Anatomy of the Urinary System

How do the kidneys and urinary system work?

The body takes nutrients from food and converts them to energy. After the body has taken the food components that it needs, waste products are left behind in the bowel and in the blood.

Illustration of the anatomy of the urinary system, front view

The kidney and urinary systems help the body to eliminate liquid waste called urea, and to keep chemicals, such as potassium and sodium, and water in balance. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys, where it is removed along with water and other wastes in the form of urine.

READ:   Polycystic Kidney disease

Other important functions of the kidneys include blood pressure regulation and the production of erythropoietin, which controls red blood cell production in the bone marrow. Kidneys also regulate the acid-base balance and conserve fluids.

Illustration of the anatomy of the kidney

Kidney and urinary system parts and their functions

  • Two kidneys. This pair of purplish-brown organs is located below the ribs toward the middle of the back. Their function is to remove liquid waste from the blood in the form of urine; keep a stable balance of salts and other substances in the blood; and produce erythropoietin, a hormone that aids the formation of red blood cells. The kidneys remove urea from the blood through tiny filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.
  • Two ureters. These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters.
  • Bladder. This triangle-shaped, hollow organ is located in the lower abdomen. It is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder’s walls relax and expand to store urine, and contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to two cups of urine for two to five hours.
  • Two sphincter muscles. These circular muscles help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder.
  • Nerves in the bladder. The nerves alert a person when it is time to urinate, or empty the bladder.
  • Urethra. This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals occur in the correct order, normal urination occurs.
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Facts about urine

  • Adults pass about a quart and a half of urine each day, depending on the fluids and foods consumed.
  • The volume of urine formed at night is about half that formed in the daytime.
  • Normal urine is sterile. It contains fluids, salts and waste products, but it is free of bacteria, viruses and fungi.
  • The tissues of the bladder are isolated from urine and toxic substances by a coating that discourages bacteria from attaching and growing on the bladder wall.
End-stage renal disease ICD-9: 585.6 Description End-stage renal disease (ESRD), usually the result of chronic renal failure, is the gradual, progressive deterioration of kidney function to the point that the kidneys cannot sustain their necessary dayto-day life activity. As the kidney tissue is progressively destroyed, the kidney loses its ability to excrete the nitrogenous end products of metabolism, such as urea and creatinine, which accumulate in the blood and eventually reach toxic levels. As kidney function diminishes, every organ in the body is affected, and dialysis or kidney transplantation is eventually needed for survival. Etiology Causes of ESRD include diabetes mellitus (leading cause), hypertension, chronic glomerulonephritis, pyelonephritis, obstruction of the urinary tract, congenital anomalies such as polycystic kidneys, vascular disorders, infections, medications, and toxic agents. Signs and Symptoms The early signs and symptoms are oliguria and azotemia, or the presence of n...
Acute Tubular Necrosis ICD-9: 584.5 Description Acute tubular necrosis is the rapid destruction or degeneration of the tubular segments of nephrons in the kidneys. The disease is characterized by a sudden deterioration in renal function, with resulting accumulation of nitrogenous wastes in the body. Impaired or interrupted renal function from acute tubular necrosis is considered reversible. Etiology The majority of cases of acute tubular necrosis are due to renal ischemia, or the interruption or impairment of blood flow in and out of the kidneys. This disease is the most common cause of acute renal failure in critically ill persons. Although there can be numerous causes for such impairment, renal ischemia leading to acute tubular necrosis is most frequently produced by severe bodily trauma or as a complication following surgery. The renal tubules also can be damaged in other ways. Acute tubular necrosis may be toxin induced (as a result of exposure to solvents, heavy metals, or certain medication...
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...
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...
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...