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Human Body
Hormones are chemicals released into the blood from various glands. ...
It is believed that a Russian woman who lived in the 1700s holds this ...
The menopause is when a woman's body changes so that she is no longer ...
A growth hormone tells your body to grow. This is produced in the ...
Most people in the developed world live until they are over 70 and ...
The cells of the body are constantly being renewed, except for brain ...
Young babies cannot sit up until their back muscles have grown strong ...
When a baby is born the muscles in its back and neck are very weak, ...
By its first birthday, a baby is usually already pulling itself up on ...
A boy may be growing so fast during puberty that the muscles that ...
Boys and girls grow quickly during puberty, and then they grow more ...
A baby can breathe, suck, and swallow from the moment it is born, so ...
A baby cries when it needs something-when it is hungry or lonely. It ...
Most of the cluster of cells that embeds itself in the womb grows ...
When a girl is born she already has thousands of eggs stored in her ...
If the egg is not fertilized by a sperm, it passes out of the woman's ...
Sperm are made in the testicles, two sacs that hang to either side of ...
A condom is a thin rubber sheath that fits over the man's penis. It ...
A fetus is an unborn baby from eight weeks after conception until ...
You inherit a mixture of genes from your parents, so in some ways you ...
Genes are a combination of chemicals contained in each cell. They ...
Labour is the process of giving birth. The neck of the womb stretches ...
As the unborn baby gets bigger, it exercises its muscles by kicking, ...
Sweating helps to cool you down. When the body becomes hot, sweat ...
When it is hot, you sweat more and so lose more water, which you then ...
Although some people have lived for several weeks without food, you ...
You need to drink about 2 3/4 to 3 1/4 pints (1.2 to 1.5 liters) of ...
An adult's bladder can hold up to about 1/4 pints (600 ml) of urine, ...
The bladder stretches as it fills. When it has about 1/4 pint (150 ...
Urine contains traces of waste bile and this makes it yellowish. If ...
Bile is a yellow-green liquid made by the liver and stored in the ...
Blood goes around the body about once a minute or 1,500 times a day.
Blood travels around the body through tubes called arteries and ...
As different parts of the body burn up energy they make heat. Blood ...
If a person loses a lot of blood, perhaps due to an accident or ...
There are four main groups of blood, called groups A, B, AB, and O. ...
An average man has between II and 13 pints (5 and 6 liters) of blood; ...
Just over half the blood is a yellowish liquid called plasma. It is ...
White blood cells surround and destroy germs and other intruders that ...
The heart is made of a special kind of muscle, called cardiac (heart) ...
The heart is about the same size as your clenched fist. It lies ...
A child's heart usually beats about 80 times a minute, a bit faster ...
An adult's lungs hold about 13 1/2 pints (6 liters) of air, while a ...
You cough when extra mucus, dust or other particles clog the air ...
Sometimes the diaphragm begins to contract in short, sharp spasms. ...
Muscles use up oxygen as they work. When you run, your muscles are ...
When you sneeze, air rushes down your nose like a mini hurricane at ...
When you breathe out, the air passes over the vocal cords in the ...
You can probably hold your breath for about a minute. The longer you ...
The air you breathe out contains water vapor. On a cold day this ...
In order to provide a huge surface across which oxygen and carbon ...
Bacteria in the large intestine help to break down waste material, ...
The appendix is a spare part of the large intestine that plays no ...
The small intestine is more than three times as long as the whole ...
An adult's stomach holds about 2 1/4 pints (I liter) of food, and a ...
The epiglottis is a kind of trap door that closes off your windpipe ...
Foods such as milk, cheese, fish, meat, and beans contain a lot of ...
Foods such as bread, rice, potatoes, and pasta contain a lot of ...
When you vomit you bring back partly digested food into your mouth. ...
Each person has two sets of natural teeth during their life. The ...
The outside of a tooth is made of enamel and is the hardest substance ...
Most people prefer things that taste sweet or slightly salty, but ...
Your elbows and feet are more sensitive to heat than many other parts ...
Any part of the body that has lots of touch receptors is particularly ...
Blind people can tell what something is like by feeling it. Outside, ...
Unpleasant tastes can warn you when food has gone bad or is ...
The back is one of the least sensitive areas of the body.
Many animals rely on smell for finding food and smelling attackers. ...
When you eat, you both taste and smell the food. If your nose is ...
Things that smell strongly, such as perfume or food cooking, give off ...
A smell is made by tiny particles in the air. As you breathe in, some ...
The smell receptors are at the top of your nose, so when you sniff ...
A whisper is between 10 and 20 decibels. Some animals can detect much ...
Sound is waves of energy that are carried as vibrations through air, ...
If you spin around and around and then stop, the world seems to carry ...
This tube joins the middle ear to the empty spaces behind your upper ...
This yellow-brown wax is made by glands in the skin lining the ear ...
Any noise over about 120 decibels can damage your hearing ...
If you are flying in an aircraft and it changes height quickly, you ...
The loudness of a sound is measured in decibels. The sound of a pin ...
Two ears help you to detect which direction sounds are coming from.
The cells that react to colored light-called cones-only work in ...
Different nerve cells in the retina react to the colors red, blue, ...
If dust or something gets into your eye, the tear gland above the eye ...
The eyeball is held firmly in place by six muscles attached to the ...
Your eyelashes help to protect your eyes by stopping dust and dirt ...
Two eyes help you to judge how far away something is. Each eye gets a ...
Sunshine contains ultraviolet rays, which can damage your eyes as ...
The blind spot is a spot on the retina where the optic nerve leaves ...
The pupil becomes smaller in bright light to stop too much light from ...
An adult eyeball is about the size of a golf ball, but most of the ...
Even while you are asleep the brain carries on controlling body ...
People may walk in their sleep because they are worried or anxious. ...
You probably dream about five times every night, but you are only ...
A 10-year-old sleeps on average nine or 10 hours a night, but sleep ...
Most people are right-handed because the left side of their brain is ...
The skull is a hard covering of bone that protects the brain like a ...
One side of the brain deals more with music and artistic skills, and ...
On the whole you remember things that are important to you in some ...
The brain consists of water and billions of nerve cells and nerve ...
The brain looks soft and grayish pink. The top is wrinkled like a ...
If a nerve gets squashed, it cannot carry nerve signals. If you kneel ...
The longest nerve is the tibial nerve. It runs alongside the tibia ...
Thousands of millions of nerves reach out to all parts of the body.
An anesthetic stops you feeling. A local anesthetic deadens the ...
The spinal cord is the largest nerve in the body. It is 3/4 in (2 cm) ...
A chain of nerve cells carries a signal to or from the brain. The ...
A nerve signal is a tiny pulse of electricity. It travels at about 3 ...
A reflex action is something you do automatically, without thinking ...
You have about 650 muscles that work together. Most actions-including ...
The strongest muscle is the one that shuts your mouth! It is called ...
A tendon is like a tough rope that joins a muscle to a bone. If you ...
Freckles are small patches of darker skin made by extra melanin. ...
Goose flesh is bumps on your skin formed by the tiny muscles that ...
Skin has tiny holes in it called sweat pores to let out sweat and ...
Some people's hair stops making melanin as they grow older. ...
The color of your hair is determined mainly by the pigments (colored ...
A muscle is made of bundles of fibers that contract when you use the ...
Muscles work by contracting. This makes them shorter and thicker so ...
Humans, like most other animals, have a muscle behind each ear. ...
The biggest muscle is the gluteus maximus in the buttock. You use it ...
The smallest bone is called the stirrup and is no bigger than a grain ...
The thigh bone in the upper part of your leg is the longest bone in ...
Inside a bone is a crisscross honeycomb of lighter bone. Blood ...
The shoulder joint is a ball and socket joint and it allows the ...
A vertebra is a knobbly bone in your spine. The 26 vertebrae fit ...
Ligaments are strong, bendy straps that hold together the bones in a ...
Your skull is made up of more than 20 bones fused together in joints ...
As a baby you had over 300 bones, but, as you grow, some bones join ...
Joints are cushioned by soft, squashy cartilage. Many joints also ...
The iris is the colored ring around the pupil. The color is formed by ...