Urinary System Organs And Functions – Kidneys – Ureters – Urinary bladder – Urethra

Urinary system organs and their functions

The organs of the urinary system are: two kidneys , two ureters, the urinary bladder and the urethra. They work together, ensuring blood filtration, urine production and elimination. In the following table, we have the organs that make up the urinary system and their respective functions.

→ Kidneys

Urinary system: The kidneys are found in number of two in our body, being the organs responsible for the production of urine. They are located along the posterior wall of the abdomen, below the diaphragm.

They are about 10 cm long, weigh approximately 120 to 280 g and have a shape reminiscent of a bean, with a convex edge and a concave edge. In the concave part, it is possible to observe a region called the hilum, the place where blood vessels enter and exit, nerves enter and the ureters exit.

When we look internally, we see that the kidneys have two very distinct regions: a cortex and a medulla. The cortex is located more externally, while the medulla is located more internally and is visualized as a darker region. The upper, expanded portion of the ureter is called the renal pelvis and communicates with the renal medulla. The pelvis branches toward the medulla into major calyces, which ramify into minor calyces.

The functional units of the kidneys are the so-called nephrons, which are made up of the renal corpuscle and the renal tubules. The renal corpuscle, also called Malpighian corpuscle , is formed by a glomerulus (coiled capillaries) surrounded by a capsule ( Bowman’s capsule ). The renal tubules depart from the capsule and appear as a sequence of tubules: proximal tubule, loop of Henle, and distal tubule. The latter opens into the collecting duct.

Nephrons are classified into cortical and juxtamedullary. Cortical nephrons are those that only a portion enter the renal medulla, while juxtamedullary nephrons extend deeper into the medulla.

→ Ureters

The ureters are ducts that carry urine from the kidney to the bladder. There are two ureters found in our body, each starting from one of the kidneys. On average, ureters are 25 to 30 cm long and 4 to 5 mm in diameter.

→ Urinary bladder

The urinary bladder is a hollow muscular organ that serves as a reservoir for urine and gradually distends as this product accumulates. There are muscles near the junction between the urethra and the bladder, which act to regulate urination.

→ urethra

Urinary system: The urethra is an organ that ensures the elimination of urine to the external environment. In men, the urethra has an average length of 20 cm and can be divided into three parts: prostatic, membranous and cavernous or penile. The prostate passes close to the bladder and inside the prostate, the membranous is only one centimeter long and connects with the cavernosa, which is located inside the cavernous body of the penis. The female urethra is about 4 cm long.

How the urinary system works: the formation of urine

As we know, the urinary system is the system responsible for the formation of urine. Urine is produced in the kidneys, passes through the ureters, is temporarily stored in the bladder, and is later released to the outside of the body via the urethra.

Urine formation occurs in the region of the kidneys called nephrons. Initially, the process of filtration occurs within the renal corpuscle. The blood reaching the glomeruli is at high pressure and the glomerulus acts as a semipermeable membrane, ensuring that part of the plasma passes into the capsule (filtration). The filtrate formed is similar to blood plasma, but has no proteins.

The filtrate then travels to the renal tubules, where it undergoes the processes of reabsorption and secretion . In reabsorption, some substances are reabsorbed into the blood, while in the process of secretion, substances are added to the filtrate. Reabsorption is important as it ensures that water, ions and glucose, for example, are reabsorbed. Urine is the result of the processes of glomerular filtration, tubular reabsorption and tubular secretion.

After passing through the renal tubule, the urine goes to the collecting duct, which carries the compound to the renal pelvis (upper portion of the ureter), leaving the kidney, therefore, via the ureter. As stated earlier, from the ureter, urine travels to the bladder, where it is stored and then eliminated through the urethra.

→ Differences between the male and female urinary system

The male and female urinary system have the same organs. Therefore, if you evaluate this system in people of different sexes, you will find: two kidneys, two ureters, a urinary bladder and a urethra. However, some differences can be observed. See some of them below:

• The bladder is located in front of the rectum. In men, it is separated from the rectum by the seminal vesicles, while in women, the vagina and uterus are present.
• The urethra in men has another function besides ensuring the elimination of urine. In this sex, the urethra also gives passage to the semen during ejaculation. In females, in turn, the urethra is considered an exclusive organ of the urinary system.
• The male urethra is larger than the female urethra. While the male urethra is about 20 cm, the female urethra is only 4 cm.

→ Curiosity of the urinary system

• Each kidney has approximately one million nephrons.
• A newborn’s kidney is three times larger, in proportion to body weight, than an adult’s kidney.
• The right kidney is slightly lower than the left kidney due to the presence of the liver.
• The kidneys receive about 1.2 liters of blood per minute.
• On average, an individual eliminates between 1000 and 1500 ml of urine per day.
• The presence of glucose in the urine can be a sign of diabetes.
• The proximity of the female urethra to the anus favors the emergence of urinary infection.
• The average bladder capacity is 700 to 800 ml.
• Bladder cancer is the most common cancer of the urinary tract. Blood in the urine, pain when urinating, the urge to urinate, but not being able to urinate are some of the signs that deserve attention.
• Hemodialysis is a procedure in which a machine is used to clean and filter the blood, acting as an artificial kidney.
• In 2017, Brazil performed 5948 kidney transplants.
  

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