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FOREARM MUSCLES

     The human forearm and hand muscles allow humans to use their hands with incredible dexterity whether they are making tools, playing the piano, or performing sign language.  These muscles are not unique to humans; they are typical of tetrapods.  Many tetrapods ranging from frogs to opossums to primates are capable of dexterous hand movements.  Apes have even been taught to communicate through human sign language.

     In tetrapods, there is a general pattern of forearm musculature.  The common sheet of extensors is split into two layers: a superficial extensor digitorum and a deeper set of muscles composed of the extensor pollicis longus and extensores proprii (Hartman, 1933, p. 141).  The dorsal compartment of the forearm extends the wrist and digits and it contains a number of muscles such as the extensor carpi ulnaris and extensor carpi radialis.  Muscles which evolved in the early tetrapods include the extensor digitorum communis, extensor carpi radialis, extensor carpi ulnaris, extensores digitorum breves, supinator, dorsal interossei, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, pronator profundus (quadratus), flexor palmaris (digitorum) profundus (Romer, p. 302-3). The posterior compartment also contains the extensor digitorum and supinator. The primitive condition for the forearm flexors consists of a flexor ulnaris, a flexor radialis, and a central flexor sheet with superficial and deep components.  In humans the proximal pronator teres and the distal pronator quadratus are remnants of a continuous ancestral pronator sheet. (Hartman, 1933,p 137).  There are a number of muscles in the anterior compartment of the forearm, including the flexor carpi ulnaris, flexor digitorum superficialis, flexor carpi radialis, flexor digitorum profundus, pronator teres, palmaris longus, and pronator quadratus.

FROG

SALAMANDER

SALAMANDERSALAMANDER

SALAMANDERSALAMANDER

TURTLE

FOREARM MUSCLES

FOREARM MUSCLES
FOREARM MUSCLES

ALLIGATOR

FOREARM MUSCLES

FOREARM MUSCLES

CHICKEN

FOREARM MUSCLES

OPOSSUM

FOREARM MUSCLES

FOREARM MUSCLES
FOREARM MUSCLES FOREARM MUSCLES
HAND HAND

CAT

FOREARM MUSCLES

FOREARM MUSCLES
FOREARM MUSCLES FOREARM MUSCLES
FOREARM MUSCLES  

GOAT

FOREARM MUSCLES

SHEEP

FOREARM MUSCLES

COW

FOREARM MUSCLES

PIG

FLEXORS

EXTENSORS
MONKEYFOREARM MUSCLES FOREARM MUSCLES
MONKEY

HUMAN MODEL

FOREARM MUSCLES

FOREARM MUSCLES
FOREARM MUSCLES FOREARM MUSCLES
HAND MUSCLES HAND MUSCLES