What is different, never mind, there is peripheral vascular disease in the veins.
One of the best books I've ever read is by Dr. Malcolm Kendrick, titled The Great Cholesterol Con He also asks this question, and points out that if an artery is replaces by a vein, the vein will develop atherosclerosis, and if a vein is replaced by an artery, it never develops atherosclerosis. This book is an eye-opener. Another point he makes about statins and cholesterol: if a man takes statins, he will live approximately 3 weeks longer, and for women taking statins, there is NO difference in the mortality rate, not one day!
And he also points out that the World Health Organization's ongoing study has shown that there is no correlation whatsoever in heart disease rates and cholesterol levels.
Because arteries carry fat to the cells but lymph vessels carry it back to the liver through the spleen.