Anatomy LC 10A: Muscular System PDF

ANATOMY LC 10A: Muscular System: Head and Neck - Dr. Ana Patricia Villanueva - De Grano SKELETAL MUSCLE Major components of the muscular system ○ Connective tissue ○ Skeletal Muscle tissue ○ Blood vessels ○ Nerves...

ANATOMY LC 10A: Muscular System: Head and Neck - Dr. Ana Patricia Villanueva - De Grano SKELETAL MUSCLE Major components of the muscular system ○ Connective tissue ○ Skeletal Muscle tissue ○ Blood vessels ○ Nerves Figure 13. Example of Raphe IV. ORGANIZATION OF MUSCLE TISSUE Muscles are covered by fascia For large muscle groups many are encased in both a superficial and a deep fascia. Example: Muscles of the upper limbs and lower limbs Figure 11. Skeletal Muscle of the Body Structure of Skeletal muscles ○ Belly Fleshy part of the muscle Figure 14. Fascia Figure 12. Muscle Belly CONNECTIVE TISSUE COVERINGS ○ Raphe Interdigitation of the tendinous 1. Fascia ends of fibers of flat muscles Surrounds an individual skeletal muscle, Example: The mylohyoid is a flat separating it from other muscles. muscle that interdigitates with Fascia may extend beyond the ends of the muscle each other to form the raphe. to become a tendon (Tough cord-like structure). 4 ANATOMY LC 10A: Muscular System: Head and Neck - Dr. Ana Patricia Villanueva - De Grano Fascia may connect muscle to muscle and is called an aponeurosis (Tough sheet-like structure) Fascicles: arranged bundles of skeletal muscle Skeletal Muscle Fibers (cells) are arranged into fibers (cells). bundles called fascicles. ○ Bound by connective tissues Figure 17. Organization of Muscle Tissue: A muscle, a Figure 15. Tendons fasciculus, and a fiber all visualized. Fascicles are bound by connective tissue ○ Epimysium Closely surrounds skeletal muscle, CONNECTIVE TISSUES binds fascicles together ○ Perimysium 1. Epimysium Connective tissue that divides a muscle Closely surrounds the skeletal muscles, binds into sections called fascicles; allows fascicles together activation of a specific subset of muscle Surrounds individual muscle fibers within a fascicle Composed of irregular, dense connective tissue. ○ Endomysium Found just below the fascia of the muscle. Covering of connective tissue (Collagen Separates muscles and other organs in the area. and reticular fibers) that surrounds Allows muscle to contract and move powerfully individual muscle cells; plays a role in while maintaining its structural integrity transferring force produced by the muscle fibers to the tendons 2. Perimysium Connective tissue that divides the muscle into sections called fascicles. Surrounds fascicles. Allows activation of a specific subset of muscle fibers within a fascicle 3. Endomysium Made up of collagen and reticular fibers. It surrounds a muscle fiber ○ Muscle Fiber Composed of myofibrils that is further composed of thick and thin filaments. Figure 16. The layers of the deep fascia from the epimysium of the muscle to the endomysium; the individual wrapping for each muscle fiber. 5 ANATOMY LC 10A: Muscular System: Head and Neck - Dr. Ana Patricia Villanueva - De Grano When Golgi Tendon Organ (GTO) is stimulated, it causes a muscle to relax by interrupting its contraction. AUTOGENIC INHIBITION: process when a muscle is inhibited by a GTO. Main function is opposite of the muscle spindles. Makes sure that a muscle does not over contract or over work itself because it may lead to injury. SYMPATHETIC FIBERS: nonmyelinated fibers that pass to the smooth muscle in the walls of the Figure 18. Organization of a Fasciculus blood vessels supplying the muscles. ○ Regulate blood flow to the muscles The nerve enters the muscle at about the midpoint on its deep surface, often near the margin (motor point). Figure 19. Organization of a Muscle Fiber NERVE SUPPLY nerve going to the muscle is a MIXED NERVE. MIXED NERVE is composed of: MOTOR: 60% Figure 20. Innervation of Skeletal Muscle: Sympathetic ○ Supplied by: Fibers ○ ALPHA FIBERS: from large cells in the Anterior Gray Horn. ○ GAMMA FIBERS: smaller cells in the spinal cord. ATTACHMENTS AND ACTIONS OF SKELETAL MUSCLES SENSORY: 40% ○ Provided by myelinated fibers which arise from specialized sensory endings lying within Muscle actions depend largely on what the the muscle or tendon. muscles are attached to. ○ MUSCLE SPINDLES: stretch receptors Attachment sites are divided into: Origin (proximal within the body of a muscle which primarily end; mostly fleshy; less movable bone) & detects changes in the length of a muscle. Insertion (distal end; mostly fibrous; more Relay length information to the Central movable bone) Nervous System via afferent nerve ○ Example for the biceps brachii: origin fibers. (proximal end) is at the coracoid process This information can be processed by which is a less movable bone & insertion the brain as PROPRIOCEPTION (the (distal end) is at the radius which is a awareness of body position). This plays highly movable bone a role in flexibility. Main function is to produce muscle contraction. ○ TENDON SPINDLES (Golgi Tendon Organ): works with muscle spindles reflexively to regulate muscle stiffness. 6