Your kidneys make urine by filtering wastes and extra water from your blood. The waste is called urea. Your blood carries it to the kidneys. From the kidneys, urine travels down two thin tubes called ureters to the bladder. The bladder stores urine until you are ready to urinate. It swells into a round shape when it is full and gets smaller when empty. If your urinary system is healthy, your bladder can hold up to 16 ounces (2 cups) of urine comfortably for 2 to 5 hours.

You may have problems with urination if you have

• Kidney failure
• Urinary tract infections
• An enlarged prostate
• Bladder control problems like incontinence, overactive bladder, or interstitial cystitis
• A blockage that prevents you from emptying your bladder

Some conditions may also cause you to have blood or protein in your urine. If you have a urinary problem, see your health care provider. Urinalysis and other urine tests can help to diagnose the problem. Treatment depends on the cause.

The main organs of our urinary system are the kidneys – our body’s “sewage treatment plants”: They filter toxins out of the body, as well as other substances that we no longer need. These waste products leave your body in the urine produced in your kidneys. This is how water and substances like urea, uric acid, salts and amino acids are removed from the blood. Every day, all of the blood in your body (between five and six liters) passes through the kidneys about 300 times. So your kidneys filter about 1,700 liters of blood per day in total. This leads to the daily production of about 170 liters of primary urine (glomerular filtrate) – which later becomes urine.

Inside the kidney there is a renal medulla, which has small tubules and larger collecting tubes running through it. As the primary urine flows through this system of tubes, the kidney cells re-absorb about 99 percent of the fluid in it, as well as many substances that can still be used, and at the same time release other substances. About 1.7 liters of urine are produced like this each day. The urine passes from the kidneys through the ureter into the urinary bladder, where it is stored.

Urinary bladder and urethra

The bladder expands when it fills up, like a balloon. Nerves in the bladder wall detect the expansion and send a signal to the brain, letting it know that the bladder is full.

The urinary bladder can store up to 500 ml of urine in women and 700 ml in men. People already feel the need to urinate (pee) when their bladder has between 150 and 250 ml of urine in it. When you empty your bladder, the muscle in your bladder wall tightens to squeeze the urine out of your bladder, while at the same time the sphincter muscles at the base of your bladder relax, allowing the urine to flow out through your urethra.

In men, the urethra leads through the penis and is about 20 cm long. In women, it ends above the opening of the vagina. The urethra is shorter in women (only 3 to 5 cm long), so it’s easier for germs from the anus to enter their bladder. This is one of the reasons why urinary tract infections (UTIs) like cystitis are more common in women. In older men, a benign enlarged prostate might push against the bladder and urethra, making it difficult to urinate normally.

How does bladder control develop?

The ability to hold your urine and pass urine is complex and involves the coordination of muscles, nerve signals and hormones, which is regulated by the brain and the spinal cord. Babies and toddlers can’t yet voluntarily control the emptying of their bladder – they only learn to do so gradually. Also, the pelvic floor muscles that stabilize the bladder need to develop first. The brain has to learn how to control the internal organs, too. Although the most important bodily functions work right after birth, the fine-tuning of the organs takes time. This also applies to bladder control, which takes longer to develop in some children and can’t be sped up.

In babies, the brain reacts to the signal “bladder is full” by telling the sphincter muscles of the bladder to relax. The muscles then open the passage to the urethra and the bladder is emptied. As children get older, they learn to ignore this reflex and keep their urine in voluntarily until they get a chance to go to the bathroom. Eventually, they can do this in their sleep too. Instead of emptying their bladder, they wake up. At the same time, their sleep pattern develops.

The brain also has to learn to regulate the production of certain hormones, including vasopressin. During early childhood, the brain starts releasing larger amounts of vasopressin at night. This hormone travels through the bloodstream to the kidneys, where it decreases urine production. As a result, the bladder doesn’t fill up as quickly and the child doesn’t have to wake up at night.

Urinary incontinence in adults

Although bladder control problems are more common in children, they can affect people of all ages. If people can’t voluntarily hold urine back and it leaks out of their bladder, it is known as urinary incontinence. This happens if the sphincter muscle stops working properly and it can no longer keep urine in the bladder. The possible causes include very weak pelvic floor muscles or paralysis (problems with nerve function) in the pelvic area.

Having reviewed the anatomy and microanatomy of the urinary system, now is the time to focus on the physiology. You will discover that different parts of the nephron utilize specific processes to produce urine: filtration, reabsorption, and secretion. You will learn how each of these processes works and where they occur along the nephron and collecting ducts. The physiologic goal is to modify the composition of the plasma and, in doing so, produce the waste product urine.

Failure of the renal anatomy and/or physiology can lead suddenly or gradually to renal failure. In this event, a number of symptoms, signs, or laboratory findings point to the diagnosis.

Glomerular Filtration Rate (GFR)

The volume of filtrate formed by both kidneys per minute is termed the glomerular filtration rate (GFR). The heart pumps about 5 L blood per min under resting conditions. Approximately 20 percent or one liter enters the kidneys to be filtered. On average, this liter results in the production of about 125 mL/min filtrate produced in men (range of 90 to 140 mL/min) and 105 mL/min filtrate produced in women (range of 80 to 125 mL/min). This amount equates to a volume of about 180 L/day in men and 150 L/day in women. Ninety-nine percent of this filtrate is returned to the circulation by reabsorption so that only about 1–2 liters of urine are produced per day.

GFR is influenced by the hydrostatic pressure and colloid osmotic pressure on either side of the capillary membrane of the glomerulus. Recall that filtration occurs as pressure forces fluid and solutes through a semipermeable barrier with the solute movement constrained by particle size. Hydrostatic pressure is the pressure produced by a fluid against a surface. If you have a fluid on both sides of a barrier, both fluids exert a pressure in opposing directions. Net fluid movement will be in the direction of the lower pressure. Osmosis is the movement of solvent (water) across a membrane that is impermeable to a solute in the solution. This creates a pressure, osmotic pressure, which will exist until the solute concentration is the same on both sides of a semipermeable membrane. As long as the concentration differs, water will move. Glomerular filtration occurs when glomerular hydrostatic pressure exceeds the luminal hydrostatic pressure of Bowman’s capsule. There is also an opposing force, the osmotic pressure, which is typically higher in the glomerular capillary.

To understand why this is so, look more closely at the microenvironment on either side of the filtration membrane. You will find osmotic pressure exerted by the solutes inside the lumen of the capillary as well as inside of Bowman’s capsule. Since the filtration membrane limits the size of particles crossing the membrane, the osmotic pressure inside the glomerular capillary is higher than the osmotic pressure in Bowman’s capsule. Recall that cells and the medium-to-large proteins cannot pass between the podocyte processes or through the fenestrations of the capillary endothelial cells. This means that red and white blood cells, platelets, albumins, and other proteins too large to pass through the filter remain in the capillary, creating an average colloid osmotic pressure of 30 mm Hg within the capillary. The absence of proteins in Bowman’s space (the lumen within Bowman’s capsule) results in an osmotic pressure near zero. Thus, the only pressure moving fluid across the capillary wall into the lumen of Bowman’s space is hydrostatic pressure. Hydrostatic (fluid) pressure is sufficient to push water through the membrane despite the osmotic pressure working against it. The sum of all of the influences, both osmotic and hydrostatic, results in a net filtration pressure (NFP) of about 10 mm Hg.

A proper concentration of solutes in the blood is important in maintaining osmotic pressure both in the glomerulus and systemically. There are disorders in which too much protein passes through the filtration slits into the kidney filtrate. This excess protein in the filtrate leads to a deficiency of circulating plasma proteins. In turn, the presence of protein in the urine increases its osmolarity; this holds more water in the filtrate and results in an increase in urine volume. Because there is less circulating protein, principally albumin, the osmotic pressure of the blood falls. Less osmotic pressure pulling water into the capillaries tips the balance towards hydrostatic pressure, which tends to push it out of the capillaries. The net effect is that water is lost from the circulation to interstitial tissues and cells. This “plumps up” the tissues and cells, a condition termed systemic edema.

Net Filtration Pressure (NFP)

NFP determines filtration rates through the kidney. It is determined as follows:

NFP = Glomerular blood hydrostatic pressure (GBHP) – [capsular hydrostatic pressure (CHP) + blood colloid osmotic pressure (BCOP)] = 10 mm Hg

That is:

NFP = GBHP – [CHP + BCOP] = 10 mm Hg

Or:

NFP = 55 – [15 + 30] = 10 mm Hg

As you can see, there is a low net pressure across the filtration membrane. Intuitively, you should realize that minor changes in osmolarity of the blood or changes in capillary blood pressure result in major changes in the amount of filtrate formed at any given point in time. The kidney is able to cope with a wide range of blood pressures. In large part, this is due to the autoregulatory nature of smooth muscle. When you stretch it, it contracts. Thus, when blood pressure goes up, smooth muscle in the afferent capillaries contracts to limit any increase in blood flow and filtration rate. When blood pressure drops, the same capillaries relax to maintain blood flow and filtration rate. The net result is a relatively steady flow of blood into the glomerulus and a relatively steady filtration rate in spite of significant systemic blood pressure changes. Mean arterial blood pressure is calculated by adding 1/3 of the difference between the systolic and diastolic pressures to the diastolic pressure. Therefore, if the blood pressure is 110/80, the difference between systolic and diastolic pressure is 30. One third of this is 10, and when you add this to the diastolic pressure of 80, you arrive at a calculated mean arterial pressure of 90 mm Hg. Therefore, if you use mean arterial pressure for the GBHP in the formula for calculating NFP, you can determine that as long as mean arterial pressure is above approximately 60 mm Hg, the pressure will be adequate to maintain glomerular filtration. Blood pressures below this level will impair renal function and cause systemic disorders that are severe enough to threaten survival. This condition is called shock.

Determination of the GFR is one of the tools used to assess the kidney’s excretory function. This is more than just an academic exercise. Since many drugs are excreted in the urine, a decline in renal function can lead to toxic accumulations. Additionally, administration of appropriate drug dosages for those drugs primarily excreted by the kidney requires an accurate assessment of GFR. GFR can be estimated closely by intravenous administration of inulin. Inulin is a plant polysaccharide that is neither reabsorbed nor secreted by the kidney. Its appearance in the urine is directly proportional to the rate at which it is filtered by the renal corpuscle. However, since measuring inulin clearance is cumbersome in the clinical setting, most often, the GFR is estimated by measuring naturally occurring creatinine, a protein-derived molecule produced by muscle metabolism that is not reabsorbed and only slightly secreted by the nephron.

Chapter Review

The entire volume of the blood is filtered through the kidneys about 300 times per day, and 99 percent of the water filtered is recovered. The GFR is influenced by hydrostatic pressure and colloid osmotic pressure. Under normal circumstances, hydrostatic pressure is significantly greater and filtration occurs. The hydrostatic pressure of the glomerulus depends on systemic blood pressure, autoregulatory mechanisms, sympathetic nervous activity, and paracrine hormones. The kidney can function normally under a wide range of blood pressures due to the autoregulatory nature of smooth muscle.

Overview

The entire volume of the blood is filtered through the kidneys about 300 times per day, and 99 percent of the water filtered is recovered. The GFR is influenced by hydrostatic pressure and colloid osmotic pressure. Under normal circumstances, hydrostatic pressure is significantly greater and filtration occurs. The hydrostatic pressure of the glomerulus depends on systemic blood pressure, autoregulatory mechanisms, sympathetic nervous activity, and paracrine hormones. The kidney can function normally under a wide range of blood pressures due to the autoregulatory nature of smooth muscle.

Rather than start with urine formation, this section will start with urine excretion. Urine is a fluid of variable composition that requires specialized structures to remove it from the body safely and efficiently. Blood is filtered, and the filtrate is transformed into urine at a relatively constant rate throughout the day. This processed liquid is stored until a convenient time for excretion. All structures involved in the transport and storage of the urine are large enough to be visible to the naked eye. This transport and storage system not only stores the waste, but it protects the tissues from damage due to the wide range of pH and osmolarity of the urine, prevents infection by foreign organisms, and for the male, provides reproductive functions.

Urethra

The urethra transports urine from the bladder to the outside of the body for disposal. The urethra is the only urologic organ that shows any significant anatomic difference between males and females; all other urine transport structures are identical (Figure 25.3).

Figure 25.3 Female and Male Urethras The urethra transports urine from the bladder to the outside of the body. This image shows (a) a female urethra and (b) a male urethra.

The urethra in both males and females begins inferior and central to the two ureteral openings forming the three points of a triangular-shaped area at the base of the bladder called the trigone (Greek tri- = “triangle” and the root of the word “trigonometry”). The urethra tracks posterior and inferior to the pubic symphysis (see Figure 25.3a). In both males and females, the proximal urethra is lined by transitional epithelium, whereas the terminal portion is a nonkeratinized, stratified squamous epithelium. In the male, pseudostratified columnar epithelium lines the urethra between these two cell types. Voiding is regulated by an involuntary autonomic nervous system-controlled internal urinary sphincter, consisting of smooth muscle and voluntary skeletal muscle that forms the external urinary sphincter below it.

Female Urethra

The external urethral orifice is embedded in the anterior vaginal wall inferior to the clitoris, superior to the vaginal opening (introitus), and medial to the labia minora. Its short length, about 4 cm, is less of a barrier to fecal bacteria than the longer male urethra and the best explanation for the greater incidence of UTI in women. Voluntary control of the external urethral sphincter is a function of the pudendal nerve. It arises in the sacral region of the spinal cord, traveling via the S2–S4 nerves of the sacral plexus.

Male Urethra

The male urethra passes through the prostate gland immediately inferior to the bladder before passing below the pubic symphysis (see Figure 25.3b). The length of the male urethra varies between men but averages 20 cm in length. It is divided into four regions: the preprostatic urethra, the prostatic urethra, the membranous urethra, and the spongy or penile urethra. The preprostatic urethra is very short and incorporated into the bladder wall. The prostatic urethra passes through the prostate gland. During sexual intercourse, it receives sperm via the ejaculatory ducts and secretions from the seminal vesicles. Paired Cowper’s glands (bulbourethral glands) produce and secrete mucus into the urethra to buffer urethral pH during sexual stimulation. The mucus neutralizes the usually acidic environment and lubricates the urethra, decreasing the resistance to ejaculation. The membranous urethra passes through the deep muscles of the perineum, where it is invested by the overlying urethral sphincters. The spongy urethra exits at the tip (external urethral orifice) of the penis after passing through the corpus spongiosum. Mucous glands are found along much of the length of the urethra and protect the urethra from extremes of urine pH. Innervation is the same in both males and females.

Bladder

The urinary bladder collects urine from both ureters (Figure 25.4). The bladder lies anterior to the uterus in females, posterior to the pubic bone and anterior to the rectum. During late pregnancy, its capacity is reduced due to compression by the enlarging uterus, resulting in increased frequency of urination. In males, the anatomy is similar, minus the uterus, and with the addition of the prostate inferior to the bladder. The bladder is a retroperitoneal organ whose "dome" distends superiorly when the bladder is filling with urine.

Figure 25.4 Bladder (a) Anterior cross section of the bladder. (b) The detrusor muscle of the bladder (source: monkey tissue) LM × 448. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)

The bladder is a highly distensible organ comprised of irregular crisscrossing bands of smooth muscle collectively called the detrusor muscle. The interior surface is made of transitional cellular epithelium that is structurally suited for the large volume fluctuations of the bladder. When empty, it resembles columnar epithelia, but when stretched, it “transitions” (hence the name) to a squamous appearance (see Figure 25.4). Volumes in adults can range from nearly zero to 500–600 mL.

The detrusor muscle contracts with significant force in the young. The bladder’s strength diminishes with age, but voluntary contractions of abdominal skeletal muscles can increase intra-abdominal pressure to promote more forceful bladder emptying. Such voluntary contraction is also used in forceful defecation and childbirth.

Micturition Reflex

Micturition is a less-often used, but proper term for urination or voiding. It results from an interplay of involuntary and voluntary actions by the internal and external urethral sphincters. When bladder volume reaches about 150 mL, an urge to void is sensed but is easily overridden. Voluntary control of urination relies on consciously preventing relaxation of the external urethral sphincter to maintain urinary continence. As the bladder fills, subsequent urges become harder to ignore. Ultimately, voluntary constraint fails with resulting incontinence, which will occur as bladder volume approaches 300 to 400 mL.

Normal micturition is a result of stretch receptors in the bladder wall that transmit nerve impulses to the sacral region of the spinal cord to generate a spinal reflex. The resulting parasympathetic neural outflow causes contraction of the detrusor muscle and relaxation of the involuntary internal urethral sphincter. At the same time, the spinal cord inhibits somatic motor neurons, resulting in the relaxation of the skeletal muscle of the external urethral sphincter. The micturition reflex is active in infants but with maturity, children learn to override the reflex by asserting external sphincter control, thereby delaying voiding (potty training). This reflex may be preserved even in the face of spinal cord injury that results in paraplegia or quadriplegia. However, relaxation of the external sphincter may not be possible in all cases, and therefore, periodic catheterization may be necessary for bladder emptying.

Nerves involved in the control of urination include the hypogastric, pelvic, and pudendal (Figure 25.5). Voluntary micturition requires an intact spinal cord and functional pudendal nerve arising from the sacral micturition center. Since the external urinary sphincter is voluntary skeletal muscle, actions by cholinergic neurons maintain contraction (and thereby continence) during filling of the bladder. At the same time, sympathetic nervous activity via the hypogastric nerves suppresses contraction of the detrusor muscle. With further bladder stretch, afferent signals traveling over sacral pelvic nerves activate parasympathetic neurons. This activates efferent neurons to release acetylcholine at the neuromuscular junctions, producing detrusor contraction and bladder emptying.

Figure 25.5 Nerves Innervating the Urinary System

Ureters

The kidneys and ureters are completely retroperitoneal, and the bladder has a peritoneal covering only over the dome. As urine is formed, it drains into the calyces of the kidney, which merge to form the funnel-shaped renal pelvis in the hilum of each kidney. The renal pelvis narrows to become the ureter of each kidney. As urine passes through the ureter, it does not passively drain into the bladder but rather is propelled by waves of peristalsis. As the ureters enter the pelvis, they sweep laterally, hugging the pelvic walls. As they approach the bladder, they turn medially and pierce the bladder wall obliquely. This is important because it creates an one-way valve (a physiological sphincter rather than an anatomical sphincter) that allows urine into the bladder but prevents reflux of urine from the bladder back into the ureter. Children born lacking this oblique course of the ureter through the bladder wall are susceptible to “vesicoureteral reflux,” which dramatically increases their risk of serious UTI. Pregnancy also increases the likelihood of reflux and UTI.

The ureters are approximately 30 cm long. The inner mucosa is lined with transitional epithelium (Figure 25.6) and scattered goblet cells that secrete protective mucus. The muscular layer of the ureter consists of longitudinal and circular smooth muscles that create the peristaltic contractions to move the urine into the bladder without the aid of gravity. Finally, a loose adventitial layer composed of collagen and fat anchors the ureters between the parietal peritoneum and the posterior abdominal wall.

Figure 25.6 Ureter Peristaltic contractions help to move urine through the lumen with contributions from fluid pressure and gravity. LM × 128. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)

At a Glance

• Researchers discovered a gene that may be responsible for the powerful urge to urinate that we normally feel many times throughout the day.
• These findings expand the growing list of newly discovered senses under the gene’s control.

But how your body senses a full bladder isn’t known. Certain proteins can be activated by cells being stretched or squeezed. One gene, called PIEZO2, holds the instructions to make such proteins. PIEZO2 has been shown to play a role in sensing mechanical stimulation, including touch, vibration, pain, and proprioception (the awareness of one’s body in space).

To investigate whether PIEZO2 also helps the body sense a full bladder, a research team led by Dr. Ardem Patapoutian at the Scripps Research Institute, Dr. Alex Chesler at NIH’s National Center for Complementary and Integrative Health (NCCIH), and Dr. Carsten Bönnemann at NIH’s National Institute of Neurological Disorders and Stroke (NINDS) studied how mutations in PIEZO2 affect people and mice. Results were published on October 14, 2020 in Nature.

The researchers examined 12 patients at the NIH Clinical Center, ages 5 to 43 years, who were born with inactivating mutations in their PIEZO2 genes. The team reviewed medical records, performed ultrasound scans, administered questionnaires, and conducted detailed interviews with the patients and their families.

Most patients reported problems with urination. Nearly all could go an entire day without feeling the urge to urinate. Most urinated less than the normal five to six times per day. Seven said they found it difficult to urinate. They either had to wait for it to happen or needed to press their lower abdomen for it to start.

The researchers also studied PIEZO2 in the cells involved in bladder control in mice: dorsal root ganglion (DRG) neurons, which send nerve signals from the mouse bladder to the brain, and “umbrella” cells that line the inside of the bladder.

Genetically removing PIEZO2 from either the neurons or the umbrella cells reduced the cells’ response to the bladder filling. It also caused the mice to have urination problems. Mice with the genetically altered cells required more fluid and greater pressure in the bladder to trigger urination. This phenomenon was similar to the patient reports. Mice with the mutated gene also had thicker bladder muscles than the controls, suggesting that the loss of sensation altered the bladder over time.

“Our results show how the PIEZO2 gene tightly coordinates urination,” Chesler says. “This is a major advance in our understanding of interoception—or the sense of what’s going inside our bodies.”

“Urination is essential for our health. It’s one of the primary ways our bodies dispose of waste,” Patapoutian adds. “We hope that these results provide a more detailed understanding of how urination works under healthy and disease conditions.”

Ever wonder why urine is yellow or why skin looks yellow in people with jaundice? Scientists have known for more than a century that urobilin is the chemical responsible for that yellow color. But the enzyme responsible for making urobilin was a mystery…until recently. Researchers at the National Library of Medicine (NLM) found the answer in an unexpected place: the gut microbiome. Their findings can help us better understand certain health conditions, how our bodies work, and why some babies get jaundice.

Why does urine look yellow?

When your body replaces old red blood cells, it creates bilirubin. This substance then moves to your gut, where it either gets absorbed back into the bloodstream or is broken down into a chemical called urobilinogen. Your kidneys then turn urobilinogen into urobilin—this makes your urine yellow.

While researchers knew about this process, one piece of the puzzle was still missing: What causes bilirubin to break down into urobilinogen? But researchers at NLM and the University of Maryland Hall Lab recently found the missing puzzle piece—a key enzyme called bilirubin reductase.

How did researchers discover this?

Their first step was to find a group of bacteria that could reduce bilirubin. Many gut bacteria need low-oxygen environments to survive. This is hard to do in a lab setting, so the scientists also used computer experiments to look at the genomes of multiple bacteria at a time. A genome is the entire set of DNA instructions found in a cell. is the entire set of DNA instructions found in a cell.

Then from the bacterial genomes, researchers waded through all that bacterial data to find the gene that encoded the enzyme that breaks down bilirubin.

"We were able to confirm their functions and then look at bigger picture trends, like the relationship of that gene to different kinds of diseases," said Keith Dufault-Thompson, Ph.D., a staff scientist in NLM's Division of Intramural Research (DIR).

Why does this research matter?

Most of the time, our bodies break down bilirubin every day without any issues. But when something goes wrong, bilirubin can build up in the blood. This can lead to health problems such as jaundice, in which your skin and the whites of your eyes turn yellow. Jaundice is common in infants and people with liver disease. It can lead to pain, fevers, hearing loss, and even brain damage in severe cases.

Researchers wanted to see how the bilirubin reductase enzyme affects our health. After their discovery, they analyzed data from past studies on the gut microbiome (the ecosystem of bacteria and other microbes that live in the intestines). They took genetic samples from the microbiomes of healthy adults, young infants, and patients with inflammatory bowel disease (IBD) and searched for the gene that produces bilirubin reductase. Xiaofang Jiang, Ph.D., a principal investigator in the NLM DIR, and her team found that about 70% of infants don’t have the bacterial gene key to producing bilirubin reductase in their first month of life. This may explain why jaundice affects many newborns—their gut microbiomes aren’t as developed. The study also showed that more than 30% of adults with IBD don’t have the bacterial gene present, either.

This new research may lead to better outcomes for infants and other people with these conditions. It can also teach us more about the gut microbiome’s role in overall human health.

What’s next for this research?

Since the bilirubin reductase discovery, the research team went back to look at previous data on gut microbiomes. They want to understand how the enzyme evolved in the gut environment.

Dr. Dufault-Thompson said this work could help us understand bilirubin-reducing bacteria and pave the way for new treatments. Thanks to this study, the team can better understand what kind of functions gut bacteria can do and how they affect our bodies. These include how microbes metabolize (break down) artificial sweeteners and different types of hormones.

“These projects have helped us broaden our understanding of the impact of microbes on human health and demonstrate the wide range of functions that our microbiomes carry out,” he said.

*This article was adapted from the NLM Director’s Musings from the Mezzanine blog. Read the original article to learn more about this study and the researchers behind it.

The urinary tract is your body’s drainage system for removing urine. Urine is composed of wastes and water. The urinary tract includes your kidneys, ureters, and bladder. To urinate normally, the urinary tract needs to work together in the correct order.

Urologic diseases or conditions include urinary tract infections, kidney stones, bladder control problems, and prostate problems, among others. Some urologic conditions last only a short time, while others are long-lasting.