Human urinary system: structure and functions of organs

Structural features

The urinary system consists of the following organs: kidneys, ureters, bladder, urethra or urethra. Accessory organs include: sphincters, adrenal glands, neurons and blood vessels. The paired structure of the system and the most important is the kidneys. They cleanse the body of processed products, performing filter tasks. At the same time, the kidneys participate in detoxification. The organs are located near the lower back, on either side of the spine.

If we look at the ureters, they can be compared to the tubes that connect the renal pelvis to the bladder. In the first element, urine accumulates. The length of the tube is 32 cm, and the thickness is 1.2 cm. The walls of the organ are lined with a muscular and mucous layer, and connective tissue. The bladder is a hollow organ. It is necessary for urine to accumulate.

If its volume exceeds 200 ml, the urge to urinate occurs. Since the walls of the organ are easily stretched, it can hold more than 0.4 liters. Structure of the urinary sac:

• neck;
• tops;
• bottom;
• body.

The end of the urinary tract is considered to be the urethra. It is presented in the form of a tube through which urine is excreted. Its anatomy is similar to the ureter and has 3 layers.

The structure of organs of the system is studied in biology lessons in the 8th grade:

Taking into account age characteristics, the structure of the system changes. Gradually, the size of the organs increases, and the volume of urea increases.

Arterial pressure.

The kidneys are able to control the body's blood pressure to help maintain homeostasis. When blood pressure is high, the kidneys can help lower blood pressure by reducing the volume of blood in the body. The kidneys are able to reduce blood volume by reducing the reabsorption of water into the blood and produce watery, dilute urine. When blood pressure becomes too low, the kidneys can produce the enzyme renin, which constricts blood vessels and produces concentrated urine, allowing more water to accumulate in the blood.

Age-related changes

The urinary system in men is characterized by some differences. For example, the canal is long (up to 24 cm), but narrow (about 8 mm). The urethra is responsible for the seminal function. Unlike women, the bladder has a more round shape. Muscle mass plays an important role in urine output. In women it goes from the external opening of the urethra, and in men it goes to the seminal tubercle.

In women, the urinary system has the following features:

• short channel (about 5 cm), so inflammation often develops;
• oval bubble shape.

The system works the same for men and women. Children exhibit some distinctive features in organ development. At the time of birth, the kidneys are not formed. The filtration area does not exceed 30% of that in adults. Nephron tubules are characterized by short and narrow features.

In a one-year-old child, the organ has a lobular structure. The cortical layer is underdeveloped. To cleanse the body of toxins, you will need a significant amount of water. Therefore, it is beneficial to breastfeed children up to 2 years of age. Mother's milk is completely absorbed, so the excretion of waste products is insignificant.

If you introduce other foods into complementary foods, the load on the organ will increase. There are also differences in the functioning of other organs of the system. The ureters in children are tortuous and wide. The urethra in girls is completely open, but this does not increase the risk of developing inflammation.

Hormone production

The kidneys produce and interact with several hormones that are involved in the control of systems outside the urinary system.

Calcitriol. Calcitriol is the active form of vitamin D in the human body. It is produced by the kidneys from precursor molecules produced by UV radiation falling on the skin. Calcitriol works in conjunction with parathyroid hormone (PTH) to raise the level of calcium ions in the blood. When the level of calcium ions in the blood falls below a threshold level, the parathyroid gland produces PTH, which in turn stimulates the kidneys to release calcitriol. Calcitriol helps the small intestine absorb calcium from food and place it into the blood. It also stimulates osteoclasts in the skeletal system to break down the bone matrix and release calcium ions into the blood.

Erythropoietin. Erythropoietin, also known as EPO, is a hormone produced by the kidneys to stimulate the production of red blood cells. The kidneys control the condition of the blood that passes through the capillaries, including the oxygen-carrying capacity of the blood. When the blood becomes hypoxic, meaning that it carries deficient levels of oxygen, the cells lining the capillaries begin to produce EPO and release it into the blood. EPO travels through the blood to the bone marrow, where it stimulates blood-forming cells to increase the rate of red blood cell production. Red blood cells contain hemoglobin, which significantly increases the blood's ability to carry oxygen and effectively overcome hypoxic conditions.

Renin. Renin is not a hormone itself, but an enzyme that the kidneys produce at the beginning of the renin-angiotensin system (RAS). RAS increases blood volume and blood pressure in response to low blood pressure, blood loss, or dehydration. Renin is released into the blood where it converts angiotensinogen from the liver into angiotensin I. Angiotensin I is further catalyzed by another enzyme into angiotensin II.

Angiotensin II - stimulates several processes, including stimulating the adrenal cortex to produce the hormone aldosterone. Aldosterone then modifies kidney function to increase the reabsorption of water and sodium ions into the blood, increasing blood volume and increasing blood pressure. The negative impact of high blood pressure finally turns off the RAS to maintain healthy blood pressure levels.

Functionality

Adults consume more than 1.5 liters of fluid daily. The excretory system is used to cleanse the body of harmful components. The urinary organs are characterized by the following functions:

• support of homeostasis (immobility);
• release of metabolic products of various substances;
• hormonal.

Each organ performs specific tasks. Kidneys are essential for filtering blood, breaking down and absorbing harmful components. With their help, urine appears. It penetrates the renal pelvis and then the ureters. The last organ is used to transport urine into the bladder.

With the help of urea, the accumulative function is performed. It ensures the collection of urine in 3.5 hours and its subsequent discharge into the urethra.

The sphincter is entrusted with the following task: preventing the spontaneous release of urine at the moment the bladder fills. The urethra removes urine from the body.

Maintaining Homeostasis

The kidneys maintain the homeostasis of several important internal conditions by controlling the elimination of substances from the body. Ions. The kidney can control the excretion of potassium, sodium, calcium, magnesium, phosphate and chloride ions into the urine. In cases where these ions accumulate above normal concentrations, the kidneys can increase their excretion from the body to return them to normal levels. Conversely, the kidneys can retain these ions when they are present at less than normal levels, allowing the ions to be absorbed into the blood during filtration.

pH. The kidneys can monitor and regulate the levels of hydrogen ions (H+) and bicarbonate ions in the blood to control the pH of the blood. H+ ions are produced as a by-product of the natural metabolism of dietary proteins and accumulate in the blood over time. The kidneys excrete excess H+ ions into the urine for elimination from the body. The kidneys also store bicarbonate ions, which act as important pH buffers in the blood.

Osmolarity. Body cells must grow in an isotonic environment in order to maintain their water and electrolyte balance. The kidneys maintain the body's osmotic balance by regulating the amount of water that is filtered from the blood and excreted from the body in urine. When a person consumes large amounts of water, the kidneys reduce its reabsorption to allow the excess water to be excreted from the body in urine. This results in a dilute, watery urine solution. When the body becomes dehydrated, the kidneys retain as much water as can be returned to the bloodstream to produce highly concentrated urine full of excreted ions and waste products. Changes in water excretion are controlled by antidiuretic hormone (ADH). ADH is produced in the hypothalamus to help the body retain water.

Pathological conditions

The main diseases occurring in the urinary system develop against the background of various infections. Inflammation is most often diagnosed. The most difficult symptoms to relieve are those caused by genital infections. Due to their complications, infertility occurs. To prevent serious consequences, it is recommended to diagnose and treat pathologies in a timely manner.

With bacteriuria, bacteria are present in the urine, but in normal quantities. This condition is considered sterile. To prevent bacteriuria, it is recommended to maintain personal hygiene and use personal protective equipment. A hyperactive bladder condition is often diagnosed. It accounts for up to 17% of cases. The pathology is accompanied by a frequent desire to defecate. To prevent it, constant strengthening of the muscles located in the pelvic area is required.

If an additional sac is identified in the bladder area, a diagnosis of diverticulum is made. The disease is accompanied by problematic urination, which occurs in 2 stages. Description of other system diseases:

1. Candidiasis. Develops against the background of infections and as a result of excessive proliferation of the fungus. For prevention, it is recommended to strengthen the immune system, avoid hypothermia and casual sexual intercourse.
2. Incontinence. Involuntary urine loss is associated with muscle weakness in women. This phenomenon occurs due to hormonal imbalance. Incontinence is common after childbirth.
3. Oliguria. With this diagnosis, insufficient urine production occurs. Normally its volume is 1.5 liters. With oliguria, the figure does not exceed 0.5 l. Pathology is not considered independent. It develops against the background of another disease.
4. Cystitis. The bladder becomes inflamed more often in women. To prevent illness, it is recommended to maintain personal hygiene.
5. Enuresis. Against the background of neuralgia, involuntary urination at night occurs. Therapy is prescribed not only by a urologist or gynecologist, but also by a neurologist.

If the lesion is in the urinary system, it is recommended that men visit a urologist. When the disease occurs in the genitals, consultation with an andrologist (men) and a gynecologist (women) is required. Since the urinary system has a direct connection with the reproductive system, it is therefore necessary to consult a doctor when the first signs appear.

If there is an accumulation of harmful substances, intoxication can spread to the entire body. The process can be inflammatory, infectious, or toxic. To make an accurate diagnosis, a physical examination of the patient is performed. At the next stage, tests and instrumental studies are scheduled.

Based on the results obtained, adequate therapy is prescribed. If the etiology of the process is bacterial, antibiotic therapy is performed. In order not to disturb the intestinal microflora, taking probiotics is also recommended. Protecting the urinary system from various pathogens includes proper nutrition, avoiding hypothermia, and maintaining personal hygiene.