Answer:
Two ureters.
These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop.
Explanation:
True they are in the heart as well as the rest of your body
True! because if you have more than one variable, you aren’t going to know which variable changed the dependent variable.
In general, yes, the dorsal blood vessel of a worm be seen from the worm's exterior because a worm's "skin" is very thin. Although of course there are exceptions.
A vaccine works by stimulating the immune system to produce antibodies without actually infecting someone with that disease. They trigger the immune system to produce its own antibodies as though the body has been infected with the disease. But a vaccine will not make someone immune to a disease, it will simply help the body be able fight the infection better.
