The names of the skeletal muscles often relate
to muscle characteristics such as fiber direction, size,
shape, action, number of origins, and location
(see
Table 6.1).
Characteristics used to name skeletal muscles Table 6.1
Name
Meaning
Example
Direction:
Orientation of muscle fibers relative to the body's midline
Rectus
Parallel to midline
Rectus abdominis
Transverse
Perpendicular to midline
Transverse abdominis
Oblique
Diagonal to midline
External oblique
Size:
Relative size of the muscle
Maximus
Largest
Gluteus maximus
Minimus
Smallest
Gluteus minimus
Longus
Longest
Adductor longus
Latissimus
Widest
Latissimus dorsi
Longissimus
Longest
Longissimus muscles
Magnus
Large
Adductor magnus
Major
Larger
Pectorallis major
Minor
Smaller
Pectorallis minor
Vastus
Great
Vastus lateralis
Shape:
Relative shape of the muscle
Deltoid
Triangular
Deltoid
Trapezius
Trapezoid
Trapezius
Serratus
Saw-toothed
Serratus anterior
Rhomboid
Diamond-shaped
Rhomboid major
Orbicularis
Circular
Orbicularis oculi
Pectinate
Comblike
Pectineus
Piriformis
Pear-shaped
Piriformis
Platys
Flat
Platysma
Quadratus
Square
Quadratus lumborum
Gracilis
Slender
Gracilis
Action:
Principal action of the muscle
Flexor
Decreases joint angle
Flexor carpi radialis
Extensor
Increases joint angle
Extensor carpi ulnaris
Abductor
Moves bone away from midline
Adductor longus
Levator
Produces superior movement
Levator scapulae
Depressor
Produces inferior movement
Depressor labii inferioris
Supinator
Turns palm anteriorly
Supinator
Pronator
Turns palm posteriorly
Pronator teres
Sphincter
Decreases size of opening
External anal sphincter
Tensor
Makes a body part rigid
Tensor fasciae latae
Number o f Origins:
Number of tendons of origin
Biceps
Two origins
Biceps brachii
Triceps
Three origins
Triceps brachii
Quadriceps
Four origins
Quadriceps femoris
Location:
Structure near which a muscle is found
Example: Temporalis, a muscle near the temporal bone.
Origin and Insertion:
Sites where muscle originates and inserts
Example: Brachioradialls, originating on the humerus and inserting on the radius (brachii
= arm).
172 CHAPTER 6
The Muscular System
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