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LOWER LEG MUSCLES

     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)

FROG

FROG

FROG

TURTLE

TURTLE

 
   

ALLIGATOR

LOWER LEG MUSCLES

LOWER LEG MUSCLES

CHICKEN

LOWER LEG MUSCLES

PIGEON

PIGEON

PIGEON

OPOSSUM

LOWER LEG MUSCLES

 

CAT

LOWER LEG MUSCLES

LOWER LEG MUSCLES
LOWER LEG MUSCLES LOWER LEG MUSCLES

GOAT

LOWER LEG MUSCLES

 

SHEEP

LOWER LEG MUSCLES

PIG

GASTROCNEMIUS

TIBIALIS

MONKEY

LOWER LEG MUSCLES

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).

HUMAN MODEL

LOWER LEG MUSCLES

LOWER LEG MUSCLES
LOWER LEG MUSCLES LOWER LEG MUSCLES
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).