Health dictionary - C

A type of birthmark which is the colour of milky coffee, hence the name. They don’t usually cause any problems, but they can be associated with a disease called neurofibromatosis.


A substance that is very important for keeping your bone, hair and nails strong. It’s found in dairy products and some other foods too.

Calcium deposits

These are growths that can appear on bones or soft tissue. Their cause is unknown.


A group of diseases that are caused by cells forming in an uncontrolled way. There are lots of different types of cancer – some are easier to treat than others and some affect children more than adults. Research has meant that cancer is much more treatable than it was thirty years ago.


A cannula is an extremely thin plastic tube that is put into a vein to give medicines.


These are the smallest blood vessel – most of them are only big enough to allow a red blood cell through. They're about 0.008mm in diameter – really small!


A group of substances found in food that the body converts into energy. Food containing carbohydrates include potatoes, rice, pasta and bread.

Carbon dioxide

A gas, which we breathe out into the atmosphere. Its chemical symbol is CO2

Carbon monoxide

A gas, which can be dangerous if we breathe it in for too long. Car exhausts and faulty gas fires produce it and its chemical symbol is CO.


This is just another word for the heart.

Cardiac arrest

Another way of describing a heart attack.


The study of the heart and how it works.

Cardiopulmonary resuscitation

This is sometimes called CPR for short. It’s a way of starting breathing and circulation again if a person has stopped breathing or their heart has stopped.


A substance that holds our body together. You’ve got cartilage in your ear, which is what makes it bendy, and also inside your joints, which stops the ends of the bones rubbing together.


Breaking a bone can hurt a lot, but having a cast on it will help it to get better more quickly. They can be made from a lot of different materials, including plaster, plastic and even air.

Casts protect broken bones and help them to grow back together properly. When your bones are better, the doctor will remove your cast, but don't worry, it doesn't hurt.

'Cat' or CT Scan

If you've heard someone talking about a cat scan, they actually mean a CT scan. This is a special type of x-ray that can see inside your body. Normal x-rays can only see bones but CT scans can see a lot more, and they help doctors to find out what's going on.


An eye condition where the lens becomes cloudy. This stops you seeing very well. It can affect anyone but it’s more common in older people. It’s fixed by removing the lens and replacing it.


A flexible plastic tube that is used for draining off liquid – for instance, from your bladder.


These are the building blocks of your body. Every part is made up of billions of cells each of which do a different job.

Central nervous system

This consists of your brain and spinal cord and is referred to as the CNS system for short.


Part of your brain that is responsible for movement and balance. It’s at the bottom of your brain, lying next to your spinal cord.

Cerebral palsy

A group of disorders where a person’s brain is damaged in early childhood. This means that the person may have stiff muscles, jerky movements and problems with co-ordination. He or she may also have speech problems.

Cerebrospinal fluid

This is the fluid that surrounds the brain and spinal cord. It’s often called CSF.


The main part of your brain where most of your thinking happens. It’s split into two parts (hemispheres). While we know how the brain is formed, we still don’t really understand how it works.


The cervix is the narrow lower part of the womb. It is often referred to the neck of the womb or the entrance to the womb.


Also known as a pharmacist – this is the person who can advise you on medicines and supplies them to you either with or without a prescription.


This is a type of drug treatment used for people with cancer. The medicines are very strong and some have side effects, like making your hair fall out.

Chicken pox

An infectious disease that makes you break out in tiny blisters which then scab over. These blisters are often very itchy and it can be difficult not to scratch them. When you have chicken pox you should stay away from people with low immune systems as chicken pox can cause quite severe problems for them.


This is when you can’t breathe because something is stuck in your airway. Sometimes coughing can remove the blockage or sometimes you’ll need someone to give you the Heimlich manoeuvre to dislodge it.


Structures that are found in every cell, which carry genetic material that makes you like your parents. Chromosomes are arranged in pairs and each cell contains 22 pairs of chromosomes and two others called sex chromosomes. It’s the sex chromosomes that decide whether you’re a boy or a girl. If you’re a boy, you have one X chromosome and one Y chromosome and if you’re a girl, you have two X chromosomes.


Something that develops slowly or is around for a long time. For instance, you can have chronic kidney disease, which develops slowly over a period of time.


The medical word for your collarbone – the ridge you can feel from your shoulders to in front of your neck.

Cleft lip

This is where a baby is born with a vertical split in his or her lip. It happened while the baby was developing in the womb and can be fixed in an operation. Sometimes a baby can have both a cleft lip and a cleft palate.

Cleft palate

This is where a baby is born with a split in the roof of his or her mouth. It happened while the baby was developing in the womb and can be fixed in an operation. Sometimes a baby can have both a cleft lip and a cleft palate.


The four lowest vertebras in your back and they’re the leftovers from our tails before we developed into humans!


The bit of the inner ear that turns sounds into nerve messages which travel to the brain.

Cochlear implant

A piece of equipment for helping someone who is severely deaf to hear.


A cold is a type of viral infection that causes a runny nose and a sore throat. There’s no cure for a cold, but you can take medicines for the symptoms.

Cold sore

This is caused by the herpes virus, and makes a sore spot around your mouth that can weep pus and then scab over. They’re quite catching – so don’t kiss anyone with a cold sore, because you might catch one too!


The colon is also known as the large bowel and it's a part of your intestines - which help you to process food.

Colostomy bag

A pouch which is used to collect waste products from a stoma (an opening made by a doctor) in a patient who is no longer able to pass their body’s natural waste naturally.


When a person is in a coma, they are deeply unconscious and don’t respond to anything going on around them. People can recover from being in a coma sometimes after months or years!


Congenital means that you have a problem or illness from the time you were born.


This is when the membrane over the front of your eye becomes infected and swollen. It makes your eye go really red and sore. If you’ve got conjunctivitis in one eye, don’t rub it and then touch your other eye, as it will spread. You should also avoid sharing flannels and towels with other people while you’ve got conjunctivitis too. It’s treated with eye drops and ointments.


The legal term for when you agree to something happening. If you’re due to have an operation, your parents will be asked to give their consent if you’re under 16 years old. If you’re 16 or older, the doctors will ask you. Usually, you’ll have to sign a form to give your consent. You don’t have to agree to something if you don’t want to – this is totally OK.


A consultant is a special kind of doctor who has extra knowledge about one type of illness or treatment.


If you're contagious, it means that anyone around you can catch your illness. This is more common than you might think - colds are contagious, because you can catch them from someone else.


This is a way of stopping a woman getting pregnant. There are lots of different sorts of contraception – you can find out more about them from your doctor or family planning clinic.


The front part of your eye that is very tough and prevents you injuring your eye. It’s transparent and covers the coloured part of your eye (iris) and the pupil too.


A reflex action to clear your airway. You could do this because of a blockage of some sort, or because your lungs are clogged up with mucus when you have a cold. If your coughing is stopping you sleeping, you can take some cough medicine, but generally it’s better not to stop it.


This is when you’re muscles go into spasm and hurt. They’re really common and usually happen if you’ve kept the muscle tightened and in the same position for a long time. You can get writer’s cramp, which is when the muscles in your hand seize up when you’ve been writing for a long time. You can get rid of cramp by massaging or stretching the muscle that is in spasm.


This is a sac of tissue that is separate from the surrounding tissue (for example, skin). It can contain air, fluid or semi-solid substances.

Cystic fibrosis

A disease that affects the lungs and intestines, by clogging them up with heavy sticky stuff called mucus. People with cystic fibrosis have to have regular physiotherapy to get the mucus out of their lungs and also have to take lots of tablets each day.


A test that lets the doctor look inside and around your bladder.