Humans have two kidneys and each kidney is supplied with blood from the renal artery. The kidneys remove from the blood the nitrogenous wastes such as urea, as well as salts and excess water, and excrete them in the form of urine.This is done with the help of millions of nephrons present in the kidney.umans have two kidneys and each kidney is supplied with blood from the renal artery. The kidneys remove from the blood the nitrogenous wastes such as urea, as well as salts and excess water, and excrete them in the form of urine.
This is because the speed of sound waves depends upon the material through which they are travelling. Sound travels 15 times faster through the metal railway tracks than through air, giving the cowboy an early warning of the train's arrival. How much plainer could it be? I, personally, had never thought of it that way. I love this illustration.
Confidence votes 55. Sound can travel through any medium. If you remove the medium you would end up with a vacuum. It is in vacuums that sound cannot travel as it needs a medium to travel (it travels as a compression wave or shear wave).Space is almost a perfect vacuum so sound is unable to travel through space.onfidence votes 55. Sound can travel through any medium. If you remove the medium you would end up with a vacuum. It is in vacuums that sound cannot travel as it needs a medium to travel (it travels as a compression wave or shear wave).