamber
Anterior chamber
Aqueous humor
Scleral venous sinus
The greatest degree of refraction, about two thirds of the eye’s refractive power, occurs how? It has a refractive index like what?
Occurs as light passes through the cornea
Like water
Additional refraction occurs how? It has a refraction index like that? What does this part of the provide for?
As light passes through the lens
Like the aqueous humor
Fine refractive adjustments
