Video: Internal structure of the kidney

Hello, everyone. This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we’re going to be talking about the internal structure of the kidney.

And what I'm going to be doing is exploring this structure that belongs to, of course, as the name indicates, the kidney. But to do so, as you can see here on this image, we just removed the upper half of the organ, so in a mid longitudinal section. And then we’re going to also remove the lower part on other images. But right now we’re looking at the left kidney from a posterior view.

On this tutorial, we’re going to be talking about the internal structure of the kidney. And as you probably know, the kidneys are bilateral organs of the urogenital system. They are located in the retroperitoneal region of the abdomen. And their main function is to eliminate excess bodily fluid, salts, and by-products of protein metabolism.

Now, the main body of the kidneys can be divided functionally into a cortex, a renal medulla, and the hilum. And in this tutorial, we will discuss the renal cortex and other related structures.

Now, as you can see here in this section of the kidney, we see the renal cortex, highlighted in green, which is, then, the outer layer of the body of the kidney found between this structure which is known as the fibrous capsule of the kidney and also the renal medulla.

This outer layer is an estimated six millimeters in thickness, and ultrafiltration occurs in the renal cortex.

Now, structures found in the renal cortex include the renal corpuscles, the distal renal tubules, and the proximal renal tubules.

The next structures that we’re going to be seeing here, highlighted in green, now on the image, are known as the renal columns. And the renal columns are extensions of the renal cortex that extend down between the pyramids of the renal medulla. And these renal columns contain urinary tubules and blood vessels.

Now, I'm ready to move to the next one, the next structures here, highlighted, which are known as the bases of the renal pyramids. And the base of each renal pyramid is located between the renal cortex and the renal pyramids at the cortical medullary border.

The renal pyramids are formed by the renal medulla, which is the next structure that we’re going to be talking about, and now, seen here, highlighted in green. This is the renal medulla. And the renal medulla is divided into renal pyramids that are separated by the renal columns of the renal cortex.

Now, the ascending and descending limbs of the loops of Henle as well as the collecting ducts (nephrons) are located in the renal medulla. The apex of the renal pyramids, also known as the papilla, opens into the minor calyx of the kidney. And you can clearly see here on this image them opening to the minor calyces of the kidney.

The next structures that we’re going to be highlighting here are known as the renal papillae. The renal papillae are located at the apex of the renal pyramids. And they are formed by the openings of the uriniferous tubules in the area cribrosa. And they open into the minor calyces of the kidneys.

We’re now moving on to another set of highlights here, structures that we briefly mentioned before, these are known as the minor calyx, singular, minor calyces in plural which collect urine from the renal papillae which open into them, and it is, then, passed into the major calyces.

Three minor calyces make one major calyx.

Now, the next structure that we just briefly mentioned that is now seen, highlighted in green, is known as the major renal calyx. And one major calyx is formed by the convergence of three minor calyces. The major calyces open into the renal pelvis then.

Each kidney has three major calyces.

The next structures, one that we also talked about, this is, then, the renal pelvis. And the renal pelvis is formed by the convergence of the major calyces. Urine from the major calyces goes into the renal pelvis which is continuous with the, then, the ureter, as you can see here on this image.

Now, the renal pelvis is located behind the renal artery and vein, and it exits the kidney at the renal hilum, which is this structure right about here that you see here. This is where you could find the hilum.

The next structure that we’re going to be highlighting now that is seen on your screen, this is the ureter. And the ureter is an excretory duct situated between the renal pelvis and the urinary bladder. It is comprised of smooth muscle fiber, and its inner lining is made up of transitional epithelium.

The ureter enables urine to drain from the renal pelvis into the urinary bladder. And the ureter is innervated by nerves or is supplied by nerves that arise from T12 to L2 segments of the spinal cord.

The next structure that I'm highlighting now, on your screen, is known as the renal capsule, we talked about it before. The renal capsule is a tough, protective fibrous layer fused to the surface of the kidney. It is covered by adipose capsule comprised of perinephric fat. This fibrous capsule can be removed when dissecting the kidneys.