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.

frontalis

Facial expressions

Mastication

neck

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