My Science School

          Impairment of hearing is generally called deafness. It is caused by any interference with the reception or transmission of sound waves along the canal through the middle ear to the inner ear and then along the auditory nerve to the brain. Deafness is either congenital or caused by some disease or accident after the birth. 

          The congenital deafness can be caused by many different factors. For example, if a pregnant woman suffers from measles within three months of conception, the child born can be deaf. At least 50% of such women have been found to be giving birth to deaf children.

          However, in many cases deafness occurs after the birth. In such cases sound waves are not able to reach the eardrum because they get obstructed by the deposition of a waxy substance on the eardrum. You might have noticed the formation of a brown coloured waxy substance inside the ears. This regularly comes out of the ear in small bits. In some cases this material is deposited on the eardrum. As a result of this sound waves get reflected back and are unable to reach the eardrum. In another case, the internal nerves of the ear get burst due to some injuries or very intense sounds and consequently the ear is unable to hear any sound.

          The people who live in very noisy areas also get their hearing power impaired. They are able to hear only loud sounds. In the Second World War, 58,000 soldiers developed deafness because of the fierce sounds of tanks and machine guns. Deafness can be caused by ear diseases also. Sometimes due to the bad effects of the diseases in other parts of the body also cause deafness. Even aging reduces the power of hearing. Excessive use of some intoxicating medicines can also affect the power of hearing. At times undesirable growth of some bones inside the ear also causes deafness because these prevent the sound waves from reaching the main parts of the ear. 

          Today sophisticated instruments are available by which one can hear feeble sounds. Such instruments are known as ‘hearing-aids’. In some cases surgery is also helpful in the treatment of deafness.

          Most of the people think that parching of mouth or throat is only caused by thirst. But, this is not a fact. Such parching can occur due to many other causes also. When we do exercises, our throat gets dry. Tension or production of less saliva by the salivary glands can also produce this effect. The question arises: why do we feel thirsty?

          We know that water and salt are always present in our blood. The body tissues also contain these two substances. Under the normal conditions, the proportion of these two materials in blood remains constant. If due to some reason, the amount of water in blood gets reduced, the proportion of the two materials also changes. In such a situation the ‘thirst centre’ located in the brain sends signals to the throat. As a result of this the throat starts contracting. This contraction makes it dry and we start feeling thirsty, and so we drink water.

          However, sometimes, the salivary glands secrete enough saliva and our stomach and blood too have enough water and yet we feel thirsty. For example, when man drinks liquor he takes enough quantity of salted preparations along with the drink. Though the amount of water goes increasing with the intake of liquor, yet consumption of salted foods increase the quantity of salt in blood. As a result of this the amount of salt in blood exceeds the normal level. This disturbs the normal proportion of salt and water in the blood. In such a situation we feel thirsty. Excessive thirst may be a symptom of diabetes or kidney ailments. In such cases immediate medical checkup should be undertaken.

 

          Pulmonary tuberculosis is an extremely infectious and serious disease. It is commonly known as T.B. This is spread by bacteria called Mycobacterium tubercle bacillus. When afflicted with this disease, tubercles of hard tissues grow inside the lungs. These nodules are composed of millions of cells. The German scientist Robert Koch discovered the bacteria of this disease in 1882. They are rod shaped, and the size is approximately 1/7000 mm in length and 1/6000 mm in breadth.

          While coughing, a T.B. patient sprays small drops of water and sputum into the air around. These contain the bacteria of this disease. In pulmonary TB there are two stages of infection. In primary infection there are no significant symptoms; only dormant small hard masses called tubercles are formed. In post-primary infection the dormant bacteria are reactivated due to weakening of the body’s defences and clinical symptoms become evident. Symptoms include fatigue, weight loss, persistent cough with green or yellow sputum and possibly blood. When the water drops and sputum dry up, the bacteria start flying in the air. If somebody inhales them, he may also get infected. A man suffering from this disease can transmit it to the people around him.

          For thousands of years, there was no treatment of this disease. Anybody who caught it was sure to die. In 1944, a miracle drug called, ‘streptomycin’ was discovered for the treatment of this disease. A few years later two more medicines, para-aminosalicylic acid and isonicotinic acid hydrazide, were discovered. Nowadays this disease is effectively treated with these triple drug therapies. Though the treatment of this disease takes several months, yet the patient regains his health.

          A patient of tuberculosis should not be kept at home, because he can infect his family members or neighbours. He should be immediately admitted to some T.B. sanatorium or hospital. This disease can be easily detected with X-rays. Tuberculin skin tests are also used to detect this disease. A small amount of the killed germs is injected into the skin. If the person is suffering from tuberculosis (TB), the skin around the injection mark becomes red and hard. Each year an estimated two million people in the world die from tuberculosis. Of late, due to the progress made in the field of medicine, TB is no more considered as a dreaded disease.

 

          Normally a woman delivers only one child at a time. This child can either be a male or a female. Sometimes, however, two or more children are born at a time. Two children born of the same mother at one time are known as twins. Do you know how twins are born?

          Between the 10th and the 18th day from the onset of menstruation, the reproductive organs of the female produce an egg called ovum. If during this period a female mates with a male, one of the male sperms enters into the ovum. This union of the ovum and sperm is known as fertilization and the female is said to have become pregnant. Two hundred eighty days later, the woman gives birth to a child.

          But sometimes after the conception the ovum divides itself into two parts. Both these parts develop in the womb separately as two embryos. As a consequence, such a woman delivers two children simultaneously. The two children so produced are similar in complexion and appearance. Most of their traits are similar. Both the children will always be either boys or girls. This is because they are produced from the same ovum. Such twins are called identical twins.

          Sometimes there is another possibility too. Two sperms from the male semen enter separately into two ova of the same female. This leads to the development of two embryos in the womb and the woman delivers two children. The children so produced may be different from one another. They may or may not have the same sex. Their other habits may also differ. Such twins are called n0n-identical or fraternal twins.

          Sometimes we come across the term ‘Siamese twins’. The term Siamese for conjoined twin is derived from the famous celebrated twins, Chang and Eng-Bunker born in Mecong, Siam (now Thailand) in 1811. They were joined by cartilaginous band at the chest. Both of them died in a gap of three hours at the age of 62 in 1874. However, such twins are very rare.

          Some women have given birth to more than two children at a time. On 22nd April, 1946, a woman in Brazil gave birth to ten children at a time - 2 boys and 8 girls. Spain and China also hold record of having women who gave birth to 10 children at a time. On 13th June, 1971 Mrs. Geraldine Broderick gave birth to nine children in the Royal Hospital of Sydney (Australia). Five were boys and four, girls. Of course, we often hear of women giving birth to 3, 4 or 6 children at a time. 

 

          The human body requires a constant supply of food in order to carry on its numerous activities. The food we take performs two main functions in our body. First, it supplies proteins for the growth of the body and second, it supplies energy to the tissues for the day-to-day work. Do you know how the food is digested in our body and how we get essential substances from it?

          The process of digestion is very complex and elaborate. It starts from our mouth itself. When we chew food the saliva produced in the mouth moistens it. The saliva contains a substance called ptyalin which converts the starch of the food into sugar. This is the first stage of digestion. Therefore we should swallow the food only after properly chewing it. 

          After that the food material passes through the oesophagus to the stomach where the gastric juices get mixed with it. The walls of the stomach secret juices containing an enzyme called pepsin and hydrochloric acid. Pepsin converts the molecules of proteins into peptones.

          From stomach the food goes to the small intestine, where it mixes with three other digestive juices - bile, pancreatic juice and intestinal juice. Bile is produced by the liver. Its main function is to digest the fats. The pancreatic juice is basic in nature and neutralizes the acids. It digests the proteins also. The intestinal juice converts sugar into glucose. Here many enzymes also mix with the food. Food is mainly digested here. The digested food is absorbed by the blood vessels present in the walls of the small intestine. The remaining waste of the food now goes to the large intestine and is finally excreted out of the body through the anus. 

          The nose is an organ used for smelling and breathing. If it is not working properly we cannot distinguish between foul smell and fragrance. Do you know how the nose detects smell?

          The nose is composed of two bones and is situated between the eyes below the head and above the lips. These two bones form a kind of bridge. In between them lies a wall of cartilage which divides the nose into two parts called the nasal cavities. At the end of the nasal cavities lies a thin membrane called the mucous membrane which secretes a special fluid. This fluid keeps the nose wet. There are hairs inside the nose which prevent dust particles from entering the lungs. The air filtered by the nose goes to the lungs through the trachea.

          The smell is detected by the cells present in the two olfactory nerves situated at the end of the nasal cavities. These cells are called ‘receptors’ and are embedded in the mucous membrane. They are spread over an area of 250 square millimetres.

          According to one theory, our nose has seven kinds of receptors - each telling a different smell. The seven smells are of: flowers; burning; alcohol; fruits; peppermint; musky and pungent smell. When we smell something, particles coming out of it reach this sensitive area through the nasal cavities. They generate electric impulses in the nerves there. These electric impulses reach the ‘smell centre’ of the brain and we detect the smell.

          We often confuse smell with taste because gaseous particles of many of the food we eat reach the receptors for smell as we eat. Food often seems to lose its taste when we catch cold. Our sense of smell is blocked during a cold attack, and this has an effect on our taste. 

          All of us get headache at one time or the other. Headache is not a disease. It is a symptom. It is simply an indication that there is something wrong in some parts of the body or the nervous system. Do you know what causes it?

          The brain is a very important part of our body. It is protected and covered by the skull. There are certain arteries, veins and tissues in the skull that are sensitive to pain. When these arteries, veins or tissues get hurt, we experience pain in the head or headache.

          These particular areas sensitive to pain are affected by many factors. Whenever any parts of our body get hurt, their pain reaches these places causing headaches.

         If, due to any reason, there is a contraction in the muscles near the head and above the neck, there can be headache. It can be caused by a brain tumour too. But it will be limited to the area where it is located.

          Headache is also caused by hunger, dislocations in the bones of neck, loss of sight, fever, etc. Anxiety, mental tension, excessive drinking and anger, etc., are also the causes of headaches. Under these conditions, the arteries, veins, tissues and muscles undergo certain changes and cause headache. Allergies can also cause headaches. Migraine is a common condition characterized by paroxysmal headache, occurring in bouts, often affecting only one side of the head and frequently preceded by visual disturbances, nausea and vomiting. In such cases often a family history exists to this extent. If the headache persists for a long time, we should consult a competent neurologist. A neurologist can distinguish between a headache caused by a serious nerve or brain disease and one that is caused by a less serious condition. 

          Whenever some part of our body is hurt or cut, we experience intense pain. But when we cut our nails and hairs for shaping and dressing, we don’t feel any pain. Do you know why it is so?

          We have, in all, twenty nails on our hands and feet. We do not experience any pain in cutting them because they are composed of dead cells. Nails are special structures of the body formed from the outer layer of the skin. They are made up of a hard material called keratin. Keratin is a kind of dead protein. The base of the nails is located inside the skin of the fingers. The skin beneath the nails is similar to that in other parts of the body, but it has flexible fibres. These fibres are attached to the nails and keep them an in fixed position. Generally nails are thick but their roots inside the skin are very thin. The portion near their roots is white and semicircular. It is known as lunule. The finger nails grow at the rate of about 2 inches per year.

          Nails are very useful for our body. They help us in picking up of things as well as in doing artistic work. They protect the fingertips too. For ladies, nails have an intimate relationship with their beauty. They decorate them by painting with different colours.

          Similarly, hair is also a filamentous structure made of karatine - a dead protein. The hair grows on our head about 12 mm. each month. We have about 100,000 hairs on our head. The base of the hair - the root, as it is often called, is in the form of a round bulb. About 50 head hairs fall every day. Each head hair usually last for about 3 years and then it falls out to grow a new one. They grow out of pits in the skin and are called foliates. And it is the shape of these follicles which makes our hair straight, wavy or curly.

          The custom of cutting and arranging the hair has been practiced by men and women from very ancient times. By 20th century hair dressing itself had become an occupation and practical art in large proportions.

          Since both nails and hairs are composed of dead protein like karatine, we do not feel pain while we scrape our nails and dress our hair in a routine way.

 

          Of all the five senses, sight is the most precious and miraculous sense. Any defect in the eyes or any harm caused to them handicaps a man to a great extent. The eye diseases are both of permanent and temporary nature. Do you know what are the common eye disorders and how are they caused?

          Among the common disorders of the eye, myopia or short-sightedness and Hypermetropia or long-sightedness are the most common. In myopia, the light entering the eye is bent too much so that it focuses at a point in front of the retina. As a result a person can see the nearby objects well but can not see distant objects clearly. Whereas in Hypermetropia, the light is not bent sufficiently and focuses at a point behind the retina. Hence the patient sees distant objects well but near vision becomes difficult and causes strain. Corrective glasses are used to get a clear vision.

          Conjunctivitis is another common disease of the eyes. It brings about an inflammation of the conjunctiva of the eyelids and the eye ball. It can be caused by allergy, irritation or infection. A viral form of conjunctivitis is called trachoma which is a major cause of blindness in Europe and Asia. Another infection of the eye is ‘sty’ that affects a gland at the corner of the eyelid. Cataract is a condition in which the lens becomes cloudy or opaque, reducing the amount of light that enters the eye. Its treatment may require surgical removal of lens, and then either implantation of an artificial lens or the use of special corrective glasses becomes necessary.

          ‘Glaucoma’ is an eye ailment that causes increased pressure within the eye ball which puts pressure on the optic nerve. If the pressure is higher than a certain level and not controlled, then it may lead to blindness. Night blindness is caused by the deficiency of Vitamin A, which results in the damage of special cells, called ‘rods’ that enable us to see in dim light. In a ‘retinal detachment’, the retina gets separated from the choroid and floats in the vitreous humor. This can be caused by a fall, a blow on the head or by any other trauma to the eye. It is treated surgically and in many cases laser beams are used to fix the retina back in place.

          Sometimes the retina gets degenerated and leads to total blindness. The disease of retinal degeneration is called Retinitis pigmentosa. There is no treatment for this disease and it eventually leads to permanent blindness.

          A corneal abrasion is a very painful scratch on the surface of the cornea. It usually heals automatically without causing any ill effects. Corneal scarring, however, results from a more severe injury or disease. Since scar interferes with or totally obscures the vision, the cornea may be removed and transplanted.  

 

          The process of growing up is a natural way of life. Plants, animals, birds, human beings - all start growing up just after the conception. In the first nine months the foetus develops in the mother’s womb and keeps on growing after birth also. When a child is born, he is about 50 cms high. And in the next 20 years his height becomes more than triple. Man’s growth stops after the age of 20-22 years. Do you know how man grows up and why his growth stops after a certain age? 

            In its simplest sense, growing means adding living matter to the matter that is already present in the body. In fact, these are mainly proteins that help the body to grow. We get these proteins from meat, fish, eggs, seeds, grains, vegetables, fruits, milk and its products. During the process of digestion these proteins get converted into amino acids. These amino acids produce cells and tissues. Minerals like calcium, magnesium, phosphorus, sodium, potassium and iron are also helpful in the physical growth. Tissues, muscles and bones are produced by proteins and minerals. Broken cells and tissues are repaired by proteins.

              Now the question arises: why do we stop growing up after a certain age? In fact, the endocrine glands which secrete hormones directly into the blood stream control our body-growth. These glands are the thyroid glands (in throat), pituitary gland (in brain), thymus gland (in thorax) and some sex-glands. The pituitary gland controls the growth of bones. When a child is born, his thymus gland is very large, but it starts shrinking after the age of 13-14 years. The body attains full maturity by the age of 20-22 years and after that the growth stops. The glands responsible for the physical growth become less active after this age. After 40 years of age the body starts contracting. It contracts by about one centimetre every ten years. This contraction is due to the drying up of the cartilages in our joint and spinal column. 

          Pneumonia is a disorder of one or both the lungs usually caused by micro-organisms such as pneumococcus and myco-plasma. It may also be caused by exposure to radiation, such as X-rays, or by breathing in chemical fumes or powders. Its affliction causes irritation in the sacs of the lungs. At this stage, the body pours fluids and white blood cells into air sacs to fight the infection. Pneumonia may develop when a person is already ill, either very young or old, or when the immune system is not very strong.

          The symptoms of pneumonia include chills, fever, chest pain, cough and difficulty in breathing. Frequently, the infected person coughs out rust-coloured phlegm - mucous that contains blood from the irritated lung tissues. The symptoms usually last from seven to ten days until the body’s defence mechanism begins to gain control over the disease.

            Its remedy includes administering of antibiotics that make the patient feel better at a faster pace. Antibiotics have played a major role in reducing the number of deaths due to pneumonia.

           Pneumonia caused by the bacterium pneumococcus is clinically very severe. The pneumococci is present in the bodies of many healthy persons, but is normally kept under control. If the body becomes weak because of sickness, cold, surgery or exhaustion, the pneumococci can quickly upset the body’s defences and cause pneumonia.

          The mycoplasmal pneumonia caused by mycoplasma pneumonia usually afflicts younger people in the age group of 15-20 years. Once afflicted, the body can produce immunity to the organism. The mycoplasma pneumonia grows on the mucous membrane that lines most of the internal lung structures. The bacteria can produce an oxidizing agent that might be responsible for some cell damage. The organism inflames the bronchi and alveoli (air sacs).

          Pneumonia is called after the internal body organs it affects. The lobar pneumonia affects one or more lobes of the lung. Double pneumonia is lobar pneumonia in both lungs. Broncho-pneumonia affects the bronchi and bronchioles, the tubes leading to the lungs.

          Pneumonia is a serious disease that should always be treated by a doctor. The patient should get plenty of rest, fluids and fresh air. He should avoid crowds and contact with other people. Penicillins are the preferred drugs for the treatment of pneumonia. 

          Most of the people in the world do most of their work with the help of their right hands, but four per cent of the world population is left-handed. If we go through the history of mankind we find that many of the great men of the world have been left-handed. The world famous sculptors Leonardo da Vinci and Michelangelo were both left-handed. Parents of the left-handed children usually feel worried about this habit. They make efforts to correct it. But psychologists are of the opinion that if a child is a left-hander, he should not be forced to change this habit.

           Now the question arises: why are some people left-handers? If we examine the constitution of the body a little minutely, we will notice that our body is not fully symmetrical. There is a little asymmetry between the left and right side of the body. Generally right side of the body is slightly heavier than the left side. Our brain has also right and left parts. Even the functions of these parts are somewhat different. Usually the left half of the brain is ‘predominant’ over the right half. In such cases, the nerves from the brain cross over at the level of the neck and go to the right side of the body. Such persons are right-handed. Most people of the world fall under this category. But in those cases where right half of the brain is predominant than the left, nerves coming out of the brain pass onto the left parts of the body. Such people perform all their functions with their left hands. That is why some children write and even eat food with left hand.

          Now the question arises: why are the left-handers in such a minority in comparison to the right-handers? Scientists have not been able to solve this riddle till now. Since the number of right-handers is so large, the door handles, locks, screw-drivers, motor cars, musical instruments all are designed keeping in view the convenience of the right-handers. Even buttons are fixed on our clothes on the right side for this reason only. The left-handed people experience some difficulty in handling all these but, of course, they somehow manage them.

 

          There are 639 muscles in our body. The shape and structure of these muscles vary. A medium-sized muscle consists of about 10 million cells. All the muscles of the body put together have about 6,000 million cells. Each of these muscle cells is like a motor containing ten cylinders arranged in a row. The cylinders are tiny boxes that contain fluid. A muscle contacts when the brain sends a message to these tiny boxes. For a fraction of second, the fluid in the tiny box congeals; then it becomes a fluid again. It is this action that causes the muscle to move. Muscles make up about 40% weight of the body.

          From birth to death these muscles perform very useful work in the body. They produce heat and help in the movement of food from one place to another in the digestive system. They take the air to the lungs. If they stop working all the functions of our body would come to a halt. The throbbing of the heart and the expansion and contraction of intestines would also stop.

          Our body has three kinds of muscles: striated or voluntary, smooth or involuntary and cardiac. Most of the muscles of the hands, legs, neck and head are voluntary because all these limbs function as we want them to do. Most of them are attached to bones and are called skeletal muscles. Striated muscles are made up of many fibres. Smooth or involuntary muscles are those which function on their own. The muscles of the stomach and intestine are involuntary because the process of digestion continues on its own. These muscles help in blood circulation. The cardiac muscle is found in the heart. It is also controlled automatically. It is most important and is fibrous in structure. With the help of this muscle the heart beats 2,500 million times in a life span of 70 years.

          In the working of muscles several body parts such as brain, spinal cord and nerves are involved. The many tiny fibres that make up a muscle contract when they receive a signal from the nerve. Muscle fibres either contract completely or not at all. When only a few of its fibers contract, the muscle only shows a weak contraction. The muscle contracts more powerfully when more of its fibres contract. All muscles work by contraction.