freewheel. 1  a device in the transmission of a motor vehicle that automatically disengages the drive shaft whenever it begins to turn more rapidly than the engine. 2  a form of rear bicycle wheel that has a device freeing it from the driving mechanism, as when the pedals are stopped in coasting.
Ampullae are an important part of the water vascular system of starfish, which is the responsible for the animal's locomotion. The only function of the ampullae is to store the water that enters the vascular system and send it to the minuscule tube feet, located in the ventral side of the starfish's arms.he contraction of the muscles also causes the water stored in the ampullae to move to the tube feet, which are the locomotion organs of the starfish. Nerve cells connected to the ampullae and other parts of the vascular water system control the relaxation and contraction of the ampullae's muscle fibers.
The renal medulla is split up into a number of sections, known as the renal pyramids. Blood enters into the kidney via the renal artery, which then splits up to form the arcuate arterioles. The arcuate arterioles each in turn branch into interlobar arterioles, which finally reach the glomeruli.he renal medulla only receives about 10% of all the blood flowing through the kidneys. You could say that the function of the renal medulla, or the kidney in general, is maintaining homeostasis of a large number of solutes and water.