Sense Organs: Eyes, Ears, Nose, Mouth, Skin

It  is through the sense organs chiefly eyes, ears, nose, mouth (tongue), and skin that the brain comes in contact with the reality of the external environment which human beings and other living creatures inhabit. Without senses vision, hearing, touch, smell, taste and others a human being as such can hardly be said to exist.

Perception of reality finally takes place in the brain, but the impressions which make this possible come via the nerve pathways of the sensory organs. The brain "dwells in utter darkness" in the cavity of the skull; but it is the brain that sees, hears, feels, and makes interpretations of all the sensory impressions brought to it.

Here we will place emphasis on the princi­pal sense organs. There are several practical reasons for this. Eyes, ears, and skin particu­larly are complex and specialized organ sys­tems, each of which demands its own special­ized kind of care and attention. Furthermore, all the sensory organs (with the exception of the eye) have functions beyond reporting sense impressions to the brain. For a com­plete understanding of the human organism, these specialized systems deserve to be studied   in   their   own   right.   They   are   often abused.

Eyes and ears are two of the greatest assets a human being possesses. Yet many people fail to make the most of them. Eye special­ists (ophthalmologists) constantly encounter people with faulty vision who have accepted the blurred, imperfect images of the world they half-see as perfectly normal. "Oh, I see fine," they say until they surprisingly dis­cover how much better they can see when their visual defects have been properly cor­rected. Ear specialists (otologists) similarly report that patients have usually lost a full third of their hearing before they take any steps to overcome their partial deafness.

End Organs of the Peripheral

Nervous System

To provide a more exact picture of the op­eration of sensory organs, we must briefly describe the operation of the peripheral ner­vous system. As its name implies, it is located at the periphery or outside ends of the ner­vous systems. It consists primarily of nerve trunks, attaching to the central and auto­nomic nervous systems, and end-plates, or end-organs. These end-organs pick up specific types of stimuli (light, sound, heat, cold, pain,

Pressure,etc. They also deliver back message or orders to the organs to which they are attached. End plates that pick up sensations are called receptors. Those that deliver orders are effectors. The end plates are specific for their particular sensations. Thus, the eye reacts to light, the ear to sound, the nose and tongue to chemicals in solution.

The specificity of the end plates explains some peculiar reactions. Why do you sometime see stars when you get a punch in the eye? Because the receptors server only one function. The end plates on the retina of the eye connect directly with the visual center in the brain. Stimulating the end plates of the retina with a powerful blow can be translated by the brain only in visual images that is, the flashes of light we describe as seeing stars. Similarly a blow on the ear may come as an explosive sound.

Man has far more than the traditional five senses. There are end organs for hot and cold sensations, for pressure, for pain and combinations of impacts on end organs that give a sense of vibration, a feeling of fullness or tension, a sense of balance, even the most basic feelings of hunger, thirst, and sexual desire. The end organ for hot and cold are irregulary distributed on the skin and in the mouth and esophagus, there are many of them of the feet and very few on the chest. The designers of women‘s fashions, though not deliberately, abide by these hot and cold spots.

THE HAIR AND NAILS

Like the skin, the hair and nails are part of the tegumentary system of the body. We shall therefore discuss them briefly here. They are not sense organs, although the hair, as noted, is highly sensitive even to a light touch.

The distribution and growth of hair on the head and on the body are definitely linked to

the endocrine tides of life. Hair growth is overt evidence of secondary sex characteris­tics, and its relationship to sexual attractive­ness is commonly recognized. The Biblical story of Samson and Delilah demonstrates how ancient is the concept that hair means strength and cutting it, loss of essential man­hood or womanhood.

The emotions involved with human hair have given rise in our time to a number of commercially inspired superstitions which are costly nonsense. The brand of soap or oil used on the hair is usually irrelevant to sim­ple proper hair care. Too frequent washing may remove essential oils. The hair is cleaned by combing and brushing with a stiff brush. It is hygienically immaterial whether the hair is waved and set with a "home permanent" or by a beauty-shop treatment.

No "Cure" for Baldness or Gray Hair

There is no scientifically demonstrated "cure" for baldness (alopecia). The receding hairline is apparently a hereditary charac­teristic transmitted through mother to son. No hair tonic or "treatments" will restore hair to the head that is bald by reason of he­reditary tendency. The loss of hair that occa­sionally follows acute diseases will, however, usually be made up. Hair cells are not "starved" through lack of circulation in the scalp, though stimulation of the scalp may possibly help to prevent premature baldness.

No "cure" for gray hair has yet been dis­covered either. The color of the hair is deter­mined by the pigment in the cells of the cen­tral shaft of the hair, which is no longer living tissue when it emerges from the hair follicle. Gray hair, which lacks pigment, can be dyed to change its color, but there is no known and practicable way of stimulating the production of hair pigment.

One type of cosmetic preparation that must be used with special caution is the depilatory for removing unwanted hair. Those which claim to "dissolve" the surface hairs may also same kind of protein substance. The saf­est and surest way to remove unwanted hair is with the electric needle in the hands of a competent technician under medical supervi­sion. The needle actually destroys the hair root. Other methods, such as shaving, rubbing with pumice stone, or yanking out with wax, do not.

The Skin-Tactile Sensation

Like the nose and tongue, the skin is a sense organ with many other functions. Covering approximately 17 square feet of tangible surface in adults and weighing together about five pounds the skin is the largest single organ of the human body. It is a vital organ. Destruction of a little more than one-third of the skin area, as by burning or scalding, is usually fatal.

Clendening speaks lyrically of the skin as "one of the most interesting and mystic of structures." He calls it "that outer rampart which separates us from the rest of the uni­verse, the sack which contains that juice or essence which is me or which is you, a moat defensive against insects, poisons, germs. The very storms of the soul are recorded upon it."

The variety of sensations recorded and re­ported to the brain by the skin is undoubtedly one of the factors that make it so "interest­ing." Tactile sensation touch is only one of five types of sensation to which the specific end-organs of the skin respond. They can also be stimulated by pain, pressure, heat and cold, and combinations of sensations. Pain, apparently, is registered by bare nerve endings; but for each of the other sensations there are specific types of end-organs, called corpuscles and discs. Meissner's corpuscles, located mainly in the hairless parts of the skin, are the chief end-organs of the sense of touch. They react individually to touch and collectively to pressure. Another type of tac­tile sense organ surrounds the individual hairs on the skin. These end-organs are highly responsive to the slightest movements of the hairs, such as those caused by a light touch or a draft of air.

The end organs for touch are distributed unevenly on the total skin surface of the body. Most sensitive areas are the lips and the tip of the tongue. Fingertips are quite sensitive; back, arms, and legs much less so.

The eyes

 The eye is an extremely complex organ, and we need not enter into all the technical details of its structure and function. Seeing however, depends on the relationship of the eye with that even more complicated structure, the brain. Mechanically speaking, the eye functions as a camera whose images are relayed to the visual centers of the brain

Protected by eyelids and eyelashes, the eye itself, set in the sockets of the skull, is a globe or sphere filled with fluid. Three coats or membranes enclose the fluid. The fluid in the rear of the eyeball is called the vitreous fluid; it has a jellylike consistency. That in the front bulge of the eye is known as the aque­ous fluid.

The outer membrane of the eyeball is known as the sclera a tough, fibrous mem­brane, it covers the entire eyeball and ap­pears as "the white" of the eye. However, at the front of the eye, this coat is crystal clear and is called the cornea.

The middle layer of membrane, called the choroid, also encloses the whole eyeball ex­cept altogether at the front of the eye, where the pupillary opening is found. The middle layer is pigmented and makes up the iris or colored part of the eye. The iris has tiny radiating and circular muscle fibers which enable it to expand when light is dim and to contract when light is bright so that light can enter its central opening, the pupil, in the right amount.

The inner layer of the eyeball is the retina; it lines the entire inner (posterior) chamber of the eye except in the region of the iris. This layer is composed of nerve tissue and millions of light sensitive receptors, known as rods and cones. These are connected with the optic nerve, which attaches to the back of the eye­ball. Where the optic nerve connects with the retina, there is a small "blind spot." The optic nerve conveys images to the brain, where they are "interpreted."

One more crucial part of the human camera must be mentioned, namely the crystalline lens of the eye. It is situated immediately be­hind the iris, which lies between the two chambers of the eye. It is held in place by suspensory ligaments and can be flattened or thickened by the operation of ciliary muscles. The lens is transparent and refracts light. The changes in its shape (degrees of convex­ity) serve to focus light rays on the retina.

THE EARS

Next to the eyes, the ears are the most important sense organs and avenues of commu­nication with the world about us. Like the eyes, they are complicated anatomical structures whose receptor end-organs communicate with the brain. The sensation of sight is carried by light waves capable of traveling in a vacuum. The sensation of sound is transmitted to the ears through vibrations in the air. You cannot hear in a perfect vacuum.

The value of good hearing can hardly be overestimated.  Cover your ears with your hands tightly for two minutes and you will begin to understand what a lonesome world apart the deaf and partially deaf inhabit. It is no wonder that they often become seclusive and suspicious. In human experience danger is usually heard before it is seen.

All ears are divided into three parts: an outer, a middle, and an inner ear. The middle ear is a small, irregular chamber, lined with mucous membrane. It is connected with the throat through the narrow, short (IV2 inches long) mucus-lined opening called the auditory or Eustachian tube. The purpose of this tube is to permit equalization of air pressure in the middle ear, so that the pressure on the ear­drum will be the same on both sides. Air is forced into the Eustachian tube whenever you swallow, as you do automatically every few moments. You can "open" your Eustachian tubes by yawning. The inner ear is a very small, delicate, and complicated structure set deep in the temporal bone of the skull. It con­sists of two parts:

(1) a series of three semi­circular canals, which are essential to the maintenance of equilibrium, and

(2) the cochlea, a snail-shaped bony structure about the size of a pea, which carries the end-organ receptors of the hearing process.

Over stimulation of the receptors of the semi­circular canals confusion of them, one might say can produce dizziness, vertigo, and concomitant nausea and vomiting. This is what happens in motion sickness, when rid­ing in a tossing ship, a bumpy airplane, a fast automobile, or an ordinary merry-go-round. Many changes in the direction of motion over stimulate the receptors in the semicircu­lar canals. It is unaccustomed motion that produces motion sickness. Seasick individuals recover when they become used to the mo­tions of the boat. With experience in riding, people outgrow carsickness and trainsickness.

The middle ear is the most vulnerable to serious infections. These often travel up the Eustachian tube from the nose and throat. Swimming and diving can encourage such infections.

Two self-inflicted complications must be mentioned: indiscriminate use of nasal drops or sprays and improper blowing of the nose Infectious material from the running nose or sore throat is often forced up the Eustachian tube by noseblowing. When you blow your nose, especially if you have a cold, blow it gently. Do not close both nostrils at the same time.

Wax in the Ear

The accumulation of wax in the external auditory canal on occasion forms a plug which temporarily impedes hearing. This can be a frightening sensation, but it is not a serious condition. The important thing here is not to try to get the wax out by digging into the ear with a hairpin, matchstick, nail file, or paper clip. Such effort may force the plug in tighter, and may even result in scratching or perfo­rating the eardrum.

Wax plugs are best removed by a competent physician or an ear specialist, who will usu­ally float them out by irrigating the ear with a syringe. This is the best way to remove a foreign body, even an insect, from the ear There is much merit in the old axiom, "The only thing to put in your ear is your elbow."

Sun Tan

The protective mechanism of the skin is expressed in still another way, namely, the release of skin pigment (melanin) to protect against injury to the skin from strong doses of sunlight. In the white races, which have comparatively little skin pigmentation, exposure to sunlight increases the amount of pigment produced by the specialized Malpighian cells. The result is a coat of sun tan. The tan­ning is caused by the invisible ultraviolet rays from the sun. The coat of tan disappears as the more highly pigmented cells die and move toward the surface of the skin.

The development of additional skin pig­ment under the influence of sunlight is not an instantaneous process. The attempt to get a coat of tan too quickly, therefore, usually re burn like any other and should be treated accordingly. It can be serious.

The right way to get a sun tan is to limit your exposure at first and gradually increase the amount of time spent in the direct sun­light. If you know that you do not tan, because your skin is light-sensitive, avoid exposure.

Freckles are produced by the same mecha­nism as skin tanning. In this case, however, the areas of increased pigmentation are spotty instead of consistent.

Cosmetics

Cosmetics are beauty aids. Since the search for beauty is a universal and perennial pas­time, the history of cosmetics stretches back into remotest antiquity and may be expected to be reformulated in all future generations. Today in the United States cosmetics are big business. Well over a billion dollars a year is now spent annually on all varieties of cos­metic preparations, including soaps, sham­poos, hand lotions, and the like.

From the standpoint of mental health, the increasing use of cosmetics is probably justi­fied. The pursuit of beauty is a legitimate aim of civilized life. The woman who does not use cosmetics today stands starkly apart from her "sisters under the skin." It is not uncommon to hear a woman say, "I feel positively un­dressed without my lipstick."

The people in the cosmetics business know all this and they say, "We don't sell merchan­dise, we sell illusion." The danger in this is that many cosmetic preparations are over-enthusiastically promoted and overpriced. Women are repeatedly cozened to expect mir­acles from cosmetics, and those miracles never happen.

Cosmetics are not and can never be a sub­stitute for good health. There is no way to "nourish" the skin by creams or lotions or falsely labeled "skin foods" applied from the outside. The skin is nourished, like all body tissues, through its own blood supply. False and misleading names are applied to many cosmetic products. You ought to know that there is no known substance or combination of substances that can live up to the promises suggested in any of the following names: contour cream, crow's-foot cream, deep pore cleaner, enlarged pore preparation, eye wrin­kle cream, miracle oil, nourishing cream, pore paste, rejuvenating cream, scalp food, skin conditioner, skin firm, skin food, skin tonic, eyelash grower, wrinkle eradicator, spot re­ducer, bust developer, bust reducer.

No better cleansing agent than ordinary soap and water has yet been developed. Fre­quent bathing rather than the use of any spe­cial kind of soap is the best way to prevent body odor. On the other hand, too frequent bathing can be harmful to the skin and may occur as compensation for guilt feelings. Skin deodorants and antiperspirants are not objec­tionable, but they are by no means as impor­tant to social success as the advertisements make them out to be.

Structure of the Skin

 Perspiration

There are from 2 to 3 million sweat glands in the human body. They are most plentiful in the armpits, on the hands and feet, and on the forehead. These tiny coils extract water and some other substances such as salt and urea from the blood flowing through the capil­lary vessels in the true skin. The extracted water (i.e. sweat or perspiration! is then re­leased to the surface of the skin through the minute tubules or openings which we call body pores.

The quantity of perspiration released daily varies greatly and depends on many factors. The sweat glands are never entirely idle. The body, even though it does not feel wet, is con­stantly releasing some water through the skin. This so-called insensible perspiration may amount to a quart a day.

Loss of body heat through perspiration, both visible and invisible, involves not the blood vessels but the sweat glands. The per­spiration that exudes from the pores is re­moved from the surface of the skin by evapo­ration. A stream of warm, dry air speeds evaporation. That is why the warm breeze from an electric fan on a hot day still pro­duces the sensation of cooling.

Underneath the true skin is a layer of sub­cutaneous tissue which is usually largely in­filtrated with fatty tissue. This layer gives the body its more delicate curves and con­tours. It serves as a cushion between the tegumentary covering of the body and the underlying muscles and permits the free rip­pling of the skin during muscular activity.

The Functions of the Skin

The skin serves many vital functions for the body. It is, first of all, a protective covering, a barrier against the invasion of pathogenic bacteria. Second, it is the impor­tant regulator of body temperature and is provided with the mechanism with which to perform this task. Third it is an organ of sensation that provides warning against some of the threats to life or health, found in the im­mediate external environment.

 Fourth, it concerns itself with those reactions which heighten the body's immunity to disease. And, finally, it is an organ of expression, a mirror if you will, of many disorders, both Infection and psychic, which may affect the body.

Bacterial resistance on the part of the skin is high. This applies also to the mucous mem­branes of the lips, mouth, and other parts of the body. So long as the skin is clean, it very quickly gets rid of unwelcome bacteria that may come to lodge upon it. The mechanism of this repellent action is not altogether clear. Unless the skin is cut, broken, punctured (as by an insect), or abraded, harmful bacteria have a difficult time getting through its horny layer. Of course some bacteria always lie on the surface of the skin, just as some are al­ways to be found in the mouth.

Skin blemishes such as blackheads, pim­ples, sores, and scabs should not be picked at anywhere on the body, but this warning should be doubly observed concerning the area that is called "the danger triangle of the face." This area is bounded by the bridge of the nose and the corners of the mouth. Be­cause of the peculiar arrangement of veins and arteries feeding this area, bacterial in­fections originating here may be carried di­rectly into the brain and set up a possibly fatal inflammation.