Naming Muscles
I.
Skeletal muscles are named according to certain criteria
A. Location- may indicate bone or body region that muscle is
associated with
Ex. Zygomaticus- associated with the zygomatic arch in the skull
B. Shape- Muscles often have a definitive shape, after which they are
name
Ex. Deltoid means triangle (and the deltoid muscle is triangular)
C. Relative Size
1. Maximus= largest
2. Minimus= smallest
3. Longus= long
4. Brevis= short
Ex. Gluteus maximus (larger)
and minimus (smaller)
Naming Muscle
D. Direction of Muscle Fibers
- may reflect the direction of the
fibers in relation to midline or other axis
1. Rectus= straight (runs parallel)
2. Transversus/oblique ( right angles)/ obliquely
Ex. Rectus femoris- muscle that runs parallel with the femur
E. Number of Origins
1. Biceps= two origins
2. Triceps= three origins
3. Quadriceps= four origins
Ex. Biceps Brachii
F. Location of origin and insertions
1. may be named according to the attachment points
2. Origin is always named first
Ex. Sternocleidomastoid (dual origin on sternum and clavicle;
insertion on mastoid process
Naming Muscle
G. Action
1. Uses words such as flexor, extensor, or adductor
Ex. Adductor longus on thigh adducts the thigh
H. Sometimes several criteria are combined in a name.
Ex. Extensor carpi radialis longus
1. muscle’s action (extensor)
2. joint it acts on (carpi= wrist)
3. Where it is (radialis = radius of forearm)
4. size (long relative to other wrist muscles
Criteria for Naming Muscles
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Location (region or bone)
Action (flexor carpi radialis)
Number of attachments (biceps brachii)
Shape (trapezius)
Size (longus, maximus, minimus)
Directions of fibers (obliques-diagonal)
IMPORTANT things about MUSCLES
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Attach to bone by tendon or aponeurosis
MUST CROSS a joint
MUST have two attachments
Can affect the shape of the bone
ALWAYS “pull” and get shorter (contract)
Work in opposing pairs
• Example: biceps and triceps
• Have striations in the direction of their
movement
Naming Muscle
II. Muscle Interactions- four functional groups
A. Prime mover- provide the major force for
producing a specific movement. Also
called the agonist
Ex. Biceps Brachii for forearm flexion
B. Antagonist- oppose or reverses a
particular movement
Ex. Triceps brachii for forearm extension
(oppose biceps)
C. synergist- aid agonist (prime movers) by
promoting the same movement or reducing
undesireable or unnecessary movements
that might occur as the prime mover
contracts.
Ex. Semimembranosis helps the biceps
femoris with thigh extension and knee
flexion
Naming Muscle
D. Fixators- a synergist that immobilizes or stabilizes a bone or a
muscle’s origin
Ex. Rotator cuff muscles (terest minor, infraspinatus, supraspinatus,
subscapularis)
E. Example of movement of all four involved in a movement
a. prime mover= pectoralis major (shoulder flexion)
b. antagonist= lattisimus dorsi
c. synergist= biceps brachii
d. fixator= rotator cuff
Naming Muscle
III. Muscle MovementsMuscles move toward their origin from the insertion of
the muscle. Origin is the bone point that does not move
and the insertion is the bone attachment that does move.
Ex. Origin- sternum and clavicle
Insertion- mastoid
Muscle when it contracts pulls the mastoid (skull) down
toward the sternum and clavicle (bringing your head
toward your chest)
A. Flexion- bending movement that brings two
articulating bones closer together.
B. Extension- reverse of flexion, moves the bones
further apart.
Joint animations
Naming Muscle
C. Abduction- movement of limb away from the mid-line
D. adduction- movement of limb toward the mid-line.
E. Circumduction- moving a limb so it describes a cone in space
F. Rotation- turning of a bone on its long axis, this also includes
lateral and medial rotation of hip and shoulder
G. Supination- palm up
H. Pronation palm down
Naming Muscle