SomeFacts | Human Body

Human Body

What are hormones?
Hormones are chemicals released into the blood from various glands. ...

Who had the most children?
It is believed that a Russian woman who lived in the 1700s holds this ...

What is the menopause?
The menopause is when a woman's body changes so that she is no longer ...

What makes you grow?
A growth hormone tells your body to grow. This is produced in the ...

How long do most people live?
Most people in the developed world live until they are over 70 and ...

Why do people age?
The cells of the body are constantly being renewed, except for brain ...

Why can’t young babies sit up?
Young babies cannot sit up until their back muscles have grown strong ...

Why do you have to support a young baby’s head?
When a baby is born the muscles in its back and neck are very weak, ...

When do babies learn to walk and talk?
By its first birthday, a baby is usually already pulling itself up on ...

What happens when a boy’s voice breaks?
A boy may be growing so fast during puberty that the muscles that ...

When are you fully grown?
Boys and girls grow quickly during puberty, and then they grow more ...

Are newborn babies completely helpless?
A baby can breathe, suck, and swallow from the moment it is born, so ...

Why do babies cry?
A baby cries when it needs something-when it is hungry or lonely. It ...

How does an unborn baby feed?
Most of the cluster of cells that embeds itself in the womb grows ...

Where does the egg come from?
When a girl is born she already has thousands of eggs stored in her ...

What is a period?
If the egg is not fertilized by a sperm, it passes out of the woman's ...

Where does a man’s sperm come from?
Sperm are made in the testicles, two sacs that hang to either side of ...

What is a condom?
A condom is a thin rubber sheath that fits over the man's penis. It ...

What is a fetus?
A fetus is an unborn baby from eight weeks after conception until ...

Why do children look like their parents?
You inherit a mixture of genes from your parents, so in some ways you ...

What are genes?
Genes are a combination of chemicals contained in each cell. They ...

What is labour?
Labour is the process of giving birth. The neck of the womb stretches ...

What do babies do in the womb?
As the unborn baby gets bigger, it exercises its muscles by kicking, ...

Why do you sweat when you are hot?
Sweating helps to cool you down. When the body becomes hot, sweat ...

Why do you need to drink more in hot weather?
When it is hot, you sweat more and so lose more water, which you then ...

How long can you live without water?
Although some people have lived for several weeks without food, you ...

How much liquid do you need to drink?
You need to drink about 2 3/4 to 3 1/4 pints (1.2 to 1.5 liters) of ...

How much urine does the bladder hold?
An adult's bladder can hold up to about 1/4 pints (600 ml) of urine, ...

What makes you urinate?
The bladder stretches as it fills. When it has about 1/4 pint (150 ...

Why is urine yellow?
Urine contains traces of waste bile and this makes it yellowish. If ...

What is bile?
Bile is a yellow-green liquid made by the liver and stored in the ...

How often does blood go around the body?
Blood goes around the body about once a minute or 1,500 times a day.

What is a capillary?
Blood travels around the body through tubes called arteries and ...

Why do you go red when you are hot?
As different parts of the body burn up energy they make heat. Blood ...

What is a blood transfusion?
If a person loses a lot of blood, perhaps due to an accident or ...

What are blood groups?
There are four main groups of blood, called groups A, B, AB, and O. ...

How much blood do you have?
An average man has between II and 13 pints (5 and 6 liters) of blood; ...

What is plasma?
Just over half the blood is a yellowish liquid called plasma. It is ...

What do white blood cells do?
White blood cells surround and destroy germs and other intruders that ...

What is the heart made of?
The heart is made of a special kind of muscle, called cardiac (heart) ...

How big is the heart?
The heart is about the same size as your clenched fist. It lies ...

How often does the heart beat?
A child's heart usually beats about 80 times a minute, a bit faster ...

How much air do your lungs hold?
An adult's lungs hold about 13 1/2 pints (6 liters) of air, while a ...

Why do you cough?
You cough when extra mucus, dust or other particles clog the air ...

What happens when you hiccup?
Sometimes the diaphragm begins to contract in short, sharp spasms. ...

Why does running make you puff?
Muscles use up oxygen as they work. When you run, your muscles are ...

What happens when you sneeze?
When you sneeze, air rushes down your nose like a mini hurricane at ...

How do you talk?
When you breathe out, the air passes over the vocal cords in the ...

How long can you hold your breath?
You can probably hold your breath for about a minute. The longer you ...

Why does your breath sometimes look misty?
The air you breathe out contains water vapor. On a cold day this ...

Why do the lungs have so many alveoli?
In order to provide a huge surface across which oxygen and carbon ...

Why do feces smell?
Bacteria in the large intestine help to break down waste material, ...

What is the appendix?
The appendix is a spare part of the large intestine that plays no ...

How long are the intestines?
The small intestine is more than three times as long as the whole ...

How big is your stomach?
An adult's stomach holds about 2 1/4 pints (I liter) of food, and a ...

What is the epiglottis?
The epiglottis is a kind of trap door that closes off your windpipe ...

Which foods make you grow?
Foods such as milk, cheese, fish, meat, and beans contain a lot of ...

Which foods give you energy?
Foods such as bread, rice, potatoes, and pasta contain a lot of ...

Why does vomit taste sour?
When you vomit you bring back partly digested food into your mouth. ...

How many teeth do you have?
Each person has two sets of natural teeth during their life. The ...

What are teeth made of?
The outside of a tooth is made of enamel and is the hardest substance ...

Why do you like some tastes better than others?
Most people prefer things that taste sweet or slightly salty, but ...

Which parts of the body are most sensitive to heat?
Your elbows and feet are more sensitive to heat than many other parts ...

Which parts of the body are most sensitive to touch?
Any part of the body that has lots of touch receptors is particularly ...

How do blind people use touch to see?
Blind people can tell what something is like by feeling it. Outside, ...

Does taste matter?
Unpleasant tastes can warn you when food has gone bad or is ...

Which part of the body is least sensitive to touch?
The back is one of the least sensitive areas of the body.

Why do some animals have keener smell?
Many animals rely on smell for finding food and smelling attackers. ...

Why does a blocked nose stop you tasting?
When you eat, you both taste and smell the food. If your nose is ...

Why do some things smell more than others?
Things that smell strongly, such as perfume or food cooking, give off ...

How do you smell?
A smell is made by tiny particles in the air. As you breathe in, some ...

Why does sniffing help you detect smells better?
The smell receptors are at the top of your nose, so when you sniff ...

How loud is a whisper?
A whisper is between 10 and 20 decibels. Some animals can detect much ...

What is sound?
Sound is waves of energy that are carried as vibrations through air, ...

Why do you get dizzy?
If you spin around and around and then stop, the world seems to carry ...

Where does the Eustachian tube go?
This tube joins the middle ear to the empty spaces behind your upper ...

What is earwax?
This yellow-brown wax is made by glands in the skin lining the ear ...

Is loud noise dangerous?
Any noise over about 120 decibels can damage your hearing ...

Why do your ears pop?
If you are flying in an aircraft and it changes height quickly, you ...

How do you measure sound?
The loudness of a sound is measured in decibels. The sound of a pin ...

Why do you have two ears?
Two ears help you to detect which direction sounds are coming from.

Why can’t you see color when it starts to get dark?
The cells that react to colored light-called cones-only work in ...

How do you see color?
Different nerve cells in the retina react to the colors red, blue, ...

What makes you cry?
If dust or something gets into your eye, the tear gland above the eye ...

What keeps the eye in place?
The eyeball is held firmly in place by six muscles attached to the ...

What are eyelashes for?
Your eyelashes help to protect your eyes by stopping dust and dirt ...

Why do you have two eyes?
Two eyes help you to judge how far away something is. Each eye gets a ...

Can sunshine damage the eye?
Sunshine contains ultraviolet rays, which can damage your eyes as ...

What is the blind spot?
The blind spot is a spot on the retina where the optic nerve leaves ...

Why does the pupil change size?
The pupil becomes smaller in bright light to stop too much light from ...

How big is your eyeball?
An adult eyeball is about the size of a golf ball, but most of the ...

Does the brain ever rest?
Even while you are asleep the brain carries on controlling body ...

Why do some people sleepwalk?
People may walk in their sleep because they are worried or anxious. ...

How often do you dream?
You probably dream about five times every night, but you are only ...

Why do you need to sleep?
A 10-year-old sleeps on average nine or 10 hours a night, but sleep ...

Why are some people left-handed?
Most people are right-handed because the left side of their brain is ...

What does the skull do?
The skull is a hard covering of bone that protects the brain like a ...

Why are some people more artistic than others?
One side of the brain deals more with music and artistic skills, and ...

Why do you remember some things and forget others?
On the whole you remember things that are important to you in some ...

What is the brain made of?
The brain consists of water and billions of nerve cells and nerve ...

What does the brain look like?
The brain looks soft and grayish pink. The top is wrinkled like a ...

What causes “pins and needles”?
If a nerve gets squashed, it cannot carry nerve signals. If you kneel ...

Which is the longest nerve?
The longest nerve is the tibial nerve. It runs alongside the tibia ...

How many nerves do you have?
Thousands of millions of nerves reach out to all parts of the body.

How do anesthetics work?
An anesthetic stops you feeling. A local anesthetic deadens the ...

What is the spinal cord?
The spinal cord is the largest nerve in the body. It is 3/4 in (2 cm) ...

How does a nerve work?
A chain of nerve cells carries a signal to or from the brain. The ...

How fast do nerves act?
A nerve signal is a tiny pulse of electricity. It travels at about 3 ...

What is a reflex action?
A reflex action is something you do automatically, without thinking ...

How many muscles are there?
You have about 650 muscles that work together. Most actions-including ...

Which is the strongest muscle?
The strongest muscle is the one that shuts your mouth! It is called ...

What is a tendon?
A tendon is like a tough rope that joins a muscle to a bone. If you ...

What are freckles?
Freckles are small patches of darker skin made by extra melanin. ...

What is goose flesh?
Goose flesh is bumps on your skin formed by the tiny muscles that ...

Why does skin have pores?
Skin has tiny holes in it called sweat pores to let out sweat and ...

Why do old people have gray hair?
Some people's hair stops making melanin as they grow older. ...

What gives hair its color?
The color of your hair is determined mainly by the pigments (colored ...

Why does exercise make muscles stronger?
A muscle is made of bundles of fibers that contract when you use the ...

How do muscles work?
Muscles work by contracting. This makes them shorter and thicker so ...

Why can’t most people move their ears?
Humans, like most other animals, have a muscle behind each ear. ...

Which is the biggest muscle?
The biggest muscle is the gluteus maximus in the buttock. You use it ...

Which is the smallest bone?
The smallest bone is called the stirrup and is no bigger than a grain ...

Which is the longest bone?
The thigh bone in the upper part of your leg is the longest bone in ...

What’s inside a bone?
Inside a bone is a crisscross honeycomb of lighter bone. Blood ...

Which joint moves the most?
The shoulder joint is a ball and socket joint and it allows the ...

What is a vertebra?
A vertebra is a knobbly bone in your spine. The 26 vertebrae fit ...

What are ligaments?
Ligaments are strong, bendy straps that hold together the bones in a ...

Which joints move the least?
Your skull is made up of more than 20 bones fused together in joints ...

How many bones do you have?
As a baby you had over 300 bones, but, as you grow, some bones join ...

Why do joints not squeak?
Joints are cushioned by soft, squashy cartilage. Many joints also ...

Why do people have different colored eyes?
The iris is the colored ring around the pupil. The color is formed by ...