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LOWER
LEG MUSCLES
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The lower leg of humans can be
divided into a posterior compartment whose muscles include the muscles
which allow plantar flexion of the foot (the gastrocnemius, soleus) and
toes and an anterior compartment with muscles which allow the dorsiflexion
of the foot (tibialis anterior) and toes.
The peroneus muscles allow eversion of the foot.
These muscles are not unique to humans.
The primitive condition of the gastrocnemius seems to be 2 separate
muscles. (Hartman, 1933). The reptilian gastrocnemius
internus forms gastrocnemius medialis and flexor hallucis longus in mammals
(Kardong, p. 388) and the reptilian gastrocnemius externus forms gastrocnemius
lateralis, soleus, and plantaris in mammals (Kardong, p. 388) |
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FROG |
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TURTLE |
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ALLIGATOR |
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CHICKEN |
PIGEON |
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OPOSSUM |
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CAT |
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GOAT |
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SHEEP |
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PIG |
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MONKEY |
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Although the peroneus
tertius has frequently been described as a muscle which only exists in
humans as an adaptation to bipedal locomotion, it occasionally occurs
in gorillas and rarely in chimps (Hartman, 1933, p. 166). The flexor digitorum brevis in apes is intermediate
between humans and lower primates (Hartman, 1933,p 172). In gorillas, chimps, and humans, the peroneus
brevis may insert onto digit V proximal and middle phalanges and the origin
of soleus frequently on tibia (Gibbs, 2002).
In chimps and humans, the origin of extensor digitorum is on crural
fascia, the insertion of the abductor hallucis may include the medial
cuneiform, and the origin of flexor digitorum brevis is on plantar aponeurosis
(Gibbs, 2002). |
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HUMAN MODEL |
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One
anomaly of the soleus in humans is an enlarged fibular head which reaches
the head and neck of the fibula, a condition also known in other primates. Some humans lack a soleus or possess a soleus
which is fused to the gastrocnemius or completely separate with a separate
insertion on the calcaneus. In some,
the plantaris is anamolous and forms an accessory soleus (Barbaerini, 2003). |
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