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Muscle Tissue

PART 1. Muscle Tissue. Muscle. Muscle – a Latin word for “little mouse” Muscle is the primary tissue in the Heart (cardiac MT) Walls of hollow organs (Smooth MT) Skeletal muscle Makes up nearly half the body’s mass. Overview of Muscle Tissue. Functions of muscle tissue Movement

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Muscle Tissue

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  1. PART 1 Muscle Tissue

  2. Muscle • Muscle – a Latin word for “little mouse” • Muscle is the primary tissue in the • Heart (cardiac MT) • Walls of hollow organs (Smooth MT) • Skeletal muscle • Makes up nearly half the body’s mass

  3. Overview of Muscle Tissue • Functions of muscle tissue • Movement • Skeletal muscle - attached to skeleton • Moves body by moving the bones • Smooth muscle – squeezes fluids and other substances through hollow organs

  4. Overview of Muscle Tissue • Functions of muscle tissue (continued) • Maintenance of posture – enables the body to remain sitting or standing • Joint stabilization • Heat generation • Muscle contractions produce heat • Helps maintain normal body temperature

  5. Functional Features of Muscles • Functional features • Contractility • Long cells shorten and generate pulling force • Excitability • Electrical nerve impulse stimulates the muscle cell to contract

  6. Functional Feature of Muscles • Functional features • Extensibility • Can be stretched back to its original length by contraction of an opposing muscle • Elasticity • Can recoil after being stretched

  7. Types of Muscle Tissue • Three types of MT • Skeletal muscle tissue • Packaged into skeletal muscles • Makes up 40% of body weight • Cells are striated

  8. Types of Muscle Tissue • Three types of MT (continued) • Cardiac muscle tissue – occurs only in the walls of the heart • Smooth muscle tissue – occupies the walls of hollow organs • Cells lack striations

  9. Similarities of Muscle Tissue • Cells of muscles • Are known as fibers • Muscle contraction • Depends on two types of myofilaments (contractile proteins) • One type contains actin • Another type contains myosin • These two proteins generate contractile force

  10. Similarities of Muscle Tissues • Plasma membrane is called a sarcolemma • Cytoplasm is called sarcoplasm

  11. Skeletal Muscle • Each muscle is an organ • Consists mostly of muscle tissue • Skeletal muscle also contains • Connective tissue • Blood vessels • Nerves

  12. Basic Features of a Skeletal Muscle • Connective tissue and fascicles • Connective tissue sheaths bind a skeletal muscle and its fibers together • Epimysium – dense regular connective tissue surrounding entire muscle • Perimysium – surrounds each fascicle (group of muscle fibers) • Endomysium – a fine sheath of connective tissue wrapping each muscle cell

  13. Basic Features of a Skeletal Muscle • Connective tissue sheaths are continuous with tendons • See Figure 10.1a

  14. Connective Tissue Sheaths in Skeletal Muscle Figure 10.1a

  15. Basic Features of a Skeletal Muscle • Nerves and blood vessels • Each skeletal muscle supplied by branches of • One nerve • One artery • One or more veins

  16. Basic Features of a Skeletal Muscle • Nerves and blood vessels • Nerves and vessels branch repeatedly • Smallest nerve branches serve • Individual muscle fibers • Neuromuscular junction – signals the muscle to contract • Draw a picture of neuromuscular junction

  17. Basic Features of a Skeletal Muscle • Muscle attachments • Most skeletal muscles run from one bone to another • One bone will move – other bone remains fixed • Origin – less movable attachment • Insertion – more movable attachment

  18. Muscle Attachments Figure 10.3

  19. Basic Features of a Skeletal Muscle • Muscle attachments (continued) • Muscles attach to origins and insertions by CT • Fleshy attachments – CT fibers are short • Indirect attachments – CT forms a tendon or aponeurosis • Bone markings present where tendons meet bones • Tubercles, trochanters, and crests

  20. Microscopic and Functional Anatomy of Skeletal Muscle Tissue • The skeletal muscle fiber • Fibers are long and cylindrical • Are huge cells – diameter is 10–100µm • Length – several centimeters to dozens of centimeters • Each cell formed by fusion of embryonic cells • Cells are multinucleate • Nuclei are peripherally located

  21. Diagram of Part of a Muscle Fiber Figure 10.4b

  22. Myofibrils and Sarcomeres • Striations result from internal structureof myofibrils • Myofibrils • Long rods within cytoplasm • Make up 80% of the cytoplasm • Are a specialized contractile organelle found in muscle tissue • A long row of repeating segments called sarcomeres (functional unit of Skeletal MT)

  23. Sarcomere • Basic unit of contraction of skeletal muscle • Z disc (Z line) – boundaries of each sarcomere • Thin (actin) filaments – extend from Z disc toward the center of the sarcomere • Thick (myosin) filaments – located in the center of the sarcomere • Overlap inner ends of the thin filaments • Contain ATPase enzymes

  24. Sarcomere Structure • A bands – full length of the thick filament • Includes inner end of thin filaments • H zone – center part of A band where no thin filaments occur

  25. Sarcomere Structure (continued) • M line – in center of H zone • Contains tiny rods that hold thick filaments together • I band – region with only thin filaments • Lies within two adjacent sarcomeres

  26. Sarcoplasmic Reticulum and T Tubules • Sarcoplasmic reticulum • A specialized smooth ER • Interconnecting tubules surround each myofibril • Some tubules form cross-channels called terminal cisternae • Cisternae occur in pairs on either side of a t-tubule

  27. Sarcoplasmic Reticulum and T Tubules • Sarcoplasmic reticulum • Contains calcium ions – released when muscle is stimulated to contract • Calcium ions diffuse through cytoplasm • Trigger the sliding filament mechanism

  28. Sarcoplasmic Reticulum and T Tubulesin the Skeletal Muscle Fiber Figure 10.6

  29. Sarcomere and Myofibrils Figure 10.4c

  30. Mechanism of Contraction • Sliding filament theory • Myosin heads attach to actin in the thin filaments • Then pivot to pull thin filaments inward toward the center of the sarcomere PLAY Sliding Filament Theory

  31. Sliding Filament Mechanism Figure 10.7a

  32. Changes in Striation During Contraction Figure 10.8a–c

  33. Microscopic and Functional Anatomy of Skeletal Muscle Tissue • Muscle extension • Muscle is stretched by a movement opposite that which contracts it • Muscle fiber length and force of contraction • Greatest force produced when a fiber starts out slightly stretched • Myosin heads can pull along the entire length of the thin filaments

  34. The Role of Titin • Titin – a spring-like molecule in sarcomeres • Resists overstretching • Holds thick filaments in place • Unfolds when muscle is stretched Figure 10.4d

  35. Sarcoplasmic Reticulum and T Tubules • Muscle contraction • Ultimately controlled by nerve-generated impulse • Impulse travels along the sarcolemma of the muscle cell • Impulses further conducted by T tubules • T tubule – a deep invagination of the sarcolemma PLAY Anatomy Review: Skeletal Muscle Tissue

  36. Innervation of Skeletal Muscle • Motor neurons innervate skeletal muscle tissue • Neuromuscular junction is the point where nerve ending and muscle fiber meet

  37. Innervation of Skeletal Muscle Figure 10.9

  38. Innervation of Skeletal Muscle Figure 10.10

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