Bladder Health, Anatomy, and Physiology - Diane Newman

July 21, 2023

Diane Newman delves into the anatomy and physiology of the lower urinary tract. Dr. Newman’s specialty involves treating men and women who suffer from bladder control problems or pelvic floor dysfunction through behavioral therapy. In this lecture, she explains how the urinary system functions, beginning with the kidneys and detailing the journey of waste removal through the ureters and bladder. She highlights the differences in urinary anatomy between men and women and discusses how common conditions such as pregnancy or constipation can affect bladder control. In addition, she explains the critical role of the sphincters and pelvic floor muscles in maintaining urinary control. Finally, she educates on normal voiding patterns and the impact of aging on bladder control. The talk emphasizes the importance of understanding and educating patients about these physiological processes to manage urinary tract dysfunctions effectively.


Diane K. Newman, DNP, ANP-BC, BCB-PMD, FAAN, Adjunct Professor of Urology in Surgery, Research Investigator Senior, Perelman School of Medicine, University of Pennsylvania, and Former Co-Director of the Penn Center for Continence and Pelvic Health, Philadelphia, PA

Read the Full Video Transcript

Diane Newman: Welcome. I'm Diane Newman. I'm an advanced practice nurse practitioner. I'm also a continent nurse specialist and I've specialized in lower urinary tract dysfunction since the late 1980s.

My practice is treating men and women with behavioral therapy. They come to see me because they have bladder control problems or pelvic floor dysfunction. So I next want to go over with you the anatomy and physiology of the lower urinary tract. So I want you to understand the bladder and maybe why you may have a bladder problem or maybe you're going to be treating someone with a bladder problem.

So basically the urinary tract starts at the kidneys which are behind the 12th, and 13th ribs, so they're towards the back. There are two kidneys, one on either side. We don't know why we have two, but you could live with only one and some people are only born with one kidney and it's called a kidney because they are shaped like kidney beans.

You then have the pelvis of the kidney, which has the ureters. I always say these are like hook number 12, spaghetti noodles. They're long and they go from the pelvis of the kidney all the way to the base of the bladder, which is where they come in and they carry the urine from the kidneys. Kidney is a very sophisticated organ. It knows what to get rid of and it gets rid of the waste in our body. And if you have kidney failure, you can't get rid of the waste, which is why you need something like dialysis. So it knows what to keep, which is good, maybe electrolytes and what's to get rid of. And then it produces urine and the urine is carried through the ureters down to the bladder. The bladder is the lower urinary tract where the kidneys and the ureters are called, the upper tracts, we call them.

The lower urinary tract is the bladder and the urethra. And by this picture you can see and it's a side view of a person. Men have a long urethra, what we call S-curves. Women have a much shorter one. This kind of gives you an overview about what the different organs in the urinary tract do. The kidneys filter waste and water from your blood and it makes urine, which is called pee. Urine leaves the kidneys through the ureters and enters the bladder more towards the base of the bladder.

The ureters, which some people call the womb, it lies on top of the bladder in women. The bladder is like a storage tank, it holds the urine. Okay? I always say to patients, that's the tank and the urethra is like the hose. So the urethra is at the neck, it starts at the neck of the bladder, the base of the bladder, and that carries the urine to the outside and the prostate in men surrounds that urethra.

And another term for urinate, some people say urinate, some people say void. Well my patients say, do you pee?

Now the bladder, the bladder is a muscle, okay? So it can enlarge and hold a lot if you go for hours and not urinate or you can shrink it over time if you urinate frequently. A lot of my patients I see have voiding dysfunction and they have actually overactive bladder, which means they go to the bathroom too frequently. So it holds the urine made by the kidneys. The bladder is in the pelvis, which is why we call it the pelvic floor. So that bladder, the urethra, the pelvic floor muscles, and actually the rectum are all on the pelvic floor that's at the base of our body.

The bladder changed shape depending on how much urine's in it. So it's kind of flat like a pancake in the pelvis and as the kidneys make urine, it rises up into the abdomen closer to your belly button, your umbilicus, almost like a football. Okay? And one thing that I think is really important to realize is that urine is made slowly over three to five hours. People say to me, "Well, I drink water Diane and I have to rush to the bathroom right away." Water's the trigger, the kidneys don't make urine that fast, so it really takes three to five hours.

Now these are just pictures of really looking at the bladder, the urethra, and the different structures in men and women. And I think we do have differences. It's important. The most important thing is that we have a shorter urethra as women, which some people believe that's why we have more urinary tract infections because the bacteria has just a short distance to travel to the bladder. Men have a long urethra and that's why they get more strictures and scarring maybe over time, especially if there's any surgery on the prostate. But basically we have differences in anatomy, but the bladder is the same really for men and women. There's no difference there. With us women though the uterus can push on the bladder. So if we have a baby in the uterus, it can push on the bladder, which is why pregnant women go to the bathroom more frequently.

If we have fibroids that may impact the bladder. The other thing that's important about the bladder is the rectums right behind that. So if I tell patients all the time, what is your bowel function? Do you have regular soft stools? If you have hard stools, if you strain to have a bowel movement, you basically are putting pressure on that bladder and some people tell me they leak if they have constipation. Now the other important thing about this picture is the structures of the sphincters, the sphincters are valves. We have an internal sphincter, which is more of a mechanism at the base of the bladder and we have an external sphincter. The external sphincter is voluntary and it is surrounded by the pelvic floor muscles and basically, it's always closed. So as the bladder fills up with urine, that internal sphincter is autonomic, which means we don't control it.

Our brain and our spinal cord, our nerves control it. That opens up as we get more urine in our bladder, but our external sphincter gets tighter because it's like a valve, it doesn't want to open up unless we say we are going to allow it to open up. So those sphincters are very important and this really talks to you about the sphincter and the pelvic floor muscles. The pelvic floor muscles are a supportive structure for that sphincter. And I explained to a patient is like, it's like keeping a garden hose, that's what the sphincter is like. It's a valve that keeps the urethra closed and the pelvic floor muscle hugs it. So when I teach patients about pelvic floor muscle exercises and what's going on if say they have stress incontinence is I tell them that sphincter is not tight and with increased pressure it's a little bit open and that's why they leak urine.

And basically the norm is the sphincter has static tone, which means that the sphincter is tight at rest, it's contracted at rest, we don't have to do it and the pelvic floor muscle hugs it. When we go to the bathroom without thinking, women should sit, relax the pelvic floor, which opens that valve, that's sphincter. Men stand and use abdominal force and they open the valve by relaxing the pelvic floor. So that's a person with good bladder control should not leak urine and also sphincter control.

Now the pelvic floor muscles, I've mentioned them and they're called the pelvic floor muscles because they're in the floor of the pelvis. So the point is that they are a supportive structure. They go from the front to the back, so they attach the pelvic bone, the front, they sling around the rectum and come back around and the end is attached to the pelvic bone.

Think of it like a hammock, okay, they surround the urinary sphincter and they surround the rectal sphincter. There is also an internal and external rectal sphincter. That's why we don't lose stool, okay, because that sphincter, that valve keeps the stool in until we want to defecate. Okay? The pelvic floor muscles are under voluntary control and they have a major role in keeping us with control of our bladder. They keep us controlled and that's really important and that's why with aging, say with vaginal delivery, those muscles may weaken. That's why we see a change with bladder control. And these are just two pictures that kind of show you sideways what the whole pelvis looks like With women, you can see that that uterus is really sitting right on the bladder there and the pelvic floor as it slings around the rectum and the fact that it's supportive.

And then in men you can see that it comes around at the base of the prostate. A lot of men think that the sphincter is cut. That's why they may have what we call post prostatectomy incontinence. The sphincter is not cut, it just its fine nerves may be damaged with removal of the prostate, which may weaken the sphincter, but they can get it back by working and strengthening that pelvic floor muscle. And these are just other pictures that kind of show you again the pelvis in men and women. I use these pictures when I teach patients, I literally have them in color and I sit them right down and say this is what's going on, this is why you have your problem and this is what we're going to work on. I think education is very important.

Now understanding the bladder and voiding or peeing urination, as I said, is voiding or passing urine, some people say, or peeing is controlled by the lower urinary tract, which is the bladder, the urethra. You do have to have an intact brain and spinal cord and nerves, all right. So anyone that has a neurologic impairment such as spinal cord injury, multiple sclerosis, which affects the spinal cord and the brain, Parkinson's, traumatic brain injury, they may have bladder dysfunction and that's important to know. So they might either have incontinence or emergency frequency or they may not be able to empty their bladder when they should because the sphincter is not working. One of the things you see with MS is they don't relax the sphincter to open it up. They have dysuria, which means when the bladder's contracting, the sphincter is actually tightening. And that's one of the results that you see of MS, which is why I'm sure if you're a clinician watching this, many of us see MS patients who have bladder control problems.

This is a nice picture of what happens when we pee with the bladder and the sphincter. So first the bladder pressure increases because there's more urine in it. The bladder muscle, which is called the detrusor muscle, it's a muscle called the detrusor muscle because one of the layers of the bladder is the detrusor. Sometimes you'll hear people say, oh, the detrusor, which means the bladder, basically it's relaxed as it fills with urine and basically what we call the outlet, which is the urinary sphincter is tight, okay? The kidneys are making urine, just dumping into the bladder. Then we get the first sensation to void, which is about 200MLs or 250MLs, so less than a can of soda. All right? And some of us will say, oh, I'm going to go to the bathroom now because I have a meeting, so I won't be able to go or I'm going to be driving home.

But most of us defer the initial urge, that initial sensation and the bladder muscle remains relaxed and basically the sphincter again is tight. Then we get the normal desire to void. Now that might be, it's stronger, it's not urgency, but it's the urgent sensation, oh yeah, I drank a lot, I usually... 450 is maximum capacity, we may get that normal desire is 350, 400 and then we make the decision to go to the bathroom. But remember voiding is voluntary, you should have control and go when you want. So micturition means voiding. So we decide to urinate. Well, what happens? Well, the bladder muscle is relaxed, it opens the outlet and basically it contracts down and we urinate. So that bladder muscle contracts down whenever the sphincter opens up. And then basically we go back to what we call storage phase. So that's really the normal as far as micturition.

Now, what is a normal voiding pattern? I get asked that a lot. Well, how often should I go to the bathroom? This is a rule of thumb because it is dependent on how much you drink, but normally someone should void every four to five hours under the age of 65. Okay? So under the age of 65 you void four to five hours, zero at night, you should be able to go through the night, unless you had a lot to drink, maybe you had five beers in the evening, you're going to pee during the night, but normally no.

Over the age of 65, remember I told you before that bladder is not as efficient. It can't hold as much. It's three to four hours and then once a night and you add one more per decade as you age. So that's a really quick review of the anatomy and physiology of the lower urinary tract dysfunction. Hope that was helpful, but hopefully if you really want to understand this and understand your patients, you really need to understand what voiding means, and also you need to educate your patient on it. Thank you.
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