Describe the changes that occur in kidney and bladder function in old age

The kidney is made up of filtering units called nephrons. The number and size of nephrons slowly decreases with age, the kidneys start to lose its function, meaning, the waste and extra fluid are not filtered out of the body as effectively in older people. The kidneys become smaller with age, Blood flow to the kidneys is also reduced. This also impairs the filtering process. 

Another function of the kidneys is to balance the amount of salt and acid in the body. This function also decreases with age, the production and efficiency of hormones that tell the body it is becoming dehydrated declines with age. This poses a risk for dehydration. 

Bladder tissue becomes much less stretchable as one gets older. This decreases the amount of urine the bladder can hold. The muscles of the bladder also become weaker, making the bladder unable to squeeze hard enough to get rid of all the urine it contains, so more urine is left in the bladder after a person urinates. These two changes may cause an older person to have to urinate more often. 

The sensation of needing to urinate is often delayed in older people. When an older person finally feels the need to urinate, the need may be sudden.

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