Gonads are not part of the circulatoruy system. the way I remember most of them is
Ectoderm= skin, teeth, lens of eye, nervous system
Endoderm= Tracts and Lining (PLT= pancreas, liver and thyroid) and bladder
- I use PLT because its also the order pathway for respiration
(Phrynax,Larynx and Trachea)
Mesoderm= everything else