Organization of Skeletal Muscle

Skeletal Muscle Organization Connective Tissue Coverings Skeletal muscles are attached to tendons which attach the muscle to bone Belly: Thicker part of muscle Epimysium: connective tissue layer that covers the muscle Separates muscles from other structures/organs Perimysium: Layer underneath the epimysium Separates muscles into individual bundles Endomysium: Layer underneath the perimysium Surrounds each individual muscle fiber

Skeletal Muscle Organization

Micro-anatomy of Muscle tissue Skeletal Muscle bundle (covered by Epimysium) Many Muscle Fascicles (covered by perimysium) Many Muscle Fibers (covered by endomysium)  Many Myofibrils  Many Sarcomeres Many Actin and Myosin Filaments

Structure of a Skeletal Muscle Fiber Individual Muscle Fiber consists of: (outside to inside) Outside of muscle fiber Sarcolemma: cell membrane of muscle fiber Sarcoplasm: cytoplasm of muscle fiber Transverse Tubules or T-Tubules: connections from the sarcolemma to interior of muscle fiber for connection Inside muscle fiber Myofibrils: proteins that run the length of each fiber, surrounded by Sarcoplasmic Reticulum S. R. stores Ca2+ ions which dictates muscle contraction

Structure of a Skeletal Muscle Fiber Myofibril Components: Several Sarcomeres made up of: Actin: Thin Filaments, bundles with globular sections that fit into the binding sites on actin Myosin: Thick Filaments, has binding sites to which actin attaches to during contraction

Muscle Contraction T-tubules are stimulated from the nervous system T-tubules release Ca2+ ions The thin filaments/actin then are pulled along the thick filaments/myosin in place of where the Ca2+ ions were http://www.youtube.com/watch?v=Ae0UYxqj3cM

Rigor Mortis After death, ion pumps stop functioning  calcium builds up in the sarcoplasm causing a fixed muscular contraction

Muscle Pain Soreness after a workout Stretching the muscle tissue farther than usual Small microscopic tears to an individual muscle fiber Skeletal muscle tissue is multinucleated + many neuromuscular junctions  you mind sends signals when you are injured

Skeletal muscle identification Muscular system can be divided into 2 groups: Axial Muscles (60 %) Appendicular Muscles (40%)

Neuromuscular Junction Each skeletal muscle is controlled by a nerve cell called a motor neuron Where the motor neuron and muscle fiber meet = Neuromuscular Junction

Axial Muscles Muscles that position the head, spinal column, and move the rib cage. Divided into 4 groups based on location and function: Muscles of the head and neck Muscles of the vertebral column Oblique and rectus muscles Muscles of the pelvic

Axial Muscles Muscles of the Skull Orbicularis oris Orbicularis Oculi Nasalis Zygomaticus Major Zygomaticus Minor Frontalis

Axial Muscles Muscles of the Skull continued… Platysma Buccinator Temporalis Occipitalis Masseter* Sternocleidomastoid* Sternomastoid on cats

Axial Muscles Trapezius* Latissimus Dorsi* Muscles of the Back Clavotrapezius on cats Latissimus Dorsi*

Axial Muscles Pectoralis major* Serratus Anterior* Rectus Abdominis* Muscles of the Oblique Pectoralis major* Serratus Anterior* Serratus ventralis on cats Rectus Abdominis* External abdominal oblique*

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Appendicular Muscles Muscles that support the pectoral and pelvic girdles, and the limbs. Separated into 2 major groups: Muscles of shoulders and upper limbs Muscles of pelvis and lower limbs

Muscles of Pectoral girdle: Appendicular Muscles Muscles of Pectoral girdle: Pectoralis major* Deltoid* Clavodeltoid on cat Latissimus Dorsi

Appendicular Muscles Deltoid* Supraspinatus* Subscapularis Muscles that move the arm: Deltoid* Clavodeltoid on cat Supraspinatus* Subscapularis Infraspinatus* Pectoralis major* Latissimus dorsi*

Appendicular Muscles Biceps brachii* Triceps brachii* Brachialis* Muscles of the arm: Biceps brachii* Triceps brachii* Brachialis* Brachioradialis*

Appendicular Muscles Flexor carpi ulnaris* Flexor carpii radialis* Muscles of the arm: Flexor carpi ulnaris* Flexor carpii radialis* Palmaris longus* Extensor carpi radialis* Extensor carpi ulnaris*

Appendicular Muscles Muscles of the Pelvic Girdle: Gluteus maximus* Gluteus medius*

Appendicular Muscles The “Quad”: Sartorius* Biceps femoris Muscles that move the lower limb: The “Quad”: Rectus femoris* Vastus Medialis * Vastus Lateralis* Sartorius* Biceps femoris Semitendinosus*

Appendicular Muscles Gastrocnemius* Soleus* Tibialis posterior* Muscles of the lower limb: Gastrocnemius* Soleus* Tibialis posterior* Tibialis anterior Calcaneal tendon

Appendicular Muscles Muscles of the lower limb: Gastrocnemius* Soleus* Tibialis posterior* Tibialis anterior Calcaneal tendon*