To prevent blood flowing back after each heartbeat. They ensure that the blood flows only in one direction (back to the heart).
The correct answer to go in the blank would be ''laws''.
Hmmm let me think.........
That organ is called the rectum, or more coomonly, the anus. The rectum is the final part of the large intestine and the digestive system, where food that has had all its nutrients extracted (as much as possible, anyway) is sent to be compacted and sent out through the anus in the form of excreta. The contents in the rectum is mostly indigestible fiber and other materials. The rectum at its end connects to the bodily orifice known as the anus.