Urinary system anatomy and physiology review

The urinary system is responsible for the production and elimination of urine when a type of waste called urea is removed from the blood. Urea is produced when protein-containing foods are broken down in the body. Urea is carried in the bloodstream to the two kidneys, where urine is formed. The two ureters, the urinary bladder, and the urethra, are responsible for the elimination of urine. Figure illustrates the urinary system in relationship to the body, and Figure illustrates the interior and exterior features of the urinary system organs.

The urinary system

FIGURE. The urinary system

Frontal section of the right kidney showing internal structures and blood vessels

FIGURE. (A) Frontal section of the right kidney showing internal structures and blood vessels. (B) Magnified section of the kidney shows several nephrons. (From Scanlon, VC, and Sanders, T: Essentials of Anatomy and Physiology, ed 5. FA Davis, Philadelphia, 2007, p 422, with permission.)

The kidneys, each about the size of a fist, help to regulate the water, electrolyte (ionized salt), and acid-base content of the blood, and they selectively filter the waste products of metabolism.

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They also play an important role in regulating blood pressure. Each kidney contains more than 1 million nephrons, which are the principal filtering units of the kidney. Each nephron houses a ball of tiny blood capillaries called the glomerulus and a renal tubule. It is here that the three-part process of selective filtration of wastes, reabsorption of vital minerals and fluid, and secretion of waste products and other substances takes place. As urine is formed, it passes through the nephrons into the renal tubules of the kidneys.

Nephron with associated blood vessels

FIGURE. Nephron with associated blood vessels

From the kidneys, urine travels into the ureters, thin tubes about 8 to 10 inches in length, on its way to the urinary bladder. Small amounts of urine drip into the urinary bladder about every 12 seconds. The urinary bladder is a balloon-shaped muscular organ that stores urine until it is emptied. It can hold about 16 ounces of urine for 2 to 5 hours. Nerves in the urinary bladder indicate when it should be emptied. Sphincter muscles keep urine from leaking into the urethra too soon and relax when it is time to urinate.

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It is worth emphasizing the reabsorption process of the kidneys’ nephrons. Were it not for this process, the body would rapidly be depleted of its fluid. Typically, only 1% of the fluid passing through a nephron is excreted as urine.

A routine diagnostic test for suspected urinary disease is a urinalysis, which includes testing the specific gravity; pH; and presence of protein, blood, sugar, and ketones. It includes a microscopic examination for the presence of white blood cells (WBCs) and red blood cells (RBCs), casts, bacteria, and crystals. Normal urine is amber in color with a slightly acid reaction, has a peculiar odor, and frequently deposits a precipitate of phosphates when fresh. The specific gravity varies from 1.005 to 1.030. The greater the rate of urine excretion, the lower is the specific gravity. Refer to Table, Significance of Changes in Urine, throughout the chapter, noting possible abnormalities and their significance to the disease in question.

Table. Significance of Changes in Urine

Significance of Changes in Urine

Urinary System: Facts, Functions & Diseases The urinary system, also known as the renal system, produces, stores and eliminates urine, the fluid waste excreted by the kidneys. The kidneys make urine by filtering wastes and extra water from blood. Urine travels from the kidneys through two thin tubes called ureters and fills the bladder. When the bladder is full, a person urinates through the urethra to eliminate the waste. The urinary system is susceptible to a variety of infections and other problems, including blockages and injuries. These can be treated by a urologist or another health care professional who specializes in the renal system. Description of the urinary system The urinary system works with the lungs, skin and intestines to maintain the balance of chemicals and water in the body. Adults eliminate about 27 to 68 fluid ounces (800 to 2,000 milliliters) per day based on typical daily fluid intake of 68 ounces (2 liters), National Institutes of Health (NIH). Other factors in urinary system function include fluid ...
Can You Have Sex with a Urinary Tract Infection (UTI)? Can you have sex with a UTI? Urinary tract infections (UTIs) are common. UTIs can develop anywhere in the urinary tract, from the urethra to the kidneys. Symptoms include: a persistent urge to urinate pain when urinating pelvic pain or tenderness Although these symptoms can be irritating, they won’t prevent you from having vaginal sex. That doesn’t mean you’ll feel up to it, though. A UTI can irritate the sensitive tissue in your urinary tract, and sexual activity can irritate those tissues even more. Sexual activity can also increase your risk of complications and potentially put your partner at risk. That’s why doctors usually recommend that you wait to have sex until you’re symptom-free and you’ve finished your entire treatment. It may cause pain and exacerbate other symptoms A UTI may irritate and inflame the sensitive tissues in your urinary tract. Any penetrative object — fingers, a toy, or a penis — can put pressure on the urinary organs during vagi...
Bladder cancer ICD-9: 188.x* Description Tumors of the bladder arise from the epithelial cell membrane lining the bladder interior. These neoplasms are almost always malignant, and they metastasize readily. Bladder tumors are staged according to their depth of penetration. Transitional cell carcinoma is the most common type of bladder cancer in the United States. Etiology The cause of bladder tumors is unknown; however, cigarette smoking is thought to be the predominant cause. Predisposing factors may include exposure to certain types of industrial chemicals. Individuals with chronic cystitis also seem prone to develop bladder tumors. The disease affects men three times more frequently than women and generally occurs between ages 50 and 70. Bladder cancer is the fourth most common cancer in men. Signs and Symptoms Many persons are asymptomatic until advanced stages of the disease. For those presenting with symptoms, however, painless, gross hematuria is the most common indicator. Le...
Renal cell carcinoma or Kidney cancer ICD-9: 189.x Description Renal cell carcinoma (RCC), also known as renal cell adenocarcinoma, is by far the most common type of kidney cancer, accounting for 90% of kidney cancers. RCC usually grows as a single mass within the kidney but can be found in more than one part of the kidney or in both kidneys. It occurs most often in individuals over age 40. Etiology The cause is essentially unknown; however, risk factors include smoking, obesity, hypertension, long-term dialysis, and exposure to chemicals and irritants, such as asbestos or cadmium in the workplace. Signs and Symptoms Symptoms may include hematuria, flank or side pain that does not go away, a lump or mass palpated in the side or abdomen, weight loss, and fever. Some clients report feeling listless and not well. Diagnostic Procedures A complete physical examination may reveal an enlarged mass. BUN and creatinine levels are checked. A CT scan using contrast media is often used in diagnosis, as is the i...
Hydronephrosis ICD-9: 591 Description Hydronephrosis is the distention of the renal pelvis and calyces of a kidney due to pressure from accumulating urine. The pressure impairs, and may eventually interrupt, kidney function. One or both kidneys may be affected. Etiology Hydronephrosis is caused by a urinary tract obstruction. The ureters and renal pelvis dilate proximal to, or behind, the obstruction. This swelling causes the hydronephrosis with resultant destruction of functional tissue. In children, the obstruction is usually the result of some congenital defect in urinary tract structure. In adults, the obstruction is more often acquired, resulting from blockage by neoplasms or uroliths, commonly called kidney stones or renal calculi. Urinary tract obstruction in men may be produced by benign or malignant enlargement of the prostate. Women may experience urinary tract obstruction as a complication of pregnancy. Underlying disorders such as neurogenic bladder also may allow urine to acc...