Learn about the bodys urinary system

The urinary system includes the kidneys, ureters, bladder, and urethra. The function of the urinary system is to remove waste from the body, regulate blood volume and blood pressure, control the amount of electrolytes and metabolites, and regulate blood pH. The urinary tract is the body's drainage system for the final elimination of urine. The male and female urinary systems are very similar, differing only in the length of the urethra.


1. Structure of the urinary system

The urinary system refers to the structures that produce and transport urine to the point of excretion.

1.1. Kidney

Urine is formed in the kidneys through the process of filtering the blood. Urine is then carried through the ureters to the bladder, where it is stored. During urination, urine is passed from the bladder through the urethra to the outside of the body. About 800 – 2,000 ml of urine is normally produced per day in a healthy person. This amount of urine varies with fluid intake and kidney function.

In the urinary system, there are two kidneys located in the abdomen, behind the peritoneum, on the left and right sides. Urine formation begins in the functional unit of the kidney, called the nephron. Urine then flows through the nephrons, through a system of converging tubes known as collecting ducts. From here, urine continues to flow from the renal pelvis into the ureters, transporting urine into the bladder and storing it there.

See also:  Adrenal gland: Structure and function .

1.2. Bladder

The bladder is a hollow, ball-shaped organ located in the pelvis. It is suspended in place by ligaments attached to other organs and the pelvis. They store urine until the brain signals the bladder that the person is ready to empty it. A normal, healthy bladder can hold up to nearly half a liter of urine comfortably in two to five hours. To prevent urine leakage, the sphincter muscles close tightly around the opening of the bladder into the urethra.

See also:  Bladder exposure and things to know .

1.3. Urethra

  • In men, the urethra begins at the inner urethral orifice of the bladder, continues through the external urethral orifice, and then becomes the prostatic urethra, the membranous urethra, and the spongy urethra. The female urethra is much shorter, starting at the bladder neck and ending at the vaginal vestibule.
  • In females, the urethra is about 3.8 to 5.1 cm long and lies between the clitoris and the vagina. In men, it is about 20 cm long, runs the length of the penis and opens at the end of the penis - the flute. The male urethra is used to remove urine as well as semen during ejaculation.

Learn about the body's urinary system

Structure of the urinary system in the human body.

2. Functions

The main functions of the urinary system and its components are:

  • Regulates blood volume and blood composition (eg, sodium, potassium, and calcium).
  • Regulate blood pressure.
  • Blood pH homeostasis.
  • The kidneys contribute to the production of red blood cells.
  • Helps synthesize calcitriol (active form of Vitamin D).
  • Stores body wastes (mainly urea and uric acid) and other products and removes them from the body.

2.1. Formation of urine

The average urine output in an adult is about 1-2 liters per day, depending on hydration status, activity level, environmental factors, weight and health of the individual. Producing too much or too little urine requires examination for physical diseases. Polyuria is excessive urine production (>2.5 L/day). Oliguria when < 400="" ml="" water="" urine="" is="" produced="" and="" in="" urine="" when=""> <100 ml="" water="" urine="" per="">

The first step in urine formation is the filtration of blood by the kidneys. In a healthy person, the kidneys receive 12 to 30% of cardiac output, averaging about 20% or 1.25 L/min.

The basic structural and functional unit of the kidney is the nephron. Its main function is to regulate the concentration of water and solutes such as sodium by filtering the blood, reabsorbing the necessary substances and excreting the rest as urine.

In the first part of the nephron, the Bowman filter filters blood from the circulatory system into the tubules. The difference in hydrostatic and osmotic pressure facilitates transmembrane filtration to occur. The filtrate consists of water, small molecules and ions that easily pass through the membrane. However, larger molecules such as proteins and blood cells are prevented from passing through the membrane. The amount of filtrate produced per minute is called glomerular filtration rate or GFR and is up to 180 liters per day. About 99% of this filtrate is reabsorbed as it passes through the nephron and the remaining 1% becomes urine.

Learn about the body's urinary system

Urine production.

The urinary system is regulated by the endocrine system by hormones such as antidiuretic hormone, aldosterone, and parathyroid hormone.

2.2. Regulate blood volume

The urinary system is influenced by the circulatory system, the nervous system, and the endocrine system.

Aldosterone plays a central role in the regulation of blood pressure through its effects on the kidneys. It acts on the distal tubules and increases the reabsorption of sodium from the glomerular filtrate. Sodium reabsorption leads to water retention, which increases blood pressure and blood volume. Antidiuretic hormone (ADH), is a neurophysiological hormone found in most mammals. Its two main functions are water retention in the body and vasoconstriction. Vasopressin regulates the body's water retention by increasing water reabsorption in the tubules of the kidney.

2.3. The process of urinating

Urination is the pushing of urine from the bladder through the urethra to the outside of the body. In healthy humans and many other animals, urination is under voluntary control. In infants, some elderly people, and people with nerve injuries, urination may occur as an involuntary reflex.

See also:  The truth about your urine .

3. Diseases of the urinary system

Urinary tract disease may be related to congenital or acquired dysfunction of the urinary system. For example, a urinary tract obstruction is a urinary disease that can cause urinary retention.

Diseases of the kidney tissue are usually treated by nephrologists, while diseases of the urinary tract are treated by urologists. Gynecologists can also treat women's urinary incontinence.

3.1. Kidney stones

Calcium oxalate blocks can be found anywhere in the urinary tract. Kidney stones form when chemicals in the urine are concentrated enough to form a solid mass. They can cause pain in the back and sides. Kidney stones can be treated with minimally invasive measures, such as transurethral lithotripsy. This method dissolves kidney stones using high-frequency waves.

See more articles: Are you bewildered because of kidney stones?

Learn about the body's urinary system

Illustration of pathology of kidney stones.

3.2. CKD

Is a temporary (usually acute) condition or can become a chronic condition where the kidneys are unable to filter waste from the blood. Medical conditions, such as diabetes and high blood pressure, can cause chronic kidney disease. Acute cases can be caused by trauma or other damage, and may improve over time with treatment. Kidney diseases can lead to chronic kidney failure, which may require dialysis or even a kidney transplant

3.3. Urinary tract infections

This condition occurs when bacteria enter the urinary tract. They can affect the urethra, bladder, or even the kidneys. Most UTIs involve only the urethra and bladder, in the lower urinary tract. However, UTIs can involve the ureters and kidneys, in the upper urinary tract. Although upper urinary tract infections are rarer than lower urinary tract infections, they are often made worse by infection.

While urinary tract infections are more common in women, they can also occur in men. Most UTIs are caused by bacteria, but some are caused by fungi and, in rare cases, viruses. Urinary tract infections are one of the most common infections in humans.

What are the symptoms of a UTI?

Symptoms of a UTI depend on which part of the urinary tract is infected.

  • Symptoms of a lower urinary tract infection include:
    • Burning when urinating.
    • Increased frequency of urinating without a lot of urine.
    • Urgent urination.
    • Bloody urine.
    • Cloudy urine.
    • There is blood in the urine.
    • Urine has a strong odor.
    • Pelvic pain in women.
    • Rectal pain in men.

Learn about the body's urinary system

Illustration of a urinary tract infection.

  • Upper urinary tract infections affect the kidneys and ureters. These can be potentially life-threatening if bacteria move from the infected kidney into the bloodstream. Symptoms of an upper urinary tract infection include:
    • Pain in the back and sides.
    • Chills.
    • Fever.
    • Nausea and vomiting .
    • Treatment of urinary tract infections.

Treatment for a UTI depends on the cause. Your doctor will be able to determine which organism is causing the infection from the results of urine and blood tests.

In most cases, the cause is bacteria. Bacterial UTIs are treated with antibiotics.

3.4. Diabetes

It can also have a direct effect on urination due to peripheral neuropathy, which occurs in some people with poorly controlled blood sugar.

See also:  Top 8 foods for diabetics that you need to know .

3.5. Urinary incontinence

This condition can be the result of weakening of the pelvic floor muscles caused by factors such as pregnancy, childbirth, aging, and being overweight. Pelvic floor exercises can help with this condition by strengthening the pelvic floor. There may also be underlying reasons for urinary incontinence. In children, this condition is called bedwetting.

3.6. Cancer

Some cancers also target the urinary system, including bladder cancer, kidney cancer, ureteral cancer, and urethral cancer. Because of the role and location of these organs, treatment is often complex.

The above article hopes to have provided some useful knowledge to help you understand the urinary system of the human body. Stay tuned for the next health articles from SignsSymptomsList!

Doctor Hoang Thi Viet Trinh

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