THE MUSCULOSKELETAL SYSTEM

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THE MUSCULOSKELETAL SYSTEM

• Chapter 34

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• A. Types of Skeletons
• 1. Hydrostatic skeleton
• Consists of liquid within a layer of flexible
  tissue.
• Functions to provide shape allow movement.
• Ex. hydra, jellyfishes, sea anemones, slugs
  annelids

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• 2. Exoskeleton
• A braced framework skeleton on the outside of
  organism.
• Functions to provide shape, protection sites
  for muscle attachment.

mollusks (calcareous shells that enlarge as
animal grows)
arthropods (chitinous shells that must be
periodically molted)
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• 3. Endoskeleton
• A braced framework skeleton on the inside of
  organism.

sponges (calcareous or silica spicules)
echinoderms (calcareous plates)
vertebrates (primarily bone cartilage in some)
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• Functions of the Vertebrate Skeleton
• support
• protection
• lever system for movement
• production of blood cells
• mineral storage

Vertebrate skeletons are similar, but exhibit
species specific adaptations.
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• Tissues of the Vertebrate Skeleton

• Cartilage
• consists of chondrocytes embedded in a
  collagen/elastin matrix
• located at ends of long bones between vertebrae
• functions as shock absorber

• Bone
• consists of osteocytes embedded in a mineralized
  collagen matrix
• good blood supply
• constantly being remodeled

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• Spongy bone
• found in expanded ends of long bones flat bones
• contains red marrow
• Compact bone
• found in shaft of long bones
• contains yellow marrow
• Presence of spongy bone marrow cavity reduces
  bone weight.

Marrow cavity
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• B. Human Skeleton
• Axial skeleton
• skull
• vertebral column
• 7 cervical vertebrae
• 12 thoracic vertebrae
• 5 lumbar vertebrae
• 1 sacrum
• 1 coccyx
• ribs - 12 pair in both males females
• sternum

skull sternum ribs vertebral column
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• Appendicular skeleton
• pectoral girdle
• clavicles
• scapulae
• pelvic girdle
• pelvic bones
• upper appendages (arms)
• lower appendages (legs)

clavicle scapula humerus radius ulna pelvic
bone femur patella tibia fibula
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• C. Muscle Diversity
• Animal muscles are composed primarily of the
  proteins actin myosin.
• 1. Smooth muscle

• spindle-shaped cells
• uninucleate
• nonstriated
• involuntary
• Adductor muscle of bivalve mollusks walls of
  blood vessels iris of eye walls of hollow
  organs (stomach, intestines, bladder).

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• 2. Cardiac muscle

• Branched, uninucleate cells
• striated
• involuntary
• possess intercalated disks

Unique to the heart 3. Skeletal muscle

• long, multinucleate cells
• striated
• voluntary
• Usually attached to skeleton

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• D. Skeletal Muscle - a closer look
• 1. Structure
• Skeletal muscles contain bundles (fascicles) of
  skeletal muscle fibers (cells).

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• Each muscle fiber is surrounded by a plasma
  membrane (sarcolemma) contains

• numerous mitochondria nuclei
• extensive endoplasmic (sarcoplasmic) reticulum
  packed with Ca2
• several myofibrils consisting of overlapping
  actin myosin myofilaments.

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• 2. Contraction
• action potential triggers release of
  acetylcholine at neuromuscular junction

• electrical wave spreads over sarcolemma enters
  muscle fiber
• sarcoplasmic reticulum dumps Ca2 into cytoplasm
• Ca2 enable actin myosin myofilaments to slide
  past each other requires ATP

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• Muscle relaxes (myofilament sliding stops) when
  Ca2 are removed from the cytoplasm.

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• Large amounts of ATP are required for muscle
  contraction AND relaxation.
• breaks/reforms connections between actin myosin
• powers pumps that return Ca2 to the sarcoplasmic
  reticulum
• Muscle cells generate ATP
• from creatine phosphate
• by aerobic respiration
• by anaerobic respiration
• What is rigor mortis?

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• 3. Athletic performance
• Linked to proportion of fast-twitch and
  slow-twitch fibers in muscles.
• Muscles containing a high proportion of
  fast-twitch fibers (contract rapidly/fatigue
  quickly) function best in short, fast events.
• Muscles containing a high proportion of
  slow-twitch fibers (contract slowly/resist
  fatigue) function best in endurance events.

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• E. Joints
• Junctions between bones.
• Joints are classified as
• Immovable
• Ex. suture
• Slightly moveable
• Ex. vertebrae
• Freely moveable
• Ex. synovial

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• Synovial joints enable muscles to interact with
  bones, producing movement.

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• Most common type of joint problem is arthritis
  (joint inflammation).
• Osteoarthritis (wear-and-tear arthritis)
• Cartilage covering the ends of bones slowly wears
  away, causing stiffness soreness.
• Rheumatoid arthritis

Autoimmune disease in which the bodys immune
system attacks the synovial membranes.