Category Human Body

               There are over 600 muscles arranged around the frame of a human skeleton and inside the body. These muscles are responsible for various movements of the body. When these muscles are active, as happens in the case of muscle contraction and stimulation, they produce electric impulses. Electromyogram or EMG is a record of such impulses.

               Electromyogram provides valuable information regarding the disorders of the muscles. The electric signals from the muscles are obtained during voluntary contraction. For this purpose, an instrument is used whose electrodes are connected to the particular muscle. These electrodes carry the electrical impulses through the wires to a pen recorder which marks these in the form of a graph on a paper.

               Now the question arises, how do muscles produce electric impulses? A muscle is made up of many motor units. A motor unit consists of a single branching neuron from the spinal cord to the muscle fibres. This gives rise to a potential difference. In fact, this potential difference is recorded in the form of electromyogram.

               Single muscle cells are usually not monitored in an EMG examination because it is difficult to isolate a single fibre. Instead, EMG electrodes record the electric impulses from several fibres. EMG gives valuable diagnostic information about muscles. With the help of an EMG the contraction of a muscle can be known.

               EMG can also be recorded with electric stimulation. A typical stimulating pulse may have amplitude of 100V and lasts from 0.1 to 0.5 m-secs. With the help of an EMG we can study the reflex responses of the muscles and can know their working level. For instance our heart muscles go on pumping blood. If there is any disorder in pumping system, the device can identify heart muscles which may not be in its normal state. The major muscles in humans can be stimulated at a rate between 5 and 15 hertz. Normal nerves and muscles show some changes during prolonged restimulation. On the basis of EMG we can gather information about any malfunctioning of the muscles. 

            Insemination, which means the injecting of sperms into the female reproductive organ, takes place during the mating of a male and a female. However, in recent years different methods of artificial insemination have been developed by which not only females in the animals but also the women’s ova can be fertilized by such artificial methods. Do you know how the artificial insemination is done?

            Artificial insemination is done by taking sperm of a prized animal and injecting it into the reproductive organs of a female animal. This method is used to improve the breed of animals like cows. The method is that the sperm of a prized ox is taken and introduced into the reproductive organ of a cow. This fertilizes the cow. It helps impregnate far more cows in less time than possible with natural insemination. Thus this process of artificial insemination is very useful in increasing the number of livestock of a better breed.

            Artificial insemination is being used for conception in women also. With this method of artificial insemination a woman can conceive if the husband is sterile or cannot produce sufficient amount of semen. So, semen is obtained from another person and injected with a syringe at the mouth of the womb of the woman. There are however, various methods by which babies can be conceived outside of the mother’s body and can be artificially carried out in a laboratory. These children are usually known as ‘test-tube’ babies and the technique is called I.V.P. (In Vitro Fertilization). The world’s first test-tube baby was born on 25 July 1978 in Oldham General Hospital, USA. 

               Ringworm is a common skin disease. It is caused by fungi. It is so called because the fungus often produces a ring-shaped infection. The fungi of this disease live and multiply on the surface of the skin and feed on keratin, the horny protein constituting the major part of the outer layer of the skin and of the hair and the nail. The lesions are usually round or ring shaped and can be either dry or moist. They might cause several patches on the skin.

               Ringworm is also called tinea. This word indicates the part of the skin affected by it, e.g. ringworm of the scalp, beard, and nails are called as Tinea capitis, Tinea barbane and Tinea unguium respectively. Similarly ringworms of the body, groin, hands and feet are referred to as Tinea magnum and Tinea pedis. Tinea pedis is also referred to as athlete’s foot. This ringworm can be dry or moist. Watery ringworm may be found between the toes and fingers of the foot. The dry type may involve the sole and sides of the foot. The scalp ringworm is very contagious and may cause an epidemic among school children.

               Ringworms are usually controlled by various fungicides sold as medicines by pharmacists. Fungicide is a substance that kills fungi and can be used for the treatment of ringworm. The infected area should be kept dry and powdered. Limited exposure to ultraviolet light may also be helpful. 

               We have two sets of teeth during our life time. The initial 20 milk teeth are replaced by 32 permanent teeth. These are bony cells that grow out of the gum in the mouth. Each tooth consists of a crown and one to three roots depending on its type and position. The crown is that part which appears above the surface of the gum, while the root is contained in the socket in the jaws. The bulk of the tooth consists of a hard yellow material known as dentine. The exposed surfaces of the crown are covered by the dense white enamel which is the hardest tissue in our body. Its molecules are Iived up in patterns called crystals. The sort middle part of a tooth is called the pulp and is filled with nerves and blood vessels.

               Fluoride is a chemical substance that can make enamel even stronger. If we brush our teeth with fluoride tooth paste, molecules of fluoride arrange themselves in the crystalline pattern, replacing other molecules. Since the fluoride molecules fit more tightly than the others, they make the enamel harder to break. The harder the enamel, the fewer the cavities. In many cities today fluoride is added to the water supply. Fluoride in the crystals strengthens the teeth by making the enamel hard.

               Fluorides are compounds of fluorine and another element or group of elements. Most of the fluorides are salts. They are produced by the reaction of hydrofluoric acid with a metal oxide.

               Some diseases pass on from one generation to the next, i.e. from parents to their children. Heredity describes how parents pass on their characteristics to their children. Sometimes it is a tendency towards a certain illness. These diseases are known as hereditary or genetic diseases because they are traceable to the genes of the parents. Do you know which diseases are hereditary diseases?

               As we know that the sex of a child depends on the respective number of chromosomes X and Y obtained from the parents. There are some other genes connected to sex, called the sex-linked genes. The chromosomes in the cells of a new born baby are a mixture of its parent’s genes.

               Colour blindness is one of the sex-linked diseases. The incidence of this disease is more in males than in females.

               Haemophilia, a rare disease in which blood does not clot or clot very slowly, is another sex-linked disease. This is due to X-chromosomes which are carried by females only. This disease is inherited by male children only from their mother.

               Albinism is another inherited disease in which a person lacks in melanin, a dark pigment which gives colour to the skin, hair and eyes. The persons suffering from this disease have pinkish skin, greyish hair and are very sensitive to light.

               The chances of a child to suffer from diabetes and cancer are more if the parents suffer from these diseases. Sickle cell anaemia, a physical disorder in which blood cells are formed irregularly like a sickle in shape, is also inherited from parents. This disease produces abnormal haemoglobin with sickle blood cells.

               There are some diseases which are produced due to some disorder in chromosomes. Some children have small flat face, small fingers, weak muscles and squint eyes. Their lifespan is short, just 20 to 30 years and mental development is not more than that of a four years old child. This is due to the presence of 47 chromosomes instead of 46, and their abnormal combination. In medical terminology this disease is called Monogolism or Down’s syndrome after the name of the doctor John Down, who studied it. 

              Our skin is one of the largest functional organs of the body. In an adult it counts about seven per cent of the total body weight. It protects the internal parts of the body from the harmful effects of the outer environment like injury or attack by hostile organisms. A piece of skin — size of a 5 paise coin — has over 3 million cells, 1 metre of blood vessels, and 80 sweat glands. The inner layer of our skin is called the dermis, where exist our nerve-endings. The outer Layer is called epidermis. Although this layer contains tile-like dead cells, they constantly get water from the living cells below. When water reaches the top layer, it evaporates. It also contains a tough protein called “Kerratin”. The epidermis also contains cells which produce the “Melanin” responsible for skin pigmentation. It provides protection against sun’s ultra-violet rays.

              Sebaceous glands present in the surface of the skin secrets an oily liquid called sebum which continues to flow along the ducts and comes to the outer skin. It is due to this secretion that our skin is soft and flexible as this liquid saves our skin from being dried out. It also protects the skin from physical damage. The sebum also provides the first line of defence against invasion by bacteria as it is slightly antiseptic. The secretion of sebum is particularly important in tropical areas where the surface layer is constantly drying out on account of the warm climate. So without this greasy protective lubricant, the skin would not be able to withstand the daily wear and tear and lose its natural moisture. Sweat and blood vessels in the skin help to keep the body at the right temperature.

              In cold weather air becomes dry. When this dry air comes in contact with the skin it evaporates the water fast, and as a result outer layer begins to develop cracks and flakes. Skin also contains nerve cells that send message of heat, cold and pain to the brain. Since our lips do not have oil glands, they get chapped or cleaved first.

              Creams and ointments soothe chapped skin. If a mixture of water and oil is applied on the skin it helps the skin from being dried out. The water is absorbed by the skin and oil coats it making it moist. If one’s hands get chapped, they should be soaked in the warm water and then massaged with an ointment by applying it on the skin. By this method we can protect our skin in cold weather.