33.3: Introduction to the Urinary System
By the end of this section, you should be able to:
- 33.3.1 Describe the structure and function of the urinary system.
- 33.3.2 Discuss common conditions that affect the urinary system.
Urethra
Newly formed urine exits the kidney pelvis, flows through the ureters (see Figure 33.4), and enters the bladder at the trigone on the posterior surface. The volume of urine in the bladder triggers the micturition response, and the urine exits the body through the urethra.
Common Conditions Affecting the Urinary System
A number of problems can affect the urinary system, including conditions that affect the ability to void properly and infections resulting from bacterial contamination of a normally sterile tract. This section will describe two common conditions, incontinence and urinary tract infection.
Incontinence
As noted in the previous section, micturition is a complex process that requires coordination between the central nervous system and the peripheral nervous system, adequate structure and function of the bladder and urethra, and cognitive control of the process. Urinary incontinence (UI) is defined as the involuntary loss of urine (Tran & Puckett, 2022). The condition is more common in female clients; however, male clients also experience incontinence with associated conditions of the urinary system.
There are multiple forms of UI, including:
- Urge incontinence: The client experiences a sudden strong urge to void and frequently does not have sufficient time to respond to the urge before urine leaks from the bladder. It is often the result of an overactive detrusor muscle. Risk factors include age, infection, and obstruction of the bladder outlet by an enlarged prostate gland. This form of UI is also common in clients with degenerative nerve diseases such as Parkinson disease, multiple sclerosis, or a history of stroke, due to CNS damage.
- Stress incontinence: This is caused by a sudden increase in intra-abdominal pressure as with sneezing, coughing, and bending, causing the urine to leak from the bladder. This form of UI may be due to loss of pelvic muscle support of the bladder and urethra. Risk factors include estrogen depletion, obesity, childbirth trauma, and cancer therapies. There is also evidence that damage to the spinal nerves due to diabetes may also contribute to the loss of support.
- Mixed incontinence: This presents with combined symptoms of urge and stress incontinence. This type of incontinence is prevalent in older female clients.
- Overflow incontinence: This type of UI results from obstruction of the urethra, which limits the amount of urine that is emptied with each void. This increases the residual volume of urine, which can lead to stasis of the urine and infection. This condition is most common in older adult male clients with benign prostatic hypertrophy.
- Functional incontinence: This form of incontinence results from a factor other than urinary system alterations. It often presents with other deficits such as immobility. The client has an intact urinary system but cannot respond quickly enough to avoid incontinence.
Diagnosis of the type of UI is made through review of the client’s voiding diary, review of the client’s history, and urodynamic studies. Treatment is aimed at eliminating the underlying cause, strengthening the pelvic floor structures, the use of drugs to modify detrusor activity, and surgery.
Clinical Tip
Assessing Incontinence
The voiding diary is one of the most important assessment tools for the diagnosis and treatment of all types of incontinence. The nurse provides the client with basic instructions and a template for recording liquid intake, urinary output, and any occurrences of incontinence. This information can be used by the health care providers to evaluate the client’s symptoms.
Urinary Tract Infection
A urinary tract infection (UTI) develops when bacteria enter the urinary system, causing an infection in any part of the urinary tract. As described earlier, pyelonephritis is a kidney infection. Cystitis is bladder inflammation usually caused by bacteria. Risk factors for urinary tract infections include increasing age, female sex, diabetes, obesity, congenital defects, neurogenic bladder, vesicoureteral reflux, and catheterization of the urinary tract. Careful monitoring of susceptible clients is required to prevent recurrent infections. The use of urinary catheters is a significant concern for hospitalized clients. The current recommendation is for short-term use only when necessary. Successful treatment depends on identifying the causative agent and ensuring that all prescribed anti-infectives are consumed.
Link to Learning
Urinary Stress Incontinence
This Picmonic online resource reviews the causes and treatments of urinary stress incontinence.
Urethra
The urethra transports urine from the base of the bladder to outside the body. The mucosal lining is composed of transitional epithelium, smooth muscle, and connective tissue. The urine exits the urethra at the external meatus. The internal urinary sphincter, consisting of smooth muscle, surrounds the urethra as it exits the bladder. Control of the internal sphincter is involuntary. The location of the external urinary sphincter is sex-specific and is discussed in the following sections. The two sphincters coordinate the flow of urine from the bladder.
Female Urethra
The female urethra is approximately 3–4 cm long, and the external urinary sphincter surrounds the urethra as it exits the pelvic diaphragm just behind the pubic bone. The urethra is then connected to the anterior vaginal wall, which is a critical requirement for urinary continence. The external urinary meatus is anterior to the vaginal orifice.
Male Urethra
The male urethra is approximately 20 cm in length and carries urine and semen. It consists of four areas. The first section, the preprostatic urethra, which is composed of transitional epithelium tissue, passes from the inferior surface of the bladder to the prostate gland. The second section, the prostatic urethra, is completely encircled by the prostate gland and is approximately 3–4 cm long. The third section, the membranous urethra, goes through the floor of the pelvis and the external urinary urethra and then enters the penis. The final section, the spongy urethra, extends to the tip of the penis, traveling through the corpus spongiosum. This segment of the urethra is approximately 15 cm long.