MUSCLES OF THE PELVIS AND THIGH.
_The Buttock._--_Gluteus maximus_, its thickness and form; its
relations to the great trochanter.--_Gluteus medius._--The
subjacent muscles (_gluteus minimus_, _pyriformis_,
etc.).--Muscles of the thigh; 1st, External region _tensor
fasciæ latæ_ (_vaginæ femoris_), its importance with regard
to external form; aponeurosis of _fascia lata_; 2nd, Anterior
region, _sartorius_, peculiarities of this muscle during
contraction; _quadriceps extensor_ (_rectus_, _vastus internus_,
_vastus externus_, _crureus_); 3rd, Internal region, the
_adductors_; 4th, Posterior region, _hamstring_ muscles
(_biceps_, _semi-tendinosus_, and _semi-membranosus_).
_Muscles of the Pelvis._--The muscles of the pelvis visible on the
model are all situated on the posterior surface of that part of the
skeleton, and form the buttock, or _gluteal region_. In front the
anterior wall of the abdomen, descending to Poupart’s ligament and the
pubis (Fig. 70, page 197), conceals the muscles which proceed from the
interior of the pelvis towards the thigh--muscles of which a short
sketch will be given along with those of the front of the thigh.
Of the muscles of the gluteal region two only are superficial and well
marked on the model--viz., the _gluteus maximus_ and _gluteus medius_.
The _gluteus maximus muscle_ (Fig. 72, page 201) is the largest and
thickest of all the muscles of the body. It is composed of large fleshy
fibres directed obliquely from the sacro-iliac region towards the upper
part of the femur. Its fibres arise from the posterior extremity of the
crest of the ilium (4, Fig. 34, page 107), by an aponeurosis from the
back of the sacrum, from the sacrum itself, and from the sacro-sciatic
ligament. The coarse fleshy fibres are directed downwards and outwards
through the gluteal region (Fig. 67). At the level of the great
trochanter these fibres are for the most part inserted into a broad,
thick, tendinous lamina, which is continuous with the aponeurosis of
the thigh or _fascia lata_. The lower and deeper part of the muscle is
inserted directly into the gluteal ridge of the femur (page 133). The
gluteus maximus muscle presents four borders: (1) an _internal border_,
corresponding to its origin, and convex inwards, and (2) an _external
border_, also slightly convex at its insertion. This border corresponds
to the line along which the fleshy fibres terminate; it forms a
prominence, which curves posteriorly round the great trochanter. When
we have enumerated the muscles lying beneath the gluteus maximus, it
will be more easy to understand how the muscular structure of the
gluteal region as a whole is so prominent that the great trochanter
actually forms on the model the centre of a depressed area, bounded
behind and above by the prominence of the gluteal muscles, and in
front by the tensor muscle of the fascia lata (see _Muscles of the
thigh_). (3) The _inferior border_ of the gluteus maximus is thick,
and forms an oblique elevation, beneath which the posterior muscles of
the thigh emerge; it is this which helps to form the lower limit of
the prominence of the buttock. In the erect position the lower limit
of the gluteal region is indicated by a transverse fold (_the fold of
the nates_). This line runs diagonally across the lower border of the
gluteus maximus, and is produced not by the edge, but by the weight
of the relaxed muscle, and the fat which covers it. (4) The _superior
border_ is thin (Fig. 74, page 217), and is continuous with the fascia
lata, which covers the gluteus medius, so that its prominence is little
marked on the model, being more or less lost in the area corresponding
to the position of the gluteus medius muscle.
The _gluteus maximus_ is an extensor of the thigh on the pelvis. In the
upright position it supports the pelvis behind and prevents it from
inclining forwards. It is by its action that the trunk is raised so as
to be in the same line as the upright lower limb. The gluteus maximus
is therefore the muscle of the upright position, and we observe the
large size which it presents in the human subject compared with its
small proportions in animals which do not adopt the biped attitude.
The _gluteus medius muscle_ is situated both above and beneath that
of the gluteus maximus--that is to say, the postero-inferior part
is covered by the preceding muscle, but its antero-superior part is
superficially placed. This latter part (Fig. 74, between 22 and 23)
is, however, covered by the thick fascia lata of the thigh, which
binds down the muscle to the dorsum ilii. Arising from the anterior
three-fourths of the crest of the ilium, and from the dorsum ilii as
well as from the fascia over it, the fibres of the gluteus medius
descend, converging towards the great trochanter, into the external
surface of which they are inserted by a thick aponeurotic tendon. The
fleshy fibres cease a little above the great trochanter so as to form
a prominence along a curved line with its concavity downwards, which
forms the superior boundary of the depression corresponding to the
region of the great trochanter, referred to above. The gluteus medius,
by its posterior fibres, acts like the gluteus maximus; by its anterior
fibres it draws the thigh outwards, acting as an abductor.
[Illustration: FIG. 80.
THE DEEP GLUTEAL MUSCLES.--1, Dorsum ilii;--2, sacrum;--3,
posterior sacro-iliac ligament;--4, tuberosity of ischium;--5,
great, 6, lesser sacro-sciatic ligament;--7, great
trochanter;--8, gluteus minimus;--9, pyriformis;--10, 11, 12,
gemelli and obturator internus 13, quadratus femoris;--14,
adductor magnus;--15, vastus externus;--16, biceps and
semi-tendinosus--17, gracilis;--18, semi-membranosus.]
The gluteus maximus and gluteus medius muscles conceal a series of deep
muscles filling up the large space which we observe on the skeleton
between the great trochanter and the pelvic wall. These muscles, which
we only need to enumerate in order to understand the importance of the
prominence of the buttock, are, taking them in order, as follows--the
_gluteus minimus_, which lies exactly beneath the gluteus medius, and
proceeds from the dorsum ilii to the superior and anterior border
of the great trochanter; the _pyriformis_, which arises within the
pelvis from the anterior surface of the sacrum, escapes from the pelvis
through the great sciatic notch, and is directed obliquely towards
the great trochanter, into the upper border of which its tendon is
inserted; the _obturator internus_, which proceeds also from the
interior of the pelvis, is reflected over the lesser sciatic notch and
is inserted into the internal surface of the great trochanter along
with two accessory muscles, the _gemelli_; and finally, the _quadratus
femoris_, formed by short horizontal fibres, which extends from the
outer part of the tuberosity of the ischium to the posterior surface of
the femur between the two trochanters.
_Muscles of the thigh._--The muscles of the thigh are arranged around
the femur, and frequently in a direction so oblique that they appear
in one portion, for example, on the front, and in another portion
on the inner side of the thigh. We can, however, class them in four
series--external, comprising the _tensor vaginæ femoris_ (_fasciæ
latæ_); anterior, comprising the _sartorius_ and _quadriceps extensor_;
internal, comprising the _adductors_; and posterior, comprising the
_biceps_, the _semi-membranosus_, and the _semi-tendinosus_.
[Illustration: FIG. 81.
THE MUSCLES OF THE ANTERIOR SURFACE OF THE RIGHT THIGH.--1, the
iliacus;--2, the psoas;--3, the tensor vaginæ femoris;--4, its
tendon (fascia lata);--5, the sartorius;--6, the rectus (long
head of quadriceps;--7, vastus externus (the external head);--8,
vastus internus (the internal head);--9, the gracilis;--10, the
adductor longus;--11, the pectineus.]
I. _Outer side of the thigh._ The _tensor vaginæ femoris muscle_
(3, Fig. 81).--This muscle lies in the plane of the gluteus maximus
(23, Fig. 74, page 217), and forms a distinct prominence in front of
the great trochanter. It arises from the anterior superior spine of
the ilium, and is directed downwards and slightly backwards on the
outer side of the thigh, to terminate a short way below the level
of the great trochanter by being inserted into the broad and thick
aponeurosis--the _fascia lata_--which covers this region (4, Fig. 81).
This aponeurosis is specially thickened by the addition of vertical
fibres, which form a tendon of insertion known as the _ilio-tibial_
band. This band descends to the outer side of the knee as a distinct
prominent tendon, which is inserted finally into the outer tuberosity
of the tibia (see page 135). This muscle rotates outwards the thigh
and the whole lower limb, and contributes also to the flexion of the
thigh on the pelvis; therefore, when the thigh is extended and not
turned inwards, the tensor muscle forms beneath the iliac spine a long
muscular elevation, but when it is in action its form becomes short and
broad, and forms a characteristic globular mass. This contrast in the
form of the tensor muscle in repose and in action has been beautifully
shown on the Gladiator, in which there is contraction of the tensor of
the right thigh and relaxation of that of the left.
The ilio-tibial band and the aponeurosis of the fascia lata cover,
on the outer side of the thigh, the large fleshy mass of the _vastus
externus_ (a part of the quadriceps extensor muscle), which belongs
to the anterior region of the thigh. This muscle, thus covered in,
is shown throughout its entire extent on the surface. Though covered
by the fascia lata, it forms a marked convexity on the outer side of
the thigh, as a gentle curve in women, and a strongly bowed line in
well-developed, muscular men.
II. _Front of the Thigh._ The _sartorius muscle_ (5, Figs. 81, and 23,
Fig. 70, page 197).--This is the longest muscle in the human body. It
forms a narrow fleshy band, which arises from the anterior superior
iliac spine, and is directed obliquely downwards and inwards. Crossing
the front of the thigh obliquely, it descends round the inner side of
the knee over the inner condyle of the femur (Fig. 86), describing a
curve with the concavity forward. It finally terminates at the upper
part of the inner surface of the shaft of the tibia in a flat tendon
(19 and 20, Fig. 86) which sweeps forward to be inserted into that bone
just below the inner tuberosity in front of and along with the gracilis
and semi-tendinosus muscles.
The sartorius flexes and abducts the thigh on the pelvis, and flexes
the leg on the thigh; so that it gives to the lower limb a position
similar to that of a tailor when seated, hence the name of this muscle
(_sartor_, a tailor). With regard to surface form, this muscle is
indicated externally in a peculiar manner. When it contracts, only its
superior extremity presents a superficial prominence; throughout the
rest of its extent, the presence of the muscle, lying in the depressed
groove between the quadriceps extensor in front and the adductor
muscles on the inner side, is indicated during contraction by a large
shallow furrow, particularly noticeable on the inner side of the thigh,
at the junction of the upper two-thirds with the lower third.
_Quadriceps extensor_ (6, 7, 8, Fig. 81).--The quadriceps extensor
muscle belongs to the outer and inner regions of the thigh as well
as to the front of the limb, but the element of the muscle of most
importance in relation to external form--the _rectus femoris_--is
situated anteriorly. The muscle, as its name implies, is composed of
four portions: one, the _rectus_, in the middle; the _vastus internus_
and the _vastus externus_, on each side; and the _crureus_, the deepest
part, concealed by the other portions of the muscle.
The _rectus femoris_ (21, Fig. 70, and 6, Fig. 81) is long and fusiform
in shape--that is to say, larger at its centre than at its extremities.
Its superior extremity, the more slender of the two, arises by a double
tendon from the anterior inferior iliac spine and the dorsum ilii, and
appears on the front of the thigh between the tensor fasciæ femoris
and the sartorius muscles. Lying in the angular space which separates
these two muscles (Fig. 81), the rectus descends vertically on the
front of the thigh, and about four inches above the patella forms a
broad tendon (Figs. 81 and 84), the borders of which give insertion on
either side to the vastus internus and vastus externus muscles, while
its deep surface gives insertion to the crureus muscle, and its base
broadens out to be inserted into the patella. From the lower end of
the patella a broad ligament--_the ligament of the patella_--arises
(page 134), which is inserted into the tubercle of the tibia; it
follows, therefore, that by means of the tendon of the rectus femoris,
the patella, and the ligament of the patella, the quadriceps extensor
muscle is eventually inserted into the tibia (Fig. 45, page 137).
The _vastus internus muscle_ (8, Fig. 81) is a very large fleshy mass,
which covers the inner side of the femur. Arising from the inner lip of
the linea aspera of the femur, from the edge of the bone (spiral line)
above, and from the internal supra-condyloid ridge below, its muscular
fibres are directed downwards and forwards, to be inserted into the
deep surface and the inner border of the tendon of the rectus femoris,
into the side of the patella, and into the capsule of the knee-joint.
It conceals the crureus and partly blends with that muscle. The outline
of the vastus internus is easily discernible on the surface, forming a
somewhat triangular, convex, and rounded contour; bounded internally
by the furrow of the sartorius, externally by a vertical line where
it joins the tendon of the rectus femoris, and below by its lower
border, it forms a well-marked rounded line sweeping outwards over the
internal condyle of the femur to the side of the patella. These details
are of great importance in regard to the contour of the region above
the patella, and are in marked contrast, as we shall see, with the
arrangement presented at the same level by the lower part of the vastus
externus.
The _vastus externus_ (7, Fig. 81) lies external to the rectus
femoris, and conceals the crureus, with which its deep surface is
partially blended. Its origin, which underlies the tensor fasciæ
femoris and the ilio-tibial band, is from the upper half of the shaft
of the femur, from the outer lip of the linea aspera. Its fibres sweep
downwards and slightly forwards to be inserted into the tendon of the
rectus, the patella, and the capsule of the knee-joint. The line along
which it is inserted into the rectus tendon describes a curve of which
the convexity looks towards the supero-external angle of the patella,
from which it is separated by a considerable interval (Figs. 81 and
85). Consequently on the surface the flat surface above the patella
forms a sort of triangle, of which the borders are very different,
the inner border being vertical, the outer one oblique, curved, and
higher in position; the base of the triangle corresponds to the patella
and the lateral parts of the capsule of the knee-joint; its truncated
summit corresponds to the inferior extremity of the fleshy part of the
rectus; and the borders of this flat surface, formed by the fleshy
insertions of the vasti muscles, become very prominent when the leg is
forcibly straightened on the thigh.
The _crureus_ muscle, deeply placed, is the fourth element in the
quadriceps muscle. It arises from the upper three-fourths of the shaft
of the femur, externally and in front, and forms a thick, fleshy mass,
responsible to a great extent for the general contour of the front
and sides of the thigh, though it is not actually noticeable directly
on the surface. It is almost wholly concealed by the three previous
muscles. It is partially blended on each side with the vasti muscles;
and it is inserted as well into the deep surface of the tendon of the
rectus femoris. It is hardly necessary to point out, since it is clear
from its anatomical arrangement, that the quadriceps muscle, passing by
means of the patella and the patellar ligament to the tubercle of the
tibia, is essentially the extensor muscle of the leg.
It is to be noted that the two vasti muscles have a very different
effect in the shaping of the contours of the thigh. The vastus externus
has its greatest prominence well above the patella on the outer side:
the most prominent part of the vastus internus is formed by its lowest
fibres, as they sweep across over the inner condyle of the femur.
III. _The inner side of the thigh._ The _adductor muscles_.--We
understand by _the adductors_ the numerous muscles that occupy the
inner part of the thigh, and which, passing down from the pubis and
ischium along the entire length of the femur, fill up the triangular
space which appears in the skeleton between the inner surface of the
femur and the pubic part of the hip-bone. Some of the muscles of this
series take the special name of adductors. We will study in succession
three muscles clearly visible on the model--viz. the _pectineus_, the
_adductor longus_, and the _gracilis_; afterwards we will mention
briefly the muscles almost hidden by the preceding--namely, the
_adductor brevis_ and the _adductor magnus_ muscles.
[Illustration: FIG. 82.
THE POPLITEAL REGION AND POSTERIOR SURFACE OF THE RIGHT LEG.--1,
internal gastrocnemius;--2, external gastrocnemius;--3,
space between gastrocnemii;--4, 5, tendo Achillis;--6, 7, 7,
plantaris muscle and its tendon;--8, tendons of deep muscles
(common flexor and posterior tibial);--9, peroneus longus;--10,
peroneus brevis;--11, soleus;--12, biceps femoris;--13,
semi-tendinosus;--14, semi-membranosus;--15, gracilis;--16,
sartorius.]
The _pectineus muscle_ (22, Fig. 70, and 11, Fig. 81), the first and
shortest of the muscles of this region, is a broad fleshy band which
extends from the horizontal ramus of the pubis to the upper part of
the shaft of the femur (to a rough line passing from the linea aspera
to the lesser trochanter). The lower part of this muscle is hidden by
the sartorius, and the upper part does not show itself clearly beneath
the skin, being covered by the large vessels of the thigh, and also in
most cases by a quantity of fat. The pectineus forms the middle part of
the floor of a triangular space in the upper third of the thigh, with
its apex below, known in surgical anatomy as _Scarpa’s triangle_, which
is bounded externally by the sartorius muscle. The base of the triangle
corresponds to the groin, and is formed by Poupart’s ligament. The
outer part of the floor of the triangle is formed by a large muscle, of
which the greater part is situated in the cavity of the abdomen. This
is the _ilio-psoas_ muscle (1 and 2, Fig. 81), which arises from the
lateral parts of the lumbar vertebræ (_psoas_) and from the iliac fossa
(_iliacus_), passes beneath Poupart’s ligament (page 199), and after
traversing Scarpa’s triangle is inserted into the lesser trochanter of
the femur. This muscle is not visible superficially except just below
and internal to the anterior superior iliac spine, where it forms a
slight bulging beneath the skin.
The inner part of the floor of Scarpa’s triangle is formed by the
_adductor longus_, triangular in shape (10, Fig. 81); arising by a
narrow tendon from the angle of the pubis, it is inserted, beneath the
sartorius, into the middle portion of the linea aspera of the femur.
The _gracilis_ is visible throughout its entire length on the inner
surface of the thigh (9, Fig. 81). It forms a long slender fleshy
band, broader above and narrower below. Arising from the symphysis and
descending ramus of the pubis, it descends vertically; a little above
the inner condyle of the femur it is replaced by a narrow tendon (15,
Fig. 82), which sweeps round the condyle, behind the sartorius, and in
front of the semi-tendinosus, to be inserted into the upper part of the
inner surface of the shaft of the tibia behind the sartorius and above
the semi-tendinosus.
Covered by the preceding muscles and placed more deeply, are the
adductors, brevis and magnus, which fill up the space between the
gracilis and the femur. The _adductor brevis_ extends from the pubis to
the upper part of the linea aspera; the _adductor magnus_ is a thick,
fleshy, triangular muscle which arises from the tuberosity and ramus
of the ischium, and is inserted into the entire length of the linea
aspera of the femur, so that its superior fibres are horizontal and
its inferior fibres almost vertical in direction; among these last the
most internal, which arise from the ischial tuberosity, form below a
distinct tendon, which projects above the inner side of the knee-joint
and is inserted into a tubercle (the _adductor_ tubercle of the femur)
placed above the inner condyle of the femur.
[Illustration: FIG. 83.
HAMSTRING MUSCLES. 1, gluteus medius;--2, gluteus maximus;--3,
vastus externus;--4, biceps (long head)--5, biceps (short
head)--6, semi-tendinosus;--7, semi-membranosus;--8,
gracilis;--9, adductor magnus;--10, sartorius;--11, popliteal
space;--12, gastrocnemius.]
The action of all the muscles which we have just studied, except the
pectineus, is to draw the thigh inwards towards the axis of the body;
they also bring the knees close to each other, hence they are called
the adductors of the thigh.
IV. _The back of the thigh._ The _posterior_ muscles of the thigh
(_hamstring muscles_).--These muscles, three in number, arise from
the tuberosity of the ischium, and thus their origins are hidden
beneath the gluteus maximus. They emerge below the lower border of
that muscle and descend vertically; above the posterior surface of the
knee (or ham) they divide into two masses, one, the external, formed
by a single muscle, the _biceps femoris_, the other internal, formed
by two muscles placed one on the other, the _semi-tendinosus_ and the
_semi-membranosus_.
The _biceps femoris_ (4, Fig. 83) is so called because, like the biceps
in the arm, it is formed above by two heads, a _long_ head which arises
from the tuberosity of the ischium, and a _short_ head, more deeply
placed, which arises from the linea aspera of the femur. These two
heads unite in a stout tendon (12, Fig. 82) which the muscular fibres
accompany for the greater part of its length, and which is directed
downwards on the outer side of the knee, to be inserted into the summit
of the superior extremity of the head of the fibula. This muscle flexes
the leg on the thigh, and when it accomplishes this action its tendon
becomes very prominent, forming the outer boundary of the region of the
ham or popliteal space.
The _semi-tendinosus_ (13, Fig. 82; 6, Fig. 83), visible throughout
its entire extent (except at its origin, which is hidden beneath the
gluteus maximus), has been so called because in a great part of its
length, almost equal to its lower half, it is represented only by
its tendon. It arises above from the ischium, and descends parallel
to the long head of the biceps, to the inner side of which it is
situated; towards the junction of the middle with the lower third
of the posterior surface of the thigh, its fleshy belly becomes
narrower, and is replaced by a long, thin tendon (13, Fig. 82) which
inclines inwards, and passes behind the internal condyle of the femur,
describing a slight curve with its concavity forwards behind the
tendons of the sartorius and gracilis. With them (pages 258 and 264)
it is inserted into the upper part of the internal surface of the
shaft of the tibia (24, Fig. 86). This muscle flexes the leg, and in
this movement the prominence of its tendon starts out as the internal
boundary of the region of the ham.
The _semi-membranosus_ is broader than the semi-tendinosus (7, Fig.
83). It is situated beneath it and projects beyond it on both sides.
It is so called because its upper half is formed by a broad membranous
tendon arising from the tuberosity of the ischium. The muscular fibres
commence below the middle of the thigh and form a large fleshy belly,
thick, broad, and short, which passes into a strong tendon (14,
Fig. 82) inserted mainly into the posterior surface of the internal
tuberosity of the tibia.
The fleshy belly of this muscle projects beyond the tendon of the
semi-tendinosus on each side, and reaches to the middle line of the
posterior surface of the thigh and knee, forming a large muscular
prominence. When the leg is flexed on the thigh, the tendons of
the biceps and semi-tendinosus become prominent, bounding a deep
pit (the ham or popliteal space) corresponding to the upper part
of the posterior surface of the knee, and the fleshy part of the
semi-membranosus remains hidden in the bottom of this pit; but
when the leg is extended on the thigh there is no longer a hollow,
but the posterior surface of the knee presents, on the contrary, a
prominent form, produced in the upper part by the fleshy mass of the
semi-membranosus, and in the lower part by the muscles of the calf, to
be described in the next chapter.