Yes and yes.

Estrogen is not only produced by the ovaries.  The other production
route is through the enzyme aromatase, which converts other hormones to
estrogen in various tissues, particularly fat and muscle.  It is this
path that aromatase-inhibitors such as Arimidex block, whereas Tamoxifen
blocks the estrogen receptors on breast cells, thus blocking estrogen
from all sources, but leaving the hormone in the bloodstream to affect
other tissues (eg bone).

Aromatase inhibitors have no effect on estrogen produced by the ovaries,
that is why they are unsuitable for pre-menopausal women (unless they
have had ovarian ablation etc.).

Tim Jackson