Scalene muscles

Scalene anterior

O: anterior tubercles of transverse process of C3-C6
I: scalene tubercle on first rib
In: anterior rami of 4-6 cervical nerves
F: elevates first rib, flexes

Scalene medius

O: transverse process of c2-c7
I: superior surface of first rib
In: anterior rami of C3-c8
F: elevates first rib

Scalene posterior

O: posterior tibercles of transverse process C4-c6
I: external surface of second rib
In: anterior rami of cervical nerve
F: elevates second rib