Under this head will be described the muscles of the outer surface of
the pelvis and thigh, and those which form the posterior contour of the
latter. They are given in the order in which they may be conveniently
examined.
1. =Tensor fasciæ latæ= (Fig. 178).—This is the most anterior muscle of
the superficial layer. It is triangular in form, with its apex at the
external angle of the ilium.
_Origin._—The external angle of the ilium.
_Insertion._—The fascia lata, and thus indirectly to the patella, the
external straight ligament, and the crest of the tibia.
_Action._—To tense the fascia lata, flex the hip joint, and extend the
stifle joint.
_Structure._—The muscle arises by a rather small head, about two inches
(ca. 5 cm.) wide, on the antero-inferior eminence of the external angle
of the ilium. Below this the belly spreads out and terminates about
midway between the point of the hip and the stifle in the aponeurosis.
The belly fuses to a considerable extent with the superficial gluteus.
The aponeurosis fuses with the fascia lata, and detaches a lamina which
passes with the tendon of insertion of the superficial gluteus to the
external border of the femur.
_Relations._—Externally, the skin and fascia; internally, the obliquus
abdominis externus, the iliacus, superficial gluteus, rectus femoris,
and vastus externus, branches of the circumflex iliac, ilio-lumbar, and
iliaco-femoral arteries, and the anterior gluteal nerve; anteriorly, the
precrural lymph glands. A considerable quantity of connective tissue is
found between the deep face of the muscle and the abdominal wall.
_Blood-supply._—Circumflex iliac, ilio-lumbar, and iliaco-femoral
arteries.
_Nerve-supply._—Anterior gluteal nerve.
2. =Gluteus superficialis= (Figs. 178, 199) (Superficial gluteus;
gluteus externus).—This muscle lies behind and partly underneath the
tensor fasciæ latæ. It is triangular and consists of an anterior and a
posterior head united by the gluteal fascia.
_Origin._—(1) The external angle and the adjacent part of the external
border of the ilium (anterior head); (2) the gluteal fascia (posterior
head).
_Insertion._—The third (external) trochanter of the femur.
_Action._—To abduct the limb, flex the hip joint, and tense the gluteal
fascia.
_Structure._—The anterior head of the muscle is not completely separable
(except artificially) from the tensor fasciæ latæ. The attachment to the
border of the ilium is by means of an intermuscular septum, which passes
beneath the thick outer border of the gluteus medius. The posterior head
arises from the deep face of the gluteal fascia, and so indirectly from
the dorsal sacro-iliac ligament. The two heads unite and terminate on a
strong flat tendon, which is inserted into the edge of the third
trochanter of the femur, beneath the biceps femoris.
_Relations._—Superficially, the skin, fascia, and biceps femoris;
deeply, the gluteus medius, iliacus, rectus femoris, and branches of the
iliaco-femoral artery; in front, the tensor fasciæ latæ; behind, the
biceps femoris.
_Blood-supply._—Gluteal and iliaco-femoral arteries.
_Nerve-supply._—Anterior gluteal nerve.
3. =Gluteus medius= (Figs. 178, 179) (Middle gluteus; gluteus
maximus).—This is a very large muscle which covers the dorsal surface of
the ilium and the greater part of the lateral wall of the pelvis, and
extends forward also on the lumbar part of the longissimus.
_Origin._—(1) The aponeurosis of the longissimus, as far forward as the
first lumbar vertebra; (2) the gluteal or dorsal surface and internal
and external angles of the ilium; (3) the dorsal and lateral sacro-iliac
and sacro-sciatic ligaments, and the gluteal fascia.
_Insertion._—(1) The summit of the trochanter major of the femur; (2)
the crest below the trochanter; (3) the outer aspect of the trochanteric
ridge.
_Action._—To extend the hip joint and abduct the limb. By its connection
with the longissimus a muscular mass is formed which is one of the chief
factors in rearing, kicking, and propulsion.
_Structure._—The anterior extremity of the muscle is relatively thin,
and lies in a depression on the surface of the longissimus, from the
strong aponeurosis of which the fibers take origin. The pelvic portion
of the muscle is very voluminous, and forms the bulk of the muscular
mass which gives the haunch its rounded contour. This part of the muscle
is intersected by several tendinous sheets. One of these is particularly
distinct, and is attached to the gluteal line on the ilium. This divides
the muscle incompletely into superficial and deep strata. The
superficial part is inserted by a strong tendon into the summit of the
great trochanter, and by a pointed fleshy mass with a tendinous border
into the trochanteric ridge. The deep part (Gluteus accessorius) is
smaller, and arises entirely from the ilium between the gluteal line and
the external angle (Fig. 455). It has a strong flat tendon which passes
over the convexity of the trochanter to be inserted into the crest below
it. The convexity is covered with cartilage, and the =trochanteric
bursa= (Bursa trochanterica) is interposed between the tendon and the
cartilage.[63]
_Relations._—Superficially, the skin, lumbo-dorsal and gluteal fasciæ,
the tensor fasciæ latæ, gluteus superficialis, and biceps femoris;
deeply, the longissimus, the ilium, sacro-iliac and sacro-sciatic
ligaments, the gluteus profundus, iliacus and rectus femoris, the
iliaco-femoral artery, the gluteal and internal pudic vessels and
nerves, and the great sciatic nerve.
_Blood-supply._—Gluteal, ilio-lumbar, lumbar, and iliaco-femoral
arteries.
_Nerve-supply._—Gluteal nerves.
4. =Gluteus profundus= (Deep gluteus; gluteus internus;
scansorius).—This much smaller, quadrilateral muscle lies under the
posterior part of the preceding muscle, and extends over the hip joint,
from the superior ischiatic spine to the anterior part of the great
trochanter (Fig. 455).
_Origin._—The superior ischiatic spine and the adjacent part of the
shaft of the ilium.
_Insertion._—The edge of the anterior part or convexity of the
trochanter major of the femur.
_Action._—To abduct the thigh and to rotate it inward.
_Structure._—The muscle is short and thick and contains numerous
tendinous intersections. The fibers are directed almost transversely
outward over the capsule of the hip joint and converge at the convexity
of the trochanter.
_Relations._—Superficially, the gluteus medius and branches of the
gluteal vessels and nerves; deeply, the shaft of the ilium, the hip
joint, and the rectus femoris and capsularis.
_Blood-supply._—Gluteal artery.
_Nerve-supply._—Anterior gluteal nerve.
5. =Biceps femoris= (Gluteo-biceps s. paramero-biceps).—This large
muscle lies behind and in part upon the superficial and middle glutei.
It extends in a curved direction from the sacral and coccygeal spines to
the outer surface of the stifle and leg (Figs. 178, 199, 200, 201, 202).
_Origin._—(1) The dorsal sacro-iliac ligament, the gluteal and coccygeal
fasciæ, and the intermuscular septum between this muscle and the
semitendinosus; (2) the tuber ischii.
_Insertion._—(1) A tubercle on the posterior surface of the femur near
the external trochanter; (2) the anterior surface and external straight
ligament of the patella; (3) the tibial crest; (4) the anterior and
internal surface of the tuber calcis.
_Action._—The action is somewhat complex, because the muscle is composed
of three portions, has several points of insertion, and acts on all the
joints of the limb except those of the digit. The general action is to
extend the limb, as in propelling the body, rearing or kicking, and to
abduct it. The anterior part, by its attachment to the posterior surface
of the femur and to the patella, would extend the stifle and hip joints
and abduct the limb. The middle part, being inserted chiefly on the
tibial crest and the external straight ligament, would extend the hip,
and, with the semitendinosus, flex the stifle. The posterior part, by
virtue of its attachment to the tuber calcis, assists in extending the
hock.
[Illustration: