Homeostasis [4]: Kidneys (A Level Biology)


Uploaded by freeeschool on 01.09.2012

Transcript:
A Level Biology: Homeostasis 4 – Kidneys
Hi! Welcome to today’s video. Today, we are going to be looking at Osmoregulation,
but we are going to split it up into two parts. The first part that we are going to focus
on is the kidneys.
If you are wondering where your kidneys are, if you were to place both your hands on your
hips, the location of where your fingers are should be roughly where your kidneys are found.
Most people are actually born with two kidneys, but you can survive with just one. Those who
have only one kidney need to have dialysis.
Your kidneys do three very important jobs. The first job being removal of urea from the
blood; production of urine, as I have already stated; and Osmoregulation.
The kidneys are involved in excretion, primarily of urea. What urea actually is it’s a poisonous
waste product and it is made within the liver. What happens is when we eat proteins, proteins
are made up of amino acids, if we got an excess of proteins, they need to be broken down and
gotten rid of. The excess proteins are broken down into their individual monomers which
are amino acids. These are then converted to ammonia through a process known as deamination.
That’s then converted to urea and then urea is released into the blood where it travels
around the body until it is removed by the kidneys.
Now, let’s take a look at the structure of the kidneys. As you can see, each kidney
is connected to two blood vessels. You got the renal vein which carries blood away from
the kidney and you have the renal artery which carries blood towards the kidney. You also
got the urethra there as well. That is where the waste or the urine is transported out
towards the bladder.
If we then look at a cross-section of the kidney, you can see, here you got one individual
kidney and you can see that it is basically split up into two parts. You got the outer
part which is known as the cortex which is this bit here and an inner part which is known
as the medulla which is this bit here. If we take an even closer look, you got a single
kidney tubule here. A kidney tubule, one tubule is actually known as a nephron. Here you got
the structure of a nephron here. This is the collecting duct and this leads towards the
urethra and the bladder. Here, you got the distal convoluted tubule. This bit here is
known as the Loop of Henle. Here you got the proximal convoluted tubule and here, you got
the Bowman’s capsule.
These massive capillaries here are known as the glomerulus. So as you can see here, you
also got the renal artery. What happens is the blood containing urea and other waste
substances passes through these massive capillaries here. What happens is the water, glucose,
urea, salts and everything comes out minus the red blood cells. As it passes through
the proximal tubule, some useful substances get reabsorbed. So they passed back into the
blood. Those are things like water, glucose and some salts as well.
Down here in the Loop of Henle, some of the water also passes back into the blood and
we will focus on this when we look at Osmoregulation. Blood which has had the urea and other waste
substances removed then heads back towards the renal vein while the products which are
left within the tubule forms urine. It dissolved into water and forms urine. That goes towards
the collecting duct and out towards the urethra and bladder.
There you have it. That’s the structure of the kidney.
That concludes the short presentation. I hoped you enjoyed it. Don’t forget to keep a lookout
for some more videos coming out soon.
[end of audio – 04:47] A Level Biology: Homeostasis 4 - Kidneys
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