During EMBRYOLOGICAL development of (Gonads) testes/ovaries in a developing baby a structure called "Intermediate mesoderm" is formed on each sides of vertebral column(spine, back bone).Then it differentiates into 3 parts:-

1>"Pronephros" on each side of spine of NECK(neck region) of developing baby(embryo). It dissolves off & does NOT make any important structure in fully developed human baby.

2>"Mesonephros" is part of "intermediate mesoderm" between spine & ribs (thoracic region)on each side. It develop lots of tubules which later form testes. & sperms r formed in these tubules. Then testes migrates(proceeds) downwards(DESCEND) from here to it's final place , scrotum. In some premature babies testes r un-descended completely & r found in abdomen & have to b surgically corrected.

3>"Metanephros" is part of "intermediate mesoderm" on each side of abdominal backbone of developing baby.It also form tubulus & develop into kidneys. Kidneys r in pelvis of developing baby. Then they ASCEND to reach final position in upper abdomen.
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So testes are formed in chest region between spine & ribs.
“Quran:86:5:"So let the man consider from what he is created.. 6:He is created from a fluid emitted. 7:proceeding from between the backbone and the rib. 8:Surely He(Allah) is able to bring him back (to life) (that is; He can duplicate the same processes of development again). 9:On the day when hidden thoughts shall be searched out.”