Video: Female urinary bladder
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Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we're going to be focusing on the female urinary bladder. Now, the urinary bladder is a hollow o... Read more
Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we're going to be focusing on the female urinary bladder. Now, the urinary bladder is a hollow organ that serves to collect urine filtered through your kidneys. Throughout this tutorial, we will focus on the structure and parts of the urinary bladder in the female pelvis. Now, one important thing before we continue is that we’re going to be mainly exploring this image that you now see on this screen which is essentially a coronal section of the female urinary bladder. You see a lot of structures here which we will be highlighting to understand what’s happening around the urinary bladder that this is the urinary bladder as you can see here.
First structure I would like to highlight here is known as the peritoneum. Now, before I go and talk about the actual bladder, I would like to just briefly mention the peritoneum and the pelvic fascia that cover part of the bladder. Now, the peritoneum is a serous membrane that lines the peritoneal cavity and this membrane supports and lines the organs of the abdomen and pelvis.
The next structure we’re going to be highlighting here, this is known as the visceral pelvic fascia. Now, this is a fibrous covering over the various pelvic viscera that is attached to the diaphragmatic part of the pelvic viscera, and in this illustration, we see the part of the pelvic fascia that covers the bladder. Also worth noting that it forms the anterior and lateral ligaments of the bladder.
And let’s now talk about the actual bladder starting off with this structure that you see now highlighted in green which is known as the body - so, this is the body of the bladder – and the urinary bladder when empty has a pyramidal shape. It has a base known as the fundus, an apex, a superior surface, and two inferolateral surfaces which we will discuss later on on this tutorial.
Now, the body of the urinary bladder is lined with transitional epithelium and as you see here on this image as well this is a hollow pear-shaped part of the urinary bladder that holds the urine before it is voided. The body is located between the fundus and the apex of the urinary bladder. The entire volume of the bladder varies but it can hold between 400 mL to 1000 mL. The ureters will be opening into the body of the bladder posteriorly and you see here the orifices where they are going to be connecting with the bladder and we will talk about them later on on this tutorial.
Let’s continue on to the next structure that you see here highlighted in green which is known as the fundus. Now, the fundus of the urinary bladder is basically the base of the bladder. It has the shape of an inverted triangle faces posteroinferiorly and is formed by the posterior wall of the bladder. The trigone of the bladder, triangular in shape, as you can see here, faces posteriorly and is drained by the external iliac lymph nodes. And continuing on with this trigone here now highlighted in green, this is the trigone of the urinary bladder, which is the smooth triangular part of the organ, and as you can see in this illustration, the mucosal lining of the trigone is smooth and firmly attached to the underlying wall of the bladder and like elsewhere in this organ where the mucosa is then folded and loosely attached to the wall.
Now, this triangular region is formed by the left and right ureteral orifices which you can see here, and we’re going to talk about them later on. They’re essentially openings of the ureters into the bladder and the internal urethral orifices. Once the trigone of the urinary bladder is stretched to a certain degree, then there is a signal sent to your brain that the bladder – your bladder – needs to be emptied and you need to find the closest toilet.
The next structures that we’re going to be highlighting here on these two images are structures that I talked about before, the ureteral orifices. They are slit-like openings of the left and right ureters on the posterolateral angles of the trigone of your bladder through which then the ureters enter this organ. And next, there is this structure here now highlighted which has a similar name but we call it then interureteral folds, the muscle fibers between the two orifices – as you can see here. They will be raising and forming a fold which is known as the interureteral fold. Now, the interureteral fold is a mucous membrane fold located between the two ureteral orifices.
Next, we’re going to be a bit further down to highlight what is known to be as the neck of the urinary bladder. Now, the neck of the urinary bladder is the portion of this organ from which the urethra arises, and you can see here part of the urethra. It is the lowest part of the bladder, and as you can see here in our illustration, it is the uppermost part before the urethra will be starting and then the lowest part of the bladder. And since we’re talking about it, mind as well as highlight it, this is then the urethra.
It is a canal used for the removal of urine from the urinary bladder out of your body – so this is a passageway. The upper portion of the urethra is lined with transitional epithelium which becomes pseudostratified columnar epithelium – this is definitely a tongue-twister – and then stratified columnar epithelium, and then stratified squamous epithelium closer to the external urethral orifice. In females, the urethra is 4.8 to 5 cm long and its opening is located between the clitoris and the vagina. The epithelium of the lower end of the urethra contains then urethral glands which are mucous-secreting glands that protect the lining of the urethra from corrosive urine.
The next structure we’re going to be highlighting here is the vagina immediately posterior to the external opening of the urethra then we find here the opening of the vagina. Now, the vagina is about 10 cm long fibromuscular canal leading into the uterus. In this illustration, we see the opening of the vagina in relation to the structures associated with the urinary bladder. The vaginal opening is significantly larger than the urethral orifice and is located a few cm below it.
The next structure or muscle that we’re going to be highlighting here, this is known as the detrusor urinae muscle. Now, we’re going basically back to the urinary bladder where we’ll look at the muscles of the bladder starting with this one here. Now, the detrusor muscle of the bladder – also referred to in some texts as the muscularis propria – is a true muscle of the organ of the urinary bladder. Now, this musculature is smooth muscle that is found around the wall of the bladder – as you can see here on this illustration – and is comprised of the inner and outer longitudinal layers as well as the middle circular layer. This muscle is relaxing during accumulation of urine in the bladder and contracts only during urination to void then the empty the bladder.
The next muscle we’re going to be highlighting here is known as the external urethral sphincter, which is another important muscle of the female urinary bladder. And this, in this illustration, you see here the external urethral sphincter muscles are these muscles highlighted in green. Now, these muscles are mainly responsible for controlling urination process in female pelvis and are innervated by the deep peroneal branch of the pudendal nerve. This surround the membranous part of the urethra and have their origin at the ischiopubic ramus wrapping around the urethra as you can see here upon which they act. In the female pelvis, there is no internal urethral sphincter so the external sphincter is well-developed and it is comprised of the parts known as the urethral sphincter, the urethral vaginal muscle, and finally, the urethral compressor muscle that will be extending distally from the urethral sphincter to the ramus of the ischium. The relaxation of these muscles then facilitates urination.
The next structure we can see here is also a muscle, this time the levator ani muscle. So very important muscle for urination and this muscle forms a large part of the pelvic diaphragm which is basically the muscular floor of the pelvis. It is found on either side of the pelvis, originates from each side of the pelvic wall coursing medially and joins with its opposite counterpart. It is a thin funnel-shaped muscle extending from the pubis and obturator fascia to the anus. If you remember, the levator ani is actually three muscles together namely the puborectalis, the pubococcygeus, and the iliococcygeus muscle.
Now, moving onto this image of the inferior view of the pelvis still highlighted here the levator ani muscle, to say that in the female pelvis, the levator ani has its origin on the posterior aspect of the superior pubic ramus and also the ischial spine. It will be inserting in the superior surface of the peroneal membrane, the other side around the anal canal, and the last two segments of the coccyx. Now, the innervation of the levator ani muscle is derived from the pudendal nerve and its branches as well as S3 to S5 sacral spinal nerves. Now, this muscle relaxes at the beginning of urination and also defecation and, for that reason, the levator ani muscle plays a very important role in preservation of urinary and bowel continence.
Going back to this image of the section of the urinary bladder to then highlight another muscle, this time, the obturator internus muscle. Though, it might be seen here as part of the muscles of the female pelvis, it actually acts to facilitate lateral rotation, abduction and adduction of your thigh. Has its origin in the inner surface of the obturator membrane as well as the rim of the pubis and ischium and the muscle then inserts at the trochanteric fossa. And as innervation, as for the innervation of this muscle, it comes from the sacral plexus L5 to S1.
Another muscle worth highlighting here on this image, this is the bulbospongiosus muscle, also involved in the urination process. It arises from the perineal body and the female pelvis. This muscle follows the course of the bulb of the vestibule passing laterally. It has several functions including assisting in emptying the urethra, closing the vagina as well as contributing to clitoral erection and orgasm. Now, the muscle is innervated by the perineal nerve which is a branch of the pudendal nerve.
Another muscle here to be highlighted, this time, the ischiocavernosus muscle which originates from the ramus of the ischium and the ramus of the pubis. The ischiocavernosus muscle functions to then tense the vagina during orgasm. It runs along either side of the crus and it is innervated by the pudendal nerve. Though this muscle is not vital for the urination process, we show it here to then illustrate a bit here how the muscle is positioned in relation to the urinary bladder. This also applies to the next three structures we will look at. This one is the tendinous arch of the pelvic fascia.
Now, the tendinous arch of the pelvic fascia extends from the pubic symphysis to the ischial spine and this tendinous reinforcement joins the pubocervical fascia covering then the anterior wall of the vagina. Another fascia that you see here, this time known as the superficial perineal fascia, and the superficial perineal fascia is a thin aponeurosis that forms the anterior inferior border of the superficial perineal space.
Next, we’re going to be seeing also another fascia here highlighted in green. This time, the deep perineal fascia, which surrounds the muscle of the superficial perineal pouch. It attaches from the ischiopubic ramus to the deep suspensory ligament of the clitoris and is continuous with the deep fascia of the muscles of the abdominal wall.
Next structure is a membrane. This is known as the perineal membrane, again indirectly related to the urinary bladder but just to show you where it’s positioned. It is a fascia found on the anterior inferior surface of the deep transverse perineal muscle and forms the superior border of the superficial perineal pouch. It is attached to the bony framework of the pubic arch and is continuous with the inferior part of the diaphragmatic part of the pelvic fascia. The urethra penetrates the perineal membrane vertically as it escapes the pelvic cavity.
A bit further down here on this image you see these two dots which are showing the cut of the round ligament of the uterus. The round ligament of the uterus originates in the parametrium and passes to the labia majora leaving the pelvis through the inguinal canal to the mons pubis.
The next structure we’re going to be highlighting here is known as the crus of the clitoris. This is erectile tissue attached to the inferior pubic ramus and this bilaterally-located tissue converges to form the clitoral body. The crus of the clitoris is supplied by the deep artery of the clitoris and contains then the ischiocavernosus muscle.
The next structure we’re going to be highlighting here is known as the vestibular bulb. Now, the vestibular bulbs are located near the clitoral body, the crus, the urethra, the urethral sponge and the vagina, and are found on the left and right sides primarily at the root of the labia majora. Now, this tissue correlates with the bulb of the penis and corpus spongiosum in males and is part of the erectile tissue in the female pelvis. Now, the vestibular bulbs are supplied by the artery of the bulb of the vestibule and drained by the corresponding vein.
Moving on, we’re going to be talking about the neurovasculature of the bladder, a little bit of information about the blood vessels and also nerve supply of the urinary bladder. Starting off with this image here now from the lateral views of the female pelvis, these highlighted structures which you can see here on both these images are showing the superior vesical arteries. Now, on this one, you can see the right one and, on this one, you see the left superior vesical artery. Now, these are paired terminal branches of the umbilical artery and they supply the upper and middle segments of the urinary bladder.
Next, we’re going to be talking about veins, these that you see here highlighted in green is the plexus known as the venous plexus of the urinary bladder. Now, this plexus is found primarily on the inferior aspect of the urinary bladder and it drains into the hypogastric plexus via the vesical veins.
Moving onto now the nerves that you see here from this lateral view of the female pelvis, we’re now highlighting then the vesical plexus which arises from the superior hypogastric plexus and contains then parasympathetic fibers. This nerve plexus is located on both sides of the urinary bladder and regulates the emptying mechanism of the bladder.
Now, just a few structures that we still see here on the coronal section of the bladder just for a bit of understanding what’s happening here around the urinary bladder, and now we’re looking at the inferior pubic ramus. Now, this is the only part that you see here highlighted in green which is a thin and flat part of the pubic bone that merges with the inferior ramus of the ischium.
Now, on this coronal section, you still see here very important bones, the hip bones, which is comprised of, if you remember well, the ilium, the ischium and the pubic bone. Now, the hip bones including the sacrum and coccyx make up or form the pelvic girdle and the pelvic part of the vertebral column.
The next structure worth highlighting here is known as the extraperitoneal space that is part of the pelvis and abdomen that lies outside the peritoneum. Now, this connective tissue space also includes the retroperitoneal space and the preperitoneal space.
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Now, good luck everyone, and I will see you next time.