II. THE MUSCLES OF THE THIGH

1. THE ANTERIOR FEMORAL MUSCLES (fig. 643)

Tensor fasciae latae
Sartorius
Quadriceps
femoris
(Rectus femoris,
Vastus lateralis,
Vastus intermedius &
Vastus lateralis)
Articularis genus

The superficial fascia forms a continuous layer over the whole of the thigh; it consists of areolar tissue containing much fat in its meshes, and may be separated into two or more layers, between which are found the superficial vessels and nerves. It varies in thickness in different parts of the limb; in the groin it is thick, and the two layers are separated from each other by the superficial inguinal lymph-glands, the long saphenous vein and several smaller vessels. The superficial layer is continuous above with the superficial fascia of the abdomen. The deep layer of the superficial fascia is a very thin, fibrous stratum, best marked on the medial side of the long saphenous vein and below the inguinal ligament. It is placed behind the subcutaneous vessels and nerves and upon the surface of the fascia lata. It is intimately adherent to the fascia lata a little below the inguinal ligament. It covers the saphenous opening (fossa ovalis), being closely united to its circumference, and is connected to the sheath of the femoral vessels. The portion covering the opening is perforated by the long saphenous vein; small blood-vessels and lymph-vessels, hence it has been termed the cribriform fascia, the openings for these vessels having been likened to the holes in a sieve. A large subcutaneous bursa is found in the superficial fascia over the patella.

The deep fascia of the thigh is named, from its great extent, the fascia lata (fig. 644); it invests the whole of this region of the limb, but varies in thickness in different parts. Thus, it is thicker in the upper and lateral parts of the thigh, where it receives a fibrous expansion from the Gluteus maximus and where the Tensor fascia lata is inserted between its layers; it is very thin behind, and at the upper and medial parts, where it covers the Adductor muscles, but becomes stronger around the knee, where it receives fibrous expansions from the tendon of the Biceps femoris laterally; from the Sartorius medially, and from the Quadriceps femoris in front. The fascia lata is attached; above and behind, to the back of the sacrum and coccyx; laterally, to the iliac crest; in front, to the inguinal ligament and to the superior ramus of the pubis; and medially, to the inferior ramus of the pubis, to the ramus and tuberosity of the ischium, and to the lower border of the sacrotuberous ligament. From its attachment to the iliac crest it descends as a dense fascia over the Gluteus medius to the upper border of the Gluteus maximus, where it splits into two layers, one passing superficial and the other deep to this muscle; at the lower border of the muscle the two layers reunite. Over the lateral aspect of the thigh the fascia lata is specially thickened and forms a strong band which is termed the iliotibial tract. At its upper limit, where it splits into two layers, the tract receives the insertion of the Tensor fasciae latae and, posteriorly, it receives the insertion of the greater part of the tendon of the Gluteus maximus. Of the two layers the more superficial ascends on the lateral surface of the Tensor fascia latae to reach the iliac crest; the deeper layer passes upwards and medially, under cover of the muscle, and blends with the lateral part of the capsule of the hip-joint. At its lower limit the iliotibial tract is attached to the lateral condyle of the tibia, but in this situation it is intimately blended with an aponeurotic expansion from the Vastus lateralis. Below, the fascia lata is attached to all the prominent points around the knee-joint, viz. the condyles of the femur and tibia, and the head of the fibula. On each side of the patella it is strengthened by transverse fibers from the lower parts of the Vasti, which are attached to and support this bone; of these fibers the lateral are the stronger and are continuous with the iliotibial tract. The fascia lata gives off two intermuscular septa, which are attached to the whole length of the linea aspera of the femur and its prolongations above and below : the lateral and stronger septum, which extends from the insertion of the Gluteus maximus to the lateral condyle, separates the Vastus lateralis in front from the short head of the Biceps femoris behind, and gives partial origin to these muscles; the medial and thinner septum separates the Vastus medialis from the Adductors and the Pectineus. Resides these there are numerous smaller septa, separating the individual muscles and enclosing each in a distinct sheath.

The saphenous opening (fossa ovalis) (fig. 644).-At the upper and medial part of the thigh, a little below the medial end of the inguinal ligament, the fascia lata presents a large oval aperture; it transmits the long saphenous vein and other smaller vessels, and is termed the saphenous opening. The cribriform fascia, which is pierced by the structures passing through the opening, covers the aperture and must be removed to expose it. The fascia lata in this part of the thigh is described as consisting of a superficial and a deep portion.

The superficial portion of the fascia lata is the part on the lateral side of the saphenous opening. It is attached to the crest and anterior superior spine of the ilium, to the whole length of the inguinal ligament, and to the pectineal line of the pubis (pecten pubis) in conjunction with the pectineal part of the inguinal ligament (lacunar ligament). From the pubic tubercle it is reflected downwards and laterally, as the arched falciform margin, which forms the anterior, lateral and lower boundaries of the saphenous opening; this margin overlies and is adherent to the anterior layer of the sheath of the femoral vessels, and the cribriform fascia, is attached to it. The upward and medial prolongation of the falciform margin is named the superior cornu; its downward and medial prolongation, the inferior corms. The latter is well defined, and is continuous behind the long saphenous vein with the deep portion of the fascia.

Figure 644
Medial thigh, great saphenous vein, inguinal ligament, medial view - Figure 644
The deep portion is situated on the medial side of the saphenous opening. and is continuous with the superficial portion at the lower margin of the fossa traced upwards, it covers the Pectineus, Adductor longus and Gracilis, and passing behind the sheath of the femoral vessels, to which it is closely united, is continuous with the iliopectineal fascia, and is attached to the pectineal line of the pubis.

From this description it may be observed that the superficial portion of the fascia lata lies in front of the femoral vessels, and the deep portion behind them, so that an apparent aperture (the saphenous opening), exists between the two.

The Tensor fascia latae (fig. 643) arises from, the anterior 5 cm. of the outer lip of the iliac crest; from the outer surface of the anterior superior iliac spine, and part of the outer border of the notch below it, between the Gluteus medius and Sartorius; and from the deep surface of the fascia lata. It is inserted between the two layers of the iliotibial tract of the fascia lata about the junction of the middle with the upper one-third of the thigh.

Nerve-supply.-The Tensor fasciae latae is supplied by the superior gluteal nerve (L. 4 and 5 and S. 1).

Actions-The Tensor fascia lata tightens the fascia lata; continuing its action it abducts the thigh and rotates it medially. In the erect posture, acting from below, it serves to steady the pelvis on the head of the femur; through the iliotibial tract it steadies the condyles of the femur. on the tibia and helps to maintain the erect attitude by keeping the knee extended.

The Sartorius (figs. 643, 645, 647), which is the longest muscle in the body, is narrow and ribbon-life: it arises by tendinous fibers from the anterior superior iliac spine and the upper one-half of the notch below it. It crosses the upper and anterior parts of the thigh obliquely, from the lateral to the medial side, then descends vertically as far as the medial side of the knee, where a thin; flattened tendon replaces the fleshy belly. This tendon curves obliquely forwards and expands into a broad aponeurosis which is inserted, in front of the Gracilis and Semitendinosus, into the upper part of the medial surface of the shaft of the tibia (fig. 472). The upper part of the aponeurosis is curved backwards over the upper edge of the tendon of the Gracilis so as to be inserted behind it. An offset, from its upper margin, blends with the capsule of the knee-joint, and another, from its lower border, with the fascia on the medial side of the leg.

The relations of this muscle to the femoral artery are, important, as it constitutes the chief guide in tying the vessel. In the upper one-third of the thigh it forms the lateral side of the femoral triangle, the medial side of which is formed by the medial border of the Adductor longus, and the base by the inguinal ligament; the femoral artery passes through the middle of this triangle from its base to its apex. In the middle one-third of the thigh, the femoral artery is contained in the adductor canal, on the roof of which the Sartorius lies (fig. 647).

Nerve-supply.-The Sartorius is supplied by the femoral nerve (L. 2 and 3).

Actions.-The Sartorius flexes the leg on the thigh, and the thigh on the pelvis; it also abducts the thigh and rotates it laterally. Acting from below it, flexes the pelvis on the thigh and rotates it towards the opposite side.

The Quadriceps femoris (figs. 643, 645, 647) is the great extensor muscle of the leg, and consists of a large fleshy mass which covers the front and sides of the femur. It is subdivided into separate portions, which have received distinctive names. One occupies the middle of the thigh, and arises from the ilium frown its straight course, it is called the Rectus femoris. The, other three take origin from the body of the femur, which they cover from the trochanters to the condyles; that on the lateral side of the femur is termed the Vastus lateralis; that on the medial side, the Vases medialis; and that in front, the Vastus intermedius.

The Rectus femoris (figs. 643, 645, 647) is fusiform in shape, and its superficial fibers are arranged in a bipennate manner, the deep fibers running straight down to the deep aponeurosis. It arises by two tendinous heads: a straight head from the anterior inferior iliac spine, and a reflected head, from a groove above the brim of the acetabulum. The two unite at an acute angle, and spread into an aponeurosis which is prolonged downwards on the anterior surface of the muscle, and from this the muscular fibers arise. The muscle ends in a broad and thick aponeurosis -which occupies the .lower two-thirds of its posterior surface, and, gradually becoming narrowed into a flattened tendon, is inserted into the base of the patella.

The Vastus laterally (figs. 643, 645, 647) is the largest part of the Quadriceps femoris. It arises by a broad aponeurosis, which is attached to the upper part of the trochanteric line, to the anterior and inferior borders of the greater trochanter, to the lateral lip of the gluteal tuberosity, and to the upper one-half of the lateral lip of the linea aspera; this aponeurosis covers the upper three-fourths of the muscle, and from its deep surface many fibers take origin. A few additional fibers arise from the tendon of the Gluteus maximus, and from the lateral intermuscular septum between the Vastus lateralis and short head of the Biceps femoris. The fibers form a large fleshy mass, which is attached to a strong aponeurosis placed on the deep surface of the lower part of the muscle this aponeurosis contracts into a flat tendon, which is inserted into the lateral border of the .patella, blending with the Quadriceps femoris tendon, and giving to the capsule of the knee-joint an expansion, which extends downwards to be attached to the lateral condyle of the tibia and blends with the iliotibial tract. The Vastus medialis and Vastus intermedius appear to be inseparably united, but when the Rectus femoris has been reflected a narrow interval will be observed extending upwards from the medial border of the patella between the two muscles, and the separation may be carried to the lower part of the trochanteric line where, however, the two muscles are frequently continuous.

The Vastus medialis (figs. 643; 645, 647) arises from the lower part of the trochanteric line, the spiral line, the medial lip of the linea aspera, the upper part of the medial supracondylar line, the tendons of the Adductor longus and Adductor magnus, and the medial intermuscular septum. Its fibers are directed downwards and forwards, and axe chiefly attached to an aponeurosis which lies on the deep surface of the muscle and is inserted into the medial border of the patella and the Quadriceps femoris tendon. An expansion from this tendon reinforces the capsule of the knee-joint and is attached below to the medial condyle of the tibia.

Figure 645
Thigh muscles transverse section at the level of the apex of the triangle - Figure 645
The Vastus intermedius (figs. 645, 647) arises from the front and lateral surfaces of the upper two-thirds of the shaft of the femur, and from. the lower part of the lateral intermuscular septum. Its fibers end in a superficial aponeurosis which forms the deep part of the Quadriceps femoris tendon.

The tendons of the different portions of the Quadriceps unite at the lower part of the thigh to form a single strong tendon which is inserted into the base of the patella, some fibers passing over it to blend with the ligamentum patellae.

More properly, the patella may be regarded as a sesamoid bone developed in the tendon of the Quadriceps; and the ligamentum patella, which is continued from the apex of the patella to the tubercle of the tibia, as the proper tendon of insertion of the muscle, the medial and lateral patellar retinacula being expansions from its borders. The suprapatellar bursa, which usually communicates with the cavity of the knee-joint is situated between the femur and the portion of the Quadriceps tendon above the patella; the deep infrapatellar bursa is interposed between the ligamentum patella and the tipper part of the front of the tibia (fig. 565).

The Articularis genus is a small muscle, usually distinct from the Vastus intermedius, but occasionally blended with it; it consists of several muscular bundles which arise from the anterior surface of the lower part of the shaft of the femur and are inserted into the upper part of the synovial membrane of the knee-joint.

Nerve-supply.-The Quadriceps femoris and the Articularis genus are supplied by the femoral nerve (L. 2, 3 and 4).

Actions.–The Quadriceps femoris extends the leg upon the thigh. The Rectus femoris assists the Psoas major and Iliacus in supporting the pelvis and trunk upon the femur; it also assists in flexing the thigh on the pelvis, or, if the thigh be fixed, it will flex the pelvis. The Vastus medialis draws the patella medially as well as upwards. The Articularis genus pulls upwards the synovial membrane of the knee-joint during extension of the leg.

 


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