Category Zoology

          It is a matter of common experience that when we feel cold or frightened, tiny bumps, causing a tingling sensation, appear on our skin. These tiny bumps are called goose pimples. Do you know why these occur?

          The ‘goose pimples’ get their name from the actual bumps which appear on a goose’s skin when its feathers are plucked.

          If you have a close look at the bumps, you will see a hair in the middle of each bump. Attached to each hair inside your skin is a tiny muscle. When you get scared or chilled, messages go shooting off from nerve endings that pick up the feel of cold. In a flash, signals come back to the muscles and as a result each of these muscles tightens up and gets taut. The skin around each hair is also pulled up. The result is little bumps.

          This action of the hair standing on its end – actually keeps the outside air closer to the body and helps to keep it warm in case of chill. If you rub your skin the goose pimples disappear due to the warmth produced by the rubbing.

          The fur of the animals also rises up due to the same reason. The erector muscle of each hair automatically contracts and the hair stands upright. This is why a cat looks bigger on cold days. This serves a definite purpose in case of animals having fur on their skin. When our ancestors, millions of years ago, had more hair on their body, probably the hair helped them in keeping their body warm. 

            Sexual reproduction is a naturally gifted process by which human beings as well as other higher animals produce their offspring. This process involves the meeting of a male cell with a female cell to produce a fertilized egg which grows and develops into a new creature. The growth of a human body inside its mother’s womb, starting from the fertilization of cells till the birth, is a nine-month long process.

            To begin with, a fertilized egg is formed by the union of male and female sex cells called sperm and ovum respectively. The fertilized egg is termed as zygote. It settles inside a specific place in the mother’s body called the uterus. Almost immediately after it is formed, the zygote begins to divide – and in less than 30 hours two cells are formed, called blastomers. These two cells are absolutely alike. The repeated cell division, rapidly increase the number of blastomers. But then all these cells are not alike. Some are muscle cells, some are bone cells some others are nerve cells, blood cells and so on. In short, all the different kinds of cells that make up a human body are present. 

Continue reading “How does a human baby grow inside its mother’s womb?”

          The scope of heart surgery has vastly increased ever since the introduction of the heart-lung machine in the 1950s. This machine pumps blood from the veins to the arteries without having to pass through the heart. Most of these machines oxygenate the blood, thus completely bypassing the lungs as well. By using this machine, the heart can be stopped and opened for upto four hours.

          In human heart transplant, the main problem was that the body’s natural defence system tended to reject a new organ. The problem was eventually eased by the discovery of the fact that if the tissue types and the blood group of both people were carefully matched, the person receiving the heart had a much better chance of survival. 

          It was because of the use of such modern techniques and apparatus that the first human hearts transplant became possible. It took place on December 3, 1967, at Groote Schuur Hospital, Cape Town, South Africa. A team of 30 surgeons, headed by Dr. Christian Barnard, operated on Louis Washkansky, aged 55. The donor was 25 year old Denise Ann Darvall who had been killed in a road accident. 

Continue reading “When did the first human heart transplant take place?”

It has been scientifically proved that sunlight has several medicinal values that help in the prevention, cure and treatment of many diseases. Apart from its general benefits these are some special cases where sunlight plays an effective role.

Sunlight destroys certain particular fungi and bacteria that may settle on our skin. Secondly, it acts as a protective agent by further activating the white blood cells. The white blood cells defend the body from the attack of disease-causing germs, thus sunlight helps us to develop a greater resistance to fight diseases.

When sunlight falls on the skin, it causes certain substances to move into the blood and give the muscles a new tone. The muscles become tenser and thus work better. In fact, our nervous system gets a kind of ‘charge’ from sunlight and thus we feel stimulated and want to move about.

There is a substance in the skin called ergosterol that is transformed into Vitamin D by the ultraviolet rays of the sun. This vitamin is very useful for bones, particularly, in diseases like rickets.

Exposure to sunrays is just like swallowing a tea-spoon full of medicine every five minutes. But it is important to remember that this ‘medicine’ is by no means harmless.

We have to be just as careful about sunbathing as we would have to be about taking medicine. Sunbathing raises the blood pressure, so people who have heart trouble or certain lung diseases run the risk of physical harm by excessive exposure to sun. In fact, everyone should expose himself to sunlight only in phases. For instance, while taking sunbaths the best thing is to begin by exposing one-fifth of the body for about five minutes. The next day, expose another one-fifth of the body for an extra five minutes, and so on. In this way one can get all the benefits of sunlight without running into unnecessary risk.

            Jaundice is a disease of the liver in which the skin and the eyes become yellow. It occurs when some of the fluid produced by the liver, called bile, flows back to the bloodstream and gets deposited in the deeper layers of the skin.

            Jaundice is best seen in natural daylight and may not be apparent under artificial lighting. The degree of colouration depends upon the concentration of the bile pigments in the blood, its rate of tissue diffusion and the absorption and binding of bile pigments by the tissue. The bile pigments enter the tissue fluids and are absorbed more readily where there is already inflammation and edema. 

            The most common cause of jaundice is the extra secretion of bile by the liver. Congenital defects which impair the removal of bile pigments may also cause jaundice. Some liver diseases may also cause malfunctioning of the liver cells which would explain the presence of extra liver cells in the blood stream. Jaundice is usually of two types: retention jaundice and regurgitation jaundice. In retention jaundice, the pigments are retained in the bloodstream because of some removal problem. In regurgitation jaundice, there is an abnormal leak back into the bloodstream after it has been removed from the blood or directly from the bile ducts.

            Some of the diseases that can lead to jaundice are anaemia, congestion in the circulatory system, pneumonia, degeneration of the liver cells, scarring of the liver tissues and tumour in the liver and bile ducts. Newborn babies often have mild jaundice for a few days after birth. This is, however, generally harmless and soon disappears.