| In an average lifetime the heart beats over 3 billion times |
Circulation |
| Red blood cells carry oxygen to every cell and remove carbon dioxide |
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| Blood vessels help to control our bodies' temperature |
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| If stretched out, your blood vessels would extend almost 100,000 km |
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| Blood is made from red cells, white cells, plasma and platelets |
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| Our bodies produce between 1 and 2 litres of saliva every day |
Digestion |
| Food can go through the digestive system if you are upside-down |
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| The small intestine is 7 metres long. The large is just 1.5 metres |
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| Our stomachs contain hydrochloric acid |
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| We burp to release air that has been accidentally swallowed |
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| The glands that produce hormones make up the endocrine system |
Hormones |
| The hypothalamus gland regulates our hunger and thirst |
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| Our bodies create and use more than 50 different hormones |
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| The pituitary gland is one of the most important, but it's the size of a pea |
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| The pancreas releases insulin and glucagon to regulate blood sugar |
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| The immune system protects us from bacteria and viruses |
Immunity |
| There are 5 types of white blood cells which fight pathogens |
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| Fevers are caused by our bodies as a way to fight pathogens |
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| Allergies are caused by our immune system reacting to harmless things |
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| Sleep is important for a healthy immune system |
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| There are over 650 skeletal muscles in the body and billions of others |
Muscles |
| The largest muscle in the body is the gluteus maximus in your bottom |
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| Size for size, the strongest muscle is the masseter in the jaw |
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| Most of the heat produced in your body comes from contracting muscles |
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| Many muscles, like the triceps and biceps, work in pairs |
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| There are 4 different kinds of nerve cell in the nervous system |
Nerves |
| The central nervous system is the brain and the spinal cord |
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| All other nerves are part of the peripheral nervous system |
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| The brain uses more energy than any other organ |
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| Neurons can’t replace themselves so nerve damage is often permanent |
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| Our kidneys filter toxins from our blood, converting them to urine |
Renal |
| Our bladders can hold up to 800 ml of urine - about 4 cups full |
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| Urine is 95% water, 2.5% urea, and 2.5% minerals and enzymes |
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| The kidneys and bladder are linked by thin tubes called ureters |
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| Kidney stones are caused by minerals forming crystals |
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| Our lungs can hold up to 6 litres of air |
Respiration |
| The left lung is smaller than the right one to make room for the heart |
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| If the lungs were unfolded they’d be roughly the size of a tennis court |
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| Our lungs contain 3-5 million air sacs called alveoli |
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| Our lungs are protected by the epiglottis which covers the trachea |
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| There are 206 bones in an adult skeleton |
Skeleton |
| The smallest bone in the body is in your ear |
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| The femur, or thigh bone, is the longest bone in your body |
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| More than half your bones are in your hands and feet |
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| The hyoid bone in the throat is the only bone not connected to another |
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| The average person’s skin covers an area of 2 square metres |
Skin |
| A square centimetre of skin contains 6 million skin cells |
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| The skin on your soles is 1.4 mm thick. On your eyelids it's 0.2 mm |
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| Your skin sheds 30-40,000 dead cells an hour |
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| Up to 1,000 species of bacteria live on our skin |
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