Skeletal Muscle
• Skeletal muscle is attached to bone on each end by
tendons.
• Insertion:
• More movable attachment.
• Origin:
• Are pulled towards it (fixed point).
• Surrounded by connective tissues
Types of muscles
•
•
•
•
Prime mover or agonist (leader)- The muscle that causes
an action
Antagonist (ant = against), relaxes while the prime mover
contracts.
Most movements also involve muscles called synergists,
which help the prime mover function more efficiently by
reducing unnecessary movement.
Fixators stabilizing the origin of the prime mover so that
the prime mover can act more efficiently.
Skeletal Muscle
Naming skeletal muscles
•
Most skeletal muscles have names that describe some
feature of the muscle. The following are some terms
relating to muscle features that are used in naming
muscles.
• Size: vastus (huge); maximus (large); longus (long);
minimus (small); brevis (short).
• Shape: deltoid (triangular); latissimus (wide); teres
(round); trapezius (like a trapezoid).
• Direction of fibers: rectus (straight); transverse
(across); oblique (diagonally); orbicularis (circular).
Naming skeletal muscles
•
•
•
•
Location: pectoralis (chest); gluteus (buttock or rump);
brachii (arm); supra- (above); infra- (below); sub(under or beneath); lateralis (lateral).
Number of origins: biceps (two heads); triceps (three
heads); quadriceps (four heads).
Origin and insertion: sternocleidomastoideus (origin
on the sternum and clavicle, insertion on the mastoid
process); brachioradialis (origin on the brachium or arm,
insertion on the radius).
Action: abductor (to abduct a structure); adductor (to
adduct a structure); flexor (to flex a structure); extensor
(to extend a structure); levator (to lift or elevate a
structure); masseter (a chewer).
Apneurosis - A sheetlike fibrous membrane, resembling a flattened tendon, that serves as a
fascia to bind muscles together or as a means of connecting muscle to bone.
Facial expressions
Mastication
neck
frontalis
Facial expressions
Mastication
Neck
Neck – superior
to hyoid bone
Neck – inferior
to hyoid bone
Thorax and shoulder superficial
Thorax and shoulder deep
Abdominal muscles
External intercostal
Origin - lower border of a rib
within an intercostal space
Insertion - upper border of the rib
below
(muscles of quiet breathing)
Internal intercostal
Origin - upper border of a rib
Insertion - lower border of rib
above
back and shoulder muscles
Back muscles
Scapula rotators
Rotator cuff
Abdominal muscles
Action on the elbow flexors
Pronators
Action on the hand flexors
Action on the elbow extensors
Action on the hand extensors