Wee all need to do it – or die
Wee All need to do it
‘Kidneys’ have been featuring in my life of late with a family member having kidney disease ,and it has struck me that many of the people I have talked to don’t know much about kidneys and lump ‘kidney function’ with other things down below we don’t talk about . So I’m going to talk about the wee bit I know and hope its not too wrong.
Gushing Water! http://media.noupe.com//uploads/2010/04/Waterfall21.jpg
Kidneys are really clever in what they do . They act like a blood filter and remove just the right amount of waste and fluid, returning to the body what it needs. We have 2 kidneys, one on each side of the body ,and each kidney consists of about one million microscopic functional units called nephrons. Each of these act to filter our blood allowing small molecules ( water, salt, glucose etc ) in , while not allowing bigger things such as proteins and red blood cells . A nephron is a bit like a bent up tube (a tubule) – plasma ( the fluid part of blood) goes in one end (filter), and modified fluid (urine) out the other, joining the output from other nephrons, to eventually go out a bigger tube, the ureter (one per kidney), to fill up the bladder; from the bladder urine travels down the urethra (another tube) to finally end its wee journey.
Only part of the blood plasma goes on into the nephron – the rest of the blood goes on into capillaries to run beside the nephron . Our blood plasma is filtered at around 125 ml a minute, and if 125 mls per minute of urine came out, we would lose our entire blood plasma volume ( approx 2.75 litres ) in less than half an hour ! (1) Well obviously this doesn’t happen ; urine is produced , on average, at about 1 ml per minute- so water must be returned to the blood stream – and it is through the wall of the tubule(other substances too, that the body needs, are returned this way eg glucose, sodium ). Substances can also be secreted back into the tubule. So kidneys continually regulate our body’s water levels , solute levels ( eg Sodium, Potassium, hydrogen ions ), and blood pressure so that it is just right. You have no doubt noticed that your wee is a darker colour when you are dehydrated – the result of kidneys minimising the water lost from your body ; whereas a clear, pale urine is the result of the elimination of excess water.
Urine (like healthy blood) is sterile – no germs, but can become a good growth medium for bacteria if given a chance. It can easily be contaminated on exit from the body.
The urine of a healthy kidney mainly consists of unwanted water, salt, waste products of metabolism(urea, uric acid, creatinine) and foreign substances (eg drugs).
Kidney damage has many causes and appearances but where there is damage to the ‘filter’ part, then protein or red blood cells may get through to be found in the urine. Filtration rate can be reduced because of damaged nephrons and this rate can be measured using blood and urine tests. A filtration rate of ,say, 14ml per minute(my relo – much lower than 125ml/min) can give rise to a build up of waste products in the blood, and a kidney transplant/dialysis may be seriously considered depending on the type of kidney disease.
But , be aware, many people may have kidney disease and don’t even know it because outward physical symptoms don’t often appear as a warning, if at all, until the kidneys are really bad – the doctors go by blood and urine tests, looking for such things as protein in the urine ( your wee may also look foamy from this ) ,blood in the urine and elevated blood creatinine .
So, we all need to do it … or we die.
Please seek your doctor’s advice if l have worried you. Also Kidney Health Australia (2) provides an informative site .
1. Sherwood L. , Human Physiology from cells to systems, 6th ed, p506
2. Kidney Health Australia www.kidney.org.au