Morphology of the urinary system
The urinay system consists of four major organs: kidneys, ureters, bladder and urethra.
- The kidneys are the most important organs of the urinary system, since they're responsible for the formation of the urine. These are located in the back of the abdominal cavity, with around 12 centimeters of height and 6 centimeters of width. Each kidney has a convex lateral board and a median concave board. In this median concave board the artery and the renal veins end up in a hole designated hilum.
- The ureters are the channels which transport the urine to the bladder. Each one of these channels measures around 25-30 centimeters of length, with 4-5 milimeters of diameter. The peristaltic movements, of the muscle tissue layer of the ureter, boost the urine in jets until the bladder.
- The bladder is the placer where the urine is launched to. It is a void muscle tank and it is characterized by its ability to distend while it is receiving the urine.
- The urethra is a narrow channel which conducts the urine from the bladder to the outside. In the women, it has around 4 centimeters of length, and in the men, around 20 centimeters.
Urinary System Function
- The urinary system guarantees the maintenance of the internal balance of our organism, since it eliminates the residues came from the cellular metabolism, and it controls the concentration of the blood and lymph's components, by forming urine.
The formation of the urine
-The blood reaches the kidneys by the renal artery, which branches into smaller arteries, and these smaller ones, in arterioles. The afferent arteriole leads the blood to the structural and functional unit of the kidney, which name is nephron. The nephron is formed by a blood filtration unit, which name is glomerulus of Malpighi, and by a urine formation unit. This urine formation unit is composed by the Bowman's capsule, by the proximal convoluted tubule, by the loop of Henle and by the bypassed distal tube.
When the blood, which circulates in the afferent arteriole, reaches the glomerulus of Malpighi, it is filtrated, passing every single micromolecule to Bowman's capsule, forming the glomerular filtrate. The composition of this fluid is identical to the blood plasma, because it contains water, some nutrients, mineral salts and the waste resulted from the cellular metabolism. The macromolecules, such as proteins, with a high molecular weight, aren't able to pass through the walls of the capillary vessels and enter in Bowman's capsule. While the glomerular filtrate crosses the blood formation unit, 99% of the water and other useful substances to the organsim, such as glucose, are reabsorbed by the capillary vessels that are formed starting from the afferent arteriole. The remaining tubular water, the substances which were not reabsorbed and the secreted ones are excreted and they start to constitute the urine.
The function of the nephron's components
The urinay system consists of four major organs: kidneys, ureters, bladder and urethra.
- The kidneys are the most important organs of the urinary system, since they're responsible for the formation of the urine. These are located in the back of the abdominal cavity, with around 12 centimeters of height and 6 centimeters of width. Each kidney has a convex lateral board and a median concave board. In this median concave board the artery and the renal veins end up in a hole designated hilum.
- The ureters are the channels which transport the urine to the bladder. Each one of these channels measures around 25-30 centimeters of length, with 4-5 milimeters of diameter. The peristaltic movements, of the muscle tissue layer of the ureter, boost the urine in jets until the bladder.
- The bladder is the placer where the urine is launched to. It is a void muscle tank and it is characterized by its ability to distend while it is receiving the urine.
- The urethra is a narrow channel which conducts the urine from the bladder to the outside. In the women, it has around 4 centimeters of length, and in the men, around 20 centimeters.
Urinary System Function
- The urinary system guarantees the maintenance of the internal balance of our organism, since it eliminates the residues came from the cellular metabolism, and it controls the concentration of the blood and lymph's components, by forming urine.
The formation of the urine
-The blood reaches the kidneys by the renal artery, which branches into smaller arteries, and these smaller ones, in arterioles. The afferent arteriole leads the blood to the structural and functional unit of the kidney, which name is nephron. The nephron is formed by a blood filtration unit, which name is glomerulus of Malpighi, and by a urine formation unit. This urine formation unit is composed by the Bowman's capsule, by the proximal convoluted tubule, by the loop of Henle and by the bypassed distal tube.
When the blood, which circulates in the afferent arteriole, reaches the glomerulus of Malpighi, it is filtrated, passing every single micromolecule to Bowman's capsule, forming the glomerular filtrate. The composition of this fluid is identical to the blood plasma, because it contains water, some nutrients, mineral salts and the waste resulted from the cellular metabolism. The macromolecules, such as proteins, with a high molecular weight, aren't able to pass through the walls of the capillary vessels and enter in Bowman's capsule. While the glomerular filtrate crosses the blood formation unit, 99% of the water and other useful substances to the organsim, such as glucose, are reabsorbed by the capillary vessels that are formed starting from the afferent arteriole. The remaining tubular water, the substances which were not reabsorbed and the secreted ones are excreted and they start to constitute the urine.
The function of the nephron's components
- Afferent arteriole - Leads the blood which came from the renal artery and at the Bowman's capsule it branches off in capillary vessels to form the Malpighi's glomerulus.
- Malpighi's glomerule - It is made by a network of blood capillaries, rolled like a yarn ball, which facilitates the passage of the micromolecules to the Bowman's capsule.
- Bowman's capsule - It is the initial zone of the urine formation unit. Its shape is like a cup, it contains the glomerular filtrate and it is located in the cortex.
- Proximal convoluted tubule - It is the initial portion of the urine formation unit that contains the glomerular filtrate of the Bowman's capsule, and it is located in the cortex.
- Loop of Henle - It is the part of the urine formation unit which as the shape of an ''U'', where the glomerular filtrate is transformed into urine; it is located in the marrow.
- Distal bypassed tubule - It is the final portion of the urine formation unit which contains the urine; it is located in the cortex.
- Afferent arteriole - It leads the filtrated blood which leaves the renal capsule. It branches off in capillary vessels that curl off along the urine formation unit.