Expansion
External spermatic from external oblique, cremasteric from internal oblique, internal spermatic from transversalis fascia
Expansion
| Covering | Derived from |
|---|---|
| External spermatic fascia | External oblique aponeurosis |
| Cremasteric fascia and muscle | Internal oblique |
| Internal spermatic fascia | Transversalis fascia |
Transversus abdominis contributes nothing, because the testis passes below its arching lower border.
The order makes sense developmentally: the testis begins deep to transversalis fascia and pushes outwards, acquiring each layer in turn. The outermost covering is therefore derived from the outermost muscle.
The cremaster is supplied by the genital branch of the genitofemoral nerve, which is the efferent limb of the cremasteric reflex.