Urinary Tract – Kidneys, Bladder, and Function of the Urinary System

Urine is produced by the kidneys and serves primarily to remove toxins and other harmful particles from the body. In addition, the kidneys regulate the body’s water balance through urine, which is important for many bodily functions.

The urinary tract, which originates in the kidneys, transports urine, temporarily stores it, and ultimately excretes it in a controlled manner.

The location of the kidneys and urinary tract in the human body © Sebastian Kaulitzki / Fotolia

The kidneys are located above the waist, on either side of the spine. They are bean-shaped and have a hollow interior. Inside this cavity are the renal pelvises, which are funnel-shaped and collect urine.

The renal pelvises are connected to the ureters, which in turn lead to the bladder. The kidneys continuously release urine through the ureters. The bladder stores it and ensures that the urine can be voluntarily expelled later. It is very elastic, and sphincter muscles prevent urine from leaking out.

Urine is ultimately expelled through the urethra, which leads from the bladder to the outside of the body. Its structure differs significantly between men and women:

• In women, the urethra is only three to five centimeters long and runs from the bladder directly to the vestibule of the vagina. It ends in a small opening between the clitoris and the vaginal opening.
• The urethra in men is significantly longer (20 to 25 centimeters). It runs through the penis to the glans and, in addition to urine discharge, fulfills other functions: The ducts that carry semen open into the urethra, so it also serves as a semen duct. However, these two functions occur only at different times: Urine and semen cannot be expelled simultaneously. Unlike the female urethra, the male urethra has several bends and narrowings.

The entire urinary tract is lined with a special type of tissue called the urothelium. The individual cells of the urothelium overlap like scales, allowing it to stretch and contract significantly.

Among the most common urinary tract disorders are urinary tract infections (also known as cystitis). Since women have a much shorter urethra, they are affected by urinary tract infections much more frequently than men.

These are caused by bacteria, fungi, viruses, or other pathogens. Infections caused by the body’s own intestinal bacteria are very common.

Symptoms of a urinary tract infection include pain and a burning sensation when urinating, frequent urge to urinate, and lower abdominal pain. The urine may be cloudy or discolored.

A bladder infection must be treated early to prevent complications. A particularly dangerous complication is pyelonephritis, which can cause severe symptoms and become chronic.

Urinary Stones

Under certain circumstances, crystals can form from components of the urine and coalesce into urinary stones. These can grow to be several centimeters in size and are found in the kidneys, ureter, bladder, or urethra. People often do not even notice smaller stones and simply pass them in their urine.

Larger stones, when they start to move, can cause excruciating pain (colic), lead to inflammation, or block or damage the urinary tract. In such cases, the stones are usually removed during a minor surgical procedure.

Urinary Incontinence—A Problem Primarily for Women

The sphincter muscles of the bladder and urethra are significantly weaker in women than in men. Furthermore, pregnancies, childbirth, and hormonal changes during menopause can place significant strain on the pelvic floor. This can lead to urinary incontinence, which means that urine is released involuntarily.

These symptoms can often be improved with special pelvic floor strengthening exercises.

Urinary Retention – A Dangerous Emergency

When it is not possible to empty the bladder, this is referred to as urinary retention.

There are many reasons for this: The urinary tract can be obstructed by a lodged kidney stone, a foreign object in the urethra, an enlarged prostate, injuries, or tumors. Congenital abnormalities of the urinary tract can also sometimes lead to urinary retention. Certain medications or surgical procedures can contribute to urinary retention. In some cases of neurological and psychological problems, the bladder also cannot be emptied spontaneously.

Urinary retention can cause severe pain or may be almost symptom-free. If the bladder remains excessively full for an extended period, the sphincter muscle eventually gives way, resulting in an overflow bladder with involuntary urine leakage. This can cause permanent damage to the sphincter, leading to urinary incontinence. It can also result in kidney damage.

Therefore, prompt treatment is necessary in cases of urinary retention. A catheter is then used to drain the urine, thereby relieving pressure on the bladder.

Other Urinary Tract Disorders

In addition to those already mentioned, other urinary tract disorders can occur:

• Especially in male newborns, urinary tract malformations are occasionally observed, such as an abnormal course of the urethra or the presence of two urethras.
• Tumors can develop in the bladder or urethra, just as they can in most other organs.

Which organs are part of the urinary tract?

The urinary tract includes the excretory urinary tract, consisting of the ureter, bladder, and urethra. Together with the kidneys, they form the urinary system. These anatomical structures are responsible for the formation, storage, and excretion of urine.

What is the function of the kidney?

The kidney is a vital organ that filters the blood in the blood vessels. This process produces waste products that are excreted in the urine. Inside the kidney are the medulla and the cortex, which are responsible for urine formation.

How does urine reach the bladder?

Urine from the kidneys first collects in the renal pelvis, also known as the pelvis renalis. The urine then travels through the two ureters to the bladder. This connection between the kidneys and the bladder is an important part of the urinary tract.

What is the function of the bladder?

The bladder, medically known as the vesica urinaria, is a muscular hollow organ located in the pelvis. It stores urine and ensures its controlled emptying. During emptying, the muscles of the bladder wall contract, and the urine is expelled through the urethra.

What conditions affect the urinary tract?

Among the most common conditions are urinary tract infections, such as cystitis or pyelonephritis. Urinary tract infections are particularly common in women. Other problems may include urinary incontinence or congenital abnormalities such as ureter duplex or ureterectopia.