Forget anatomy for artists, Art has the upper hand. You need to be funny.
Drawings are most meaningful when they disagree with theory because accuracy is not art despite being very useful. Pythagoras believed that everything was governed by numbers, even the proportionality of the human body. Artistic body proportions are sick and Pythagoras is dead.
Mother and son have had their head drawn at approx. same size.
[source: 19th century cartoon, "image d'Epinal"]
Beware of the dangerous facial proportions rules ("drawing exactitude is never truth") because size of ear, nose and mouth are more dependent on head orientation, than on human anatomy.
On the Fabric of Human Body (Andreas Vesalius makes no bones about osteology).
Useful artistic anatomy should be kept simple.
Ratio of human body in drawing turns symbolism on its head. Forget human anatomy. Human proportion in art is an appropriately Pythagorean idea, but average humans have about one testicle and one breast: a statistician is an either unlikely or improbable source of artistic pictures of the human body. Artistic body proportions for children or people are not bound by precision and accuracy.