Naming Muscles

Muscles causing movement… ■ Skeletal Muscle – an organ made of several different types of tissue including muscle tissue, vascular tissue and nervous tissue

■ Tendon – attaches the skeletal muscle to bone and pulls on bone when the muscle contracts

Joints ■ Skeletal muscles usually cross one or more joints. When a muscle contracts it pulls one bone closer to another ■ One bone stays in place while the other moves

Parts of a skeletal muscle ■ Origin – the attachment of a muscle on a stationary bone ■ Insertion – the attachment of a muscle on the movable bone ■ Belly – the fleshy portion of muscle between the origin and insertion

Group Actions ■ Most movements occur because groups of muscles work together, generally grouped in opposing pairs ■ Ex – abductors and adductors ■ Ex – extensors and flexors

■ Agonist – muscle that produces the desired movement ■ Antagonist – muscle that relaxes when the agonist contracts ■ Synergists – another skeletal muscle that moves in the same general direction as the agonist increasing the force ■ Fixators – stabilize the origin and hold other joints still so the agonist can work more efficiently

Principle Skeletal Muscles ■ With over 700 skeletal muscles in the body, it will be easier to first learn the naming system and then learn specific muscles region by region

Naming Skeletal Muscles ■ Muscles are named according to the direction the fibers run, the size of the muscle, the shape of the muscle, the action the muscle produces, the number of origins the muscle has and/or the location of the muscle

Directions ■ The following terms refer to the direction the muscle fibers run in relation to the midline.

Rectus ■ Parallel to the midline

Transverse ■ Perpendicular to the midline

Oblique ■ Diagonal to the midline

Size ■ Relative to other muscles in that group

Maximus ■ Largest

Minimus ■ Smallest

Longus or Longissimus ■ Longest

Latissimus ■ Widest

Magnus ■ Large

Major ■ Larger

Minor ■ smaller

Vastus ■ great

Shape ■ General shape of the muscle

Deltoid ■ Triangle

Trapezius ■ Trapezoid

Serratus ■ Saw-toothed

Rhomboid ■ Diamond Shaped

Orbicularis ■ Circular

Pectinate ■ Comb-like

Piriformis ■ Pear shaped

Platys ■ Flat

Quadratus ■ square

Gracilis ■ slender

Action ■ Based on the action the muscle performs

Flexor/Extensor ■ Flexor – decreases the angle between bones ■ Extensor – increases the angle between bones

Abductor/Adductor ■ Abductor – moves a bone away from the midline ■ Adductor – moves a bone toward the midline

Levator/Depressor ■ Levator – elevates body part ■ Depressor – lowers body part

Supinator/Pronator ■ Supinator – turns palms up ■ Pronator – turns palms down

Sphincter ■ Decreases the size of an opening

Tensor ■ Makes a body part rigid

Number of Origins ■ Biceps – 2 heads ■ Triceps – 3 heads ■ Quadriceps – 4 heads

Location ■ Muscles named for the structures that they are by. Examples include the sternocleidomastoid muscle (runs from the sternum across the clavicle to the mastoid process) and the temporalis (near the temporal bone)