Category Zoology

          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.