Anatomical Features of Urinary System

What's up? Medite here. Let's talk about the anatomy of the urinary system. In this segment, we will be talking about the anatomy of the ureter, the urinary bladder and the urethra, in both male and female. So the urinary system consists of all the organs involved in handling the urine, and these are the kidneys, the ureter, the urinary bladder and the urethra. In our last video, we covered the anatomy of the kidneys, now let's do the rest of the urinary system. So in this video, our goal is to go through the functions and the course of the ureter, and then we will cover the parts and the different constrictors or narrowings the ureter has, as well as the layers of the ureteral wall. After that, we will do the parts and the layers of the urinary bladder, and then the general anatomy of the male and female urethra. Alright, so here we see the anterior view of the kidney. Remember the kidneys have an area called the helium. and from the helium you'll find the renal pelvis coming out. And at the point of where the renal pelvis ends, that's where the ureter will start. So the ureter's function is really only leading the freshly made urine from the kidneys all the way down to the urinary bladder. One of the common misconceptions regarding the ureter is that people seem to think it's just a tube without any control of the urine. All it does is that it provides a flow for the urine from the kidneys to the urinary bladder. The ureter is actually a muscular tube that transports the urine through peristaltic movements. Just like the intestines when they move the contents through contractions, the ureter does the same with the urine. And I'll show you how when we go through the walls of the ureter and the constrictions we have. Therefore, the urine flow is not continuous. So the ureter can be roughly around 30cm long, and they both lie at the very back of the abdominal cavity. And they lie right in front of the psoas major muscle. And when it reaches the terminal line of the pelvis, it then enters the lesser pelvis. And from this point, it crosses some structures differently in men and women. So in male, it crosses the ductus deferens, as you see here, right before it enters the urinary bladder. The ductus deferens, remember, is the duct that comes from the testes of the male. And then in female, it gets a little more complicated than that. So what do we see here? we see the urinary bladder, we see the ureter at the back, and we also see the uterus and the uterine tubes. The ureter will pass between a ligament you see here, called the broad ligament of the uterus, or ligamentum latum uteri, which is a ligament that attaches the lateral portions of the uterus to the lateral pelvic wall. So the ureter passes between this ligament and another ligament highlighted here in green. called the cardinal ligament of the uterus. After that, it enters the urinary bladder. So the cores differ a little bit in male and female. And then when the ureter enters the urinary bladder, it enters as an orifice called the ureteric orifice. So that's the general course of the ureter. The ureter is divided into parts according to its location. When the ureter is in the abdomen, it gets the name the abdominal part, which lies between the renal pelvis and the terminal line of the the pelvis. When the ureter is in the pelvis, it gets the name the pelvic part, which ends at the urinary bladder. And when the ureter is in the wall of the urinary bladder, it gets the name the intramural part. So the ureter has three parts generally. Abdominal part, pelvic part, and intramural part. The ureter is usually between 7-8 cm in diameter, but it has some narrowings that decreases this diameter. And when the diameter decreases, it gets roughly around 3-4 mm wide. So there are three narrowings or constrictions the ureter has. The first one is the upper narrowing at the junction between the renal pelvis. The middle one is at the linea terminalis. And the lower narrowing is when the ureter is inside the wall of the urinary bladder. So that was the narrowings of the ureter. Let's now make a transverse cut of the ureter and look at the layers of the ureter wall. And to make this easier, we will line the external surface first. So the first layer is the tunica mucosa, which is the innermost layer. It's smooth and contains transitional epithelium that are able to stretch and dilate when the urine passes through. For the other layers, we need to add a line here in the middle because the lower 1 third of the ureter will be different from the upper 2 thirds of the ureter. So the lower third of the ureter is going to have these glands present the talus submucosa, which is a layer that contains loose connective tissue, along with blood vessels, nerves and lymphoid tissue. And then under the talus submucosa, we have a muscle layer called the tubular muscle layer. The muscle layer will be different in the upper two thirds of the ureter than the lower third. The upper two thirds of the ureter is going to have two layers of muscle fibers, where the inner part are going to be longitudinal muscle fibers, and the outer part is going to be circular muscle fibers. And keep in mind that most tubes you have in your body are going to consist of circular and longitudinal muscle fibers for the peristaltic movements. The lower third of the ureter differs in that it's going to have three layers of muscle fibers. The innermost is going to be longitudinal muscle fibers, the middle part consists of circular muscle fibers, and then the outer part will be longitudinal muscle fibers. It's different here because the closer you get to the urinary bladder, the more it's going to resemble the urinary bladder. So the last layer is the outermost layer, which is going to be tunica adventitia, containing strong fibers connective tissue for protection. So, that was all for the anatomy of the ureter. Now, let's continue and look at the anatomy of the urinary bladder. Now, the urinary bladder is a sac that stores urine, and its capacity really depends on the size of the person, but in average, it should be around 250 to 500 milliliters. Alright, so here we see the ureter, and here is the urinary bladder, and in the middle of the urinary bladder, you will find the median umbilical ligament. which during embryonic life used to be the umbilical arteries, but after birth, the umbilical arteries degenerates to become the median umbilical ligament, without any proper functions in the body. But anatomically, it's there attached to the urinary bladder. Now, the urinary bladder is divided into parts. The first part closest to the median umbilical ligament is the apex of the bladder. The majority of it is the body of the bladder. And then posteriorly, you'll find the fundus of the urinary bladder. Alright, so there are two general conditions the urinary bladder can be in. It can either be empty, or rather full. The empty urinary bladder is situated behind the pubic symphysis, as you see here. And it has two surfaces. It has an anterior surface towards the symphysis, and a posterior surface towards the peritoneum. And there's usually these lateral margins that separate these two surfaces. The full urinary bladder however, has an oval shape as you see here, and it lies above the pubic symphysis. So this just shows you that the urinary bladder isn't always going to be located right behind the pubic symphysis. Now if you go back to this picture and open it up, you'll be able to see the right ureteric orifice, and the left ureteric orifice, which remember are the openings for the ureters. And then down here is an opening for the urethra, called the internal urethral orifice. And these three are going to form a triangle called the trigone of the urinary bladder, which is an area where the mucus fold is fused with the muscle layer. Now there's also going to be a fold between them, between the two openings of the ureters, called the interureteric crest. Now let's take a small piece of the urinary bladder and look at the histological picture of it to understand the layers of the urinary bladder. The urinary bladder is going to have a tunica mucosa, A Tela Submucosa, Tunica Muscularis, and Tunica Adventitia or Tunica Cirrhosa, depending on which side you're looking at. So the Tunica Mucosa is a layer that consists of transitional epithelium. And the upper layers of the cells are called umbrella cells, because they look like the top part of the umbrella in the relaxed state. Underneath the epithelium, you'll find the Lamna Propria, just like any other Tunica Mucosa in the body. And then the next layer is the Tela Submucosa. containing loose connective tissue. And you will notice that there are no folds at the region of the trigon of the bladder, because remember, this triangle doesn't have a telosubmucosa. The tunica mucosa and the muscularis are fused together in this area. Next is the tunica muscularis, which is this thick layer. And it's thick because it consists of 3 muscle layers. It has an inner longitudinal layer, a middle circular, and an outer longitudinal layer. The middle circular is going to form a sphincter at the urethral orifice called the inner urethral sphincter. So that is the tunica muscularis. The outermost layer is either going to be tunica serosa or tunica adventitia. Now what does that mean? Remember here is the peritoneum, which forms a serious coat around the organs within the abdominal cavity. The surface that is not faced against the peritoneum is called tunica adventitia. which consists of dense fibrous connective tissue. While the surface that faces the peritoneum is called tunica serosa. Notice that when the urinary bladder is full, a larger portion of the urinary bladder are going to be covered by the tunica serosa. So that was the anatomy of the urinary bladder. Now let's move under the urinary bladder and cover the anatomy of the urethra. And remember that the urethra is different in male and female. So we will start with the anatomy of the male urethra first. Alright. So what do we see here? We can see the bladder and the prostate under it. We can see the perineum, which are muscles on the pelvic floor. And then we can see the penis. So the urethra is the tube under the urinary bladder that goes within the penis. And it goes all the way from the internal urethral orifice to the external urethral orifice. So the whole urethra is about 15 to 22 cm long. And it's about 5 to 7 mm in diameter. and it has three parts. The part inside the prostate is called the prostatic urethra, and is about 3 cm long. And the part inside the perineum is called the membranous urethra, which is roughly about 1.5-2 cm long. And then we got the spongy urethra, which is about 15 cm long, lying between the spongy parts of the penis. Let's now go through each of these parts, and we will start with the prostatic urethra by looking from this perspective. It will look like this. So this is the posterior wall of the urethra in male at the prostate region. First, you will see a ridge called the urethral crest, which is an elevated crest on the posterior surface of the urethra. And then in the middle part, there's an elevation formed by the mucous membrane called the seminal colliculus. And on the seminal colliculus, you will find the prostatic utricle, which is a remnant of the paramecinephric duct during development. which is now just a depressed fossa on the seminal colliculus. And then on either side of it, you will find the openings for the ejaculatory ducts, coming from the testis that secretes out sperm into the urethra. And then on the sides, there are many small openings for the prostatic secretion, called the prostatic ductules. So that's this one. Next we have the membranous urethra. It lies between the prostate and the bulb of the penis. And this part is completely surrounded by the sphincter called the external urethral sphincter. So that's that one. Then the last part is the spongy urethra. This part extends from the membranous urethra up here, all the way to the external urethral orifice. So the whole spongy urethra is located inside the body of penis, except the upper part which is directly below the perineum. And this part is only surrounded by connective tissue. And then at the region of the bulb of the penis, the duct of the bulbourethral gland is going to open up, secreting liquid for the sperm. And so the male urethra has three narrowings and three enlargements. The first narrowing is the internal urethral orifice, the second one is the external urethral orifice, and the last one is the narrowing at the membranous urethra. The enlargements however are at the prostatic urethra, then there's the enlargement at the region of the bulb of the penis, and then the third enlargement is at the navicular fossa. Now lastly, let's look at the walls of the urethra. We have the tunica mucosa on the inside, which contains urethral lacuna, which are very small openings at which the urethral glands open up to lubricate the surface. And then here in the navicular fossa, The mucus fold forms a valve called the valve of the navicular fossa, as you see here. And it's literally a valve that prevents the backflow of urine. So that's the tunica mucosa. The next layer is called tunica muscularis, which is a muscle layer that forms sphincters. These are the internal urethral sphincter, and the external urethral sphincter. The internal urethral sphincter is made up of smooth muscle fibers, while the external one is made up of the perineum, which are skeletal muscle fibers. Meaning that this sphincter with skeletal muscle fibers is a voluntary type of sphincter. So you can voluntarily close and open that sphincter. So that's all I had for the male urethra. And now, next we have the female urethra. And for orientation sake, the bladder is here, and the vaginal opening is here. So the female urethra is this short tube right here. which measures around 2.5-4cm long and about 8-12mm in diameter. So it's much shorter than in the male's urethra, but larger in diameter. Which is the reason why the female urethra may be prone to leakage of urine more than the male urethra. However, we're still going to have the same structures as the male urethra. We're basically going to have two openings, an internal urethral orifice at the urinary bladder, and an external urethral orifice which lies roughly about 2 cm behind the glans clitoris, which is the head of the clitoris peeking out from the female genitalia. So now, let's look at the walls of the urethra as well. Again, it's more or less going to look similar to the male's urethra. We're gonna have the tunica mucosa, with small openings, called the urethral lacuna, at which the urethral glands open up, lubricating the surface. We're also going to have the tunica muscularis, which forms two sphincters, the incisor and the uterus. internal urethral sphincter, which lies at the border between the bladder and the urethra. And we're also going to have the external urethral sphincter, at the perineum of the female. So that was everything I had for the anatomy of the ureter, the urinary bladder, and the urethra. If you found this video helpful, please put a like, share, comment, whatever you find convenient to you. See you next time.

So the urinary system consists of all the organs involved in handling the urine, and these are the kidneys, the ureter, the urinary bladder and the urethra. In our last video, we covered the anatomy of the kidneys, now let's do the rest of the urinary system. So in this video, our goal is to go through the functions and the course of the ureter, and then we will cover the parts and the different constrictors or narrowings the ureter has, as well as the layers of the ureteral wall.

After that, we will do the parts and the layers of the urinary bladder, and then the general anatomy of the male and female urethra. Alright, so here we see the anterior view of the kidney. Remember the kidneys have an area called the helium. and from the helium you'll find the renal pelvis coming out. And at the point of where the renal pelvis ends, that's where the ureter will start.

So the ureter's function is really only leading the freshly made urine from the kidneys all the way down to the urinary bladder. One of the common misconceptions regarding the ureter is that people seem to think it's just a tube without any control of the urine. All it does is that it provides a flow for the urine from the kidneys to the urinary bladder. The ureter is actually a muscular tube that transports the urine through peristaltic movements. Just like the intestines when they move the contents through contractions, the ureter does the same with the urine.

And I'll show you how when we go through the walls of the ureter and the constrictions we have. Therefore, the urine flow is not continuous. So the ureter can be roughly around 30cm long, and they both lie at the very back of the abdominal cavity. And they lie right in front of the psoas major muscle.

And when it reaches the terminal line of the pelvis, it then enters the lesser pelvis. And from this point, it crosses some structures differently in men and women. So in male, it crosses the ductus deferens, as you see here, right before it enters the urinary bladder.

The ductus deferens, remember, is the duct that comes from the testes of the male. And then in female, it gets a little more complicated than that. So what do we see here?

we see the urinary bladder, we see the ureter at the back, and we also see the uterus and the uterine tubes. The ureter will pass between a ligament you see here, called the broad ligament of the uterus, or ligamentum latum uteri, which is a ligament that attaches the lateral portions of the uterus to the lateral pelvic wall. So the ureter passes between this ligament and another ligament highlighted here in green.

called the cardinal ligament of the uterus. After that, it enters the urinary bladder. So the cores differ a little bit in male and female. And then when the ureter enters the urinary bladder, it enters as an orifice called the ureteric orifice. So that's the general course of the ureter.

The ureter is divided into parts according to its location. When the ureter is in the abdomen, it gets the name the abdominal part, which lies between the renal pelvis and the terminal line of the the pelvis. When the ureter is in the pelvis, it gets the name the pelvic part, which ends at the urinary bladder. And when the ureter is in the wall of the urinary bladder, it gets the name the intramural part. So the ureter has three parts generally.

Abdominal part, pelvic part, and intramural part. The ureter is usually between 7-8 cm in diameter, but it has some narrowings that decreases this diameter. And when the diameter decreases, it gets roughly around 3-4 mm wide. So there are three narrowings or constrictions the ureter has.

The first one is the upper narrowing at the junction between the renal pelvis. The middle one is at the linea terminalis. And the lower narrowing is when the ureter is inside the wall of the urinary bladder.

So that was the narrowings of the ureter. Let's now make a transverse cut of the ureter and look at the layers of the ureter wall. And to make this easier, we will line the external surface first.

So the first layer is the tunica mucosa, which is the innermost layer. It's smooth and contains transitional epithelium that are able to stretch and dilate when the urine passes through. For the other layers, we need to add a line here in the middle because the lower 1 third of the ureter will be different from the upper 2 thirds of the ureter.

So the lower third of the ureter is going to have these glands present the talus submucosa, which is a layer that contains loose connective tissue, along with blood vessels, nerves and lymphoid tissue. And then under the talus submucosa, we have a muscle layer called the tubular muscle layer. The muscle layer will be different in the upper two thirds of the ureter than the lower third. The upper two thirds of the ureter is going to have two layers of muscle fibers, where the inner part are going to be longitudinal muscle fibers, and the outer part is going to be circular muscle fibers. And keep in mind that most tubes you have in your body are going to consist of circular and longitudinal muscle fibers for the peristaltic movements.

The lower third of the ureter differs in that it's going to have three layers of muscle fibers. The innermost is going to be longitudinal muscle fibers, the middle part consists of circular muscle fibers, and then the outer part will be longitudinal muscle fibers. It's different here because the closer you get to the urinary bladder, the more it's going to resemble the urinary bladder. So the last layer is the outermost layer, which is going to be tunica adventitia, containing strong fibers connective tissue for protection.

So, that was all for the anatomy of the ureter. Now, let's continue and look at the anatomy of the urinary bladder. Now, the urinary bladder is a sac that stores urine, and its capacity really depends on the size of the person, but in average, it should be around 250 to 500 milliliters. Alright, so here we see the ureter, and here is the urinary bladder, and in the middle of the urinary bladder, you will find the median umbilical ligament.

which during embryonic life used to be the umbilical arteries, but after birth, the umbilical arteries degenerates to become the median umbilical ligament, without any proper functions in the body. But anatomically, it's there attached to the urinary bladder. Now, the urinary bladder is divided into parts.

The first part closest to the median umbilical ligament is the apex of the bladder. The majority of it is the body of the bladder. And then posteriorly, you'll find the fundus of the urinary bladder. Alright, so there are two general conditions the urinary bladder can be in.

It can either be empty, or rather full. The empty urinary bladder is situated behind the pubic symphysis, as you see here. And it has two surfaces.

It has an anterior surface towards the symphysis, and a posterior surface towards the peritoneum. And there's usually these lateral margins that separate these two surfaces. The full urinary bladder however, has an oval shape as you see here, and it lies above the pubic symphysis.

So this just shows you that the urinary bladder isn't always going to be located right behind the pubic symphysis. Now if you go back to this picture and open it up, you'll be able to see the right ureteric orifice, and the left ureteric orifice, which remember are the openings for the ureters. And then down here is an opening for the urethra, called the internal urethral orifice.

And these three are going to form a triangle called the trigone of the urinary bladder, which is an area where the mucus fold is fused with the muscle layer. Now there's also going to be a fold between them, between the two openings of the ureters, called the interureteric crest. Now let's take a small piece of the urinary bladder and look at the histological picture of it to understand the layers of the urinary bladder.

The urinary bladder is going to have a tunica mucosa, A Tela Submucosa, Tunica Muscularis, and Tunica Adventitia or Tunica Cirrhosa, depending on which side you're looking at. So the Tunica Mucosa is a layer that consists of transitional epithelium. And the upper layers of the cells are called umbrella cells, because they look like the top part of the umbrella in the relaxed state. Underneath the epithelium, you'll find the Lamna Propria, just like any other Tunica Mucosa in the body.

And then the next layer is the Tela Submucosa. containing loose connective tissue. And you will notice that there are no folds at the region of the trigon of the bladder, because remember, this triangle doesn't have a telosubmucosa. The tunica mucosa and the muscularis are fused together in this area. Next is the tunica muscularis, which is this thick layer.

And it's thick because it consists of 3 muscle layers. It has an inner longitudinal layer, a middle circular, and an outer longitudinal layer. The middle circular is going to form a sphincter at the urethral orifice called the inner urethral sphincter.

So that is the tunica muscularis. The outermost layer is either going to be tunica serosa or tunica adventitia. Now what does that mean? Remember here is the peritoneum, which forms a serious coat around the organs within the abdominal cavity. The surface that is not faced against the peritoneum is called tunica adventitia.

which consists of dense fibrous connective tissue. While the surface that faces the peritoneum is called tunica serosa. Notice that when the urinary bladder is full, a larger portion of the urinary bladder are going to be covered by the tunica serosa. So that was the anatomy of the urinary bladder. Now let's move under the urinary bladder and cover the anatomy of the urethra.

And remember that the urethra is different in male and female. So we will start with the anatomy of the male urethra first. Alright.

So what do we see here? We can see the bladder and the prostate under it. We can see the perineum, which are muscles on the pelvic floor. And then we can see the penis.

So the urethra is the tube under the urinary bladder that goes within the penis. And it goes all the way from the internal urethral orifice to the external urethral orifice. So the whole urethra is about 15 to 22 cm long. And it's about 5 to 7 mm in diameter.

and it has three parts. The part inside the prostate is called the prostatic urethra, and is about 3 cm long. And the part inside the perineum is called the membranous urethra, which is roughly about 1.5-2 cm long.

And then we got the spongy urethra, which is about 15 cm long, lying between the spongy parts of the penis. Let's now go through each of these parts, and we will start with the prostatic urethra by looking from this perspective. It will look like this. So this is the posterior wall of the urethra in male at the prostate region. First, you will see a ridge called the urethral crest, which is an elevated crest on the posterior surface of the urethra.

And then in the middle part, there's an elevation formed by the mucous membrane called the seminal colliculus. And on the seminal colliculus, you will find the prostatic utricle, which is a remnant of the paramecinephric duct during development. which is now just a depressed fossa on the seminal colliculus. And then on either side of it, you will find the openings for the ejaculatory ducts, coming from the testis that secretes out sperm into the urethra. And then on the sides, there are many small openings for the prostatic secretion, called the prostatic ductules.

So that's this one. Next we have the membranous urethra. It lies between the prostate and the bulb of the penis.

And this part is completely surrounded by the sphincter called the external urethral sphincter. So that's that one. Then the last part is the spongy urethra. This part extends from the membranous urethra up here, all the way to the external urethral orifice. So the whole spongy urethra is located inside the body of penis, except the upper part which is directly below the perineum.

And this part is only surrounded by connective tissue. And then at the region of the bulb of the penis, the duct of the bulbourethral gland is going to open up, secreting liquid for the sperm. And so the male urethra has three narrowings and three enlargements. The first narrowing is the internal urethral orifice, the second one is the external urethral orifice, and the last one is the narrowing at the membranous urethra. The enlargements however are at the prostatic urethra, then there's the enlargement at the region of the bulb of the penis, and then the third enlargement is at the navicular fossa.

Now lastly, let's look at the walls of the urethra. We have the tunica mucosa on the inside, which contains urethral lacuna, which are very small openings at which the urethral glands open up to lubricate the surface. And then here in the navicular fossa, The mucus fold forms a valve called the valve of the navicular fossa, as you see here.

And it's literally a valve that prevents the backflow of urine. So that's the tunica mucosa. The next layer is called tunica muscularis, which is a muscle layer that forms sphincters. These are the internal urethral sphincter, and the external urethral sphincter. The internal urethral sphincter is made up of smooth muscle fibers, while the external one is made up of the perineum, which are skeletal muscle fibers.

Meaning that this sphincter with skeletal muscle fibers is a voluntary type of sphincter. So you can voluntarily close and open that sphincter. So that's all I had for the male urethra.

And now, next we have the female urethra. And for orientation sake, the bladder is here, and the vaginal opening is here. So the female urethra is this short tube right here. which measures around 2.5-4cm long and about 8-12mm in diameter.

So it's much shorter than in the male's urethra, but larger in diameter. Which is the reason why the female urethra may be prone to leakage of urine more than the male urethra. However, we're still going to have the same structures as the male urethra. We're basically going to have two openings, an internal urethral orifice at the urinary bladder, and an external urethral orifice which lies roughly about 2 cm behind the glans clitoris, which is the head of the clitoris peeking out from the female genitalia.

So now, let's look at the walls of the urethra as well. Again, it's more or less going to look similar to the male's urethra. We're gonna have the tunica mucosa, with small openings, called the urethral lacuna, at which the urethral glands open up, lubricating the surface.

We're also going to have the tunica muscularis, which forms two sphincters, the incisor and the uterus. internal urethral sphincter, which lies at the border between the bladder and the urethra. And we're also going to have the external urethral sphincter, at the perineum of the female. So that was everything I had for the anatomy of the ureter, the urinary bladder, and the urethra. If you found this video helpful, please put a like, share, comment, whatever you find convenient to you.

See you next time.

Transcript for:Anatomical Features of Urinary System

Transcript for:
Anatomical Features of Urinary System