L5 is the largest vertebrae. Although the body of L4 looks larger, the increased height of L5 makes it larger overall.
Found this info from "The Anatomy and Biology of the Human Skeleton" by D...
There are typically five lumbar vertebrae in the human body. They are located inferiorly to the thoracic vertebrae, and superior to the sacrum, at the base of the spinal column.
there is no specific number or amount of mitochondria it varies dependent on your age and gender. however they can be increase through training of the muscles especially strength training the most...