Chapter 10
The Muscular System
365
10
Muscles of the Medial Compartment of the Thigh
Adductors
(ah-duk
9
torz)
Large muscle mass consisting of three muscles (magnus, longus, and brevis) forming medial aspect of thigh; arise
from inferior part of pelvis and insert at various levels on femur. All are used in movements that press thighs
together, as when astride a horse; important in pelvic tilting movements that occur during walking and in fixing
the hip when the knee is flexed and the foot is off the ground. Obturator nerve innervates entire group. Strain
or stretching of this muscle group is called a “pulled groin.”
Adductor magnus
(mag
9
nus) (
adduct
5
move toward midline;
magnus
5
large)
Triangular muscle with
a broad insertion; a
composite muscle that is
part adductor and part
hamstring in action
O—ischial and pubic rami
and ischial tuberosity
I—linea aspera and
adductor tubercle of
femur
Anterior part
adducts
and medially rotates and
flexes thigh
; posterior
part is a synergist of
hamstrings to
extend
thigh
Obturator nerve and
sciatic nerve (L
2
–L
4
)
Adductor longus
(
longus
5
long)
Overlies middle aspect of
adductor magnus; most
anterior of adductor
muscles
O—pubis near pubic
symphysis
I—linea aspera
Adducts, flexes, and
medially rotates thigh
Obturator nerve
(L
2
–L
4
)
Adductor brevis
(
brevis
5
short)
In contact with obturator
externus muscle; largely
concealed by adductor
longus and pectineus
O—body and inferior
pubic ramus
I—linea aspera above
adductor longus
Adducts, flexes, and
medially rotates thigh
Obturator nerve
Pectineus
(pek-tin
9
e-us)
(
pecten
5
comb)
Short, flat muscle;
overlies adductor brevis
on proximal thigh; abuts
adductor longus medially
O—pubis (and superior
ramus)
I—from lesser trochanter
inferior to the linea
aspera on posterior
aspect of femur
Adducts, flexes, and
medially rotates thigh
Femoral and
sometimes obturator
nerve
Gracilis
(grah-sı˘
9
lis)
(
gracilis
5
slender)
Long, thin, superficial
muscle of medial thigh
O—inferior ramus and
body of pubis and
adjacent ischial ramus
I—medial surface of tibia
just inferior to its medial
condyle
Adducts thigh, flexes
and medially rotates leg
,
especially during walking
Obturator nerve
Muscles of the Anterior Compartment of the Thigh
Quadriceps femoris
(kwod
9
rı˘-seps fem
9
o-ris)
Arises from four separate heads (
quadriceps
5
four heads) that form the flesh of front and sides of thigh. These
heads (rectus femoris, and lateral, medial, and intermediate vasti muscles) have a common insertion tendon, the
quadriceps tendon
, which inserts into the patella and then via the
patellar ligament
into tibial tuberosity. The
quadriceps is a powerful knee extensor used in climbing, jumping, running, and rising from seated position. The
tone of quadriceps plays important role in strengthening the knee joint. Femoral nerve innervates the group.
Rectus femoris
(rek
9
tus)
(
rectus
5
straight;
femoris
5
femur)
Superficial muscle of
anterior thigh; runs straight
down thigh; longest head
and only muscle of group
to cross hip joint
O—anterior inferior
iliac spine and superior
margin of acetabulum
I—patella and tibial
tuberosity via patellar
ligament
Extends knee and flexes
thigh at hip
Femoral nerve (L
2
–L
4
)
Vastus lateralis
(vas
9
tus lat
0
er-a
9
lis)
(
vastus
5
large;
lateralis
5
lateral)
Largest head of the
group, forms lateral
aspect of thigh; a common
intramuscular injection site,
particularly in infants (who
have poorly developed
buttock and arm muscles)
O—greater trochanter,
intertrochanteric line,
linea aspera
I—as for rectus femoris
Extends and stabilizes
knee
Femoral nerve
Vastus medialis
(me
0
de-a
9
lis)
(
medialis
5
medial)
Forms inferomedial aspect
of thigh
O—linea aspera,
intertrochanteric and
medial supracondylar
lines
I—as for rectus femoris
Extends knee
Femoral nerve
MUSCLE GALLERY
Table 10.14
(continued)
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