Anatomy of the Cat

by Jacob Reighard; H. S. Jennings

Insertion into the inner surface of the tendon of the obturator internus ([Fig. 90], e) by tendon- and muscle-fibres. Some of the muscle-fibres are inserted into the capsule of the joint.

Relations.—Outer surface with the obturator internus ([Fig. 90], e). Medial surface with the ischium. Caudal border with the quadratus femoris ([Fig. 90], f). Cranial border with the gemellus superior.

Action.—Abductor of the thigh. The muscle may be considered as a separate head of the obturator internus ([Fig. 90], e).

M. quadratus femoris ([Fig. 90], f).—The quadratus femoris is a short thick muscle connecting the ischial tuberosity (2) and the proximal end of the femur. It lies just caudad of the obturator internus (e) beneath the proximal end of the biceps femoris ([Fig. 68], t).

The origin is by fleshy fibres from a considerable triangular area on the lateral surface of the ischium near the tuberosity. The area lies between the origin areas of the gemellus inferior, biceps, semimembranosus, and the obturator externus.

Insertion into the distal two-thirds of the ventral border of the great trochanter and about half the adjacent surface of the lesser trochanter.

Relations.—Outer surface with the tenuissimus ([Fig. 90], g), the biceps ([Fig. 68], t), the semitendinosus ([Fig. 90], j), and the great sciatic nerve ([Fig. 163], a). Caudal border with the semimembranosus ([Fig. 90], i). Ventral border with the adductor femoris ([Fig. 90], h); dorsal border with the obturator internus ([Fig. 90], e) and gemellus inferior.

Action.—Extensor of the thigh and rotator of the femur so as to carry the foot inward.

M. obturator externus.—The obturator externus is a flat triangular muscle beneath the adductor femoris ([Fig. 92], g).

Origin by fleshy fibres from the median lip of the obturator foramen and from both dorsal and ventral surfaces of the rami of the pubis and ischium adjacent to the lip. Also from the outer surface of the ramus of the ischium as far as the area for the quadratus femoris ([Fig. 90], f). The fibres converge to a strong flat tendon.