Answer:
Leonardo's training in the anatomy of the human body began with his apprenticeship at Andrea del Verrocchio's studio. His master insisted that all students should learn anatomy. As an artist, he quickly became a master of topographic anatomy, performing many studies of muscles, tendons, and other visible anatomical features.
As a successful artist, he was allowed to dissect human corpses at the Santa Maria Nuova Hospital in Florence, and later at the hospital in Milan and Rome. Between 1510 and 1511, physician Marcantonio della Torre collaborated in his studies, and together they elaborated a theoretical work on anatomy, in which Leonardo made more than 200 drawings. It was published only in 1680 (161 years after his death) as part of the Trattato della Pintura.
Leonardo designed many studies on the human skeleton and its parts, as well as the muscles and nerves, the heart and vascular system, the sexual organs and other internal organs. He made one of the first scientific drawings of a fetus in the womb. As an artist, Leonardo carefully observed and recorded the effects of age and human emotion on physiology, studying in particular the effects of anger. He also drew many important figures that had facial deformities or signs of disease, studying and also drawing the anatomy of various animals, dissecting cows, birds, monkeys, bears and frogs, comparing their designs in their anatomical structure with that of humans.
