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