The human body is a fascinating and, at times, very alien place with many weird-looking cells and colonies of bacteria. Over the years, many researchers have carried out experiments and made observations that have helped us to understand how it works and how to help it heal. Here are a selection of intriguing statistics and facts about human anatomy.
World Records of Human Biology
1. The tallest recorded human ever to live was was 2.72 m (8 ft 11.1 in) tall
Unusual growth like this is called ‘gigantism’ and arises when the pituitary gland over-produces growth hormone.
2. The shortest recorded human ever to live is just 54.6cm (21 1⁄2 in) tall
At the time of writing, Chandra Bahadur Dangi was still living. Humans shorter than 147 cm (4 ft 10 in) are said to be suffering from dwarfism.
3. Of the top 100 oldest people, the majority are women
In developed countries, women can expect to live 5 – 10 years longer on average than men. There is no single reason for this. Factors such as higher oestrogen levels and genetics have been suggested as being important.
4. The oldest verified human was Jeanne Calment of France
She died in August 1997 at the age of 122 years and 164 days. There are claims of greater age but none have been properly proven.
5. The heaviest recorded person was Jon Brower Minnoch
Jon suffered from the medical condition of general oedema. This caused his body to retain fluids and was incurable. His maximum weight was 635 kg (100 stones).
Myths About the Human Body
6. It is a myth that a sneeze travels at 100mph
In a scientifically controlled small scale study, a group of researchers at the National Center for Biotechnology Information in the USA found that the maximum velocity was just 4.5m/s (about 10mph).
7. Your ears and nose do not continue to grow throughout your life
The cartilage that makes up your nose and ears contains collagen and elastin fibres. These give cartilage its strength and shape. As you age, these fibres break down, causing the cartilage to sag.
8. Blood is not blue
Blood is either bright red or dark red, your veins often appear blue because of the properties of light. Only the wavelengths that we see as blue can reflect back through the skin from the veins.
9. It is a myth that we only use 10 percent of our brain capacity
If this were true, it should be possible to damage large parts of the brain without any problem. And why would the brain, a complex organ, evolve to be so inefficient?
The Heart and the Blood
10. An adult’s heart beats about 100,000 times per day
During the lifetime of the average person, the heart beats well over 2 billion times.
11. Heart muscle is resistant to fatigue
Muscle fatigue is caused by a build up of lactic acid caused by anaerobic (lacking oxygen) muscle metabolism. The muscles of the heart are very well supplied with oxygen and cardiac muscle contains more mitochondria (these release energy in the muscles) than skeletal muscles so the chance of anaerobic metabolism is reduced significantly.
12. There are an estimated 60,000 miles of blood capillaries in an average adult human
It is hard to believe, but if the blood capillaries were removed from an adult they would stretch 2.5 times round the equator! This figure is possible because blood capillaries are tiny, about a tenth of the diameter of a human hair.
13. Red blood cells last for about 4 months
When they die or are damaged, the red blood cells in your body collect in the spleen. The red cells are broken down and some products are recycled whilst the rest is excreted.
14. The three major types of white blood cells are granulocytes, monocytes and lymphocytes
Granulocytes kill invading bacteria, momocytes fight viruses and lymphocytes control your immune system.
15. Blood cells are made in bone marrow
All blood cells have a limited lifetime, most white cells for example live only for a few days, or weeks at most.
16. Your kidneys control how many red blood cells are produced
If the number of red blood cells is low or if your body is short of oxygen, the kidney releases a hormone called erythropoietin which makes the bone marrow produce more red blood cells.
The Brain and the Nervous System
17. The brain uses more energy than any other organ in the body
It is sometimes said that the brain uses as much energy as it takes to power a lightbulb – true if you were using a low energy bulb as it uses between 10 and 20 watts.
18. The structure of your brain changes when you learn
As you learn, the neurons in your brain form new connections. It is these patterns that create your memory. The more these patterns are reinforced, the less likely you are to forget what you have learnt.
19. You live in a world of interactive virtual reality.
The rods and cones on your retina don’t produce an image in the way a camera does. They send small electrical impulses to the brain about light, shade, edges of objects plus the wavelengths of the light entering the eye. The brain then interprets this and creates an image of the world around you.
20. Involuntary responses (reflexes) are not processed by the brain
Responses such as the knee jerk reflex and pulling your hand away from something hot use nerve pathways known as ‘reflex arcs’. The sensory neurons send an impulse to the spinal cord which sends it straight back to the associated motor neurons. No thought process is involved, making the response extremely fast and automatic.
21. A baby is able to make almost all of the sounds of every known language
As a baby develops and learns a language, it loses this ability.
22. The cerebellum is the part of the brain that prevents us from tickling ourselves
Research at University College London has shown that the cerebellum makes exact predictions about your body’s movements and sends a damping signal to the centre of the brain that processes touch. It cannot make predictions about the movements of someone else so no damping signal is sent.
23. There are 3 types of nerve cell (neurons)
The three types are sensory neurons (detect stimuli), motor neurons (pass instructions to muscles and other tissues and organs) and association neurons (connect sensory and motor neurons).
24. Nerve impulses are tiny electrical signals
When a nerve is stimulated, it generates a small electrical charge which passes along the length of the cell.
25. Chemicals transfer nerve impulses from one neuron to the next
The junctions between nerve cells are called synapses. Neurotransmitter chemicals from the stimulated neuron cross the tiny gaps in the synapse, stimulating an electrical signal in the neuron on the other side.
26. Each one of your taste buds contains between 50 and 100 receptor cells
Each receptor cell has a tiny taste hair sticking out of it which check the chemicals that dissolve into your saliva. Each taste hair responds best to one of the five basic tastes and sends an impulse to the brain.
27. There are about 10,000 taste buds in the mouth of an average human
Most of these are on the tongue but others are in the cheeks.
28. Your ears help you keep your balance
The inner ear contains two balance organs. One detects the rotation of your head and the other detects the position of your head. These work with your eyes and receptors in your muscles (proprioreceptors) to stop you from falling over.
29. Your eyeballs are controlled by 6 muscles
These are called the extraocular muscles and are the superior and inferior oblique muscles, the superior and inferior rectus muscles plus the medial and lateral rectus muscles.
30. Your nose can discern about 50,000 different odours
The amazing thing about this is that your brain can remember every single one.
31. Women have a better sense of smell than men
The Monell Chemical Senses Center in the USA took 32 samples of smelly perspiration and mixed them with different fragrances. Women could smell the sweat in all but 2 of the mixtures whilst 19 of the fragrances blocked the smell for men.
32. Flavour is as much about smell as taste
Both taste and smell combine to produce the flavour, which is why food can seem bland when you have a cold.
Skin and Bones
33. The outer layer of your skin is called the epidermis
The epidermis is thickest on the palms of your hands and the soles of your feet.
34. Your skin is home to millions of bacteria.
These are mostly harmless, some are permanent residents and others temporary. Bacteria on your feet, Brevibacterium linens, feed on the dead skin cells that flake off and their waste products are the cause of smelly feet.
35. Belly button ‘fluff’ is a mixture of fabric fibres, dirt, dead skin cells and bacteria
Abdominal hair traps the debris and funnels it into the navel. It has been found that men with a moderate amount of abdominal hair gather the greatest volume of debris in their belly button.
36. The average person has about 2.5 million sweat glands
Sweat evaporating from your skin helps to regulate your temperature.
37. There are two kinds of sweat glands in your skin
Eccrine sweat glands produce sweat that cools the body; they open directly onto the skin. Apocrine sweat glands open into the base of hair follicles and produce sweat that contains pheromones.
38. You are taller when you get up in the morning than when you go to bed at night
During the day, the cartilage between your bones is compressed making you just a little bit shorter at the end of the day.
39. Half of the bones in your body are contained in your hands and feet
Your hand contains 27 bones, your foot contain 26 bones. That’s a total of… well, work it out for yourself and then compare it to the total number of bones in the body, which is 206 for adult humans.
40. Babies have more bones than adults
A baby has about 350 bones but as an adult, you end up with just 206 as some of the bones fuse (join) together.
Interesting Random Facts About the Body
41. Your body could be composed of up to 75% water
The exact amount depends on the individual, varying from about 50 – 75 percent. The average figure is about 60 percent.
42. Your ‘tongueprint’ is unique to you
You probably know that fingerprints, palm prints and irises can be used to identify an individual person (biometrics) but did you know the pattern of your tongue is also unique to you?
43. The human body contains about 7 octillion atoms
That’s 7,000,000,000,000,000,000,000,000,000 which is a mind-bogglingly huge number and every single one of them was formed either during the big bang or in a supernova explosion. You are literally made from stardust!
44. You are as old as your mother
The egg from which you grew formed in your mother’s ovaries when she was still an embryo. So if you count your real age as being from when the egg from which you came formed, then you are the same age as your mother.
45. Rice has twice as many genes as humans
Only about one and a half percent of human DNA comprises our genes, the rest of it has various jobs such as switching genes on and off and making key chemicals for the body. There are around 20 – 25,000 genes on our DNA whilst over 50,000 have been found in rice.
46. At age 60, an estimated 80% of people will have eyelash mites
These harmless creatures live at the base of your eyelashes and in their follicles.
47. Ears are designed to clean themselves
As you chew, and as the skin inside the ear grows, earwax (cerumen) slowly moves to the outside of the ear canal and flakes off.
48. Some children are born with an extra finger or toe
This is called polydactyly. In postaxial polydactyly, the hand or foot looks normal other than the presence of the extra finger or toe. In the preaxial form, the extra digit appears to grow from the side of either the thumb or little finger.
49. Your saliva and stomach acids kill most of the bacteria you ingest
Occasionally some get through and it is those that cause food poisoning.
50. Food is digested in the small intestines
Many people associate the stomach with digestion of food. The stomach produces chyme which is a gooey mixture of your food and digestive juices. As it passes though the small intestine, digestion is completed.