They have a heart. Pretty much like ours, but smaller and faster.
to pump blood around the rat's body
Yes, rats thrive on blood, it is what keeps them alive.
No.
It was believed to be rats but know has found to be the fleas on the rats sucking blood and then transmitting the disease into the victims blood stream
They're not actually hairless, as they have a fine dusting of hair along the entire length. It's a adaption to allow rats to pump large amounts of blood into the veins along their tails to cool their body temperature down. It's quite effective.
Warm
The design of the mammalian heat is that there are two chambers used to receive blood from, and pump blood to the lungs, and then two more chambers used to received blood from, and pump blood to the rest of the body other than the lungs. This arrangement works more efficiently than if there are only two chambers receiving blood from and pumping blood to the entire body including the lungs.
No the heart pumps the blood but it does pump the blood through the arteries.
no
The ventricles contract to pump blood out of the heart.
Most rat poison prevents the blood from clotting. the rats bleed out internally.
pump blood you a******