Skeletal Muscle Anatomy and Microanatomy

Vocabulary flashcards covering gross muscle anatomy, connective tissue coverings, and muscle fiber microanatomy based on lab manual instructions.

Trapezius muscle

A large skeletal muscle on the posterior side of the body that functions to move the scapula and arm.

Latissimus dorsi muscle

A posterior skeletal muscle involved in moving the scapula and arm.

Triceps brachii muscle

A skeletal muscle located on the posterior side of the arm that functions to move the forearm.

Gluteus maximus muscle

A large posterior muscle of the hip region that acts to move the thigh and leg.

Semitendinosus muscle

A posterior thigh muscle that works to move the thigh and leg.

Semimembranosus muscle

A muscle located on the posterior side of the thigh that functions in moving the thigh and leg.

Biceps femoris muscle

A muscle situated on the posterior thigh that functions to move the thigh and leg.

Gastrocnemius muscle

A posterior leg muscle involved in moving the foot.

Soleus muscle

A posterior leg muscle located deep to the gastrocnemius that functions to move the foot.

Endomysium

The extracellular matrix surrounding individual skeletal muscle fibers that blends with surrounding connective tissue.

Fascicles

Groups into which individual skeletal muscle fibers are arranged.

Perimysium

A connective tissue sheath that surrounds each muscle fascicle.

Epimysium

A connective tissue sheath that covers the skeletal muscle as a whole.

Fascia

The most superficial thick connective tissue around a skeletal muscle that separates individual muscles and binds them into groups.

Sarcolemma

The specialized plasma membrane of a skeletal muscle fiber.

Sarcoplasm

The cytoplasm of a skeletal muscle fiber.

Myofibrils

Small, cylindrical organelles making up approximately $80\%$ of a skeletal muscle fiber's sarcoplasm.

Sarcoplasmic reticulum (SR)

A modified smooth endoplasmic reticulum wrapping myofibrils that stores calcium ions.

Transverse tubules (T-tubules)

Inward extensions of the sarcolemma that wrap around myofibrils.

Terminal cisternae

Swollen regions of the sarcoplasmic reticulum situated on either side of a T-tubule.

Triad

A structural unit composed of one T-tubule and two adjacent terminal cisternae that coordinates electrical stimulation with calcium release.

Myofilaments

Protein subunits that compose myofibrils, consisting of thick and thin filaments involved in muscle contraction.

Myosin

The contractile protein that makes up thick myofilaments.

Actin

The contractile protein found within thin myofilaments.

Troponin

A regulatory protein present in thin myofilaments.

Tropomyosin

A regulatory protein present in thin myofilaments.

A band

The dark region of striations containing overlapping thick and thin filaments, or thick filaments alone.

I band

The light region of striations containing only thin filaments.

Z disc

A dark line that bisects the light I band.

Sarcomere

The fundamental unit of contraction defined as the space from one Z disc to the next Z disc, consisting of a full A band and two half-I bands.