Urinary System
Yes, the kidneys are delicious when fried, perhaps with a little salt and pepper, but what do the kidneys actually do?
Kept simply, the kidneys clean and filter the blood…”but why is that needed” I hear you ask? Well, the blood contains things that would damage the body, either from what has been eaten, or what has been made as waste-products by the body, while it has been working.
Unfiltered blood enters the kidney through the renal (means kidney) artery and filtered blood leaves the kidney through the renal vein. The renal artery branches many times, into smaller and smaller blood vessels, which then supply the 1 million or so (ive not really counted them myself) nephrons. It is in the nephron that the work of filtering the blood happens.
Kept simply, the kidneys clean and filter the blood…”but why is that needed” I hear you ask? Well, the blood contains things that would damage the body, either from what has been eaten, or what has been made as waste-products by the body, while it has been working.
Unfiltered blood enters the kidney through the renal (means kidney) artery and filtered blood leaves the kidney through the renal vein. The renal artery branches many times, into smaller and smaller blood vessels, which then supply the 1 million or so (ive not really counted them myself) nephrons. It is in the nephron that the work of filtering the blood happens.
In the nephron, blood enters the glomerulus, which is
inside the Bowman’s capsule. In here, blood flow is split through many
capillaries, which act like sieves, push through clean blood and leave behind
particles of waste. The cleaned blood then goes back in to the rest of the body.
The particles and fluid that was filtered out of the blood then pass through the
proximal tubule, the loops of Henle, distal tubule and collecting tubule, where
urine is formed. This then goes to the ureter and bladder, before it finally is
removed from your body (you do a pee).
Now lets just step back a few steps and consider something really cool. If the process of filtering the blood stopped here, it would mean that lots of useful nutrients, minerals and water that were in the blood would be flushed out of the body (and down the toilet). To prevent this, as the waste mixture passes through the various tubules and loop of Henle, the useful components are reabsorbed into the filtered blood, as it passes through the peritubular capillaries, which are surrounded by the various tubules and loop of Henle.
inside the Bowman’s capsule. In here, blood flow is split through many
capillaries, which act like sieves, push through clean blood and leave behind
particles of waste. The cleaned blood then goes back in to the rest of the body.
The particles and fluid that was filtered out of the blood then pass through the
proximal tubule, the loops of Henle, distal tubule and collecting tubule, where
urine is formed. This then goes to the ureter and bladder, before it finally is
removed from your body (you do a pee).
Now lets just step back a few steps and consider something really cool. If the process of filtering the blood stopped here, it would mean that lots of useful nutrients, minerals and water that were in the blood would be flushed out of the body (and down the toilet). To prevent this, as the waste mixture passes through the various tubules and loop of Henle, the useful components are reabsorbed into the filtered blood, as it passes through the peritubular capillaries, which are surrounded by the various tubules and loop of Henle.
In the proximal tubule alone, about two thirds of the filtered water and salt is reabsorbed back into the cleaned blood, along with most of the glucose and proteins. The rest of the waste fluid then continues through the loop of Henle, which goes from the kidney cortex to the medulla and back again, causing salt to be concentrated in the peritubular capillaries. As it goes to the medulla (the descending limb), water flows out and into the peritubular capillaries by osmosis. As it goes to the cortex again (the ascending limb), water is unable to leave and instead sodium is actively pumped out. The waste fluid then reaches the distal tubule, where the cells lining the tubule are able to produce lots of energy (they have lots of mitochondria and so can make lots of ATP). This energy is used to actively transport calcium and sodium and to release phosphate (from ATP). This tubule also regulates pH, by releasing hydrogen and ammonium.