What’s up. Meditay here. Let’s talk about the anatomy of the urinary
system. In this segment, we will be talking about
the anatomy of the Kidneys. Alright, so the Urinary system consists of
all the organs involved in handling the urine. These are the Kidneys, the Ureter, the Urinary
bladder, and the urethra. Our goal is to cover the anatomy of all these
structures you see here, step by step, and we’ll start with the Kidneys
In this video, we're first going to talk about the functions of the kidneys. Then we’ll talk about the external structures
and the coverings of the kidneys. After that, we’ll open up the kidney and
cover the internal structures. When we’re done with the kidneys, we’ll
talk about the general anatomy of the nephron, which is the functional unit of the kidney. Alright, so here you see an anterior view
of the body. The kidneys are these bean-shaped paired organs
you have on the backside within the ribs. The first thing you need to keep in mind is
that the Right kidney is placed a little lower than the left kidney, possibly because the
liver occupies a huge part of the right side of the abdominal cavity. But they both start approximately from the
12th thoracic vertebrae. But the left one ends at approximately the
2nd lumbar vertebra, and the right kidney ends at approximately the 3rd Lumbar Vertebra. Ok, so first off, what are the functions of
the kidneys? There are three main functions that the kidneys
have. And they are Plasma filtration, Excretion
of waste products, and acid-base homeostasis. And the kidneys are able to do all that with
the help of something we call a nephron. We’ll talk a little more detail through
the nephron at the end of this video, but the head of the nephron, is called a Renal
Corpuscle, and this is the part that primarily filtrates the plasma. So, what is plasma? When you first draw blood from the body, into
a tube, you’ll get whole blood. And if you put this tube with whole blood
into a centrifuge, and start the machine, it’ll spin around so fast, that it’s going
to separate the blood, as you see here. Now we’re left with Pure erythrocytes at
the bottom, buffy coat, consisting of white blood cells mainly, and plasma. So when whole blood goes through the renal
corpuscle, the plasma is going to get filtrated. So that’s what we mean with plasma filtration. Next, excretion of waste products. So the plasma consists of everything that’s
not cells. That is water, proteins, nutrients, electrolytes,
and here in bold. Metabolic Waste products. As you see here. So what kind of metabolic waste products do
we have? We have (ammonia, uric acid, urea, creatine,
creatinine, and different types of amino acids) are considered as metabolic waste products,
and they get excreted out through the renal corpuscle, and this si very important, it’s
dangerous if we get too much of these waste products. Now, your body is in a perfect state when
there’s a balance between acid and base, around 7.35 to 7.45 is our natural state where
all processes within us happen optimally. But sometimes, something happens that makes
our blood either acidic or alkaline, called acidosis and alkalosis. We don’t like that, and when the pH gets
too deviated, it gets even worse. And this process is usually regulated primarily
through the lungs and the kidneys. There are other functions the kidneys have
as well, such as hormone production, producing hormones like erythropoietin that stimulate
RBC production, and Vit D metabolism by activating vit D, since most vitamin D in our blood is
in an inactive state. So that’s the functions of the kidneys-
They’re very important to our body, kidneys are. Now let’s start with the kidneys anatomy
by looking at the external structures. So the kidneys are about 120-200 grams, these
numbers really deviate depending on the source you’re studying from, but they're about
10 to 13 centimeters long and 5-6 centimeters wide, and about 4 cm thick. The kidney has an inferior Pole, and a Superior
Pole. And on the superior pole, you’ll find the
suprarenal gland resting on it as you see here. They also have two margins. There’s a lateral border or lateral margin,
and there’s the medial border. The medial border has an area called hilum
of the Kidneys, and if you remember what a hilum is. A hilum is the entrance into an organ. So this place is the only place structures
can go in and out from the kidneys. You’ll find blood vessels and nerves and
lymph vessels going in and out, as well as the ureter. So that was all the external structures of
the kidneys. Let’s now look how the kidneys are covered. Here you see a posterior view of the body. Let’s now make a transverse cut and look
at the kidneys from this perspective to see how the kidneys are covered. Ok, So here are two kidneys, superior view. Here is the Vertebra and in front of them
are the Inferior vena cava and the abdominal aorta. So the first covering that’s around the
kidneys are the fibrous capsule, which are dense fibers that protect the kidneys. Around the fibrous capsule, there are the
adipose capsule, we call it the perinephric fat, peri means around, so the fat around
the kidneys. And as you see here, this fat is thicker posteriorly
than anteriorly. And it's quite logical if you think about
it as the kidneys are closer to the posterior abdominal wall, this fatty capsule protects
it from any concussion, as well as protecting them from becoming cold. Ok, sot that’s these two. Then, externally to the fatty layer, we have
a fasciae covering it, called the Renal Fascia. And this fascia has two parts or two layers. We have an anterior layer and a posterior
layer. Laterally, they’re both going to fuse, as
you see here. Both these posterior layers are going to go
in front of the vertebra and fuse with it, while the anterior layer will go in front
of the blood vessels and fuse with the other layer on the other side. The anterior layer or prerenal layer is also
called Fascia of Toldt. While the Posterior later, or the Retrorenal
Layer, which is also called Layer of Zuckerkandl. And they both lie behind the peritoneum. These two layers remain separated below the
kidneys, creating a space between them. So that’s generally how the kidneys are
covered. Now let’s go ahead and open up the kidney,
just like that, to cover the internal structures of it. The kidneys have a compartment within them
called the Sinus Renalis, or the Renal Sinus. And it’s filled up by fat called the renal
sinus fat. And between the fat, you’ll find the renal
pelvis and the renal calyces, which lead the urine from the kidneys down to the ureter. And I’ll show you this in a little more
detail in a minute. But the actual kidneys consist of the renal
medulla and the renal cortex. Some parts of the cortex are also going to
extend down between the medulla. So let’s first cover the Renal Cortex. So the renal cortex is dark brown in color
and soft and granule in consistence. It can be between 4-11mm thick. Again these numbers deviate a lot from source
to source, but we also got parts of the cortex going down in between the medulla, which are
just extensions of the cortex, called the renal columns. Now, what makes up the renal cortex? If we take a small bit of the kidneys and
zoom in. Remember the kidneys main functional unit
are the nephrons. There’s gonna be a lot of nephrons within
one kidney, around 1 to 1,5 million nephrons. And if we divide the nephron like this. You’ll see that parts of it lie in the cortex,
and part of it lies in the medulla. So the renal Cortex is composed of the renal
corpuscle, the proximal convoluted tube, and the distal convoluted tube. The rest of the nephron is in the Medulla,
so let’s talk about the medulla a little bit. The renal medulla consists of these renal
pyramids. There are about 7-18 of those within one kidney. Here comes the tricky part with these pyramids. Each of these pyramidal structures together
with their adjacent cortex will form lobes we call renal lobes. Now the renal pyramid is called a pyramid
because of its shape. There’s going to be a base that is directed
towards the cortex. And on the other side, there’s going to
be the apex of the renal pyramid. And these apices will fuse together and form
a renal papilla. I’ll show you this in a little more detail
when we go through the nephron. But another thing that’s important to mention
when talking about the renal medulla is that there are going to be parts of the medulla
that radiated towards the cortex, which we call renal medullary rays. Now let’s go back to this picture again. Now we know that when we talk about the renal
medulla. We’re talking about the Pyramid. And you’ll find the rest of the nephron
here. Which is the Loop of Henle, and the collecting
duct. Ok. So let's continue from the renal papilla. The renal papilla is going to have these openings
of the papillary ducts, which lead the urine from the pyramids, towards the Minor Renal
Calyces. And these minor renal calyces are going to
fuse into the major renal calyces. There are usually 2 or 3 of these major renal
calyces. The urine will then flow into the renal pelvis,
to then go down towards the Ureter. So that’s all we need to know for the anatomy
of the kidney. Now let’s do the anatomy of the nephron. And to do that, we’re going to isolate one
renal lobe, and look at a detailed view of it. So the renal cortex and its renal colums go
between the renal pyramids. And below the renal pyramid, you’ll find
the minor renal calyces. Alright. SO the nephron consists of a Renal Corpuscle,
located in the renal cortex. And the renal corpuscle consists of a glomerulus,
which are many capillary loops as you see here. So blood will flow in through an afferent
arteriole, remember a stands for arrive. So afferent arterioles arrive into the glomerulus,
and they exit as efferent arteriole. E for exit. And the glomerulus is surrounded by a glomerular
capsule. Which as you see here consists of an internal
part and an external part. And between them is where the tubular system
is going to continue, so the urine flows between the two layers you see here. So that’s the renal corpuscle. After the renal corpuscle is the Proximal
Convoluted tube, which also lies in the cortex. The proximal convoluted tube has two parts. There’s a convoluted part, which curves,
and a straight part. Then the nephron continues into the renal
pyramid as the Loop of Henle. There’s a descending part and an ascending
part, which extends up to the renal cortex as the Distal Convoluted Tube. Now up until this step. The plasma has been filtrated into primary
urine. Electrolytes and other minerals have been
reabsorbed and secreted out throughout the whole tube. And at this point. The urine is now finished to be called secondary
urine, which is what we generally call urine. Now the urine will continue through the collecting
ducts. These collecting ducts will all come together,
fuse, and form the papillary ducts. At this point, the papillary ducts will open
up as small openings, into the minor renal calyces. So that was everything I had for the anatomy
of the kidneys. I really hope this video helped you understand
the anatomy of it. In the next video, we’re going to talk about
the anatomy of the Ureter, Urinary bladder, and the Urethra n both male and female.