Sense Organs The Eye and the Ear

The following texts are the property of their respective authors and we thank them for giving us the opportunity to share for free to students, teachers and users of the Web their texts will used only for illustrative educational and scientific purposes only.

All the information in our site are given for nonprofit educational purposes

The information of medicine and health contained in the site are of a general nature and purpose which is purely informative and for this reason may not replace in any case, the council of a doctor or a qualified entity legally to the profession.

Sense Organs The Eye and the Ear

Introduction

The eye and the ear are sense organs, like the skin, taste buds, and olfactory ( centers of smell in the nose)regions. They provide information regarding the external environment The eye is the receptor for light stimulation and is responsible for vision. The ear is the receptor of sound stimulation and is responsible for hearing.

The eye

Light rays enter the dark center of the eye, the pupil . The conjunctiva is a membrane lining the inner surfaces of the eyelids and anterior portion of the eyeball over the white of the eye. The conjunctiva is clear and colorless except when blood vessels are dilated. Dust and smoke may cause the blood vessels to dilate and give the conjunctiva a reddish appearance, commonly known as bloodshot eyes.
Before entering the eye through the pupil, light passes through the cornea . The cornea is a fibrous, transparent tissue that extends over the pupil and colored portion of the eye. The function of the cornea is to bend, or refract, the rays of light , so they are focused properly on the sensitive receptor in the posterior region of the eye. The normal, healthy cornea is avascular ( has no blood vessels) but receives nourishment from blood vessels near its junction with the opaque white of the eye, the sclera . Corneal transplants for people with scarred or opaque corneas are successful because antibodies responsible for rejection of foreign tissue do not reach the avascular, transplanted corneal tissue. The sclera is a tough, fibrous, supportive, connective tissue that extends from the cornea on the anterior surface of the eyeball to the optic nerve in the back of the eye.
The choroid is a dark brown membrane outside the sclera. It contains many blood vessels that supply nutrients to the eye. The choroid is continuous with the pigment-containing iris and the ciliary body on the anterior surface of the eye.
The iris is the colored ( it can appear blue, gree, hazel,gray, or brown) portion of the eye that surrounds the pupil. Muscles of the iris constrict the pupil in bright light and dilate the pupil in dim light, thereby regulating the amount of light entering the eye.The ciliary body on each side of the lens, contains muscles that adjust the shape and thickness of the lens. These changes in the shape of the lens cause refraction of light rays. Refraction is the bending of rays as they pass through the cornea, lens, and other tissue. Muscles of the ciliary body produce flattening of the lens ( for distant vision) and thickening and rounding ( for close vision) .This refractory adjustment is accommodation .
Besides regulating the shape of the lens, the ciliary body also secretes a fluid called aqueos humor, which is found in the anterior chamber of the eye. Aqueous humor maintains the shape of the anterior portion of the eye and nourishes the structures in that region.The fluid is constantly produced and leaves the eye through a canal that carries it into the bloodstream.Another cavity of the eye is the vitreous chamber, which is a large region behind the lens filled with a soft, jelly-like material, the vitreous humor. Vitreous humor maintains the shape of the eyeball and is not constantly reformed. Its escape may result in significant damage to the eye, leading to blindness. Both the aqueous and the vitreous humors further refract light rays.
The retina, is the thin, delicate, and sensitive nerve layer of the eye. As light energy, in the form of waves, travels through the eye, it is refracted ( by the cornea, lens and fluids) so that it focuses on sensitive receptor cells of the retina called the rods and cones. There are approximately 6.5 million cones and 120 million rods in the retina. The cones function in bright levels of light and are responsible for color and central vision. There are three types of cones, each stimulated by one of the primary colors in light ( red ,green ,or blue ). Most cases of colour blindness affect either the green or the red receptors, so that the two colors cannot be distinguished from each other. Rods function at reduced levels of light and are responsible for peripheral vision.
Light energy, when focused on the retina, causes a chemical change in the rods and cones, initiating nerve impulses that then travel from the eye to the brain via the optic nerve. The region in the eye where the optic nerve meets the retina is called the optic disc. Because there are no light receptor cels in the optic disc, it is known as te blind spot of the eye.
The macula is a small ,oval, yellowish area to the side of the optic disc. It contains a central depression called the fovea centralis , which is composed largely of cones and is the location of the sharpest vision in the eye.
If a portion of the fovea or macula is damaged, vision is reduced and central vision blindness occurs.The fundus of the eye is the inner part that is visualized through the ophtalmoscope.
Six muscles control the movement of the eye – the superior, inferior, lateral and medial rectus muscles, and the superior and inferior oblique muscles.These muscles are coordinated to move both eyes in a synchronized manner The front of the eye is protected by two movable folds of skin, the eyelids . The edges are lined with two or three rows of eyelashes, which protect the surface of the eye.
A thin mucous membrane called conjunctiva lines the inner surface of the eyelids and passes over the cornea. Lying superior and to the outer edges of each eye are the lacrimal glands. They produce tears to bathe and lubricate the eyes. The tears collect at the inner edges of the eyes, the canthi ( sing. canthus), and pass through pinpoint openings, the lacrimal canaliculi, of the nose.

Combining forms

blephar/o eyelid ( also palpebr/o) blepharitis___________________________

blepharoptosis________________________

cor/o pupil(also pupill/o anisocoria_____________________________

cycl/o ciliary body cycloplegic_____________________________
or muscle of the eye

dacry/o tears, tear duct dacryodenitis_____________________________
also lacri/o

ir/o iris iritis_________________________________
irid/o iridic__________________________________

iridicectomy_____________________________

kerat/o cornea keratitis_________________________________

ocul/o eye intraocular________________________________

ophtalm/o eye ophthalmologist____________________________

opt/o eye, vision optic_____________________________________

optic/o “ optician___________________________________

papill/o optic disc papilledema______________________________

phac/o lens of the eye phacomulsifiction_________________________
phak/o aphakia__________________________________

Conditions

ambly/o dull, dim amblyopia ________________________________________

dipl/o double diplopia___________________________________________

glauc/o gray glaucoma __________________________________________

mi/o smaller, less miosis_______________________________________________

mydr/o widen, enlarge mydriasis___________________________________________

nyct/o night nyctalopia__________________________________________-

phot/o light photophobia__________________________________________

presby/o old age presbyopia___________________________________________

scot/o darkness scotoma____________________________________________

xer/o dry xerophtalmia__________________________________________

Suffixes

-opia vision hyperopia_______________________________________________-

-opsia vision hemianopsia_____________________________________________

-tropia to turn esotropia_____________________________________________

Errors of Refraction

Astigmatism Defective curvature of the cornea or lens of the eye

Hyperopia ( hypermetropia) Farsightedess

Myopia Nearsightedness

Presbyiopia Impairment of vsion as a result of old age

Pathological conditions

Cataract Clouding of the lens, causing decreased vision

Chalazion Small, hard, cystic mass ( granuloma) on the eyelid; formed as a result of chronic inflammation of a sebaceous gland

Diabetic retinopathy Retinal effect of diabetes mellitus include microneurysms, hemorrhages, dilation of retinal veins, and neovascularization

Glaucoma Increased intraocular pressure results in damage to the retia and optic nerve.

Hordeolum ( stye) Localized , purulent, inflammatory staphylococcal infection of a sebaceous gland in the eyelid

Macular degeneration Progressive damage to the macula of the retina.

Retinal detachment Two layers of the retina separate from each other.

Strabismus Abnormal deviation of the eye.

Clinical Procedures and Abreviations

Ophtalmoscopy Visual examination of the interior of the eye.

Visual acuitiy test Clarity of vision is assessed.

Visual field test Measures the area within which objects are seen when the eyes are fixed.

Treatment

Enucleation Removal of the entire eyeball

Keratoplasty Surgical repair of the cornea.

LASIK Use of an eximer laser to correct errors of refraction ( myopia, hyperopia, and astigmatis)

Test za fizioterapeute

Microscopic fiber that carries the nervous impulse - ___________________________________

Lower portion of the brain that connects the cerebrum with the spinal cord - _________________

Outer region of the brain - _______________________________________

Largest part of the brain - _____________________________________

Part of the nerve cell that contains the nucleus - __________________________________

Microscopic branching fiber of a nerve cell - _____________________________________

Motor nerves carry ______________________away from the brain and the spinal cord.

Myelin sheath is ___________________tissue that surrounds, protects and insulates the axon.

A nerve cell is called - ______________________.

Essential, distinguishing tissue cells of an organ - ________________________________.

Change in the internal or external environment that evokes a response- __________________.

Main relay center of the brain - __________________________________________.

Middle vascular layer of the eye - _______________________________________.

Tough, white, outer coat of the eyeball - _____________________________________.

Light-sensitive nerve cell layer of the eye containing rods and cones - ___________________

Refraction is _______________________of light rays.

Iris is the _________________________portion of the eye.

Delicate membrane lining the eyelids and the anterior eyeball - ____________________________

Fluid produced by the ciliary body - ________________________________________.

Myopoa is also called ___________________________________________.

The opposite of myopia is _____________________________________.

Astigmatism is a defective ________________________of the cornea.

Strabismus – abnormal _____________________________of the eye.

Auricle is also known as the _________________________.

The inner ear is also known as the ______________________________________.

The ear is an important organ of ___________________________as well as for balance.

The auditory canal is ____________________from the middle ear to the pharynx.

Malleus, incus , and stapes are three small _______________________.

Cerumen is a ____________________substance secreted by the external ear.

Tympanic membrane is also called the ___________________________________.

The cochlea is _____________-shaped structure.

Loss of the ability to hear is ________________________.

Otitis media is __________________________________________________.

Tinnitus is a sensation of ________________________________in the ears.

Visual examination of the ear - ________________________________________.

Adrenaline is also called ___________________________________________.

Hormones are produced by _____________________________glands.

Progesterone is produced in _______________________________________.

GH is short for __________________________________________________.

Hypophysis is better known as the _____________________________gland.

Androgen is male hormone and _________________________is female hormone.

Wrtie down the meaning of the combining forms

lact/o - ______________________ ; dips/o - __________________________________;

glyc/o - _______________________; myx/o - __________________________________;

phac/o - _______________________; vitre/o - __________________________________

palpebr/o- ________________________; ophtalm/o - _____________________________;kerat/o - _________________________; lacrim/o - ________________________________kines/o _________________________; myel/o - _________________________________

Source :

http://zvu.hr/~prezic/download/nastavni%20materijali.doc

Web site link to visit: http://zvu.hr

Google key word : Sense Organs The Eye and the Ear file type : doc

Author : not indicated on the source document of the above text

If you are the author of the text above and you not agree to share your knowledge for teaching, research, scholarship (for fair use as indicated in the United States copyrigh low) please send us an e-mail and we will remove your text quickly.