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URINARY SYSTEM
The kidney is an organ through which most of the unnecessary metabolic
products are removed from the human body, as well as excess substances that are
harmful to the body compounds. Thanks to the kidneys, the consistency of the
composition of the liquid internal media of the body (blood, lymph, intercellular fluid)
is maintained.
Two kidneys together with two ureters, one bladder and a urethra (urethra) make
up the human urinary system (figure 23).
Urine is constantly formed in the kidneys, which then moves through the ureters
into the bladder and accumulates there. When the walls of the bladder stretch, a signal
is sent to the central nervous system, the reverse signal from which relaxes the
sphincters, there is a contraction of the bladder muscles and urination. There are two
sphincters (muscle thickenings), one at the exit of the bladder, the other at the exit of
the urethra.
Figure 23. Urinary system’s structure
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