Unit 1 - Structure & Movement: Muscle Type & Structure

Vocabulary practice flashcards covering muscle tissue types, anatomical structural organization, connective tissue layers, and the microscopic architecture of myofibrils and sarcomeres.

Skeletal muscle

A voluntary muscle tissue usually attached to the skeleton, characterized by striated, tubular, and multinucleated fibers.

Smooth muscle

An involuntary muscle tissue usually covering the walls of internal organs, characterized by non-striated, spindle-shaped, and uninucleated fibers.

Cardiac muscle

An involuntary muscle tissue found exclusively in the walls of the heart, characterized by striated, branched, and uninucleated fibers.

Fascicle

A bundle of skeletal muscle fibers grouped together and enclosed by the perimysium.

Myocyte

A muscle cell, within which individual muscle fibers and myofibrils are organized.

Epimysium

The outermost layer of connective tissue fascia that completely surrounds an entire muscle.

Perimysium

The layer of connective tissue that separates and surrounds individual muscle fascicles.

Endomysium

The innermost layer of connective tissue that surrounds each individual muscle fiber.

Deep fascia

Dense connective tissue that separates individual muscles and groups of muscles, extending to form tendons or aponeuroses.

Tendon

A cord-like band of tough connective tissue that connects muscle to bone.

Sarcolemma

The specialized plasma membrane surrounding a striated muscle fiber.

Myofibril

A cylindrical organelle packed inside a muscle fiber, composed of repeating sarcomeres and myofilaments.

Sarcomere

The fundamental contractile unit of a muscle myofibril, demarcated between two adjacent Z lines (Z discs).

Sarcoplasmic Reticulum

A specialized network of membranous tubules surrounding the myofibrils in muscle cells that stores and releases calcium ions.

Terminal cisternae

Enlarged end-sacs of the sarcoplasmic reticulum that border transverse tubules to release calcium during muscle activation.

Transverse tubule (T-tubule)

An inward invagination of the sarcolemma that conducts electrical impulses into the interior of the muscle fiber.

Triad

A three-part grouping formed by a transverse tubule flanked on both sides by the terminal cisternae of the sarcoplasmic reticulum.

Actin

A contractile protein that forms the thin myofilaments in a muscle fiber, constituting the light I bands.

Myosin

A motor protein that forms the thick myofilaments in a muscle fiber, constituting the dark A bands.

A band

The dark band of a sarcomere that spans the entire length of the thick myosin filaments, including regions of thin filament overlap.

I band

The light band of a sarcomere that contains only thin actin filaments and is bisected by a Z disc.

Z disc (Z line)

A dark protein boundary plate that anchors the thin actin filaments and marks the border of a sarcomere.

H zone

The lighter central region of the A band where only thick myosin filaments are present, without thin actin filaments.

M line

The structural line situated at the exact center of the H zone and sarcomere that cross-connects the thick filaments.