In a 2011 survey by Lassi Liikkanen, a Finnish cognitive scientist, more than 90 percent of respondents said they were bugged by an earworm at least once a week.

London - The human body is a wonder of nature: our brains react faster than a computer, our hearts beat without the need for rest. But it’s not perfect.

The appendix, for instance, seems to have no real function yet can be the cause of appendicitis and, if left untreated, life-threatening peritonitis (inflammation of the abdominal lining) - so it could be simpler to get rid of it.

Indeed, faulty body design often makes us prone to illness. Here, the experts reveal the body parts that, ideally, should go back to the drawing board.

MOUTH: Too many teeth

The major flaw with the mouth is the way the hard teeth are anchored into soft gum.

“This forms a weak junction and allows bacteria to easily proliferate in pockets in the soft tissue around the base of the teeth - it is this that leads to periodontal [gum] disease,” says Dr Margaret Kellett, director of the Leeds Dental Institute. “Really, it would have been better if teeth were anchored into a harder, more bone-like structure which bacteria could not penetrate so readily.”

And there is also absolutely no need for us to have wisdom teeth.

“We have them because our cavemen ancestors ate predominately raw meat and vegetation, which required a lot of force to chew.” says Dr Kellett.

“But, over time, our diet has become softer as we have developed methods of cooking and processing food. As a result, the muscles around the jaw need to exert less force on it - causing it to shrink over the years.

“However, our teeth have not evolved at the same rate, so we are left with a smaller jaw but the same amount of teeth.

“That is why wisdom teeth may have to be removed. There just isn’t the room and, if left, they can push into the neighbouring tooth, causing damage and infection.”

EYES: Stick out too much

A key problem with our eyes is that they stick out too far in the head, making them vulnerable to injury.

“We evolved like this so that we could scan for predators and prey,” explains Professor David Gartry, a consultant surgeon at the Moorfields Eye Hospital, London. “However having the eyes at the front means they are very vulnerable to damage because they physically go first into whatever environment we enter.”

This is bad news for the cornea, the clear dome at the very front which bends light into the eye. “A deeper set eye would have been preferable,” says Professor Gartry.

Another design flaw is that the lens itself is made of living tissue, which continues to grow throughout life. “The lens fibre cells build up like layers on an onion skin - in time, this makes the lens thicker and, crucially, less flexible,” says Professor Gartry.

“It means it’s less able to change shape quickly and zoom in and out of focus. This is why seeing things close up becomes harder past the age of 40. The older you get, the more rigid the lens becomes and the harder it is to move.”

The continued production of cells ultimately causes the clear lens to become cloudy, which is what causes cataracts.

HEART: Secret pouch causes blood clots

The problem with the heart is the left atrial appendage, a small muscular ‘pouch’ in the top of one of the upper chambers.

“It is completely redundant - it has no functional role,” says Dr Amanda Varnava, a consultant cardiologist at Spire Bushey Hospital, Hertfordshire.

“However, if someone has poor circulation, then blood can pool there. When this happens, it is easy for clots to form and cause a stroke.”

EARS: Bad ventilation triggers deafness

Here, the issue is the narrowness of a vital tube that keeps the ears ventilated.

The middle ear - the section behind the ear drum - needs to be kept at atmospheric pressure to stop the ear drum (which vibrates in response to soundwaves and passes these vibrations to the middle ear) from collapsing. It’s the pressure of oxygen that keeps the drum firm.

Unfortunately, some of this oxygen is absorbed by the surrounding blood vessels.

This is compensated for by the Eustachian tube, which runs from the back of the nose to the ear; this allows in around half a teaspoon of air a day.

However, in some parts, the tube is less than 1mm wide and is very prone to blockages from mucus. Not only does the tube get blocked, but the air can’t get in to disperse it.

“If this mucus stays in place in the middle ear for three months or more, we call it glue ear - and both adults and children can get it,” says Professor Tony Wright, of University College London Ear Institute.

Another problem is our hearing is too sensitive. “Because we have eyes at the front of the head and do not have 360-degree vision, to hear danger from behind, humans have more specialised hearing than, say, a bird, which has nearly all-round vision.

“But this extra sensitivity also brings problems,” explains Professor Wright.

Once the ear drum has collected the noise vibrations, they are passed into the inner ear.

Here, the noise vibrations are picked up by tiny crystalline rods that look like hairs.

“These are very fine and help make our hearing especially sensitive by adding volume and clarity,” he adds.

But this sensitivity also means the rods are prone to damage.

“Something like an explosion can destroy them instantly - and persistent loud noise of 85 decibels or more (such as in a noisy factory or a disco) can damage them over years. The problem is that we can’t regenerate them.”

CARTILAGE: Too weak to support joints

It’s often said a key fault of the body is the back because it wasn’t designed for our upright posture.

“Actually, the spine is brilliant and even has an ‘s’ shape in it to alleviate load on the lower back,” says Colin Natali, a consultant orthopaedic surgeon at the Lister Hospital in London.

Weak cartilage is, however, a design flaw - as a result, our joints easily become painful and damaged, says Professor Philip Conaghan, an expert in musculoskeletal medicine from Leeds University.

“Cartilage is prone to damage, but it does not have a good blood supply and, therefore, does not heal well.” This means the joint is less protected and becomes prone to degeneration. “It doesn’t even need to be a large injury to start this process,” says Professor Conaghan. “It is possible it’s trivial enough for you to not really notice it that much. It would be better to redesign the cartilage to make it more durable. This would make our joints more enduring.”

LARGE INTESTINE: Full of bacteria

Food passes from the stomach to the small intestine (where most of the nutrients are absorbed from food). After that comes the large intestine - and it is here that a design fault lurks.

“It is in the large intestine we absorb residual fluid. If that didn’t happen, we’d have constant diarrhoea,” explains Professor Chris Hawkey, professor of gastroenterology at Nottingham University. “Yet in contrast to the rest of the gut, the large intestine also contains bacteria to help break down undigested fibre.

“This yields about 20-30 calories a day which, in evolutionary terms, would have made all the difference when food was scarce,” says Professor Hawkey.

Just as peaceful co-existence between neighbours can suddenly break out in fighting, so the tolerance between bowel and bacteria can break down. This leaves the bowel inflamed, causing conditions such Crohn’s disease or ulcerative colitis. Instead we could do without the bacteria and all the problems they can cause.

NERVOUS SYSTEM: Causes too much pain

After an injury, nerves send pain signals into the spinal cord (and on to the brain) in a protective manoeuvre to try to reduce movement and reduce further damage. But this may actually cause more pain than is necessary.

“The brain’s control systems cannot distinguish between individual muscles in the area, so switches on the pain sensation in a bigger area than is necessary. That means a small injury may result in a lot of pain,” explains Dr Mike Platt, lead clinician for pain medicine at Imperial College Healthcare NHS Trust.

Another flaw is the way a pain sensation can continue after the injury itself has healed.

“This is because the nerves in the area become hypersensitive and send pain messages to the spinal cord even without any stimulus,” says Dr Platt. “The spinal cord nerve cells also become hypersensitive and send more signals to the brain, which also becomes much more aware of the pain signals.

“This is called ‘sensitisation’ or ‘wind-up’, and can make treating the pain much harder.”

STOMACH: Leaky valve can give you cancer

Stomach acid contains hydrochloric acid, which is great for killing bacteria and for helping break down food.

Unfortunately, the valve at the top of the stomach that is supposed to keep this strong acid in place is often weak, or is put under pressure if you’re overweight. As a result, the hydrochloric acid will leak up the oesophagus (gullet).

“Whereas the stomach lining is designed to withstand stomach acidity, the wall of the oesophagus is more like skin and easily damaged by acid, causing pain,” says Professor Chris Hawkey.

Under a constant bath of stomach acid the cells of the oesophagus can change and ultimately become cancerous. But redesigning it would involve a delicate balance. “If the valve was too tight, then you couldn’t swallow,” says Professor Hawkey. - Daily Mail