Muscular Tissues and Fascicles (Anatomy)

Origin

Attachment of tendons to stationary bone

Insertion

Attachment of tendons to movable bone

Muscle Fascicles

Arranged bundles of skeletal muscle fibers (cells) within muscle

Parallel Muscle Fascicle

Muscle fascicle that’s parallel to longitudinal axis of muscle; terminate at either end of flat tendons

Example of Parallel Muscle Fascicle

Sternohyoid muscle

Fusiform Muscle Fascicle

Muscle fascicle that is nearly parallel to longitudinal axis of longitudinal; also terminates at flat tendons; this muscle tapers toward tendons where diameter is less than belly

Example of Fusiform Muscle Fascicle

Digastric Muscle

Circular Muscle Fascicle

Muscle fascicles in concentric circular arrangements; forms sphincter muscles enclose an orifice

Example of Circular Muscle Fascicle

Orbicularis occuli muscle

Convergent Muscle Fascicles (Triangular)

Muscle fascicles spread over broad area, converge at thick central tendon

Example of Convergent Muscle Fascicle

Pectoralis major muscle

Pennate Muscle Fascicles

Short muscle fascicles in relation to total muscle length, tendon extends nearly entire length of muscle

Unipennate

Muscle fascicles arranged on one side of tendon

Example of Unipennate

Extensor digitorum longus muscle

Bipennate

Muscles fascicles arranged on both sides of centrally positioned tendons

Example of Bipennate

Rectus-femoris muscle

Multipennate

Muscle fascicles attach obliquely from many directions to several tendons

Example of Multipennate

Deltoid Muscle

Endomysium

Penetrates interior of each fascicle, separates individual muscle fibers; mostly composed of reticular fibers

Perimysium

Layer of dense irregular connective tissue, surrounding groups of 10-100 or more muscle fibers, separating them into muscle fascicles

Epimysium

Outer layer encircling entire muscle, consists of dense irregular muscle tissue

Tendons

White fibrous cord of dense regular connective attaching muscle to bone

Aponeuroses

Sheet-like tendon joining one muscle with another or with bone

Prime Mover

(Also called agonist) Muscle directly responsible for producing desired motion

Antagonist

Muscle that has action opposite that of the prime mover and yields to movement

Synergist

Muscle assisting prime mover by reducing undesired action or unnecessary movement

Fixator

Muscle that stabilizes the origin of prime mover so it can act more efficiently

Functions of Muscle Tissue

- Produce body movement

- Stabilize body position

- Generate heat

Skeletal Muscle Tissue

Composed of skeletal muscle cells, these cells are elongated and cylindrical, striated alternating light/dark bands due to myofibril. Work in a voluntary manner, also controlled subconsciously

Cardiac Muscle Tissue

Only in heart, forms heart wall, work involuntarily, contraction and reaction is consciously controlled (autorhythmic)

Smooth Muscle Tissue

Located in walls of hollow internal structures→ blood vessels, airways, most organs of abdominopelvic cavity skin attached to hair follicles, lacks striations, works involuntarily