Transcript A muscle must depend on other muscles to assist in a

The Muscular System, pt. 2
A muscle depends on other
muscles to assist in movement.
For this reason muscles are called
prime movers, antagonists or
synergysts.
Prime
Mover:
Muscle that
actively
produces a
movement
Antagonist: Muscle that works in
opposition to the prime movers
Synergist:
Muscles that
contract with
the prime
mover to help
execute a
movement or
steady a part
Names for muscles are based on six
points of identification:
• Action
• Origin/insertion point
• Location
• Shape or use
• Direction of their fibers
• The number of their sections
Adjectives That Describe
Muscles
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
Orbicularis oculi
Masseter
Muscles of the neck, back and
thorax.
These muscles assist in:
• Rotation of the head
• Flexion and extension of the head
on the neck
• Breathing
• 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
Important muscles of the thorax:
• External intercostals
• Internal intercostals
• Diaphragm
During respiration:
• External intercostals lift the ribs
• Internal intercostals lower the
ribs
• Diaphragm contracts and
flattens out causing thorax to
enlarge and the lungs to expand
Muscles of the Forelimbs
With help from the back and upper
thorax, the muscles of the upper
forelimbs contribute to movement of
the distal extremities.
Muscles include the triceps brachii
and biceps brachii
Triceps Brachii
Biceps brachii
Abdominal Muscles:
These muscles keep the organs in
place, support and compress the
abdomen, contract during parturition,
defecation, urination and coughing.
They also assist in rotating the
vertebral column.
Abdominal muscles
include:
• External oblique
• Internal oblique
• Rectus abdominis
• Transversus
abdominis
Linea Alba
A fibrous band running the length
of the abdomen, which is a central
attachment of the abdominal
muscles.
A very important landmark for
abdominal surgery
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: 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
Cremaster
Another large animal muscle that is
part of the spermatic cord and attaches
to the scrotum. This muscle contracts
and relaxes, raising and lowering the
testicles, helping to regulate testicular
temperature