Naming Muscles

Muscles causing movement… Skeletal Muscle – an organ made of several different types of tissue including muscle tissue, vascular tissue and nervous tissue 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 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 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 One bone stays in place while the other moves

Parts of a skeletal muscle Origin – the attachment of a muscle on a stationary bone Origin – the attachment of a muscle on a stationary bone Insertion – the attachment of a muscle on the movable bone Insertion – the attachment of a muscle on the movable bone Belly – the fleshy portion of muscle between the origin and insertion 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 Most movements occur because groups of muscles work together, generally grouped in opposing pairs Ex – abductors and adductors Ex – abductors and adductors Ex – extensors and flexors Ex – extensors and flexors

Agonist – muscle that produces the desired movement Agonist – muscle that produces the desired movement Antagonist – muscle that relaxes when the agonist contracts 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 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 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 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 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. The following terms refer to the direction the muscle fibers run in relation to the midline.

Rectus Parallel to the midline Parallel to the midline

Transverse Perpendicular to the midline Perpendicular to the midline

Oblique Diagonal to the midline Diagonal to the midline

Size Relative to other muscles in that group Relative to other muscles in that group

Maximus Largest Largest

Minimus Smallest Smallest

Longus or Longissimus Longest Longest

Latissimus Widest Widest

Magnus Large Large

Major Larger Larger

Minor smaller smaller

Vastus great great

Shape General shape of the muscle General shape of the muscle

Deltoid Triangle Triangle

Trapezius Trapezoid Trapezoid

Serratus Saw-toothed Saw-toothed

Rhomboid Diamond Shaped Diamond Shaped

Orbicularis Circular Circular

Pectinate Comb-like Comb-like

Piriformis Pear shaped Pear shaped

Platys Flat Flat

Quadratus square square

Gracilis slender slender

Action Based on the action the muscle performs Based on the action the muscle performs

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

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

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

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

Sphincter Decreases the size of an opening Decreases the size of an opening

Tensor Makes a body part rigid Makes a body part rigid

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