The Eye Flashcards by Dalton Ridley

Components of Fibrous tunic

Sclera and Cornea

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Sclera

Components: Dense irregular connective tissue

Function: Supports eye shape; Protects delicate internal structure; Extrinsic eye muscle attachment site

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Cornea

Components: Two layers of epithelium with organized connective tissue in between

Function: Protects anterior surface of the eye; Refracts (bends) incoming light

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Components of Vascular tunic

Choroid, Ciliary body, and Iris

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Choroid

Components: Areolar connective tissue; highly vascularized

Function: Supplies nourishment to retina, pigment absorbs extraneous light

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Ciliary body

Components: Ciliary smooth muscle and ciliary processes; covered with a secretory epithelium

Function: Holds suspensory ligaments (zonular fibers) that attach to the lens and change the lens shape for near or far vision; Epithelium secretes aqueous humor

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Iris

Divides anterior cavity into anterior chamber and posterior chamber

Components: Two layers of smooth muscle (sphincter pupillae and dilator pupillae) and connective tissue, with a central pupil

Function: Controls pupil diameter and thus the amount of light entering the eye

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Components of the Retina

Pigmented layer and Neural layer

Contains bipolar neurons

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Pigmented layer

Components: Pigmented epithelial cells

Function: Absorbs extraneous light; Provides vitamin A for photoreceptor cells

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Neural layer

Components: Photoreceptors, bipolar neurons, ganglion cells, and supporting Muller cells

Function: Detects incoming light rays; light rays are converted to nerve signals and transmitted to the brain

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Lens

A transparent, elastic tissue that focuses light on the retina

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Aqueous humor

A continuously flowing
liquid that carries
metabolites to and from
cells and helps maintain
an optimal micro-
environment within the
anterior cavity of the
eye.

It is secreted from
ciliary processes into
the posterior chamber of
the anterior cavity, flows
into the anterior chamber through the pupil, and drains into the scleral venous sinus (canal of Schlemm).

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Anterior Cavity

Broken into anterior chamber and posterior chamber; these two are separated by the iris

Contains aqueous humor

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Posterior Cavity

The vitreous body occupies the large vitreous chamber behind the lens. It is a
transparent, gel-like connective tissue that is 99% water (vitreous humor), with collagen fibrils and hyaluronate.

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Optic Disc

At the head of the optic nerve is the point at which ganglionic layer axons from
all regions of the retina converge, penetrate the
choroid and sclera, and
leave the eye as the optic
nerve to enter the brain.

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How does sight work in neural layers of retina?

Light comes in and hits the rod and cone layer

An impulse response is sent to the nerve fiber layer containing ganglionic cells that converge at the optic disc and form the optic nerve

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Rods

Sensitive to low levels of light

Human retinal has 92 million rod cells

Contain a light sensitive pigment called rhodopsin or “visual purple”; which is extremely sensitive to light

One of the two types of photoreceptors of the outer retina

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Cones

Need relatively bright light to perceive color

Three types of cone cells: Iodopsin pigment ; these have max sensitivity at blue (short), green (medium), and red (long) wavelengths

The human retina has about 4.6 million cone cells

Optic disc has no cone cells

One of the two types of photoreceptors of the outer retina

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Fovea

Area of retina with the greatest visual acuity or sharpness

A small specialized
area (~1.5mm) of the retina where cell bodies and axons are largely dispersed
peripherally, thinning this area and allowing light to hit the cones with very
little light scattering.

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Macula

Fovea lies in the center of the macula

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Accommodation

The lens flattens for distant vision when the ciliary muscles are relaxed and the shape of the
ciliary body holds the ciliary zonule taut, which stretches and flattens the lens.

To see closer objects, the
ciliary muscle fibers contract, changing the shape of the ciliary
body, relaxing tension on the ciliary zonule and allowing the lens to assume the rounded,
relaxed shape.

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Accommodation Reflex

An adjustment of the eye
for near vision.

There are three aspects:

Increased convexity of the lens

Pupillary constriction

Convergence of the eyes

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Lacrimal Glands

Lacrimal glands secrete most components of the tear film that moisturizes,
lubricates, and protects the eyes. They are serous tubuloacinar exocrine glands

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A subset of non-visual photoreceptive ganglion cells in the retina is unusual in that the cells do not function in vision, but rather in the

Establishment of 24-hour dawn/dusk rhythms.

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The sclera is continuous anteriorly with the transparent region called the

Cornea

True of the corneal epithelium

It is 5-6 cells thick It is densely supplied with free nerve endings that trigger the blink reflex An endothelium lines the posterior surface of the cornea.

In addition to the loss of visual acuity, one of the dangers of a detached retina is that

It cannot receive needed metabolic support from the pigmented layer and the choroid, and so the retinal cells will die eventually.

Dilator papillae innervation

The dilator papillae has sympathetic innervation for enlarging the pupil.

The ________________ has melanocytes that block light from penetrating the eye except through the pupil.

Choroid

Vision is the sharpest in the fovea region of the retina. Why?

The cone cells are abundant and tightly packed. Very few capillaries are present in the fovea. The cell bodies of the ganglion cells are peripheral to the fovea

How many cone cells are in the human retina?

4,600,000

How many rod cells are in the human retina?

92,000,000

The general name for visual pigments found in cones is called

Iodopsin

True of lacrimal glands

Tears from the lacrimal glands pass into the nasal passages by way of the nasolacrimal duct. Lacrimal glands are different than tarsal glands. Lacrimal glands are serous tubuloacinar glands.

The "blind spot" is also known as the

Optic disc

Provides physical support for the shape of the eye

Sclera

Bends incoming light

Lens

Controls the amount of light coming into the eye

Iris

Provides sites of attachment for the muscles that move the eye.

Sclera

Vascularized tissue that supplies nutrition to the retina

Choroid

Functions in change in the shape of the lens

Ciliary body

Secretes aqueous humor

Ciliary body

Converts light to nerve impulses

Neural layer of retina

Contains photoreceptors

Neural layer of retina

Composed of layers of smooth muscle

Iris

The type of fibers that form the sclera

Type 1 Collagen

The eyelid contains a series of sebaceous glands known as

Tarsal glands

Visual accommodation in humans is accomplished by

Changing the shape of the lens

The optic "nerve" is not really a nerve. Why?

Because it formed from part of the brain, not from the PNS, and is therefore a tract.

Which of these is a cause of red-green color blindness?

Defects in red or green cones; there are different causes for red-green color blindness.

Which of these is characteristics indicates that the retina is derived from the central nervous system?

The presence of glial cells

The visual pigment found in rods is

Rhodopsin

What are visual pigments

Visual pigments are proteins that change their shape due to a reaction with photons.

The channel that drains the aqueous humor from the anterior chamber is the

Canal of Schlemm

The parts of the vascular layer of the eye are

Choroid, ciliary body, and iris

Eye color is determined by the density of

Melanocytes

What structure attaches the lens to the ciliary body?

Zonular fibers

# Reversed prompt Sclera and Cornea

Components of Fibrous tunic

# Reversed prompt Components: Dense irregular connective tissue Function: Supports eye shape; Protects delicate internal structure; Extrinsic eye muscle attachment site

Sclera

# Reversed prompt Components: Two layers of epithelium with organized connective tissue in between Function: Protects anterior surface of the eye; Refracts (bends) incoming light

Cornea

# Reversed prompt Choroid, Ciliary body, and Iris

Components of Vascular tunic

# Reversed prompt Components: Areolar connective tissue; highly vascularized Function: Supplies nourishment to retina, pigment absorbs extraneous light

Choroid

# Reversed prompt Components: Ciliary smooth muscle and ciliary processes; covered with a secretory epithelium Function: Holds suspensory ligaments (zonular fibers) that attach to the lens and change the lens shape for near or far vision; Epithelium secretes aqueous humor

Ciliary body

# Reversed prompt Divides anterior cavity into anterior chamber and posterior chamber Components: Two layers of smooth muscle (sphincter pupillae and dilator pupillae) and connective tissue, with a central pupil Function: Controls pupil diameter and thus the amount of light entering the eye

Iris

# Reversed prompt Pigmented layer and Neural layer Contains bipolar neurons

Components of the Retina

# Reversed prompt Components: Pigmented epithelial cells Function: Absorbs extraneous light; Provides vitamin A for photoreceptor cells

Pigmented layer

# Reversed prompt Components: Photoreceptors, bipolar neurons, ganglion cells, and supporting Muller cells Function: Detects incoming light rays; light rays are converted to nerve signals and transmitted to the brain

Neural layer

# Reversed prompt A transparent, elastic tissue that focuses light on the retina

Lens

# Reversed prompt A continuously flowing liquid that carries metabolites to and from cells and helps maintain an optimal micro- environment within the anterior cavity of the eye. It is secreted from ciliary processes into the posterior chamber of the anterior cavity, flows into the anterior chamber through the pupil, and drains into the scleral venous sinus (canal of Schlemm).

Aqueous humor

# Reversed prompt Broken into anterior chamber and posterior chamber; these two are separated by the iris Contains aqueous humor

Anterior Cavity

# Reversed prompt The vitreous body occupies the large vitreous chamber behind the lens. It is a transparent, gel-like connective tissue that is 99% water (vitreous humor), with collagen fibrils and hyaluronate.

Posterior Cavity

# Reversed prompt At the head of the optic nerve is the point at which ganglionic layer axons from all regions of the retina converge, penetrate the choroid and sclera, and leave the eye as the optic nerve to enter the brain.

Optic Disc

# Reversed prompt Light comes in and hits the rod and cone layer An impulse response is sent to the nerve fiber layer containing ganglionic cells that converge at the optic disc and form the optic nerve

How does sight work in neural layers of retina?

# Reversed prompt Sensitive to low levels of light Human retinal has 92 million rod cells Contain a light sensitive pigment called rhodopsin or "visual purple"; which is extremely sensitive to light One of the two types of photoreceptors of the outer retina

Rods

# Reversed prompt Need relatively bright light to perceive color Three types of cone cells: Iodopsin pigment ; these have max sensitivity at blue (short), green (medium), and red (long) wavelengths The human retina has about 4.6 million cone cells Optic disc has no cone cells One of the two types of photoreceptors of the outer retina

Cones

# Reversed prompt Area of retina with the greatest visual acuity or sharpness A small specialized area (~1.5mm) of the retina where cell bodies and axons are largely dispersed peripherally, thinning this area and allowing light to hit the cones with very little light scattering.

Fovea

# Reversed prompt Fovea lies in the center of the macula

Macula

# Reversed prompt The lens flattens for distant vision when the ciliary muscles are relaxed and the shape of the ciliary body holds the ciliary zonule taut, which stretches and flattens the lens. To see closer objects, the ciliary muscle fibers contract, changing the shape of the ciliary body, relaxing tension on the ciliary zonule and allowing the lens to assume the rounded, relaxed shape.

Accommodation

# Reversed prompt An adjustment of the eye for near vision. There are three aspects: Increased convexity of the lens Pupillary constriction Convergence of the eyes

Accommodation Reflex

# Reversed prompt Lacrimal glands secrete most components of the tear film that moisturizes, lubricates, and protects the eyes. They are serous tubuloacinar exocrine glands

Lacrimal Glands