Organs which receive and convey the internal and external stimuli, from and to the Central Nervous System are called so.

Sense of touch, smell, sight, and hearing.

A physical sensation responding to pressure, heat, cold, contact, pain etc.

Skin is the main organ related to the sense of touch, covering the muscles of the body.

A protective layer spread over the entire body, having two layers - Epidermis the outer layer and Dermis the inner living layer.

Adult Male: 1.9 SQ. mtrs./20 SQ. ft.  Adult Female: 1.7 SQ. mtrs./17 SQ. ft. The skin is said to be the lartest organ.

It is composed of dead cells containing Keratin, the horny scleroprotein that also makes up hair and nails. It has no nerves or blood vessels.

1. Prevents harmful micro organisms and chemicals entering the body. 2. Protects and preserves the life sustaining body fluids. 3. Protects vital organs of the body from injury. 4. Protects the body & organs from Ultraviolet rays of the Sun. 5. Regulates body temperature. 6. Excretes some waste products like sweat.

It is a thick layer below the outer layer containing nerves, blood vessels, hair folicles, sweat glands etc.

Black: Pure Melanin. Blonde & Red: Melanin containing Sulphur and Iron. Grey: Due to deficient Melanin production.

Melanin.

Dead skin flaked of the scalp.

Skin.

Dead cells containing Keratin - a protein.

Hand nails.

Lunula.

A muscular organ extending from the Hyoid Bone in the throat to the lips, pinkish red in colour, containing numerous muscle fibres for easy manouvering, useful in taste, chewing and swallowing of food. The tongue is covered by a thin mucous membrane and the upper surface covered with small projections called "Papillae" Any discolouring of the tongue is an indication of the health problems.

Gustation.

Soles in the foot - 3 mm.

20-25 SQ.Ft.

Ultra Violet rays.

Olfaction.

Nose- divided into two parts. The visibly projected portion generally called the "Nose" and the inner portion called the "Nasal Fossae" - two cavities separated internally by Spectum. The two openings in the projected portion are called "Nostrils" which has a lining of stiff hairs called "Vibrissae" preventing the entry of insects and dust.

Hearing and smell.

Eyes.

CORNEA and CONJUCTIVITA : the outermost layer or part of the eyes. Cornea is transparent while the conjuctivita is a membrane covering the cornea.
PUPIL: An opening in the center of the eyes cornea through which the light or object passes through into the lens where the process of magnification of the object takes place. It is a circular opening or diaphragm in the Iris through which light passes.
LENS: Lies exactly behind the Pupil in the Iris through which the light passes.
RETINA: An inner lining where the images are formed. The light sensitive area of the eye.
IRIS: The coloured portion of the eyeball located behind the cornea, which automatically adjust of the pupil to the intensity of the light falling on it. The Iris shuts tight when the entering light is bright.
OPTIC NERVES.: Also called Cranial Nerve 2 - it transmits visual Information from the Retina to the brain.

Prebyopia.

Lachrymal Gland.

Weak and tired eyes.

Astigmatism.

Aqueous Humour.

Cone cells.

Benjamin Franklin.

Daltonism.

Astigmatism.

Cornea.

Farsightedness: A disease of the eye in which a person cannot see objects near to him. It can be corrected by "Convex" Lens.

Near Sightedness: A disease of the eye in which a person cannot see objects that are at distance. Can be corrected by "Concave" Lens.

A Distorted Vision - Where a person is not able to see the object clearly, infront of him. Can be corrected by "Cylindrical" lens.

It is another form of Hypermetropia, where the closest things to the eyes are not visible to the person concerned. It is the failure of the focussing machinery of the eyes like reading. It can be corrected by convex lens. Normally an age related problem.

Inflammation of the eyes, itching and reddishness. For cure, the affected eye should be daubed with simple solution of weak salt water or boric acid and use of antibiotic drops.

Always both eyes are affected by mild itching and irritation, caused by the germ Chalmydiae. Cured by oral administration of Tetracycline medicines.

An age related eye problem. A condition of opacity of lens in which a distant view is generally affected. Can be corrected by surgical means.

Eye disorder - crossed vision.

Lazy eyes.

Blink twice as much as men.

Checking the eye sight. It was designed by Herman Snellen in 1862. Nowadays, the charts used are designed by Ian Bailey and Jan Lovie.

Stops sweat from falling into the eyes.

Ears: They are divided into three main regions. (1) The outer ear, (2) The middle ear, and (3) Inner ear.

(1) Defection and Analysis of sound. (2) Maintenance of balance of the body.

Waves or vibrations in the air are collected by Pinna the projected semi circular part of the ear and is tken to the Ear Drum which vibrates. The vibration in the ear drum is transmitted by Ossicles in the middle ear to the inner ear where they cause waves in the liquid/fluid (called Perilymph) filling the coiled tube of Cochea a tube coiled like a small snail shell of 2 1/2 turns. These waves vibrate the basiliar membrane which divides the tube length ways. The membrane is turned so that each part responds to a different frequency and along it are some 10,000 sensory structures the rods or corti These structures convert the basiliar membrane vibrations into nerve impulses, which reach the brain along the auditory nerve where they are interpreted into sound.

It is maintained by three semi-circular canals and the Utricle and Saccule, all of which are filled with fluid. The semi circular canals detect movement in three phases of right angles and so provide a stream of information for the brain on movements of the head. The Utricle and Saccule detect tilting of the head and combine with the canals to give rapid contract of balance in normal circumstance.

Eustachian tube.

Middle ear.

20Hz to 20000 Hz.