Part 50

Relations.--With its medial or cranial surface the adductor longus forms part of the boundary of a depression among the muscles at the proximal end of the medial side of the leg. This depression is called the iliopectineal fossa; it contains the femoral vein and artery and saphenous nerve imbedded in fat (Fig. 127). The medial edge of the adductor longus is in relation with the integument; the lateral edge with the pectineus (Fig. 92, e). Inner or caudal surface with the adductor femoris (Fig. 92, g).

Action.--Adductor of the thigh.

a, M. tensor fasciæ latæ; a′, fascia lata; b, M. rectus femoris; c, M. vastus medialis; d, M. iliopsoas (cut); e, M. pectineus; f, M. adductor longus; g, M. adductor femoris; h, h′, M. semimembranosus; i, M. semitendinosus (i′, its tendon); j, medial head of M. gastrocnemius; k, M. popliteus; l, M. flexor longus digitorum. 1, patellar ligament; 2, ligamentum collaterale tibiale.]

=M. pectineus= (Fig. 92, e).--A flat band of fibres closely united with the adductor longus (f), of which it appears to be a lateral continuation.

Origin by fleshy fibres from the lateral one-fourth of the cranial border of the pubis. The muscle passes over the smooth outer surface of the pubis between its origin area and the acetabulum, crosses the iliopsoas (d) obliquely and has its

Insertion by muscle-fibres into an elongated area (five millimeters in length) on the shaft of the femur just distad of the lesser trochanter and between the insertion of the adductor femoris (g) and that of the vastus medialis (c).

Relations.--The cranial edge forms part of the floor of the iliopectineal fossa. Lateral surface in relation with the iliopsoas (d) and vastus medialis (c); medial surface with the adductor longus (f) and adductor femoris (g).

Action.--Adductor of the thigh.

=M. quadriceps femoris.=--The quadriceps femoris is a very powerful extensor muscle on the front of the thigh. It consists of four muscles which unite to form the great extensor of the shank. It is inserted into the patella and through it, by the ligamentum patellæ, into the tibia. It may be compared to the triceps brachii. The parts are:

(1) =M. rectus femoris= (Fig. 92, b; Fig. 90, c).

Origin by strong tendon from an elongated triangular area which has its base at the acetabulum and its apex about five to seven millimeters craniad of the acetabulum, along the ventral border of the ilium. The area is between that for the capsularis and that for the iliopsoas. The muscle is flat near its origin, but soon becomes a triangular prismatic mass which is united to the dorsal border of the vastus lateralis (Fig. 90, d) at the junction of the middle and last thirds of the thigh.

Insertion into the oblique area on the outer surface of the patella near its proximal border in connection with the vastus lateralis.

Relations.--Outer or lateral surface at the origin with the gluteus minimus, the edge of the capsularis, the gluteus medius (Fig. 90, b), and farther distad with the vastus lateralis (Fig. 90, d). Medial surface with the tensor fasciæ latæ (Fig. 92, a), sartorius (Fig. 90, a), and vastus medialis (Fig. 92, c). Inner (caudal) surface with the vastus intermedius.

(2) =M. vastus lateralis= (Fig. 90, d).--A flat triangular prismatic mass joined distally to the preceding. It covers the dorsal part of the lateral surface of the thigh.

Origin from a triangular area on the dorsal and lateral surfaces of the shaft and the great trochanter of the femur. The base of the area is at the great trochanter, and its apex is at the junction of the second and third fifths of the shaft on the linea aspera. The linea aspera forms the ventral boundary of the triangle, while its dorsal boundary is formed by a line drawn from its apex to the dorsomedial angle of the great trochanter. The mass unites with the rectus femoris (c) by its dorsal border at the junction of the middle and distal thirds of the thigh.

Insertion into the oblique area on the outer surface of the patella near its lateral border in connection with the rectus femoris.

(3) =M. vastus medialis= (Fig. 92, c) lies on the medial side of the thigh.

Origin by fleshy fibres over a diamond-shaped area on the shaft of the femur lying between the medial branch of the linea aspera and the area for the vastus lateralis. Proximad the area is bounded by the spiral line, and distad it is bounded by a line parallel to the spiral line and having its proximal end at about the junction of the first and second thirds of the bone. The muscle forms a triangular, prismatic mass. It ends in a thin aponeurosis which is continuous dorsad with the border of the rectus femoris (Fig. 92, b), and ventrad sometimes with the tendon of the gracilis (Fig. 91, b).

Insertion into the medial border of the patella and the ligamentum patellæ. The insertion may extend onto the head of the tibia.

The adjacent surfaces of the vastus lateralis and the vastus medialis are connected over their distal thirds by an aponeurosis which passes transversely beneath the rectus femoris. The distal end of the aponeurosis is inserted into the proximal border of the patella. Its proximal end receives the insertion of some muscle-fibres which form a part of the vastus medialis as here described. This mass of fibres is described by Strauss-Durckheim as the =crural= muscle. Sometimes the transverse aponeurosis is continuous with only one of the two vasti and sometimes with neither, so that the insertion of the crural of Strauss-Durckheim becomes more or less independent.

Relations of the vastus medialis.--Outer (medial) surface with the sartorius (Fig. 91, a) and the structures in the iliopectineal fossa. Cranial (or dorsal) surface with the rectus femoris (Fig. 92, b) and vastus intermedius. Caudal (ventral) surface with the pectineus (Fig. 92, e), adductor longus (Fig. 92, f), adductor femoris (Fig. 92, g), and semimembranosus (Fig. 92, h).

(4) =M. vastus intermedius.=--A flat mass of muscle which lies beneath the rectus femoris.

Origin from nearly the whole of the dorsal surface of the shaft of the femur between the areas for the vastus medialis and vastus lateralis. The area of origin extends distad to an oblique line the middle of which is about one and one-half centimeters from the patellar surface, the lateral border of the area being longer than the medial border.

Insertion by muscle-fibres into the capsule of the joint. The central fibres are inserted about one centimeter proximad of the patella, while the lateral mass passes to the level of the proximal end.

Relations.--Outer surface with the rectus femoris (Fig. 92, b); borders with the vastus medialis (Fig. 92, c) and vastus lateralis (Fig. 90, d); inner surface with the femur.

Action.--The quadriceps extensor is an extensor of the shank. The vastus intermedius acting separately is a tensor of the capsule of the knee-joint.

3. Muscles of the Lower Leg (Crus).

A. ON THE VENTRAL SIDE.--=M. gastrocnemius.=--This is the great muscular mass of the calf. It arises by two heads, the caput laterale or lateral head (Fig. 90, m), and the caput mediale or medial head (Fig. 91, k), of the gastrocnemius.