Human Body Anatomy - PART 1

Time: When your body really starts going downhill
There's no denying the ticking of a woman's biological clock - but men are not immune, either. French doctors have found that the quality of sperm starts to deteriorate by 35, so that by the time a man is 45 a third of pregnancies end in miscarriage. Here, with the help of leading clinicians, Angela Epstein identifies the ages when different parts of the body start to lose their battle with time.
BRAIN - Starts ageing at 20
As we get older, the number of nerve cells - or neurons - in the brain decrease. We start with around 100 billion, but in our 20s this number starts to decline.
By 40, we could be losing up to 10,000 per day, affecting memory, co-ordination and brain function.
In fact, while the neurons are important, it's actually the deterioration of the gaps between the brain cells that has the biggest impact, says Dr Wojtek Rakowicz, a consultant neurologist at Imperial College Healthcare NHS Trust in London.
We all assume grey hair and wrinkles are the first signs of ageing, but some parts of your body are worn out long before you look old
These tiny gaps between the end of one brain nerve cell and another are called synapses. Their job is to ensure the flow of information from one cell to another, and as we age we make fewer.
GUT - Starts ageing at 55
A healthy gut has a good balance between harmful and 'friendly' bacteria.
But levels of friendly bacteria in the gut drop significantly after 55, particularly in the large intestine, says Tom MacDonald, professor of immunology at Barts And The London medical school.
As a result, we suffer from poor digestion and an increased risk of gut disease.
Constipation is more likely as we age, as the flow of digestive juices from the stomach, liver, pancreas and small intestine slows down.
BREASTS - Start ageing at 35
BY their mid-30s, women's breasts start losing tissue and fat, reducing size and fullness.
Sagging starts properly at 40 and the areola (the area surrounding the nipple) can shrink considerably.
Although breast cancer risk increases with age, it's not related to physical changes in the breast.
More likely, says Gareth Evans, breast cancer specialist at St Mary's Hospital, Manchester, our cells become damaged with age - as a result, the genes which control cell growth can mutate, causing cancer.
BLADDER - Starts ageing at 65
Loss of bladder control is more likely when you hit 65.
The bladder starts to contract suddenly, even when it's not full.
Women are more vulnerable to bladder problems as, after the menopause, declining oestrogen levels make tissues in the urethra - the tube through which urine passes - thinner and weaker, reducing bladder support.
Bladder capacity in an older adult generally is about half that of a younger person - about two cups in a 30-year-old and one cup in a 70-year-old.
This causes more frequent trips to the loo, particularly as poor muscle tone means the bladder may not fully empty. This in turn can lead to urinary tract infections.
LUNGS - Start ageing at 20
Lung capacity slowly starts to decrease from the age of 20.
By the age of 40, some people are already experiencing breathlessness. This is partly because the muscles and the rib cage which control breathing stiffen up.
It's then harder to work the lungs and also means some air remains in the lungs after breathing out - causing breathlessness.
Aged 30, the average man can inhale two pints of air in one breath. By 70, it's down to one.
VOICE - Starts ageing at 65
Our voices become quieter and hoarser with age. The soft tissues in the voice box (larynx) weaken, affecting the pitch, loudness and quality of the voice.
A woman's voice may become huskier and lower in pitch, whereas a man's might become thinner and higher.
EYES - Start ageing at 40
Glasses are the norm for many over-40s as failing eyesight kicks in - usually long-sightedness, affecting our ability to see objects up close.
As we age, the eye's ability to focus deteriorates because the eyes' muscles become weaker, says Andrew Lotery, professor of ophthalmology at the University of Southampton.
HEART - Starts ageing at 40
The heart pumps blood less effectively around the body as we get older.
This is because blood vessels become less elastic, while arteries can harden or become blocked because of fatty deposits forming on the coronary arteries - caused by eating too much saturated fat.
The blood supply to the heart is then reduced, resulting in painful
angina.
Men over 45 and women over 55 are at greater risk of a heart attack.
A recent study by Lloyds Pharmacy found the average person in the UK has a 'heart age' five years older than their chronological age, probably due to obesity and lack of exercise.
LIVER - Starts ageing at 70
This is the only organ in the body which seems to defy the ag ing process.
'Its cells have an extraordinary capacity to regenerate,' explain David Lloyd, a consultant liver surgeon at Leicester Royal Infir mary.
He says he can remove ha a liver during surgery and it will grow to the size of a complete liver within three months.
If a donor doesn't drink, use drug or suffer from infection, then it is possible to transplant a 70-year-old liver into a 20-year-old.