(4.44)

Now we'll look at the structures of the urinary system: the kidneys, the ureters, the bladder and the urethra. We'll start by looking at the kidneys, and also, since they're nearby, at the suprarenal glands.

The kidneys are located high in the posterior abdominal wall, behind the peritoneum. They lie in front of the eleventh and twelfth ribs. The right kidney is slightly lower than the left one.

To see the kidneys and ureters we'll look at a dissection in which all the intra-abdominal organs have been removed. The kidneys are here.

As we've done in other dissections, we'll remove the lower anterior ribs to get a better view. The kidneys are surrounded by a layer of fat which we'll remove. Here are the kidneys. Here's the aorta, emerging between the crura of the diaphragm.

Here's the vena cava, quite distended in this specimen. We'll look first at the blood vessels of the kidneys, the renal vessels. The veins lie in front of the arteries. The left renal vein crosses in front of the aorta, just below the origin of the superior mesenteric artery.

The right renal vein, which is much shorter, passes steeply backwards to reach the right kidney. To see the renal arteries we'll take the veins out of the picture. In this specimen the aorta and common iliac arteries are quite tortuous. The renal arteries arise just below the superior mesenteric artery.

The renal arteries pass quite sharply backward to reach the kidneys, which lie on each side of the great midline prominence formed by the vertebral bodies. The branches of the renal artery and vein enter the kidney at the hilum.

The renal pelvis, which we'll see shortly, emerges from the hilum behind the blood vessels. It narrows to become continuous with the ureter, which takes urine to the bladder.

To see the hilum in detail, in this isolated kidney, we'll remove the fat from around the hilum. At the hilum the surface of the kidney is rolled inward, creating a deep oval pocket, the renal sinus.

To see into the sinus we'll remove this part of the kidney. In the renal sinus the artery and vein divide into numerous branches. We'll remove them too, so that we can see the structures that form the collecting system for urine.

The renal pelvis is formed by the convergence of a number of broad drainage channels. Here, we see more of them. Each of these is called a calyx. Usually three or four major calyces drain into the pelvis.

Each major calyx branches into several minor ones, that are seen better in this x-ray of an isolated kidney that has its collecting system full of contrast material. The outline of the kidney itself would be out here. This kidney has four major calyces. This one branches into three minor ones. Each minor calyx ends in a trumpet-like widening.

Here's the lower part of a kidney that's been dissected like the last one. The ureter's been cut short. The end of each calyx spreads out, and attaches here to the surface of the kidney that faces in towards the renal sinus. If we remove the calyces we can see that at the end of each one the solid tissue of the kidney projects inward in a mound or ridge called a papilla. There are two more papillae here.

Here's a kidney that's been divided longitudinally. All the blood vessels have been removed. The solid tissue of the kidney is called the renal parenchyma. It consists of an outer cortex, and an inner medulla,

The medulla is continuous with the papillae. Towards the tip of each papilla the collecting tubules, which are just visible, converge. They open into the calyces here, at the tips of the papillae.