Chapter 15 Sensory System
sclera
3 tunic layers of the eye. The outer layer of is the sclera, the middle layer is the choroid, and the inner layer is the retina. Each layer consists of additional structures and provides specific functions related to sight.
Oblique
Oblique means slanted and therefore an oblique muscle appears slanted.
eyes
The eyes are located in the bony orbits at the front of the skull. The structures of the eyes are arranged in three layers also called tunics. The eyes receive light rays, band, or refract, those rays and transmit the nerve impulses generated by the light rays to the occipital lobe of the brain. After the impulses reach the occipital lobe, they are interpreted as images and we are able to "see". Our vision is dependent on our health of our eyes, our sight-related nerves, and our brain.
3 Tunic Layers
The outer layer of is the sclera, the middle layer is the choroid, and the inner layer is the retina. Each layer consists of additional structures and provides specific functions related to sight.
conjunctiva
The outer layer of the eye consists of the sclera, cornea, and conjunctiva. The conjunctiva is a mucous membrane that lines the outer surface of the eye and the inside if the eyelid.
Retina
The posterior cavity makes up the remaining two-thirds of the eyeball. The retina lines the posterior cavity.
Tunics
The structures of the eyes are arranged in three layers, also called tunics.
Vitreous humor
Vitreous humor, also called vitreous gel, is a soft, clear, jellylike substance that contains millions of fine fibers. These fibers are attached to the retina and also help the eyeball retain its shape. Vitreous humor is necessary for gift. If the eyeball is injured and vitreous humor escapes, blindness can result. Both aqueous and vitreous humor help bend light rays as they pass through the eye and focus on the retina.
conjunctiv/o : word root
conjunctiva
corne/o : word root
cornea
kerat/o : word root
cornea
ocul/o : word root
eye
ophthalm/o : word root
eye
opt/o : word root
eye; vision
blephar/o : word root
eyelid
palpebr/o : word root
eyelid
vitre/o : word root
glassy; jellylike
ir/o; irid/o : word root
iris
phac/o; phak/o : word root
lens
photo/o : word root
light
pupill/o : word root
pupil
retin/o : word root
retina
scler/o : word root
sclera; hard
glauc/o : word root
silver; gray
dacryocyst/o : word root
tear sac
dacry/o : word root
tears
lacrim/o : word root
tears
uve/o : word root
uvea
aque/o : word root
watery
Accessory Structures:
Accessory structures of the eye include the orbit, eyebrows, eyelashes, oil glands, and lacrimal glands, fluid, sacs, and ducts. The purpose of the accessory structures is to protect the eye from disease and injury.
Three pairs of major eye muscles
In addition to the accessory structure, there are three pairs of major eye muscles. The six muscles: 1. superior oblique, superior rectus, lateral rectus, inferior rectus, inferior oblique, allow the eyes to execute a wide range of very precise movements. Rectus means straight and therefore a rectus muscle appears straight. Oblique means slanted and therefore an oblique muscle appears slanted.
Intraocular pressure
Intraocular pressure is a measurement of the fluid pressure inside the eyeball.
Uvea
The choroid, iris, and ciliary body are collectively known as the uvea.
How we see
The ciliary body and suspensatory ligaments adjust the shape of the lens to help focus light rays on the retina. When an object is near, the lens is shortened and becomes thicker; when an object is near, the lens is shortened and becomes thicker; when an object is distant, the lens is lengthened and becomes thinner.
Lacrimal Ducts : Accessory Structures
The lacrimal ducts drain lacrimal fluid away from from the eye and into the nose via the nasolacrimal duct.
Cones
The retina is the sensory nerve tissue that coats the inside of the eye. It contains nerve cells called rods and cones, which convert light rays into nerve impulses. Cones are responsible for the vision in bright light, central vision, and color vision.
Rods
The retina is the sensory nerve tissue that coats the inside of the eye. It contains nerve cells called rods and cones, which convert light rays into nerve impulses. Rods are responsible for vision in dim light and also peripheral vision.
Upper and Lower Eyelids: Accessory Structures
The upper and lower eyelids and eyelashes, along with the eyebrows, prevent foreign matter from reaching the eyes.
Lacrimal Sac : Accessory Structures
The upper expanded portion of the nasolacrimal duct is called the lacrimal sac.
Meibomian Glands: Accessory Structures
The meibomian glands, located between the conjunctiva and the tissue of the upper and lower eyelids, are small oil glands that lubricate the eyes. These glands are not visible unless they become obstructed.
choroid
3 tunic layers of the eye. The outer layer of is the sclera, the middle layer is the choroid, and the inner layer is the retina. Each layer consists of additional structures and provides specific functions related to sight.
retina
3 tunic layers of the eye. The outer layer of is the sclera, the middle layer is the choroid, and the inner layer is the retina. Each layer consists of additional structures and provides specific functions related to sight.
Rectus
Rectus means straight and therefore a rectus muscle appears straight.
Aqueous humor
The anterior cavity makes up the front one-third of the eyeball. The anterior cavity consists of the anterior chamber, the area in the front of the iris; and the posterior chamber, the area behind the iris and in front of the ligaments that hold the lens in place. These chambers are filled with a watery fluid called aqueous humor. Aqueous humor helps the eyeball maintain its shape, maintains the proper pressure within the eye; and nourishes structures in the eyeball. Intraocular pressure is a measurement of the fluid pressure inside the eyeball.
The Anterior Cavity
The anterior cavity makes up the front one-third of the eyeball. The anterior cavity consists of the anterior chamber, the area in the front of the iris; and the posterior chamber, the area behind the iris and in front of the ligaments that hold the lens in place. These chambers are filled with a watery fluid called aqueous humor. Aqueous humor helps the eyeball maintain its shape, maintains the proper pressure within the eye; and nourishes structures in the eyeball. Intraocular pressure is a measurement of the fluid pressure inside the eyeball.
refract
The eyes receive light rays, band, or refract, those rays and transmit the nerve impulses generated by the light rays to the occipital lobe of the brain.
Retina: Inner layer
The inner layer of the eye includes the retina, nerve cells, and optic disk. The retina is the sensory nerve tissue that coats the inside of the eye. It contains nerve cells called rods and cones, which convert light rays into nerve impulses. Rods are responsible for vision in dim light and also peripheral vision. Cones are responsible for the vision in bright light, central vision, and color vision. The optic disk, located at the back of the eye, is the area where the nerve endings of the retina come together to form the optic nerve. The optic nerve transmits impulses to the occipital lobe of the brain.
2 Interior eye cavities
The interior of the eye has two cavities: the anterior cavity and the posterior cavity. The anterior cavity makes up the front one-third of the eyeball. The anterior cavity consists of the anterior chamber, the area in the front of the iris; and the posterior chamber, the area behind the iris and in front of the ligaments that holds the lens in place. These chambers are filled with a watery fluid called aqueous humor. Aqueous humor helps the eyeball maintain its shape; maintains the proper pressure within the eye; and nourishes structures in the eyeball. Intraocular pressure is a measurement of the fluid pressure inside the eyeball. The posterior cavity makes up the remaining two-thirds of the eyeball. The retina lines the posterior cavity. Vitreous humor, also called vitreous gel, is a soft, clear, jellylike substance that contains millions of fine fibers. These fibers are attached to the retina and also help the eyeball retain its shape. Vitreous humor is necessary for gift. If the eyeball is injured and vitreous humor escapes, blindness can result. Both aqueous and vitreous humor help bend light rays as they pass through the eye and focus on the retina.
Iris
The iris which gives our eyes their unique color, is a muscular ring that surrounds the pupil. The iris adjusts the opening of the pupil to control the amount of light that enters the eye.
Lacrimal Glands : Accessory Structures
The lacrimal Glands located above the outer corner of each eye, produce lacrimal fluid that moisten the anterior surface of the eyeball.
nasolacrimal duct : Accessory Structures
The lacrimal ducts drain lacrimal fluid away from from the eye and into the nose via the nasolacrimal duct.
Lens
The lens also called the crystalline lens, is connected to the choroid by the ciliary body and the suspensatory ligaments.
Choroid: middle layer
The middle layer of the eye included the choroid, iris, pupil, lens, and ciliary body. The choroid is a layer of tissue beneath the sclera that contains blood vessels that supply oxygen and nutrients to the eye. The iris which gives our eyes their unique color, is a muscular ring that surrounds the pupil. The iris adjusts the opening of the pupil to control the amount of light that enters the eye. The lens also called the crystalline lens, is connected to the choroid by the ciliary body and the suspensatory ligaments. The choroid, iris, and ciliary body are collectively known as the uvea.
Optic Disk
The optic disk, located at the back of the eye, is the area where the nerve endings of the retina come together to form the optic nerve.
Optic Nerve
The optic disk, located at the back of the eye, is the area where the nerve endings of the retina come together to form the optic nerve. The optic nerve transmits impulses to the occipital lobe of the brain.
Orbit: Accessory Structures
The orbit, also called the eye socket, is the bony cavity of the skull that houses and protects the eyeball.
Cornea
The outer layer of the eye consists of the sclera, cornea, and conjunctiva. The cornea is the transparent anterior portion of the sclera that covers the iris.
sclera: outer layer
The outer layer of the eye consists of the sclera, cornea, and conjunctiva. The sclera is a tough or fibrous tissue that maintains the shape of the eyeball and serves as its protective covering. The sclera is commonly called the "white of the eyes".
posterior cavity
The posterior cavity makes up the remaining two-thirds of the eyeball. The retina lines the posterior cavity. Vitreous humor, also called vitreous gel, is a soft, clear, jellylike substance that contains millions of fine fibers. These fibers are attached to the retina and also help the eyeball retain its shape. Vitreous humor is necessary for gift. If the eyeball is injured and vitreous humor escapes, blindness can result. Both aqueous and vitreous humor help bend light rays as they pass through the eye and focus on the retina.
