Muscular System: Skeletal Muscle Tissue and Gross Muscular Anatomy

Comprehensive vocabulary review flashcards covering skeletal muscle tissue properties, microscopic anatomy, neuromuscular control, biomechanics, and body musculature organization.

Contractility

The property of muscle tissue that enables it to generate tension and forcefully shorten.

Excitability

The property of muscle tissue that allows it to receive and respond to electrical or chemical stimuli.

Extensibility

The property of muscle tissue that allows it to be stretched or lengthened without sustaining damage.

Elasticity

The property of muscle tissue that allows it to recoil back to its original resting length after stretching.

Skeletal Muscle

Striated, voluntary muscle tissue attached to bones or facial skin, consisting of single, very long, cylindrical, multinucleate cells.

Cardiac Muscle

Striated, involuntary muscle tissue located in the heart wall that circulates blood, composed of branching chains of uni- or binucleate cells.

Smooth Muscle

Nonstriated, involuntary muscle tissue found in walls of hollow organs, airways, and large arteries, consisting of single, fusiform, uninucleate cells.

Epimysium

The dense layer of connective tissue that wraps and surrounds an entire skeletal muscle.

Perimysium

The connective tissue covering that wraps around a bundle of muscle fibers called a fascicle.

Endomysium

The delicate connective tissue layer that surrounds each individual muscle fiber (cell).

Tendon

A dense cord of fibrous connective tissue that attaches muscle to bone.

Aponeurosis

A broad, sheetlike fibrous connective tissue that provides muscle-to-muscle or muscle-to-bone attachment.

Fascia

Connective tissue that surrounds, separates, and binds muscles together.

Muscle Fiber

An individual skeletal muscle cell containing sarcolemma, sarcoplasm, and multiple myofibrils.

Sarcolemma

The plasma membrane that encloses a muscle fiber.

Sarcoplasm

The cytoplasm of a muscle fiber.

Myofibril

A rod-shaped, repeating organelle structure packed inside a muscle fiber containing myofilaments arranged into sarcomeres.

Sarcomere

The basic functional unit of skeletal muscle contraction, demarcated from Z line to Z line.

Thick Filament

A contractile myofilament composed primarily of the protein myosin located in the sarcomere.

Thin Filament

A contractile myofilament composed primarily of the protein actin located in the sarcomere.

A Band

The dark band of a sarcomere where thick filaments overlap with thin filaments.

I Band

The light band of a sarcomere that contains only thin (actin) filaments.

T-Tubules

Transverse tubules in muscle fibers that conduct electrical nerve impulses inward to the sarcoplasmic reticulum.

Sarcoplasmic Reticulum

A specialized organelle network in muscle cells responsible for storing and releasing calcium to trigger contraction.

Eccentric Contraction

A muscle contraction mechanism where muscle generates force while lengthening.

Concentric Contraction

A muscle contraction mechanism where muscle generates force while shortening.

Sliding Filament Mechanism

The model of concentric contraction in which thin actin filaments slide past thick myosin filaments to shorten the sarcomere.

Neuromuscular Junction

The specific communication site where a motor neuron innervates and synapses with a muscle fiber.

Motor Unit

A functional motor control unit consisting of a single motor neuron and all the muscle fibers it innervates.

Slow Oxidative Fibers

Also called red fibers; dark, aerobic skeletal muscle fibers adapted for sustained contractions over long periods that use ATP slowly.

Fast Glycolytic Fibers

Also called white fibers; anaerobic skeletal muscle fibers adapted for rapid, powerful contractions that use ATP quickly and fatigue rapidly.

Muscular Dystrophy

A group of genetic muscle disorders that progressively destroy muscle tissue.

Myoblasts

Embryonic precursor cells that fuse together during development to form multinucleated skeletal muscle fibers.

Anabolic Steroids

Synthetic drugs that increase muscle mass and muscular strength.

Origin

The immovable or fixed end of a muscle's attachment site.

Insertion

The movable end of a muscle's attachment site that pulls toward the origin during contraction.

Lever Systems

Biomechanical arrangements in which rigid bars (bones) move on fixed pivot points (joints/fulcrums) when effort is applied.

Prime Mover (Agonist)

The primary muscle directly responsible for producing a specific movement at a joint.

Antagonist

A muscle that opposes or reverses a particular action produced by a prime mover.

Synergist

A muscle that assists the prime mover by promoting the same movement or adding force.

Fixator

A specialized synergist that immobilizes and stabilizes a bone to provide a firm base for prime mover action.

Axial Musculature

Muscles that position and move the head, vertebral column, thoracic cage, and pelvic floor.

Appendicular Musculature

Muscles that stabilize, position, and move the limbs and pectoral and pelvic girdles.

Frontalis

Anterior belly of the epicranius muscle originating from the epicranial aponeurosis/occipital bone that inserts into the skin around the eyebrows to raise them.

Orbicularis Oculi

Circular facial muscle originating on the frontal and maxilla bones that inserts into the eyelid to close the eye and blink.

Orbicularis Oris

Circular facial muscle originating from muscle near the mouth that inserts into the skin of the lips to close and protrude lips.

Buccinator

Facial muscle originating on the maxilla and mandible that inserts into the orbicularis oris to compress cheeks and blow air out.

Zygomaticus Major

Facial expression muscle originating on the zygomatic bone that inserts into the corner of the mouth to raise it in a smile.

Platysma

Superficial neck muscle originating from the fascia of the upper chest that inserts into the mandible to depress the mandible in expressions of horror or pouting.

Temporalis

Muscle of mastication originating on the temporal bone that inserts into the coronoid process of the mandible to elevate the mandible and close the jaw.

Masseter

Powerful muscle of mastication originating on the zygomatic bone that inserts into the ramus of the mandible to elevate the mandible and close the jaw.

Sternocleidomastoid

Neck muscle originating on the sternum and clavicle that inserts onto the mastoid process of the temporal bone to flex the neck or rotate the head.

Splenius

Posterior neck muscle originating on cervical and thoracic vertebrae that inserts onto the occipital bone to extend or rotate the neck.

Diaphragm

The primary muscular agonist for inhalation located at the base of the thorax that moves down to expand the thoracic cavity.

Intercostal Muscles

Thoracic muscles located between the ribs that move the rib cage during respiration.

Rectus Abdominis

Medial anterior abdominal wall muscle originating on the pubis and inserting into the xiphoid process of the sternum.

External Oblique

Superficial lateral abdominal muscle originating on the ribs that inserts into the linea alba.

Internal Oblique

Intermediate lateral abdominal muscle originating on the ilium that inserts into the linea alba.

Transversus Abdominis

Deep horizontal abdominal muscle originating on the lumbar vertebrae that inserts into the linea alba.

Hernia

A protrusion of visceral organs through the abdominal wall caused by elevated pressure inside the abdominal cavity.

Pelvic Diaphragm

Two sheets of skeletal muscle forming the pelvic floor that support the pelvic visceral organs.

Perineum

Anatomical region containing muscles that control urination and surround the external genitalia.

Serratus Anterior

Anterior pectoral girdle muscle that inserts onto the scapula to move and stabilize it against the thoracic wall.

Trapezius

Large, superficial posterior muscle of the upper trunk that inserts onto the scapula to move the pectoral girdle.

Quadriceps

Group of four anterior thigh muscles—rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius—that insert onto the patella to extend the leg.

Hamstrings

Posterior thigh muscle group—biceps femoris, semitendinosus, and semimembranosus—originating on the pelvic girdle and inserting on the tibia to flex the leg.

Safe Intramuscular Injection Sites

Clinically identified safe muscular injection locations, specifically the ventral gluteal site in the gluteus medius and the lateral thigh site in the vastus lateralis.