The cremaster muscle is derived from
|A||external oblique aponeurosis|
|B||internal oblique muscle|
|C||transversus abdominis muscle|
a. The internal oblique muscle originates from the iliopsoas fascia beneath the lateral half of the inguinal ligament, from the anterior two thirds of the iliac crest and the lumbodorsal fascia.
b. Its fibers course in a direction opposite to those of the external oblique, that is, inferolateral to superomedial.
c. The upper most fibers insert into the lower five ribs and their cartilages .
d. The central fibers form an aponeurosis at the semilunar line, which, above the semicircular line (of Douglas), is divided into an anterior and posterior lamella that envelopes the rectus abdominis muscle.
e. Below the semicircular line, the aponeurosis of the internal oblique muscle courses anteriorly to the rectus abdominis muscle as a part of the anterior rectus sheath.
f. The lowermost fibers of the internal oblique muscle pursue an inferomedial course paralleling that of the spermatic cord to insert between the symphysis pubis and the pubic tubercle.
g. Some of the lower muscle fascicles accompany the spermatic cord into the scrotum as the cremasteric muscle.