328
UNIT TWO
plates 73, 74, 75, and are listed in
table 9.14
. Muscles that
move the foot include the following:
Dorsal Flexors
Invertor
Tibialis anterior
Tibialis posterior
Fibularis tertius
Extensor digitorum longus
Extensor hallucis longus
Plantar Flexors
Evertor
Gastrocnemius
Fibularis longus
Soleus
Plantaris
Flexor digitorum longus
Dorsal Flexors
The
tibialis anterior
(tib
e-a
lis ante
re-or) is an elongated,
spindle-shaped muscle located on the front of the leg. It
arises from the surface of the tibia, passes medially over
the distal end of the tibia, and attaches to bones of the foot.
Contraction of the tibialis anterior causes dorsifl
exion and
inversion of the foot (see ±
g. 9.41).
The
f
bularis
(peroneus)
tertius
(± b
u-la
ris ter
shus) is
a muscle of variable size that connects the ±
bula to the lat-
eral side of the foot. It functions in dorsifl exion and eversion
of the foot (see ±
g. 9.41).
The
extensor digitorum longus
(eks-ten
sor dij
ı
˘-to
rum
long
gus) is situated along the lateral side of the leg just behind
the tibialis anterior. It arises from the proximal end of the tibia
and the shaft of the ± bula. Its tendon divides into four parts as
it passes over the front of the ankle. These parts continue over
the surface of the foot and attach to the four lateral toes. The
actions of the extensor digitorum longus include dorsifl exion
of the foot, eversion of the foot, and extension of the toes
(see ±
gs. 9.41 and 9.42).
The
sartorius
(sar-to
re-us) is an elongated, straplike
muscle that passes obliquely across the front of the thigh
and then descends over the medial side of the knee. It con-
nects the ilium to the tibia and fl
exes the leg and the thigh. It
can also abduct the thigh and rotate it laterally (see ± gs. 9.37
and 9.38).
Extensor
The large, fl eshy muscle group called the
quadriceps ±emo-
ris
(kwod
˘-seps fem
or-is) occupies the front and sides of
the thigh and is the primary extensor of the knee. It is com-
posed of four parts—
rectus femoris, vastus lateralis, vastus
medialis,
and
vastus intermedius
(see ± gs. 9.38 and 9.40).
These parts connect the ilium and femur to a common
patel-
lar tendon,
which passes over the front of the knee and
attaches to the patella. This tendon then continues as the
patellar ligament
to the tibia.
In a traumatic injury that compresses a muscle, such as the quadri-
ceps femoris, against an underlying bone, new bone tissue may
begin to develop in the damaged muscle. This condition is called
myositis ossif
cans
. Surgery can remove the newly formed bone when
it matures several months after the injury.
Muscles That Move the Foot
Movements of the foot include movements of the ankle and
toes. A number of muscles that move the foot are in the leg.
They attach the femur, tibia, and ±
bula to bones of the foot
and move the foot upward (dorsifl
exion) or downward (plan-
tar fl
exion) and turn the foot so the plantar surface faces
medially (inversion) or laterally (eversion). These muscles
are shown in
f
gures 9.41, 9.42, 9.43
, and
9.44
, in reference
TABLE
9.13
|
Muscles That Move the Leg
Muscle
Origin
Insertion
Action
Nerve Supply
Hamstring Group
Biceps femoris
Ischial tuberosity and linea aspera of
femur
Head of F
bula and lateral condyle of tibia
±lexes knee, rotates leg
laterally and extends thigh
Tibial n.
Semitendinosus
Ischial tuberosity
Medial surface of tibia
±lexes knee, rotates leg
medially and extends thigh
Tibial n.
Semimembranosus
Ischial tuberosity
Medial condyle of tibia
±lexes knee, rotates leg
medially and extends thigh
Tibial n.
Sartorius
Anterior superior iliac spine
Medial surface of tibia
±lexes knee and hip, abducts
and rotates thigh laterally
±emoral n.
Quadriceps ±emoris Group
Rectus femoris
Spine of ilium and margin of acetabulum
Vastus lateralis
Greater trochanter and posterior surface
of femur
Patella by common tendon, which continues
as patellar ligament to tibial tuberosity
Extends knee
±emoral n.
Vastus medialis
Medial surface of femur
Vastus intermedius
Anterior and lateral surfaces of femur
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