7 & 8. Muscular System and Major Muscles Anatomy

Comprehensive vocabulary flashcards covering the macroscopic and microscopic anatomy of the muscular system, sarcomere contraction, muscle action categories, and origins, insertions, and actions of major skeletal muscles.

Origin

The muscle attachment site typically located on the bone that has more mass and moves less during contraction.

Insertion

The muscle attachment site typically located on the bone that has less mass and moves more during contraction.

Tendon

Dense regular connective tissue that attaches muscle to bone.

Ligament

Dense regular connective tissue that attaches bone to bone.

Fascia

A continuation of tendons that covers the entire muscle, classified into four types.

Aponeurosis

A broad, flat sheet of connective tissue that acts like a wide tendon to connect muscles with wide insertions.

Linea alba

A prominent aponeurosis along the ventral midline that holds together external abdominal muscles and is incised during abdominal surgery.

Epimysium

The layer of connective tissue located directly deep to the fascia that encases and lines the entire muscle.

Fascicle

A bundle of muscle fibers encased and held together by the perimysium.

Perimysium

The connective tissue sheath that surrounds and separates individual fascicles within a muscle.

Endomysium

The fine connective tissue layer that surrounds and separates individual muscle fibers (cells).

Sarcolemma

The cell membrane that surrounds each individual muscle fiber.

Sarcoplasm

The specialized cytoplasm found inside a muscle fiber/cell.

Myofibril

A cylindrical, tube-like organelle running through a muscle fiber that holds the contractile myofilaments.

Sarcoplasmic Reticulum

The specialized endoplasmic reticulum of muscle fibers that stores and releases calcium ions ($Ca^{2+}$).

Transverse Tubules (T Tubules)

Tubular extensions of the sarcolemma that carry electrical nerve impulses into the cell's interior toward the sarcoplasmic reticulum.

Sarcomere

The repeating contractile unit within a myofibril consisting of aligned rows of actin and myosin filaments.

A-band

The dark column of a sarcomere formed by the full length of thick myosin filaments.

I-band

The lighter region of a sarcomere located between myosin columns, containing thin actin filaments.

M-line

The midline structure located at the exact center of the myosin filament column within a sarcomere.

Myosin

The thick protein filament in sarcomeres with globular heads that bind actin to generate contractile force.

Actin

The thin protein filament in sarcomeres pulled toward the M-line during muscle contraction.

Agonist

A muscle whose primary contraction directly produces a specific anatomical movement.

Antagonist

A muscle whose action opposes that of an agonist, moderating and controlling the strength of the movement.

Synergist

A muscle that assists the primary action of an agonist.

Masseter

A facial muscle that originates on the zygomatic bone, inserts on the caudal ramus of the mandible, and assists with mastication.

Temporalis

A facial muscle that originates on the parietal crest, inserts on the coronoid process of the mandible, and assists with mastication.

Brachiocephalicus

A muscle originating at the clavicular intersection and inserting on the dorsal neck and proximal humerus; pulls the limb forward and flexes the head laterally.

Sternocephalicus

A muscle originating on the manubrium of the sternum and inserting on the temporal bone; acts to flex the head laterally.

Trapezius

A triangular dorsal muscle originating on the dorsal cervical and thoracic vertebrae and inserting on the scapular spine; elevates the shoulder and draws the limb forward.

Rhomboideus

A muscle originating on the dorsal neck and thorax and inserting on the dorsal border of the scapula; draws the shoulder dorsocranially.

Splenius

A muscle originating on the dorsal spinous processes of $T1\text{--}T3$ and inserting on the occipital and temporal bones; functions in extension of the head and neck.

Latissimus dorsi

A broad muscle originating on the dorsal thoracic to lumbar vertebrae ($T4\text{--}L7$) and inserting on the proximal-medial humerus; acts to flex the shoulder.

Intercostal Muscles

Muscles located between ribs that originate on the caudal border of a cranial rib, insert on the cranial border of a caudal rib, and assist with respiration.

Serratus ventralis

A muscle originating on ribs $1\text{--}7$ and inserting on the dorsal border of the medial scapula; functions to abduct the scapula.

Pectoral Muscles

Muscles originating on the cranial sternum and inserting on the proximal humerus; function to flex the humerus.

Deltoid

A muscle originating on the spine of the scapula and acromion, inserting on the deltoid tuberosity of the humerus, and acting to flex the shoulder.

Supraspinatus

A muscle originating in the supraspinous fossa and inserting on the greater tubercle of the humerus; functions to stabilize the shoulder joint.

Infraspinatus

A muscle originating in the infraspinous fossa and inserting on the greater tubercle of the humerus; functions to stabilize the shoulder joint.

Triceps brachii

A muscle originating on the infraglenoid tubercle, caudal border of the scapula, and proximal humerus, inserting on the olecranon process; extends the elbow.

Biceps brachii

The medial flexor of the upper arm originating on the supraglenoid tubercle of the scapula and inserting on the proximal radius and ulna; flexes the elbow.

Brachialis

The lateral flexor of the upper arm originating on the proximal/lateral humerus and inserting on the proximal radius and ulna; flexes the elbow.

Sartorius

A hindlimb muscle originating on the wings of the ilium and inserting on the medial stifle; flexes the hip.

Gracilis

A hindlimb muscle originating on the pelvic symphysis and inserting on the medial stifle; adducts the hip.

Rectus femoris

A quadriceps muscle originating on the caudal ilium near the acetabulum and inserting on the tibial tuberosity; extends the stifle.

Vastus lateralis

A lateral quadriceps muscle originating on the proximal femur and inserting on the tibial tuberosity; extends the stifle.

Vastus medialis

A medial quadriceps muscle originating on the proximal femur and inserting on the tibial tuberosity; extends the stifle.

Vastus intermedius

A deep quadriceps muscle originating on the proximal femur and inserting on the tibial tuberosity; extends the stifle.

Biceps femoris

A hamstring muscle originating on the ischial tuberosity and inserting on the stifle and proximal tibia; extends the hip.

Semitendinosus

A hamstring muscle originating on the ischial tuberosity and inserting on the proximal/caudal tibia; flexes the stifle.

Semimembranosus

A hamstring muscle originating on the ischial tuberosity and inserting on the medial femur and tibia; flexes the stifle.

Gastrocnemius

A caudal lower limb muscle originating proximal to the femoral condyles and inserting on the calcaneus; extends the tarsus and flexes the stifle.

Fascia lata

A dense sheet of connective tissue that binds thigh muscles together tightly.