chapter 9: muscles and muscle tissue

Skeletal muscle

Associated with the bony skeleton; consists of large, striated cells that are under voluntary control.

Cardiac muscle

Found only in the heart; consists of small, striated cells that are under involuntary control.

Smooth muscle

Found in the walls of hollow organs; consists of small, elongated, unstriated cells that are under involuntary control.

Excitability (responsiveness)

The ability of muscle tissue to receive and respond to a stimulus.

Contractility

The ability of muscle tissue to contract forcibly when stimulated.

Extensibility

The ability of muscle tissue to be stretched.

Elasticity

The ability of muscle cells to resume their original length once stretched.

Muscle movement

Muscles produce movement by acting on the bones of the skeleton, pumping blood, or propelling substances throughout hollow organ systems.

Posture

Muscles aid in maintaining posture by adjusting the position of the body with respect to gravity.

Joint stabilization

Muscles stabilize joints by exerting tension around the joint.

Heat generation

Muscles generate heat as a function of their cellular metabolic processes.

Skeletal muscle organ

A discrete organ in which muscle fibers predominate but that also includes blood vessels, nerves, and connective tissue.

Nerve supply

Allows neural control of skeletal muscles.

Blood supply

Ensures adequate nutrient delivery and waste removal in skeletal muscles.

Connective tissue sheaths

Connective tissue coverings found at various structural levels of a skeletal muscle.

Endomysium

Connective tissue sheath that surrounds each individual muscle fiber.

Perimysium

Connective tissue sheath that surrounds groups of muscle fibers.

Epimysium

Connective tissue sheath that surrounds the entire muscle.

Muscle fiber

An individual muscle cell within a skeletal muscle.

Origin

The less movable attachment of a skeletal muscle.

Insertion

The movable attachment of a skeletal muscle.

Muscle action

Skeletal muscles span joints and cause movement from the movable attachment (insertion) toward the less movable attachment (origin).

Direct muscle attachment

An attachment in which the epimysium fuses with the periosteum or perichondrium.

Indirect muscle attachment

An attachment in which the connective tissue wrappings of the muscle extend into a rope-like or sheet-like structure that attaches to bone, cartilage, or fascia.

Tendon

A rope-like connective tissue structure that indirectly attaches muscle to bone, cartilage, or fascia.

Aponeurosis

A sheet-like connective tissue structure that indirectly attaches muscle to bone, cartilage, or fascia.

Indirect attachments

The most common type of muscle attachment because they are durable and small in size, conserving space across joints.