Urinary System Anatomy (Anatomy and Physiology)

In this lesson we’re going to look at an overview of the urinary system. We’re going to talk about the general structure and function of the various structures involved in making and excreting urine, and then in other lessons we’ll look in more detail at those actual processes.
So the urinary system consists of the kidneys, ureters, bladder, urethra, and accessory glands. In males, the accessory gland is the prostate gland. Females have glands called Skene’s glands that help to lubricate the external urinary meatus. Both of these things are talked about in more detail in the male and female reproductive system lessons, so make sure you check out those lessons.

First, we’re going to look at the kidneys. The kidneys are located on the posterior abdominal wall just above the waist. The big thing to know is that the entire urinary system is retroperitoneal – that means that it’s actually behind the peritoneum. That parietal peritoneum actually helps to suspend the kidneys and the rest of the urinary system to the abdominal wall and hold them in place. There’s another lesson on the detailed structure of the kidneys, so you’ll want to check that one out. Now, the major functions of the kidneys are to make urine, help with fluid and electrolyte balance, acid-base balance, and blood pressure regulation. Now we have individual lessons on each of these aspects of kidney function, so make sure you check those out individually as well.

So let’s look at the other parts of the urinary system and their structure and function. First is the ureters. The ureters, as with the rest of the urinary system, are retroperitoneal, and they come off the medial side of the kidneys out of a notch called the Hilum. Then they come down and insert into the posterior, inferior side of the bladder. Similarly to all of our tubular organs like this, they have 3 layers. Connective tissue on the outside, smooth muscle on the inside, and a mucous membrane on the inside – in this case it’s transitional or uroepithelium. The main purpose of the ureters is simply to help move urine from the kidneys down to the bladder. That smooth muscle peristalsis helps to propel it in the right direction and prevent it from going backwards (reflux) or getting stuck (stasis).

From the ureters, the urine dumps into the bladder. The only difference in location here is that the bladder is actually located in the pelvic cavity, but it’s still retroperitoneal. It also has 3 layers – on the top we see the parietal peritoneum and the rest is covered with connective tissue. There’s smooth muscle and in the bladder it’s called the Detrusor muscle – you’ll hear that word a lot. And, of course, on the inside we see transitional epithelium as well. Now there are a couple other unique things we see in the bladder. One is the trigone region – it’s an area of connective tissue on the inside that helps stabilize the area where the ureters enter the bladder. Last thing we want is for this area to collapse and then the urine can’t come into the bladder, right? The other is the sphincters – you have an internal sphincter, which is involuntary smooth muscle – and an external sphincter, which is voluntary skeletal muscle. The function of the bladder is to hold onto the urine as it’s created and then when we are ready to urinate, the detrusor muscle contracts and the sphincters will open.

Lastly, just past the bladder and sphincters, is the urethra. In females it’s anterior to the reproductive system and the vaginal canal. In males, the urethra passes through the prostate gland and exits the penis. In females it’s approximately 3 inches or so, and in males the length will vary based on the individual person. The function of the urethra is to connect the bladder to the external urinary meatus as a pathway for urination. And in males, it’s also the pathway for semen as well.
Okay, let’s recap here. Remember that all of these structures are retroperitoneal. The kidneys and ureters are in the abdominal cavity and the bladder and urethra are in the pelvic cavity. The kidneys function to make urine, help with fluid and electrolyte and acid base balance, and regulate blood pressure. The ureters move the urine from the kidneys to the bladder where it’s held until urination. And the urethra is the pathway from the bladder to the outside. Also remember that we have some accessory glands associated with the urinary system, and we’ll talk about those more in the male and female reproductive system lessons.
So that’s it for the overview of the anatomy of the urinary system. Make sure you check out all of the other lessons about renal structure and function. Now, go out and be your best selves today. And, as always, happy nursing!