330
UNIT TWO
erful plantar fl exor of the foot that aids in pushing the body
forward when a person walks or runs. It also fl
exes the leg at
the knee (see F
gs. 9.42 and 9.43).
Strenuous athletic activity may partially or completely tear the calca-
neal (Achilles) tendon. This injury occurs most frequently in middle-
aged athletes who run or play sports that involve quick movements
and directional changes. A torn calcaneal tendon usually requires
surgical treatment.
The
extensor hallucis longus
(eks-ten
sor hal
lu-sis
long
gus) connects the anterior fibula with the great toe.
Contraction extends the great toe, dorsifl
exes and inverts the
foot (see F
g. 9.41).
Plantar Flexors
The
gastrocnemius
(gas
trok-ne
me-us) on the back of the
leg forms part of the calf. It arises by two heads from the
femur. The distal end of this muscle joins the strong
calca-
neal tendon
(Achilles tendon), which descends to the heel
and attaches to the calcaneus. The gastrocnemius is a pow-
Biceps femoris
Gastrocnemius
Soleus
Fibularis longus
Fibularis longus
Calcaneal tendon
Vastus lateralis
Head of fibula
Tibialis anterior
Extensor digitorum
longus
Fibularis tertius
Fibular
retinacula
Fibularis brevis
Extensor retinacula
Fibularis brevis
(a)
(b)
(c)
FIGURE 9.42
Muscles of the leg. (
a
) Muscles of the lateral right leg. Isolated views of (
b
) F
bularis longus and (
c
) F
bularis brevis.
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