Why is the issue of women’s rights considered separately from general issues of human rights?:
I don't know if this fits in with the emphasis in your class, but this is my personal view...

Historically, when human rights were being defined women were not included.

For example: The US Constitution was written to protect and preserve the rights of citizens of the newly-formed United States. Women, however, were not believed to have all of the rights enshrined in that document and had to struggle to have their rights as citizens recognized.
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Although any discussion of human rights includes women by definition, the overall umbrella of "human rights" is not always seen as addressing issues specific to the female gender. These issues include child-bearing, sexual abuse and oppressive cultural traditions/laws which prevent women from enjoying the "human rights" that men have.

In a nutshell, when someone says "women's rights" they are  talking about human rights that women do not have yet---or they are discussing something gender-specific.

I hope this helps.