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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 dorsi
broadest muscle in the back, supports forelimb and
flexes shoulders
The important muscles of the
dorsum include the epaxial
group:
iliocostalis
longissimus
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
ribs
the internal intercostals lower the
ribs
the diaphragm contracts and
flattens out causing the thorax to
enlarge and the lungs to expand
Muscles of the forelimbs
in 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 oblique
internal oblique
rectus abdominis
transversus abdominis
these 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 oblique
Transversus
abdominis
Linea alba
Muscles of the hindlimb
These 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