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Muscle tissue 1 2 (comparative vertebrate anatomy)
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Muscle tissue 1 2 (comparative vertebrate anatomy)

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  • 1. Muscular System • Function – Locomotion – Posture – Protection – Heat production
  • 2. • Vertebrate muscles: • striated vs. smooth • voluntary vs. involuntary • skeletal vs. non-skeletal • Skeletal muscle (left) & Smooth muscle (right)
  • 3. Muscle Classification • Skeletal Muscle – Attached to skeleton – Striated – Muscle fiber = Muscle cell • Multinucleate • Myofibrils are striated cylinders within myofiber • Non-skeletal muscle = muscles not attached to the skeleton; most are smooth & involuntary
  • 4. • 1 - Skeletal, striated, voluntary muscles – axial • body wall & tail • hypobranchial & tongue • extrinsic eyeball muscles – appendicular – branchiomeric (homologous to the branchial/ pharyngeal muscles from fishes to mammals, striated muscles, innervated by cranial nerves) – integumentary
  • 5. • 2 - Non-skeletal, smooth, chiefly involuntary muscles –muscles of tubes, vessels, & hollow organs –intrinsic eyeball muscles –erectors of feathers & hair • 3 - Cardiac muscle • 4 - Electric organs
  • 6. • Skeletal muscles have muscular & tendinous portions: • Muscle - consists of skeletal muscle cells (which, in turn, consist of myofibrils and myofilaments) • Tendons - extensions of a muscle's tough connective tissue sheath (fascia & epimysium) that anchor a muscle to its origin & insertion
  • 7. –Origin = site of attachment that is relatively fixed –Insertion = site of attachment that is normally displaced by contraction of the muscle
  • 8. •Names of skeletal muscles are based on: •direction of fibers (e.g., oblique( •location or position (e.g., superficial( •number of divisions (e.g., triceps( •shape (e.g., deltoid( •origin and/or insertion (e.g., iliocostalis( •action (e.g., levator scapulae( •size (e.g., major( •or some combination of these
  • 9. Skeletal Muscle • Myofilaments are proteins that result in contraction within the myofibrils –Actin – thin & has a receptor site for myosin –Myosin – thick & has a receptor site for actin and ATP –Contraction – Myosin heads attach to actin and with ATP perform a Power Stroke
  • 10. Skeletal Muscle •Sarcomere •The distance from Z line to Z line •The basic unit of contraction •Sarcomere gets smaller as Power Stroke occurs
  • 11. Key Points • Why is the sarcomere the functional unit of contraction? • Why does the power stroke result in contraction? • What would happen to contraction if you ran out of ATP?
  • 12. Motor Neurons • Skeletal muscle cannot contract without stimulation from a motor neuron • Motor Unit = The motor neuron plus the myofiber(s) it innervates
  • 13. Key Points • Why would a spinal cord injury result in paralysis?
  • 14. Somatic Muscles • All of the body’s skeletal muscles except the branchiomeric muscles • Voluntary • Body wall & Appendage muscles – Trunk and Tail – Hypobranchial – Tongue – Extrinsic Eyeball
  • 15. Somatic Muscles • Myotome derivatives primarily • Some from hypomere
  • 16. Key Points • What is a myotome?
  • 17. Somatic Muscles • Orient the body in the environment
  • 18. Somatic Muscles • Red Fibers – More blood supply for aerobic metabolism – Myoglobin for oxygen storage – Fatigue resistant – Fish for cruising long distances, tetrapods for posture
  • 19. Somatic Muscles • White fibers – Less blood supply; geared for anaerobic metabolism – Fatiguable – Fish for spurts of swimming – Tetrapods for sprints
  • 20. Key Points • Why is the breast meat of the goose dark, but the breast meat of the chicken is white?
  • 21. Cardiac Muscle • Striated with intercalated disks • Involuntary • Lateral plate mesoderm (hypomere) in origin
  • 22. Smooth Muscle • Involuntary • Lateral plate mesoderm in origin • Regulates internal environment • Innervated by Autonomic Nervous System • Found in the wall of tubes and hollow organs • Intrinsic Eye muscles • Erectors of feathers and hairs
  • 23. Key Points • Besides those mentioned, give a specific example of where might you find smooth muscle?
  • 24. Gross features of skeletal muscle • Origin, insertion • Tendon • Aponeurosis • Fascia
  • 25. Muscle shapes
  • 26. Skeletal Muscle Actions • Flex/Extend • Adduct/Abduct • Levator/Depressor • Protract/Retract • Constrictor/Dilator • Rotator
  • 27. Skeletal Muscle Actions • Supinator/Pronator • Tensor (taut)
  • 28. Skeletal Muscle Actions • Agonist – primary mover • Antagonist – opposes primary mover • Synergist – helps primary mover
  • 29. Development & Phylogeny • Position • Embryology • Nerve supply
  • 30. Development • Dorsal Mesoderm – Epimere – Somite –Myotome –Sclerotome & Dermatome • Lateral plate Mesoderm – Hypomere –Somatic – body wall muscles –Splanchnic – smooth muscle of viscera
  • 31. AXIAL MUSCLES • Trunk • Tail • Hypobranchial • Tongue • Extrinsic Eye
  • 32. • Axial Muscles: • include the skeletal muscles of the trunk & tail • extend forward beneath the pharynx as hypobranchial muscles & muscles of the tongue • are present in orbits as extrinsic eyeball muscles (check slide 27 in this powerpoint presentation) • are metameric (most evident in fish and aquatic amphibians where the axial muscles are used in locomotion; in other tetrapods, metamerism is obscured due to presence of paired appendages responsible for locomotion on land) • are segmental because of their embryonic origin; arise from segmental mesodermal somites
  • 33. •Trunk & tail muscles of fish: •Axial musculature consists of a series of segments (myomeres) separated by myosepta –Myosepta serve as origins & insertions for segmented muscles •Myomeres are divided into dorsal & ventral masses by a horizontal septum that extends between the transverse processes of the vertebrae
  • 34. •Epaxials = above the septum •Hypaxials = below the septum
  • 35. • Trunk & tail muscles of tetrapods • Tetrapods, like fish, have epaxial & hypaxial masses, & these retain some evidence of metamerism even in the highest tetrapods. • Modifications: • 1 - epaxials are elongated bundles that extend through many body segments & that are located below the expanded appendicular muscles required to operate the limbs • 2 - hypaxials of the abdomen have no myosepta & form broad sheets of muscle • 3 - hypaxials are oriented into oblique, rectus, & transverse bundles
  • 36. • Epaxials of tetrapods: • lie along vertebral column dorsal to transverse processes & lateral to neural arches • extend from base of the skull to tip of the tail
  • 37. •Hypaxials of tetrapods: •1-Muscles of lateral body wall: –oblique (external & internal), transverse, & rectus muscles •2-Muscles that form longitudinal bands in roof of body cavity (subvertebral muscles(
  • 38. Rectus muscles: •weakly developed in most fish; 'stronger' in tetrapods •support ventral body wall & aid in arching the back •in mammals - rectus abdominis (typically extends from the anterior end of the sternum to the pelvic girdle)
  • 39. Appendicular muscles - move fins or limbs •Extrinsic - originate on axial skeleton or fascia or trunk & insert on girdles or limbs •Intrinsic - originate on girdle or proximal skeletal elements of appendage & insert on more distal elements
  • 40. Branchiomeric muscles: 1 - associated with the pharyngeal arches 2 - series of skeletal & smooth muscles 3 - adductors, constrictors, & levators operate jaws plus successive gill arches
  • 41. Integumentary muscles: Extrinsic integumentary muscles (e.g., platysma) •originate (usually) on the skeleton & insert on the underside of the dermis •striated •move skin of amniotes Intrinsic integumentary muscles (arrector pili muscles) •entirely within the dermis •found in birds & mammals mostly smooth muscles
  • 42. Axial Muscles •Metamerism as in myomeres
  • 43. Axial Muscles •Agnathans •Simple •Segments (myomeres( •Myotome derivatives
  • 44. Axial Muscles – Jawed Fish • Horizontal or Lateral Septum • Epaxial Muscles – From myotomes in embryology – Innervated from dorsal rami of spinal nerves – Extend spine & some lateral bending – Extrinsic eye muscles (innervated by cranial nerves) – Epibranchial muscles
  • 45. Axial Muscles – Jawed Fish •Hypaxial Muscles •From Myotomes –Innervated by ventral rami of spinal nerves –Ventroflex and lateral bending
  • 46. Hypaxial Muscles – Jawed fish •Hypobranchial muscles •Located on floor of pharynx, pectoral girdle to jaw •Are hypaxial muscles that migrated forward •Function in respiration & feeding •E.g. Coracomandibularis, Coracohyoid
  • 47. Axial Muscles - Tetrapods •Epaxial trunk muscles •Dorsal muscles from skull to tail •Dorsalis trunci in amphibians •Longissimus – long dominant spine extensor in amniotes •Iliocostalis – most lateral epaxial spine muscle important in reptiles
  • 48. Epaxial Muscles •See Vertebrate Muscles page
  • 49. Epaxial Muscles in Tetrapods • Trends • Decreased except in neck • Fewer myosepta
  • 50. Axial Muscles - Tetrapods • Hypaxial Muscles • Tend to form sling-like sheets • Lateral muscles support & compress body wall • Obliques • Transversus • Intercostals in amniotes only
  • 51. Hypaxial Muscles - Tetrapods • Rectus abdominis – ventroflexes and compresses abdomen • Diaphragm – unique to mammals for breathing
  • 52. Hypaxial Muscles in tetrapods •See Vertebrate Muscles page
  • 53. Hypobranchial and Tongue Muscles - tetrapods • Function – stabilizes hyoid and larynx • E.g. geniohyoid, sternohyoid, sternothyroid, thyrohyoid
  • 54. Hypobranchial & Tongue muscles in tetrapods •Tongue muscles •Lingu-; Gloss- •Anchors to hyoid •E.g. lingualis, styloglossus
  • 55. Hypobranchial & Tongue muscles in Tetrapods • See Vertebrate Muscles page
  • 56. Extrinsic Eye muscles in tetrapods • Voluntary • Obliques – rotates eye along its transverse axis • Rectus – up, down, left, right • Retractor in some
  • 57. Extrinsic Eye muscles • See Vertebrate Muscles Page