Martial arts is a study of human anatomy, or rather, the weakness of human anatomy, and how to apply, manipulate or avoid potential destruction of human body with various techniques.
One does not require to have extensive knowledge of anatomy to become a martial arts master. However, having some knowledge would help in understanding the application of techniques better and how to make an attack more effectively. For example, to deliver a liver shot, it would be useful to know where the liver is located.
InnerBody.com is a free virtual human anatomy website with detailed models of all human body systems. Browse the website and check out various systems. They have very useful features. For example, you can learn the name of a bone or a muscle by clicking the part. Or, use the 3D function to view the body system in all directions.
(Reproduced under fair use and with credit)