A muscle must depend on other muscles to assist in a desired movement. For this reason

muscles are called prime movers, antagonists and synergysts.

Primer Movers

Muscles that actively produce a movement

Antagonist

Muscles that are in opposition to the prime movers

Synergist

Muscles that contract simultaneously with the prime

mover to help execute a movement or steady a part

The names of muscles are based on six points of identification* named for their action* named for their origin and insertion* named for their location* named for their shape or use* named for the direction of their fibers* named according to the number of their sections

Adjectives

Azygous : not paired

Bi, Tri, Quadri : two, three, four

Externus : external or outer

Gracilis : slender

Latissimus : wide

Longissimus, longus : long

Medius : intermediate

Orbicularis : surrounding

Quadratus : square

Rectus : straight

Rhomboideus : diamond shaped

Scalenus : unequally three sided

Serratus : sawtoothed

Teres : round or cylindrical

Transversus : crosswise

Vastus : great

Facial muscles

There are many facial muscles that produce a variety of

movement.

Orbicularis oculi

masseter

Muscles of the neck, back and thorax.

These muscles assist in rotation of the head, flexion and

extention of the head on the neck, breathing and attachment

of the forelimbs to the body

Serratus muscle group

Pectoral muscle group

Latissimus dorsibroadest muscle in the back, supports forelimb and

flexes shoulders

The important muscles of the dorsum include the epaxial

group:iliocostalislongissimus

transversosspinalis

These muscles extend the vertebral column and produce lateral movement of the trunk

Transversospinalis

Three important muscles of the thorax are

*external intercostals*internal intercostals

*diaphragm

During respiration: the external intercostals lift the

ribsthe internal intercostals lower the

ribsthe diaphragm contracts and

flattens out causing the thorax to enlarge and the lungs to expand

Muscles of the forelimbsin addition to the back and upper thorax the muscles of the upper

forelimbs contribute to the movement of the distal

extremities.Included are triceps brachii and

biceps brachii

                         

                                                                                               

tricep

                                     

                                                                                   

Biceps brachii

Abdominal muscles:external obliqueinternal obliquerectus abdominis

transversus abdoministhese muscles keep the organs in place, support and compress the

abdomen, contract during parturition, defecation, urination

and coughing

These muscles also assist in rotating the vertebral column. The

linea alba is a fibrous band that runs the length of the center of the

abdomen and is the central attachment of the abdominal

muscles. This is a very important landmark for any abdominal

surgery

                                                 

                                                                       

Rectus abdominis

External oblique

Internal obliqueTransversus abdominis

Linea alba

Muscles of the hindlimbThese muscles have several

functions in movement. The most important muscle groups include

*gluteal group*quadricep group

*semi group

gluteal

Major muscles over pelvis, extends and abducts limb

Quadriceps femoris flex and extend the leg

Semi group descends the posterior hind leg and form the “hamstrings”. These muscles flex the distal extremity

                                                                                                        

Gastrocnemius: flexes the leg and foot, the tendon at the insertion is commonly called the achilles tendon

Miscellaneous muscles:arrector pili

These are smooth muscles attached to hair on the dorsum. When stimulated these muscles

raise the hair on the back.

Cutaneous trunci: a muscle that attaches to the dermis and controls the insect twich in large animals

Another large animal muscle is the cremaster, this muscle is part of the spermatic cord and attaches to the

scrotum. This muscle contracts and relaxes, raising and lowering the testicles. This movement helps to regulate testicular

temperature