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