Drawing images out of educational need

http://islamqa.org/hanafi/darululoomtt/52299 
I know that it is established from the Hadith that pictures and drawings are haram. Even a hadith state that angels do not enter the house with pictures and drawings.

Since Biology is a compulsory subject for my class and in biology we have to draw different diagrams sometimes with all body details, with private parts, with some internal organs, stages of pregnancy, sometimes of some natural human behaviour etc., does the Shari’ah allow the students to draw such diagrams?

---

A. On account of the need to study these books which are written on the different subjects, and also the need that exists to draw such diagrams, the scholars have allowed these to the extent of necessity.

And Allah knows best.

Mufti Waseem Khan