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- 1. SKELETAL MUSCLE Smoking is injuriousto health Rakesh kumar 1
- 2. Introduction Classification Microscopic structure Physiology Applied Anatomy References Protocol 2
- 3. Introduction MUSCULUS =LITTLE MOUSE Muscle tissue is the one of the basic tissues of the body. Responsible for movement . Composed of differentiated cells containing contractile proteins(actin, myosin etc.) 3
- 4. Muscles –machines - chemical energy - mechanical energy. 40-50% of the body mass. Attaches to bone, skin or fascia Developed from MESODERM except a)Arrector pili b)Muscles of iris c)Myoepithelial cells of sweat ,salivary and lacrimal glands - ECTODERM 4
- 5. Types of Muscletissue Skeletal muscle Smooth muscle Cardiac muscle 5
- 6. Skeletal Muscles • Attachedto skeleton • Voluntary control of contraction & relaxation • Each muscle cell = muscle Fiber • Muscle fibers develop from the fusion of small, individual muscle cells called myoblast. 6
- 7. Microscopic structureshows light & dark bands – Striations Straight & Un-branched Multinucleated Nuclei are located in the cytoplasm just beneath the plasma membrane(sarcolemma) LENGTH :- varies from few mm (stapedius) to many cm (sartorius) SHAPE :- long and cylindrical 7
- 8. Development of Skeletalmuscle Myotomes of paraxial mesoderm 5Th week – spindle shape – myoblast- single nucleus- repeated mitosis. join to form myotubes- single row nuclei in centre Cross striations seen in 2nd month – myofibrils-periphery Increase in no. of myofibril –nuclei pushed- periphery Myotubes converted into muscle fibres. 8
- 9. Parts of VoluntaryMuscle 9
- 10. Two parts ofa muscle 1. Belly part:- Contractile part 2. Fibrous part:- Non contractile and non elastic a) Tendon b) Aponeurosis 10
- 11. Classification According tocolour According to Insertion of muscle According to direction of muscle fibre - Parallel - Pennate - Spiral - Cruciate 11
- 12. 1. Slow (orRed) Oxidative Fibers Type I Slow but continuous contraction for extended periods Smaller diameter contain myoglobin more capillaries more mitochondria Does not fatigue as fast due to aerobic production of ATP Eg: Soleus. 12
- 13. 2. Fast (Red)Oxidative Fibers Type IIa Have attributes in between fast and slow types 13
- 14. 3. Fast Glycolytic(white)Fibers Type IIb Fast contraction after nervous stimulation Large diameter Large glycogen reserve Fewer mitochondria Densely packed myofibrils Fatigue fast due to mainly anaerobic respiration Eg. Biceps brachii, Gastrocnemius. 14
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- 16. According to insertionof muscle Insertion near the proximal end of bone Eg – biceps brachii, psoas major Insertion towards the distal end of bone, away from the joint Eg- brachioradialis Insertion at the middle of shaft of bone Eg- Coracobrachialis, pronator teres 16
- 17. According to directionof muscle fiber a) Parallel muscles The muscle fibers are parallel to line of pull The fibers are long, but their numbers are few Functions: Range of movement . ↓ total force of contraction 17
- 18. Sub divisions ofparallel muscles Strap muscle- Sartorius, Rectus abdominis Quadrate muscle- Quadratus lumborum Fusiform muscle- Biceps brachii 18
- 19. b) Pennate muscles Fibers are oblique to line of pull 19
- 20. Circumpennate Themuscle is cylindrical Oblique fibers converge into central tendon from all sides Eg- Tibialis anterior c) Spiral muscle Muscles are twisted in arrangement close to their insertion Eg- Pectoralis major & latissimus dorsi 20
- 21. d) Cruciate muscle Fasciculiin the muscle are crossed Eg: Sternocliedomastoid, Masseter 21
- 22. 22 Circular: surrounds abody orifice, constricting it when contracted Eg: Orbicularis occuli (closes the eyelids)
- 23.
- 24. Connective Tisssue Epimysium= On top of the muscle Perimysium = Around a bundle of myofibers Endomysium = Surrounds each myofiber 24
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- 26. Vessels andnerves run in epimysium and perimysium Branch in to arterioles and give off capillaries which are carried by endomysium Each muscle fiber is accompanied by a set of parallel capillaries, which give off side branches at right angles to the fiber 26
- 27. • Epimysium consistsmainly type I collagen fibers • Perimysium contain type I and III collagen fibers • Endomysium contain type III and IV collagen fibers • Collagen IV is associated with the basal lamina that invests each muscle fiber • All these connective tissue layers extend beyond the muscle belly to form the tendons, aponeurosis and fascia. 27
- 28. Attachment of tendonto skeletal muscle 28
- 29. Fascicles Myofibrils Myofilaments Actin Myosin It isimportant to remember the Heirarchy 29
- 30. Microscopic Structure Some vocabulary: Skeletalmuscle cell = fiber or myofiber Sarcolemma Sarcoplasm Sarcoplasmic reticulum Myofibril Myofilaments T-tubules Muscle Epimysium Myofibrils Sarcomere Myofilament Myofibrils 30
- 31. Muscle and Musclefibre • Each muscle divides into several muscle bundles or fasciculi by perimysium • Each fasciculus is composed of variable number of muscle fibers • Individual muscles are separated by fascia, which also forms tendons and aponeurosis 31
- 32. Muscle fibre(Cont..) •Each musclefiber is elongated, multinucleated. •Is essential for force transduction 32
- 33. Muscle fibre(Cont..) sarcolemma-Plasma membrane sarcoplasm - Cytoplasm sarcoplasmic reticulum- Smooth endoplasmic reticulum 33
- 34. Light and darkbands The cytoplasm or sarcoplasm shows alternate dark and light bands Dark band is called A-band Light band is called I-band 34
- 35. Light and darkbands 35
- 36. Sarcomere The portionof myofibrils between every two Z-lines Z disc: filamentous network of protein. Serves as attachment for actin myofilaments Titin filaments: elastic chains of amino acids; make muscles extensible and elastic 36
- 37. Myofibril Muscle fibersare filled with threads called myofibrils, separated by SR (sarcoplasmic reticulum) Myofilaments (thick & thin filaments) are the contractile proteins of muscle 37
- 38. Transverse Tubules T(transverse) tubules are invaginations of the sarcolemma into the center of the cell filled with extracellular fluid carry muscle action potentials down into cell Mitochondria lie in rows throughout the cell near the muscle proteins that use ATP during contraction
- 39. Sarcoplasmic Reticulum (SR) System of tubular sacs similar to smooth ER Placed horizontally between T-tubules Stores Ca2+ in a relaxed muscle Release of Ca2+ triggers muscle contraction 39
- 40. Proteins of Muscle Myofibrils are built of 3 kinds of protein Contractile proteins myosin and actin Regulatory proteins which turn contraction on & off troponin and tropomyosin Structural proteins which provide proper alignment, elasticity and extensibility titin, myomesin, nebulin and dystrophin 40
- 41. Neuromuscular Junction SYNAPSE: axonterminal resting in an invagination of the sarcolemma Neuromuscular junction (NMJ): Presynaptic terminal: axon terminal with synaptic vesicles Synaptic cleft: space Postsynaptic membrane or motor end-plate 41
- 42.
- 43. Sliding Filament Model Actin myofilaments sliding over myosin myofilaments result shorten sarcomeres Actin and myosin do not change length during sliding Shortening sarcomeres responsible for skeletal muscle contraction 43
- 44.
- 45. During relaxation:- Sarcomereslengthen because of some external force, like forces produced by other muscles (contraction of antagonistic muscles) or by gravity. Agonist = muscle that accomplishes a certain movement, such as flexion. Antagonist = muscle acting in opposition to agonist Synergists= they prevent undesirable movement 45
- 46.
- 47. Energy Sources ATPprovides immediate energy for muscle contractions. Produced from three sources Creatine phosphate During resting conditions stores energy to synthesize ATP ADP + Creatine phosphate------------------ Creatine + 1ATP Anaerobic respiration Occurs in absence of oxygen and results in breakdown of glucose to yield ATP and lactic acid Aerobic respiration Requires oxygen and breaks down glucose to produce ATP, carbon dioxide and water More efficient than anaerobic (Creatine Kinase) 47
- 48. Skeletal muscle: Nervesupply Supplied by motor and sensory nerves Motor fibers: Two types Alpha fibres Thickly myelinated axons supply extrafusal muscle fibres Produces movements(Contraction) Gamma fibres Thinly myelinated fibres which supply intrafusal fibers of the muscle spindle Maintains the tone of the muscle(Proprioception) Unmyelinated sympathetic fibers Supply blood vessels 48
- 49. Skeletal muscle: Nervesupply Motor end plate : Motor neuron (efferent) axons originating in the spinal cord contact muscle fibers via a structure known as the motor endplate. Motor point: The site where the motor nerve enters the muscle 49
- 50. Skeletal muscle: Nervesupply Motor unit/functional unit A single motor neuron together with the muscle fibers supplied by it. The size of the unit depends on the precision of the movement Large & Small 50
- 51. Sensory fibers Arisesfrom specialized endings Muscle spindle/tendon spindle Essential for muscle tone and body posture Essential for coordinated voluntary movements 51
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- 54. 54 Movement Posture & Body position Supportto Soft tissues Joint stabilization Body Temperature Skeletal Muscles Functions Facial Expression Protection
- 55. Properties of MuscleTissue Excitability Respond to chemicals released from nerve cells Conductivity Ability to propagate electrical signals over membrane Contractility Ability to shorten and generate force Extensibility Ability to be stretched without damaging the tissue Elasticity Ability to return to original shape after being stretched 55
- 56.
- 57. 57 Muscle Disorders Trauma Compartment syndrome Carpal tunnelsyndrome Bruisesor tear Infection Myositis Trichinosis Fibromyalgia Tetanus Inherited disorders Muscular dystrophies Tumors Myomas Sarcomas
- 58. 58 Secondary Disorders Immune problems: Myasthenia gravis GuilliainBarre syndrome Nervous system: Botulism Poliomyelitis Cardiovascular system: Anemia Heart failure Metabolic problems: Hypercalcemia Hypocalcemia
- 59. Fatigue Decreased capacity towork and reduced efficiency of performance Cause - Exhaustion of Ach in motor endplate Accumulation of metabolites like lactic acid and phosphoric acid Lack of nutrients like glucose Lack of oxygen 59
- 60. Spasticity -Tone isincreased (Eg- stroke) Flaccidity -Tone is decreased (Eg -spinal shock) Atrophy- (wasting of muscles) (Eg- Poliomyelitis) 60
- 61. Hypertrophy -New muscle fibers are not formed, Enlargement due to production of more myofibrils and cell organelles Hyperplasia – increase in number Damage of skeletal muscle – replaced by fibrous scar tissue 61
- 62. Myasthenia gravis Autoimmunedisorder - blocks the ACh receptors- NMJ The more receptors are damaged the weaker the muscle. More common in women 20 to 40 with possible line to thymus gland tumors Symptoms Treatment includes steroids that reduce antibodies that bind to ACh receptors and inhibitors of acetylcholinesterase 62
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- 65. Muscular Dystrophies Inherited,muscle-destroying diseases Sarcolemma tears during muscle contraction X linked disease - male Appears by age 5 in males and by 12 may be unable to walk Degeneration of individual muscle fibers produces atrophy of the skeletal muscle 65
- 66.
- 67. Poliomyelitis Poliovirus Underthe age of 3 Poliovirus destroys motor neuron in the AHC. Muscle of leg more affected than arm but paralysis can spread to the muscle of the thorax and abdomen 67
- 68. Sports Injuries 5year study of college football players indicate: • Mild – 73.5% • Moderate – 21.5% • Severe – 11.6% A study of 1650 joggers running 27 miles a week reported 1819 injuries in a single year. 68
- 69. Sports related conditions Bone bruise: bleeding within the periosteum Bursitis: an inflammation of bursae Muscle cramps: prolonged,involuntary,and painful muscular contraction Sprains: tear or break in ligaments or tendons Strains: tears in muscles Tendinitis: an inflammation of connective tissue surrounding a tendon 69
- 70. Muscle Memory Musclememory is not a memory stored in your muscles,but memories stored in your brain. Motor Learning. Muscle Encoding. Muscle Re-education or Rehabilitaion. 70
- 71.
- 72. Electromyography To test theaction of muscle EMG helps in testing the efficiency of lower motor neuron 72
- 73. REFERENCES 1. Gray’s Anatomy-Susan Standring. 40th Edition. 2. Inderbir singh. Textbook of human histology with color atlas, 2006, 5th edition 3. DiFiore’s , Atlas of histology, 12th edition 4. Vander’s Human physiology, 12th edition 5. Manipal manual of physiology,1st edition 6. Principal of general anatomy A.k.datta,7th edition 7. General anatomy,B D Chaurasia,4th edition 8. Principles of Human Anatomy,Gerard J.Tortora/Mark T.Nielsen, 13th edition 9. Gross Anatomy,Kyung Won Chung/Harold M. chung, 6th edition 10. A&P ,Applications Manual ,Martini &Welch 73
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