My Science School

           The place where two or more bones meet in the body is called a joint. Depending on their structure, joints permit different degrees of movement of bones. Do you know the different types of joints in our body?

           Basically, there are three kinds of joints in our body. They have been grouped on the basis of the degree of movement they allow. They are: (I) Immovable or fixed joints, (II) Partially movable or cartilaginous joints, (Ill) Freely movable or synovial joints. 

 

Immovable joints: In an immovable joint, the bones are held tightly together. Because dense bundles of tough and strong fibres hold the bones, they cannot change the position relative to each other. The elasticity essential for joint movements is almost absent. Joints in the tooth sockets and between the skulls bones are of this type. Immovable joints are also known as fibrous joints. 

 

 

 

Partially movable joints: In a partially movable joint, the bones are linked by a cartilage. A cartilage is a very tough, spiny material. These joints have very little movement. The different vertebras of the spinal column are joined together by a cartilage. The joints of the spine are partially movable so that the spine can bend. Between the vertebrae there are disks of cartilage. They are called intervertebral disks. In addition to allowing the vertebrae to move against each other, they also act as shock absorbers. At the front of the chest where the ribs meet the breastbone are also partially movable joints. 

 

 

 

Freely movable joints: These are the main joints of the body. These are found in the bones of the ankle, hip, wrist, elbow and knee. The ends of the bones that are the part of the movable joints are covered with caps of tough cartilage. A cartilage does not wear out easily. Its surfaces are very smooth and reduce friction between the moving bones.

In a freely movable joint, the space between the bones is filled with a special oily fluid called synovial fluid. It helps the parts to move easily. It is produced by a thin membrane that lies around the joint and is kept within the joint by this synovial membrane. Outside the membrane are tough, flexible ligaments (connecting tissues). The ligaments in addition to joining one bone to another also allow movement. The membrane and the ligaments together form what is called the joint capsule. Synovial (freely movable) joints may be of different types depending upon the nature of articulation and degree of freedom. They are explained below:

Ball and Socket joints: In this the ball of one bone fits into the socket of another. So it makes movement possible in all directions – bending and stretching from side to side and rotation. The shoulder and hip joints are of this type.

Hinge joints: These are found in the elbow, knee and fingers. The ends of the bones fit into each other in such a way that the movement is possible in one direction only. Angular joints: In joints like the wrist, movement is possible around two axes. Such joints are called angular joints.

Pivot joints: In these joints, turning or rotatory movement is possible around one axis only. Skull joint to the spine is a pivot joint.

Gliding joints: In joints between tarsal bones in the ankle, carpal bones in the wrist and between sternum and clavicle, the end of one bone glides across a certain portion of the surface of the other bone.

Injuries and diseases may affect joints. Arthritis is a painful disease that attacks cartilage in joints.  

          Albinism has been derived from the Latin word ‘albus’ which means ‘white’. Albinism is an inherited disease caused by genetic changes. It can be passed on from one generation to another.

          Albinism is caused by the absence of yellow, red, brown or black pigments in the eyes, skin scales, feathers or hair. The natural pigments usually provide protective colouration and act as a screen against the light rays. Since albino animals lack them, they rarely survive in the wild.

          Albinos are found in plants, animals and human beings. In human beings, it is caused by the absence of melanin, the dark brown pigment normally present in the skin, hair and eyes. It varies from complete albinism to localized albinism or spotting.

          In the case of complete albinism, the person doesn’t have any pigment in any of their cells. They have milk-white skin and hair. Their eyes appear pink because of the colour of the blood vessels. Since the light-absorbing pigments are absent, an albino is extremely sensitive to bright light like that of the sun.

          In partial albinism, only some tissues and organs lack in pigment. Some animals are also partial albinos. One case of complete albinism is found in every 20,000 people.

          However some plants too, with white flowers, are partial albinos. A complete albino plant lacks even the green pigment - chlorophyll. As a result, it is unable to make its food by photosynthesis, and dies shortly after its food supply in the seed is exhausted.

          Diagnosis of different diseases by urine examination has been a common practice since a long time. But the traditional methods were not very scientific as the modern methods. Although special urine tests in laboratory can reveal many diseases, even a casual examination can indicate certain diseases. Let us see how different urine tests help in diagnosing some diseases.

          Normal urine is straw yellow in colour due to the presence of the pigment ‘urochrome’. If a person has fever, it becomes deep yellow. In case of jaundice, it becomes still deeper in colour. Consumption of vitamin B-complex also makes the urine deep yellow. This is because of the presence of riboflavin in the tablets. If the colour of urine changes to brown or black due to atmospheric pressure, it indicates a congenital disease called alcaptonuria. If its colour is brown or black, it suggests derangement of haemoglobin metabolism.

          If the urine of a diabetic patient is left in the open for some time, it would attract ants. This is due to the presence of glucose in it. Its taste is also sweetish. To test the presence of sugar in urine, it is boiled with Benedict solution. If a red precipitate is formed, it indicates the presence of glucose. 

 

Continue reading "How do urine tests help in diagnosis of diseases? "

          Normally mammals have bigger brains in relation to their size when compared with other living creatures and the human brain is the biggest and most developed among all the mammals. It controls all the activities of the body throughout our life. It remains active every moment directing and guiding all other organs of the body. That is why it is called the control centre of the body? But what is our brain made of and how does it carry out its different functions?

          The human brain is largely made up of grey and white matter. The grey matter contains nerve cells and the white matter contains the nerve fibres. The nerve fibres carry messages from the nerve cells to different parts of the body. Thousands of electrical impulses are constantly passing through these nerve cells. All messages are first sent to the brain through different nerves from the sense organs in all parts of our body. Consequently it sends signals to different muscles and glands in the body to carry out necessary actions. The most important human activity ‘thinking’ takes place in our brain. All the energy produced in the body is used by the brain. 

          The central nervous system consists of the brain and the spinal cord. Different parts of the brain are interconnected and they control different activities of the body. The medulla and hypothalamus control the involuntary activities such as breathing and heart-beat. The cerebellum controls muscles and organs of balance in activities like walking or riding a bicycle that is, carrying out work automatically once we have learnt them. The cortex controls conscious feeling and voluntary movements such as writing and running. The front part is called cerebrum which has two cerebral hemispheres – the left hemisphere and the right hemisphere. This part (cerebrum) does most of the thinking and is responsible for our memory and emotions. The left hemisphere is associated with the right side of our body and the right hemisphere, with the left side. People with a more developed right hemisphere are left-handed and vice-versa.

          Our brain works even when we are asleep. An adult’s brain weighs about 1.4 kg and has 14 billion nerve cells in it. The fastest messages pass along the nerves at a speed of 400 km/hr. 

          Immunity is described as the ability of the body to resist or to recover from the invasion of disease-causing microbes (bacteria, viruses, and protozoas) and larger parasites (helminthes). Thus a person said to be immune to a particular disease would not contact it although others might do so.

          Microbes and parasites cause several diseases in man. The disease-causing germs often release toxins (poisonous substances). Normally our body is able to defend itself against most disease-causing microbes. First the skin acts as a barrier to the entry of many microbes. And secondly the white blood cells destroy many microbes. But if the number of microbes exceeds the capacity of white blood cells they fail to protect the body against them.

          Many persons are able to resist diseases to certain extent due to immunity mechanisms in their systems. The blood of a person produces substances called antibodies which fight the invading organisms. Each kind of antibody acts against only one type of microbe. Different antibodies have different characteristics. Some antibodies neutralize the toxins released by microbes. Certain others clump them together which can then be easily attacked by white blood cells. Some other antibodies dissolve the bacteria. Sometimes a certain amount of antibodies is permanently left in the blood plasma and this serves to protect the individual from future attacks. Such persons are said to be immune to that particular disease. 

          Immunological mechanisms are either specific or non-specific. Specific immunity, also called acquired immunity, which refers to mechanisms that are activated individually after a microbe or some other foreign material, invades the body. Non-specific immunity refers to general protective mechanisms that either kill or prevent the multiplication of microbes and other parasites.

          Some persons are immune to certain diseases right from the birth. These people are said to have natural immunity or inborn immunity. In an epidemic of a particular disease, say cholera, people with natural immunity do not suffer from cholera. If someone gets smallpox or chickenpox once, he will not get it again during his whole lifetime. The body in such a case retains adequate levels of antibodies as a protection against future infection.

          A person can also develop immunity by treatment with appropriate antigens. This is called artificial immunity. For instance, in the case of epidemics of smallpox, the health authorities vaccinate the people by which immunity is produced artificially. This vaccine was invented by Edward Jenner. It is produced by infecting a calf or horse with the smallpox virus. The virus in the calf or horse gets weakened. This weakened virus is collected as a vaccine and introduced into the human body. Since the virus is weak, it is not able to cause a severe attack of smallpox in man. But its presence induces the body, to produce antibodies and provides immunity against smallpox for several years. The introduction of weakened microbes in the body is called active immunity, the effect of which may last for even a lifetime. Immunity may also be passive. In this readymade antibodies are injected into the human body. An animal like a horse is infected with disease-producing microbes. The antibody is produced in the blood of the horse. The serum of the horse containing the antibody is extracted and introduced into the human body. The human body makes use of antibodies against the disease thus producing passive immunity. Passive immunity is produced almost instantly when the serum has been injected, but the effect lasts only for a short period.

          Vaccines are now produced to provide immunity against diseases like whooping cough, diphtheria, measles, tetanus, typhoid, polio, rabies tuberculosis, mumps, scarlet fever, German measles, and chickenpox. All infants should be provided immunity by vaccination for different diseases.

          In our country Haffkine Institute at Bombay and the Virus Institute at Poona produce several kinds of vaccines.

 

          Wine is probably the first type of hard drink to have come into existence. Archaeological evidence suggests that wine making began in the middle-east over 10,000 years ago, and gradually spread westward to the mediterranean countries and finally into Europe. The ancient Egyptian wall paintings reveal that the art of wine making was known to them long before the Westerners took to it.

          Wine was common in everyday life of the early Greeks and Romans. It also played an important role in their religious ceremonies. The God of wine was called Bacchus by the Romans and Dionysus by the Greeks.

          Wine can be made from a wide range of fruits and vegetables, but the real wine is made from grapes. Grape juice contains water, sugar, fruit acids and many trace elements. The outer grape skin has millions of tiny living organisms, primarily yeasts, including a number of moulds and bacteria, too. 

          The grapes are allowed to ripen until they attain suitable sugar content (18% or more) and acidity. When these grapes are crushed, yeasts come into contact with the juice. This brings about the process of fermentation by which grape juice changes into alcohol and carbon dioxide. During fermentation, grape juice loses its sugar and turns into wine. This wine has 10 to 14% alcohol content. The rest of wine consists of water containing traces of acids, sugar and other substances which give the wine its colour and flavour.

          Another type of hard drink, beer, is known to have been made by the Egyptians and Babylonians at least 6000 years ago and there is evidence that barley, from which it is made, was cultivated in Britain and northern Europe, some 5000 years ago. Europeans knew how to produce a fermented drink from barley. Beer is usually made from barley hops, yeast and sugar by the process of fermentation.

          Pure brandy is made by the distillation of wine made from grape juice. The wine is heated and the alcohol that evaporates out of it is condensed and collected. Apart from alcohol, other substances are also given off during distillation. Some are poisonous substances and are removed.

          Different types of whisky are made from grains such as barley, rye and corn. Rum is made from molasses, syrup obtained from cane sugar. Gin is made from grain or molasses flavoured with juniper berries.

          Major wine-producing areas of the world include France, Germany, Spain, Portugal, Italy and California in the USA. 

               A mass spectrograph is an instrument used to analyze the constituents of substances. It not only detects different kinds of atoms and molecules present in the substance, but also finds out their relative amounts. By the use of electric and magnetic fields, it separates ions of different masses. Do you know how this instrument works?

               The working of the mass spectrograph first involves the change of the substance into a gas, which is passed into a vacuum chamber. A beam of electrons is bombarded to change the gas atoms and molecules into ions. The ions are then accelerated, by passing them through an electric field. Then the ions are passed through a magnetic field, where they get deflected. The positive ions are deflected one way, and the negative ions in the opposite direction. The amount of deflection is inversely proportional to the masses of the ions. The heavier the mass, the lesser the deflection. This separates ions of different masses. Ions of the same mass and charge stay together. The ions are then allowed to fall on a photographic plate. Different ions hit the plate at different places and as a result, this photographic plate records the amounts of various atoms and molecules. Photographic plate is used to identify different ions which have hit it. From the intensity variations on the plate, we can know the relative amounts of atoms or molecules present in the substance. 

               The mass spectrograph was developed by a British scientist, William Francis Aston. He was awarded the Nobel Prize in 1922 for this invention. After this, several other mass spectrographs were developed by many leading scientists like Dempster, Bainbridge, Nier, etc but all were just modifications of Aston’s mass spectrograph.

              The mass spectrograph is widely used in geology, chemistry, biology and nuclear physics. It is a very useful instrument for isotopic studies. Aston himself discovered 212 of the 287 naturally occurring isotopes. Mass spectrographs are also used as vacuum leak detectors.

 

               Penguins are a peculiar category of sea birds which can stand up straight and flat-footed like us. Do you know where these birds are found?

               Penguins are found in Southern hemisphere. They live along the Antarctic continent and islands as well as on the cool Southern hemisphere coast of Africa, Australia, New Zealand and South America.

              The wings of penguins have evolved into flippers. As a result, they can not fly but they are excellent swimmers. They walk in a strange manner. In the earlier phases of evolution they could fly like other birds. But over a period of time, their wings became very short. The reason is that penguins lived in the remote areas of Antarctica, where they had practically no enemies to attack them. So they lived safely in land and water without ever using their wings and in course of time their wings became very small. 

            

             

               Penguins live in flocks. A single rookery may contain more than a million penguins. They feed on fish, squids and crustaceans.

               Penguins withstand extremely cold conditions on account of a very dense plumage all over their bodies. These feathers are waterproof and have tiny air spaces that help them keep warm. Underneath this thick coat of feathers, there is an insulating layer of blubber. This helps to keep the body warm and store food and water. They also have a thick coat of fat to protect them from the cold.

               Female penguins lay one or two eggs, which are brooded by both parents. They do not take food during incubation. Young penguins are fed by regurgitation. There are 17 species of penguins. The species differ mainly in head pattern and in size. Their sizes vary from 40 cm (fairy penguin) to almost 120 cm (Emperor penguin). Both sexes are alike in size. Only two, the Emperor and Adelie penguins breed on the Antarctic coast. King, Macaroni, Chinstrap and Gentoo penguins breed on Sub-Antarctic islands. The remaining 11 species breed farther North.

          It has often been said that a dog is a man’s best friend. In fact, the dog was the first animal to be domesticated by man. But dogs can also be a source of danger under certain conditions.

         A dog can harm people by biting or transmitting several bacterial, viral, parasitic, fungal and rickettsial diseases.

          Bacterial diseases transmitted by dogs are mainly tuberculosis brucellosis, splenic fever, scarlet fever, diphtheria etc. Dogs carry Salmonella enteriditis and S. typhinurium pathogens which cause gastroenteritis and typhoid in man.

Dogs along with other animals can transmit fungal diseases such as ringworm.

          Rabies is the most dangerous viral disease caused by a dog-bite. Rabies virus is found in the saliva of rabid dogs. Sometimes even pet dogs can be the cause of this disease. Therefore it is essential that they should be vaccinated against rabies every three years.

          Dogs occasionally get measles and mumps and can cause this infection to spread to human beings.

        

Continue reading "How can dogs be dangerous to us? "

               The largest of all living birds is the African Ostrich which cannot fly at all. It measures upto 2.4 m in height and may weigh more than 133 kg. On account of its weight, it finds it impossible to lift its body in the air.

               The two groups of flying birds that have the largest wingspread are the albatross and the condors. Both of them weigh about 13.5 kg. 

 

 

          The wandering albatross leads among the largest flying birds with a wing-spread of 3.3 to 3.6 m. The albatross has a long, heavy beak and long, narrow wings. It is mainly found in places south of the equator. It is a sea bird. It needs some wind and a run before taking off. So it either runs along the ground or paddles with its webbed feet across the water for a long time before being able to fly.

 

 

               Next comes the condor which has a wingspread of 3 to 3.3 m. It is a carnivorous bird. There are two species of condors in the world. The Andean condor lives in the Andes Mountains in South America. The other one is the Californian condor which is found in the mountains of Southern California. They feed on carcasses of animals. While searching for food, the condor uses its broad wings to glide high in the air.

 

 

         

              The third bird in this line is the king vulture which is found in South America, Mexico and Central America. It has a wingspread of 2.7 to 3 m. The white pelican comes after the king vulture. It has a wingspread of 2.4 to 2.7 m. It is found in Canada. One of its distinguishing features is a bag-like pouch under its bill. Functioning like the radiator in a car, it helps the pelican to keep cool.

           

   The great bustard, a large goose-like bird related to the cranes comes next. It is found in parts of Europe, Asia and Africa and has a wingspread of 2.4 to 3.7 m. The American bald eagle is the next largest flying bird having a wingspread of 2.1 to 2.4 m. Then comes the sandhill crane, with a wingspread of 1.8 to 2.1 m.

            Fly is a two-winged insect that has some 90,000 different species of it. The housefly (musca domestica) is one of tie most common of all flies. You must have seen flies rubbing their legs together. Do you know why they do so?

            The housefly has a dull gray, bristled body that is about 7 mm in length. It has large reddish compound eyes. Its mouth cannot bite but consists of a spongy pad. It has a peculiar system of feeding itself. At first it releases saliva and digestive juices over food and then sponges up the resulting solution. In this way, flies contaminate large amounts of food with germs, and cause millions of deaths every year. Hence it is widely considered as a major health hazard.

            The whole body of the housefly, including claws and padded feet, is covered with bristles. Even its tongue is coated with sticky glue. A fly rubs its legs together just to clean itself. In the process of rubbing the legs, it scraps some of the material that has gathered on the bristles and thus drops germs of dangerous diseases on the food. When we eat this food, we may get infected. Some of the most common diseases spread by the housefly are typhoid, tuberculosis and dysentery. Flies gather such germs from garbage and sewage.

            Houseflies usually live and breed in or near garbage or organic wastes. The female lays about 100 eggs at a time and as many as 1000 during her life. The eggs hatch into larvae in 12 to 30 hours. The larvae moult several times before becoming pupae. Within a few days, the pupae become adult and the cycle begins again. Most houseflies have a lifespan of about 30 days during summer and longer when the weather is cooler. Cold weather usually kills the adults; but larvae and pupae are able to survive the winter.

          The world’s deadliest animal is the sea wasp. It is a kind of jellyfish known as chironex fleckeri. Its tentacles are loaded with hundreds of thousands of microscopic stinging cells which inject cobra-like venom with poisonous barbed threads into any unfortunate creature that happens to brush against them closely. This venom is highly toxic and kills anybody in a few minutes. Pain and burning sensation caused by its venom are insufferable.

          The sea wasp is a colourless creature and has a bell-shaped body which consists of 95% water. It is so elusive that only careful eyes can spot it drifting in shallow tropical waters of seashores and beaches. 

          The size of a sea wasp varies from 4 cm to 20 cm across and 10 cm long. It has purple or blue tentacles which can be seen coming out of the bell. These may reach up to a length of 120 cm. One wasp may have upto 50 tentacles and one such tentacle may have 750,000 individual stinging cells, capable of injecting venom. They are mainly meant for securing food, and also to serve as a defence mechanism.

          Chironex fleckeri is found in great numbers in waters of Northern Australia. They are also found in the United States, waters off the Atlantic coast from North Carolina to the south of Florida Keys. They have also been discovered in West Africa and Indian Ocean.

          Scientists have not yet been able to devise any effective remedy for its venom. So one must be very careful while swimming in tropical waters!

          There are also some very poisonous sea-snakes that live permanently in the sea and are fully adapted to an aquatic existence. They swim with a sculling action of the paddle-shaped tail. They feed on fishes after immobilizing them with potent, fast-acting venom. 

          The oil that we use in our kitchen or for the manufacture of margarine and other goods is obtained from the seeds of many plants. The world production of major oilseed crops (in millions of metric tons) is Soyabeans 46.5, Peanuts 18.1, Cottonseed 22.1 and Copra 3.4. The other sources of vegetable oils are mustard, rapeseed, sunflower etc.

          The basic process for extracting oil is essentially the same for all oilseeds. It involves either pressing or solvent extraction or a combination of both. The material that remains after removal of the oil contains primarily fibres, carbohydrates and proteins. This may contain protein upto 50%. This material is discarded and used as fertilizer or animal feed.

          Most of the world’s supply of coconut oil comes from West Africa. It is taken from the dried kernel of the nut called copra which contains 70% oil. Palm oil also comes from West Africa and from South-East Asia. These oils are produced in a hard fatty form called stearine, which is used in the manufacture of chocolate, cooking fats and medicines. Crude oil is used in soaps and shampoos.

         Cottonseed provides about 37% oil. The cotton plant is grown commercially in the United States, India and Egypt. The fruit of the plant splits open to reveal fluffy white fibres and a number of seeds – each about six millimeters long. Cottonseed oil is used in margarine, cooking fat, and salad oil. It is also used in soaps, resins, grease and lubricants.

         Linseed is the seed of the flax plant which is grown primarily in the United States, Russia, Argentina, India and Canada. Flax fibres are woven into linen cloth and the seeds are used for extracting oil. Linseed oil is used in paints, varnishes, printing and lithographic inks, linoleum, oil cloth and as a water-proofing agent. The residue is a valuable cattle food.

         Groundnut or peanut is the seed of the plant Arachis Lypogea. The seeds of this plant yield oil and are cultivated mainly in China, West Africa, the United States and South-East Asia. It is mainly used as a cooking medium.

         Soyabean is the most important of all the oil seeds. It is extensively grown in China and the Far East. Soyabean oil is used for cooking and as a base for paints, plastics, adhesives, etc. It is a rich source of protein. The seeds can be ground into protein-rich flour which can be used in many foods.

          Sunflower is becoming increasingly popular in European oil markets, and so is rapeseed in Canada and Northern-Europe. Sunflower is now grown in countries like Mexico, Russia, erstwhile Yugoslavia, Turkey and South Africa.