HOW YOU SEE THINGSHave you ever entered a darkroom? Can you still see objectsinside? Without light, youcannot see anything. You needlight to see the things aroundyou.
When you look at an object, these things happen:1. light coming from every point of the object enters youreye;2. the light passes through the lens of the eye;3. the lens bends this light;4. this light falls onto the retina;5. the light forms an upside-down image on the retina;6. light-sensitive cells in the retina produce signals;7. the signals travel through the optic nerve into the brain; and8. you see an upright object.
COMMON EYE DISORDERS AND DISEASESNearsightedness - have long eyeballs or a cornea that is too curved. (Normal eyeballs are almost round.) the image of an object from afar falls in front of retina. Nearsighted people cannot clearly see far objects. They need to wear corrective eyeglasses to help them see far objects.
Farsightedness - People suffering from farsightedness have short eyeballs or a cornea that is not curved enough. The image of any near object falls behind the retina. Farsighted people also cannot clearly see the objects close to them. Farsighted people also wear corrective eyeglasses to help them see nearby objects clearly.
Astigmatism - is another eye disorder. People with astigmatism may see blurred or ghost images, whether near or far. Astigmatism is caused by a cornea that is abnormally round. The cornea of one suffering from astigmatism is similar to a football round. If you look at a football, you will see two curves – a steeper one and a flatter one. The two curves of the cornea bend light that enters the eye, forming two images on the retina. An astigmatic person sees an out-of-focus images.
Eye Disorders• One common disease is conjunctivitis, also known as sore eyes or pink eyes. It is caused by an infection of the conjunctiva.
Another eye disease is called sty, also knownas kuliti. It is an eye infection of one or moreoil glands at the edge of the eyelid or underit. A harmful kind of microorganism causesthis infection. Sty develops at the edge of aneyelid, around the base of an eyelash.
Glaucoma is caused by the abnormal orhigh pressure of liquids on the eyes. Itcauses the eyeball to harden, making itdifficult for the person to see. This affectsmostly older people. Glaucoma can causeblindness if not treated. Although glaucomahappens more often to elderly people,young children like you should have aregular check-up too.
• Cataract is the clouding of the lens of the eye.• Cataract is often seen as white spots on the lens of the eye. A person who has cataract has very poor vision.• He or she is overly sensitive to light. He or she also frequently changes eyeglasses or contact lens.• The cause of cataract is unknown. But it is strongly linked to smoking, diabetes and exposure to sunlight.• Cataract can be treated.
TAKING CARE OF YOUR EYESYour eyes are your windows to the world. They letyou see the things around you. It is thereforeimportant to take good care of them.– Eat food rich in vitamin A such as pechay, cabbage, squash, milk, cheese, eggs. Good sources of vitamin A come from yellow food.– Always read with adequate amount of light to avoid eye strain.– Avoid the glare of direct, strong light.– When strong wind blow, protect your eyes to keep dust and dirt from entering them.– Always wear sunglasses that offer maximum protection from the sun’s ultraviolet rays (UV) rays.– Etc.
YOUR EARSYou hear different sounds every. You hearsounds of people talking, birds chirping ordogs barking. You hear music over theradio. What sense organs do you use to hearthe different sound around you?
Your ears are your sense organs for hearing.It is composed of the outer ear, the middleear and the inner ear. The outer ear collectssounds, while the middle ear conducts thesound to the inner ear. The inner ear hasnerves that send the sound waves to thebrain, which then interprets the sound.
THE PARTS OF THE EAR• The outer ear is made up of the auricle, the ear canal, and the eardrum. – The cup-shaped structures on the sides of your head are the auricles. – The ear canal is a passageway for sound from the auricle to the eardrum. – The eardrum separates the outer ear from the middle ear. It moves to and fro (or vibrates) as it receives sound waves.•
• The middle ear is a hollow chamber filled with air. Inside the chamber are three little bones – hammer, anvil and stirrup – that are joined. When the eardrum vibrates, it sends the hammer vibrating. These vibrations are passed on to the anvil and the stirrup. These three bones amplify the sound vibrations and sends them into the inner ear.
• The inner ear contains both your organs of hearings and of balance. Its main parts are the cochlea, the vestibule nerve, and the semicircular canals.• The cochlean is a coiled tube. It is filled with liquid and contains nerve cells. These cells send the message it has received through vibrations to the auditory nerves, then to the brain. Your brain interprets the vibrations as specific sounds.
• The organ of Corti is found inside the cochlea, it can be thought of as the body’s microphone. It has a membrane that contains thousands of hair cells. The hair cels are excited when there is sound. The membrane containing the hair cells tells you the pitch of the sound you are hearing. It tells you whether the sound is loud or soft.
• The vestibular and the semicircular canals are your organs of balance. This means that your ears do more than just hearing. They keep you from falling while you are walking, standing and sitting.
COMMON EAR DISEASESThe ears can suffer from many diseases thatcan affect the auricle are erysipelas andseborrhoea.Erysipelas is caused by bacteria.Malfunctioning of the oil glands of the ear’sskin causes seborrhea. Both diseases causeswelling of the skin of the auricle or eventhe skin of the ear canal
An inflammation of the middle ear is calledotitis media (luga). One common cause ofotitis media is the presence of bacteria orviruses in the eardrum. The build up of pusexerts pressure against the eardrum causingearache, swelling and redness. If leftuntreated, the inflammation can impairhearing.
TAKING CARE OF YOUR EARS• Do not use cotton swabs or metallic objects to clean your ear canal. Use a moist, soft cloth instead. Your ears have a self-cleaning mechanism. Fine hairs inside the ear canal constantly move wax and dead skin out of the canal.• Always consult a doctor when you feel pain in your ear.• Avoid continuous exposure to loud noise.
• Do not use earphones or headphones to listen to music when you are about to sleep. You might fall asleep without turning them off. If this happens, your ears will be listening to a nonstop sound.• When you have cold, blow your nose gently with your mouth open.• When sleeping outdoors, plug your ears with cotton so insects won’t get into your ears.• When swimming, use earplugs. These will prevent water, dirt and other foreign objects from getting into your ears.
YOUR NOSEYour sense of smell is wonderful. Just bysmelling, you know what food your motheris cooking in the kitchen, what flowers arearound, or what cologne your friend iswearing. Your nose is made up of cartilageand bone material. People have differentsizes and shapes of noses, but all noses areused for smelling. As you breathe in airthrough your nose, you can smell the odorsthat the air is carrying.
PARTS OF NOSE• The nose has delicate parts that work together to allow you to identify odors: – The nose has openings called nostrils. The air enters through the nostrils to your nasal cavity – The nostrils are lined with short hairs called cilia that filter dust mixed with the air. The nostrils are also lined with moist membranes. This membrane warms the air that enters the nostrils. – The nostrils lead to a hollow portion called the nasal cavity. Approximately, 95% of the nasal cavity has nothing to do with smelling. Most of its area only cleans and warms the air we breathe in. – In the upper portion of the nasal cavity are the olfactory nerves. They send nerve impulses about scents to the brain.
COMMON NOSE DISEASES• Common cold can be accompanied by frequent sneezing. It brings about a discharge from the nose called mucus. Consult a doctor if the common cold does not go away after several days. You might be experiencing an allergy called rhinitis.• Rhinitis is an inflammation of the nasal mucosa. It is often due to allergic reactions to pollen, dust or other airborne substances. Sometimes, it is even mistaken for the common cold because they have similar symptoms. Rhinitis causes nasal congestion, which makes breathing difficult. There is also a watery discharge from the nose