Your Body

Bile is one of the digestive juices that help the body break down foods into usable elements. It’s a yellowish fluid produced by the liver and stored in a small pouch underneath the liver called the gall bladder. When food enters your small intestine, bile flows out of the gall bladder and into the intestine, … Read more

Your spleen is a large organ inside your body, next to your stomach. But it’s actually attached not to your digestive system, but to your blood stream. Scientists have already discovered some of the spleen’s functions, but they’re not sure they’ve found them all. They do know that the spleen helps make new red blood … Read more

An anesthetic is a drug given to a person before an operation so that he won’t feel pain. Even if you’ve never had a serious operation in a hospital, you probably received an anesthetic at some time in your life. There are two kinds of anesthetic: general and local. A general anesthetic produces unconsciousness, so … Read more

Certain kinds of baldness accompany illnesses. For instance, scarlet fever, pneumonia, and typhoid fever can sometimes result in the loss of hair. Gland problems and an imbalance of certain hormones in the body can lead to baldness. So can poor nutrition, scalp disease, and poor care of the hair and scalp. But the kind of … Read more

The right half of the brain controls the left side of the body, and the left side of the brain controls the right side of the body. In most people, the left side of the brain is better developed, so the right hand is stronger and more controllable than the left hand. But sometimes, the … Read more

Sometimes you might hear someone say: “You eat so much, you must have a tapeworm.” A tapeworm is a kind of flatworm that lives in the digestive tract of another animal or person, and takes in food which its host has partially digested. Many people believe that a person with a tapeworm will eat a … Read more

When you move the muscles in your body, they produce a substance called sarcolactic acid, also called the “acid of fatigue.” When too much of this acid forms around a muscle, the muscle becomes “tired.” The same sarcolactic acid is found in your blood too, as it travels to all parts of your body. So … Read more

The word arthritis means a swelling of the body joints, but not all arthritis involves swelling. In the type of arthritis known as rheumatism, the joints do swell up and eat into the cartilage that surrounds them. Since this cartilage acts as a sort of “shock absorber” around the joint, the loss of cartilage and … Read more

Tetanus is a disease caused by bacteria that secrete poisons. These bacteria usually enter the body through cuts or scratches. You may believe that tetanus can be caused only by cuts from old or rusty metal, but actually, a cut from any object can cause tetanus. That’s why when you get a serious cut, your … Read more

Sometimes when your body is very tired, your lungs and the rest of your respiratory system may slow down until there’s too little air in your lungs. As soon as this happens, your body sets off a quick movement, or spasm, in the muscles of your mouth, throat, and chest. This spasm forces you to … Read more

For people who suffer from hay fever and certain other allergies, it’s important to know how much pollen is in the air. Some people who are very sensitive to pollen go away during peak pollen seasons, and they want to know what the pollen count is before they return home. A pollen count is, quite … Read more

Most plants produce pollen, which is carried by insects or the air to other plants to pollinate them and produce seeds. Many people are allergic to the pollen of certain plants, and the sickness they suffer from this pollen is called hay fever. Most hay fever is caused by the pollen from ragweed and goldenrod. … Read more

The pupil, the black spot in the middle of your eye, is actually a hole that allows light to enter the eye. Around this hole is the colored part of the eye, the iris, which regulates the size of the pupil and how much light is allowed into the eye. The iris has pigment in … Read more

About one in every 12 males and one in every 200 females suffer from some form of colorblindness. But there are many different kinds of colorblindness. In one common form, a person cannot tell the difference between yellow and pale green. In another common form, a person cannot tell red and green apart. These colors … Read more

Your eyes are probably the most sensitive optical instruments ever invented, by man or by nature. In good light, your eyes can tell the difference between some 10 million colors! The best machines can recognize only four million. From ten inches away, you could see an object just 4/1000 of an inch long. And in … Read more

When you have allergies, certain things don’t “agree” with your body. These things may be foods, animal hairs, plant pollen, chemicals, or almost anything else, and may enter the body when you eat or inhale. When they do, you feel uncomfortable or even sick. Although millions of people have this problem, scientists still aren’t sure … Read more

Your body is constantly burning up sugar and other food substances to provide energy. Normally, this burning produces a body temperature of 98.6° F. But when you’re sick, your body tries to fight the sickness by working faster and harder. More blood cells and hormones are produced, your blood circulates faster, and your lungs breathe … Read more

Sometimes when your fingers or ears get very cold, even numb, you might say that they’re frostbitten. But frostbite is really very serious, and requires a doctor’s care. In very cold weather, the skin on your fingers, toes, or ears may become so cold that blood stops flowing to it. This is your body’s way … Read more

Saliva, or “spit,” helps you swallow and digest food. As soon as you start to eat, glands in your mouth begin to secrete saliva, moistening and softening food to make it easier to swallow. Saliva also contains an enzyme called ptyalin, which digests food the same way that the digestive juices in your stomach do. … Read more

By the age of 13, most people have 28 permanent teeth, including two sets of molars. Then, at age 18 or later, a third set of molars begins to come in. These molars are called wisdom teeth, because they appear later in a person’s life, when he is “supposedly” wiser. Often, wisdom teeth don’t come … Read more

The air is only one-fifth oxygen. When you take a breath, your lungs inhale oxygen from the air, and you exhale the rest, which is mostly nitrogen. But when a diver is in the water and breathing through an aqualung, there’s no way he can get rid of all this nitrogen, and some of it … Read more

Seasickness may feel like it begins in the stomach, but it actually starts in the ears! Your sense of balance is controlled by canals filled with lymph inside the ears. Now, when you’re on a ship that is rocking back and forth, the lymph rocks back and forth too, sending messages to the brain that … Read more

The organs that control your sense of balance are actually inside your ears. Three arched tubes, called semicircular canals, are inside each ear, filled with a liquid called lymph. Each tube helps to control your sense of balance in one dimension: width, height, and depth. Inside these canals are stiff hairs attached to nerve cells. … Read more

Have you ever wondered why, when you cut yourself, all the blood in your body doesn’t flow out of that cut? What stops the blood from flowing is a process called clotting. As soon as a blood vessel is cut, the blood begins to produce tiny threads of protein that form a sort of net, … Read more

A doctor takes your pulse by squeezing a blood vessel in your wrist and counting the number of beats, or pulses, he feels in one minute. But the pulse rate can be taken by feeling the beats in many other parts of your body too. Each time your heart beats, it sends a pulsation through … Read more

Water rushing through a hose exerts pressure on the hose, and in the same way, blood surging through your blood vessels exerts pressure on the vessels. It’s important for a doctor to know your blood pressure, because this tells him the strength of your heart, the condition of your arteries, and other important things about … Read more

When a doctor describes your blood type, he’ll probably not only indicate its type, 0, A, B, or AB, but also if it’s “positive” or “negative.” This refers to your Rh factor. If your blood is positive, you have the Rh factor; if it’s negative, you don’t. A person with the Rh factor has certain … Read more

The heart is a muscular organ that serves as a pump, sending blood to every part of the body. The heart is always at work, even while you sleep. If your heart were to stop for any length of time, you couldn’t live, but that doesn’t mean the heart never rests. Each “heartbeat” consists of … Read more

People need to drink water because water is a major part of every cell in our bodies. A person who doesn’t get enough water will suffer from dehydration, a lack of water in the body’s cells to allow them to work properly. If a person aboard a ship is suffering from thirst, he may be … Read more

Protein is quite different from vitamins. Our bodies take vitamins from food, use them to aid in certain chemical processes, and then discard the vitamins. But our bodies take the protein from foods and keep it, using it to make new body cells or repair old ones. Proteins are made up of substances called amino … Read more

At a certain age, your brain stops growing. You stay alive, but some of your brain cells die, and are not replaced. In fact, after the age of 18, a person may lose more than a thousand brain cells each day! But there’s no danger of your brain ever “burning out,” for the number of … Read more

The amount of food energy you need each day depends on how old you are, how big you are, and whether you’re a girl or a boy. Children from 6 to 9 years old require at least 2,100 calories a day to maintain good body health. By the age of 12, the body requires about … Read more

Not unless you include water as a food. Only water and club soda have absolutely no calories. Coffee and tea have almost none, just one or two calories for every 100 grams, or about 31/2 ounces. Among vegetables, artichokes have the least calories, about seven per 100 grams. A sour or dill pickle has 10 … Read more

Yes, all animals need vitamins, and some plants do too. But the need for a certain vitamin varies from one animal to another. Some animals can make all the vitamins they need right in their own bodies, and don’t have to take in vitamins with their food. For instance, people need to take Vitamin C … Read more

The calorie is often used to measure the fattening qualities of foods. But the calorie is not a measure of weight or of the sugar in foods or of the fat. It’s actually a measure of heat! One calorie is the amount of heat needed to raise a. gram of water one degree Centigrade. A … Read more

During the 19th century, an English doctor found that eating lemons or limes could prevent a disease known as scurvy, which had been common among sailors and soldiers for thousands of years. Beginning in 1800, all English Navy ships carried lime juice, and every sailor had to drink a ration of lime juice daily. That, … Read more

In the 1920s, scientists believed that only two vitamins existed. One was fat-soluble, which means it could dissolve in oil or fat. This vitamin the scientists called Vitamin A. The other vitamin was water-soluble; it could dissolve only in water. This, they called Vitamin B. The fat-soluble vitamins were given letters of their own. But … Read more

A vitamin is a chemical substance found mostly in foods. It is necessary for the proper working and growth of the body. Vitamins take part in chemical reactions that help bring food energy to the body’s cells. In these reactions, vitamins serve as catalysts, substances which speed up or aid reactions, but which are not … Read more

If you were born in the United States in the year 1900 and you were a male, you could probably expect to live only to the age of 46. A female born at the same time could expect to live slightly longer until the age of 49. But if you were born in the 1970s, … Read more

All human beings have reactions, or feelings, to situations or to their own thoughts. These reactions are called emotions. Emotions can be positive ones that make a person happy, love, happiness, pleasure, and pride. But emotions can also be negative ones that make a person unhappy, anger, fear, sadness, hate, disappointment, and pain. Many doctors … Read more

Most people have fears of some sort, at some times in their lives. That is natural. But people who have a fear that stays with them constantly, or keeps coming back over and over again, are said to have a phobia. Phobias can be fears of certain places, certain situations, or certain objects. Examples of … Read more

A newborn baby responds to noise by an automatic action, a reflex action. His eyes are open, but during his first month of life he can see only light and dark. By the second month, he can follow an object with his eyes. As the nerves between his eyes and brain develop, the baby begins … Read more

Most everyone is able to speak normally without realizing just what a complicated procedure it really is and what amazing coordination is required by your larynx, cheeks, tongue, and lips to get the words out. It is when this coordination is not working properly that a person stutters or stammers. In one form of stuttering, … Read more

The kind of voice you have depends on the size and position of your vocal chords. Vocal chords can be long or short, stretched or relaxed. Boys and girls have the same short, stretched vocal chords during their early years, and so have similar high-pitched voices. As a boy grows older and reaches his teens, … Read more

If you put your fingers on your throat and say a word, you will get a “buzzing” feeling, or vibration, on your fingers. These vibrations come from the voice box, or larynx, inside your throat. Your larynx is a box-shaped organ between the back of your tongue and trachea, or wind pipe. As you breathe, … Read more

Deafness and hard-of-hearing are not the same thing. Deafness means a total or near-total loss of hearing, along with an inability to understand speech. A person can be born deaf, or be born with normal hearing and become deaf because of an accident or illness. People who lose some ability to hear during their life … Read more

Sound waves are movements, or vibrations, in the air made by sounds. When these sound waves enter the canal of your outer ear, they hit your ear N drum, a thin, tough sheet of tissue stretched tightly along the canal that separates your outer ear from your middle ear. As the sound waves hit, the … Read more

If you know the functions of tools such as scissors, forks, nutcrackers, and grinders, you will understand how marvelously specialized your teeth are. Although your 20 primary, or baby, teeth first appeared when you were about six months old, your permanent teeth (32) started to grow out when you were about six or seven years … Read more

Actually calories have nothing to do with food! They are really measurements of heat energy your body needs. The food you take into your body can be considered a “fuel,” much like car runs on fuel. The breaking down of the food in the body tissues is a form burning that fuel and giving off … Read more

The cells of your body use the food you eat to do three important jobs: provide energy, make new cells, and repair cells that wear out. The carbohydrates, fats, proteins, vitamins, and minerals in the food you eat are broken down into tiny particles, or molecules, which are the materials your body needs to perform … Read more

As soon as food enters your mouth, it begins a long trip through your body. This trip is called digestion. At each stop along the way, parts of your body receive the food and each performs its specialized job before sending the food on to its next stop in the digestion trip. First, your teeth … Read more

You usually have your meals at the same time each day. Your stomach becomes accustomed to this schedule and produces its acids and enzymes with a churning activity according to that schedule. With no food going into your stomach to absorb these juices produced by the peristaltic waves, it “talks,” or “gurgles,” or “rumbles.”

Hunger begins when substances like glucose (sugar), vitamins, minerals, and amino acids are missing from your blood. Nerves in your body send a message to the hunger center in your brain telling it of the shortage. The hunger center then reacts by making the stomach and intestines more active.

When you eat, food from your mouth goes down a tube called the esophagus and into your stomach, where it is stored temporarily, then later digested. As the food arrives, the stomach wall starts its glands working. One type of gland gives off a mucus that lubricates the food. Other glands give off acids which … Read more

The human body contains about 50 quarts of water. But this body fluid is not pure water. It is actually a salt solution. Why is this so? According to one scientific theory, all land animals, including man, are descendants of organisms that once lived in the sea and arose from it. The body fluid of … Read more

A human being can live without food for more than a month, but no one can stay alive for more than a week without water! All living things need water for their bodies to function. When you take in food, water helps to dissolve it and, along with certain chemicals in your body, it turns … Read more

Your spinal cord, or spinal column, a column of bones that runs from your brain all the way down your back. Not only do these bones, or vertebrae, support you body, but they also house nerve cells which carry messages on their way to and from your brain. These vertebrae are held in place by … Read more

A “Charley Horse” is not a person or an animal. It is a thing, a cramp in your arms or legs. If you have ever exercised too much and hours later felt that you couldn’t move without your muscles aching, you’ve gat a “Charley Horse.” A “Charley Horse” is actually a strain or soreness in … Read more

If you didn’t have muscles, you wouldn’t be able to move. A muscle is a bundle of tissue cells that tighten up and get shorter when they are at work. This tightening up of a muscle is what makes a part of you move. When that part of you stops moving, the muscle relaxes and … Read more

There is a “sleep center” in your brain which regulates the sleeping and waking of your body. When this sleep center goes to work, it does two things: it blocks off part of your brain so that it goes to sleep and you no longer have the will to do anything. It also blocks off … Read more

The feeling of “needles and pins” sticking in your feet after you have been sitting with your leg curled up in one position for a long time is called “falling asleep.” What actually happens is this. Your blood usually flows freely through the blood vessels in your leg, just as water can flow freely through … Read more

There are some activities your body automatically continues whether you’re awake or asleep. Without them, you could not go on living. For example, your heart beats and you breathe; your blood continues to flow, bringing food and oxygen to all the cells in your body. Sleep is also the time when those body cells that … Read more

Most dreams are based on events that happened to you that day. Others involve deep fears you might have had since you were very young. In still others, wishes you’ve had for a long time are granted in your dreams. Sometimes, these are wishes you didn’t even know you had. As you dream, you are … Read more

The white spots that are often scattered on your nails are simply signs that the nail has been bruised or injured. However, before this was known as a medical fact, superstitious people gave other meanings to these spots. On the thumbnail, they meant you would receive a gift. On the index finger, the spots represented … Read more

“Throw them away, of course!” would probably be your answer. And that is exactly what most people do. But in some societies, where superstitions are strong, fingernail cuttings are believed to be used by sorcerers for casting evil spells against their owners. Therefore, the cuttings are carefully guarded or hidden. Another old superstition claims that … Read more

Just think what a world of long-nailed people we’d have if cutting, biting, or filing nails caused people pain. But none of these acts hurts the human body because nails are made up of hardened dead skin cells, actually a form of dead protein, much like the dead protein that forms the horns on deer, … Read more

You drop a hot potato long before you actually feel the pain that comes from burning your hand. That’s because as soon as you touched it, your nerves quickly sent a message saying, “too hot” to your spinal cord. The nerves in your spinal cord answered this message right away, they didn’t even wait for … Read more

Your hair can and will change color when you are old, but this does not happen overnight. Different hair colors, from blonde to black, are determined by the melanin, the coloring matter, in your hair cells. This melanin becomes part of your hair cells as they form in the roots. Gray hair starts to appear … Read more

Your hair is made of the same material as your nails, a horse’s hoof, a reptile’s scales and as a bird’s claws and feathers. If your hair or any parts of these animals is cut, there is no pain because your brain only receives “pain messages” from parts of your body that have nerve endings. … Read more

The hair on your head grows about half an inch each month. Even when your body stops growing taller, your hair will still keep growing. Hair grows faster in summer than in winter, and faster during the day than at night. When each strand, or shaft, of hair reaches a certain length, it stops growing … Read more

All mammals have some hair, and man is a mammal. In some mammals, that hair covers the whole body, but in man, it grows only in certain parts. Your hair has two main purposes on your body: to provide warmth and to protect your skin and body openings. While the hair on an adult’s body … Read more

Your kidneys are two purplish-brown, flat, bean-shaped organs that lie on each side of your spine near your waistline. These fist-sized organs are among the most important in your body. The kidneys’ most important function is the production of urine, which carries waste materials out of your body. It is just as important for your … Read more

The largest gland inside your body is your liver. It weighs from 3 to 4 pounds, and is a reddish-brown mass. The liver has to be large because of the complicated work that it does. It is almost like a miniature chemical laboratory in your body. Here how it works. As blood enters your liver, … Read more

Although not all scientists agree on the answer, many believe that most people’s brains develop more on one side than on the other. And since the left side of your brain controls the muscles on the right side of your body, and the right side of your brain controls the muscles on the left side … Read more

When you were born, sometimes a mole, or nevus, appeared on your skin. This is called a “birthmark” because it was present at birth. Moles are soft, dark, raised spots that can appear on almost every part of the body. They can differ from each other in what they are made of. Some moles consist … Read more

You probably figured that because an adult is bigger, he would have more bones in his body. But that isn’t so! An infant has 300 bones in its body, while an adult has only 206. What happens to them as the child grows? Do they just disappear? No! As the child grows, two or three … Read more

Scientists can’t say for certain what the man of the future will look like. But they do predict that he will have a smaller face and a bigger nose. He’ll have less hair than he does now, in fact, he might even be bald! Man’s face has been gradually getting smaller since cave-man days. In … Read more

Yes, indeed! When you were being formed inside your mother’s uterus, you were connected from your abdomen to her body by a rope-like tube called the umbilical cord. Everything you needed to live and grow during the nine months before you were born, oxygen and food from your mother’s blood, came to you from your … Read more

Even though you are not aware of it, there are tears in your eyes all the time even when you’re not crying. These tears are washing your eyes constantly, bathing them in a salty fluid made by the lachrymal, or tear, glands. Normally, this amount of fluid is so small, it can drain off into … Read more

When you feel embarrassed or upset, tiny blood vessels under the skin in your face and neck grow larger, and more blood flows close to the surface. The skin then has more color in it than usual, and feels warmer because this extra blood brings extra heat along with it. No one knows exactly why … Read more

Athlete’s foot is really a fungus infection of the foot, and not a special kind of foot. Anyone at all is liable to get this highly contagious infection, whether he is an athlete or not. In athlete’s foot, the skin between the toes becomes scaly, cracked, and itchy. Athlete’s foot can be spread by walking … Read more

Boy’s muscles are usually bigger than girls’, but bigger is not necessarily better! Boys’ muscles tend to be bigger because boys usually use them more in sports and other physical activities. This also makes their muscles harder. Later, when boys reach their teens, or the period called adolescence, their glands produce special chemicals, or hormones, … Read more

A bruise is an injury on the surface of your body. It is usually caused by a blow or a fall. Even though your skin is not broken, the small blood vessels under your skin are. As more blood rushes to the damaged tissues, your skin becomes swollen and red. The bruised area later turns … Read more

Usually when you sneeze, you are trying to get rid of an irritation or harmful object in the air passage of your nose. Sneezing is a reflex action, an automatic reaction of your body without your controlling or willing it. The irritation stimulates the nerve cells in your nose to send a message to your … Read more

When you get sick, your white blood cells fight the harmful germs with special germ killers called antibodies. White cells manufacture antibodies for each particular sickness, so if you have chicken pox, your white blood cells make chicken pox antibodies. After you are recovered, these antibodies stay in your blood and keep killing any chicken … Read more

Your body has the ability to resist or overcome a disease by a process called immunity. Your body acquires this immunity in several ways. For example, if you had a disease such as yellow fever and had recovered from it, you would never get it again. This is because your body has produced antibodies to … Read more

Attached to one end of your large intestine is a narrow tube-shaped sac called the appendix. It is about the size of your longest finger. Scientists feel that at one time, thousands of years ago, this appendix may have served a purpose in early man’s digestive system. Now, however, it seems to be of no … Read more

Your tonsils are small masses of tissue located at the back of your mouth in your throat. Because this tissue manufactures germ-fighting white blood cells, it is able to trap harmful bacteria that may enter your nose and mouth when you breathe. Fighting infection is the normal work of your tonsils, since they are the … Read more

The most common contagious disease in the world is the common cold. Colds are actually infections of the mucous membranes of your nose and throat, but sometimes they spread to your air passages and lungs. The cold germs, or viruses, that cause these infections and make you cough or sneeze travel through the outside air … Read more