The human body is like a city, the blood vessel is the river of transportation, the cholesterol is the passenger, the ship that carries the cholesterol specially is called "Apolipoprotein".
These ships also have a division of labor, "low density lipoprotein" or "LDL" is the ordinary ferry, specifically from the liver and other organs to send passengers to the river , to the need for cell tissue.
And "high-density lipoprotein" or "LDL" is equivalent to "police boat", responsible for the blood vessels stranded passengers back to liver metabolism, to ensure the smooth flow of river transport.
When there are not many passengers, the river traffic is very orderly, but what if the cholesterol intake is excessive?
The body of the city also has a head called "hormones", these extra cholesterol equivalent to the foreign passengers, destination is other cell tissue.
Adhering to the "Customer is God" principle, "hormones" had to arrange more ships to send them to the blood vessels. But the river is so wide, so many ships are prone to traffic accidents, resulting in-"traffic jam".