00:01
It's important before we look at the
urinary system, and particularly the
kidney, to at least understand its growth
or general structure. On this slide, there
is a list of important structures. On the
left-hand side, there is a diagram in the
center of the kidney. And on the
right-hand side,
there is a diagram of the region of the
cortex and the medulla illustrating
the nephrons. And I want to just go through
the central diagram and explain
a few points about the general anatomical
structure of the kidney.
00:42
You can see a renal artery comes into the
kidney at the hilum of the kidney.
00:47
The hilum is the region where blood vessels,
nerves, and in this case, the ureter, pass
in or out of an organ. Where the renal artery
travels in to the kidney, it breaks up into
various components and then supplies the
different lobes of the kidney which I'll
describe shortly. Then this artery divides
into an interlobar artery and
travels up between the lobes, and then
bends around and travels parallel to
this region as an arcuate artery. And this
region that these vessels have travelled
through is the medulla of the kidney. These
arcuate arteries then give rise to
interlobular arteries that travel up through
the cortex. And those interlobular
arteries are going to supply the glomerulus,
a component of nephron we'll
mention in a moment. And the vein is drawing
back through the renal vein. So the
kidney is divided into the medulla and
the cortex. In the cortex on the
right-hand side diagram,
you can see the structure of a
cortical nephron, and I will describe its
structure in a moment. But really, if you
look at the cortical nephron, the
glomerulus, and the major components are
up high in the cortex. And then you see
these straight tubules passing down into
the medulla region. I want you to push that
last little bit or last loop from the medulla
up into the cortex, because really,
the very thin loop you see there, the very
thin loop of Henle it's called, doesn't really
extend down into the medulla from these
cortical nephrons. There is also a
juxtaglomerular, or should I say juxtamedullary
nephron, where the nephron and
the glomerulus sit on the border between the
cortex and the medulla. And in this
case, those straight tubules do descend in
the medulla. So, when you see parts of
medulla, you can see tubules running in the
same parallel direction, and they tend to
be of different length. And because of
that, when you look at the growth
structure of the kidney, you can see pyramids.
These pyramids, labelled on
the diagram, represent all these tubules,
these straight tubules and the collecting
ducts running in parallel. And those pyramids
are the boundaries of the lobe
of the kidney. On either side are the
interlobar arteries that I referred to
earlier. And then when neuron passes all through
the tubules and down through the
collecting duct, that collecting duct
opens at the base of this, or should I
say the apex of this pyramid because the
base is actually up against the
border of the cortex. The pyramid, by name,
is a triangular-shaped region of all
these straight tubules and the collecting
ducts, as I mentioned before.
04:18
So you imagine the triangle with the base
up against the cortex and the apex
is at the tip, the papilla of the pyramid
that actually opens into the minor calyx.
04:33
So urine will drip into that minor calyx
and then flow into the major
calyxes and then out through the ureter,
that you can see on the diagram. So that's
a general arrangement of the kidney, mainly
its anatomical details, but also
some of the microscopic details you'll see
in a moment, particularly of the
nephron. Let's now look at the kidney in
more detail. Here is a section of the
kidney on the left-hand side,
low power. This is actually a section
through the lobe of a kidney. And on
the right-hand side is a higher
magnification of the cortex of the
kidney. I want you to look at this section,
or both these sections, very carefully.
05:21
Look at the cortex and then locate the
medulla. This medullary region represents a
section through the pyramid that I've
described earlier. That pyramid will open
at the papilla, the apex of the pyramid,
into the minor calyx which is shown
there, and then the urine will flow out
through the ureter, as I explained before.
05:45
And you can see components of the heart
and there're also a bit of fatty tissue, but you
also see a very small artery, a branch of
the renal artery. Now, on either side of that
pyramid or that medullary region, you have
components of the cortex more or less
overflowing the lobe. They're called the
renal columns. Turn your attention now
to the right hand section of the cortex,
and you could see little dots or specs.
06:15
They represent the renal corpuscle. That's
the filtering component of the
nephron, and I will describe that in more
detail in a moment. You can also see some
straight tubules that are called medullary
rays. There are number of
these in this section,
several. Have a look at the section and
just see if you see regions where they
appears to be parallel tubules
arranged next to each other.
06:45
They represent the straight tubules in
the cortex and collecting tubules as
well, and some of the collecting ducts.
And they actually define the central
component of the kidney lobule. And if you
look in the middle towards the
middle part of that section, and also a
little bit towards the top, you can see
the renal corpuscles are arranged in a
sort of a line. And that's because the peripheral
border of the kidney lobule is in fact
the interlobular artery. They run up on the
periphery of the lobule and they give
rise to blood to supply the glomerulus
inside those renal corpuscles, and then
the glomeruli then filter that blood
from a filtrate which goes through all the
tubule systems, and then follows the
collecting ducts in those medullary rays.
So again, the medullary rays are
the centre of the lobule, and the
interlobular arteries are on the
periphery. It's hard to see here, I know,
because there aren't connective tissue
components that separate the lobules
apart, as you see in other organs.