Bones, Joints and Muscles

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Bones, Joints and Muscles
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Bones 206 in human body

• Function
• support (eg) pelvic bowl, legs
• protect (eg) skull, vertebrae
• mineral storage (eg) calcium, phosphate,
  inorganic component
• movement (eg) walk, grasp objects
• blood-cell formation (eg) red bone marrow
• Osteoblasts secrete organic part of bone matrix
  osteoid
• Osteocytes mature bone cells, maintain bone
  matrix

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Some Reminders about Bones

• Bone bone tissue (type of CT)
• A Bone an organ
• Compact vs. Spongy Bone
• Composition Hydroxyapatite, protoplasm,
  collagen, blood vessels, marrow
• Skeleton bones, cartilage (avascular, no
  nerves, 80 H2O), joints, ligaments
• Shapes of Bones
• Long, Flat, Irregular, Short
• Before 8 weeks, embryo is all cartilage

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Structure of Bone
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Anatomy of a Long Bone

• Diaphysis
• Medullary Cavity
• Nutrient Art Vein
• 2 Epiphyses
• Epiphyseal Plates
• Epiphyseal Art Vein
• Periosteum
• Outer Dense irregular CT
• Inner Osteoblasts, osteoclasts
• Does not cover epiphyses
• Attaches to bone matrix via collagen fibers
• Endosteum
• Osteoblasts, osteoclasts
• Covers trabeculae, lines medullary cavity

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2 Types of Bone Formation

• 1) Intramembranous Ossification
• Membrane bones most skull bones and clavicle
• Osteoblasts in membrane secrete osteoid that
  mineralizes
• Osteocytes maintain new bone tissue
• Trabeculae forms between blood vessels
• Grows into thickened plates at periphery
  compact bone
• Periosteum forms over it

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2 Types of Bone Formation

• 2) Endochondral Ossification All other bones
• Begins with a cartilaginous model
• Perichondrium becomes replaced by periosteum
• Cartilage in diaphysis calcifies
• Trabeculae forms from Periosteal bud
• Periosteal bud arteries veins, cells forming
  bone marrow, osteoblasts, osteoclasts
• Medullary cavity is formed by action of
  osteoclasts
• Epiphyses grow and eventually calcify
• Epiphyseal plates remain cartilage for up to 20
  years

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Bone Growth Remodeling

• GROWTH
• Appositional Growth widening of bone
• Bone tissue added on surface by osteoblasts of
  periosteum
• Medullary cavity maintained by osteoclasts
• Lengthening of Bone
• Epiphyseal plates enlarge by chondroblasts
• Matrix calcifies (chondrocytes die and
  disintegrate)
• Bone tissue replaces cartilage on diaphysis side
• REMODELING
• Due to mechanical stresses on bones, their tissue
  needs to be replaced
• Osteoclasts-take up bone ( breakdown)
• release Ca2 , PO4 to body fluids from bone
• Osteoblasts-lay down bone
• secrete osteoid to form new bone
• Ideally osteoclasts and osteoblasts work at the
  same rate!

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Joints (articulations)

• Where parts of skeleton meet
• Allows varying amounts of mobility
• Classified by structure or function
• Arthrology study of joints

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Classification of Joints

• Function
• Synarthroses no/little movement
• Amphiarthroses slight movement
• Diarthroses great movement

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Joints by Functional Classification
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Joint Classification

• Structure
• Cartilagenous
• Synchondrosis connected by hyaline cartilage
  (synarthroses)
• Symphysis connected by fibrocartilage
  (amphiarthroses)
• Fibrous
• Sutures connected by short strands of dense CT
  (synarthroses)
• Syndesmoses connected by ligaments (varies)
• Gomphosis peg in socket w/short ligament
  (synarthroses)
• Synovial (diarthroses)

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Joints by Structural Classification
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Components of SYNOVIAL JOINTS (Structural
Joint Classification continued)

• Articular cartilage hyaline covers ends of both
  bones articulating
• Synovial (joint) cavity space holding synovial
  fluid
• Articular capsule Made of 2 layers
• Fibrous external, dense CT for strength
• Synovial membrane internal, produces synovial
  fluid
• Synovial fluid viscous lubricates and
  nourishes contained in capsule and articular
  cartilages
• Reinforcing ligaments extracapsular/intracapsular
  
• Nerves vessels Highly innervated, Highly
  vascular
• Meniscus (some) fibrocartilage improves the fit
  of 2 bones to increase stability

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Synovial Joint
pg 215
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Bursae Tendon Sheaths

• Bursae flat, fibrous sac w/synovial membrane
  lining
• Tendon Sheaths elongated bursae that wraps
  around tendons
• 3 Factors in Joint Stability
• Muscle Tone
• Ligaments
• Fit of Articular Surface

pg 219
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Joint Shapes
pg 224

• Hinge cylindrical end of 1 bone fits into trough
  shape of other
• angular movement-1 plane (eg) elbow, ankle,
  interphalangal
• Plane articular surface in flat plane
• Short gliding movement
• (eg) intertarsal, articular processes of vertebrae

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Joint Shapes
pg 225

• Condyloid egg-shape articular surface oval
  concavity
• side-to-side, backforth movement
• (eg) metacarpophalangeal (knuckle)
• Pivot round end fits into ring of bone
  ligament
• rotation on long axis
• (eg) prox. radius/ulna, atlas/dens

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Joint Shapes
pg 225

• Saddle articular surface both concave convex
• side-to-side, back-forth movement
• (eg) carpometacarpal jt of thumb
• Ball Socket spherical head round socket
• multiaxial movement
• (eg) shoulder, femur

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!Muscles!

• Function 1) movement
• 2) maintain posture
• 3) joint stability
• 4) generate heat

!Muscles!
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Special Features of Muscle

• Contractibility cells generate pulling force
• Excitibility nervous impulses travel through
  muscle plasma membrane to stimulate contraction
• Extensibility after contraction muscle can be
  stretched back to original length by opposing
  muscle action
• Elasticity after being stretched, muscle
  passively recoils to resume its resting length

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Muscle System uses levers to move objects

• How it works A rigid bar moves on fixed point
  when a force is applied to it, to move object
• Lever rigid bar bone
• Fulcrum fixed point joint
• Effort force applied muscle contraction
• Load object being moved bone

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Movements of Muscles

• Extension increasing angle between body parts
• Flexion decreasing angle between body parts
• Dorsiflexion vs. Plantarflexion
• Inversion vs. Eversion
• Abduction moving away from the median plane
• Adduction moving towards the median plane
• Rotation moving around the long axis
• Circumduction moving around in circles

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Movements of Muscles

• Elevation lifting body part superiorly
• Depression moving body part inferiorly
• Supination rotating forearm laterally
• Pronation rotating forearm medially
• Protraction Anterior movement
• Retraction Posterior movement

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Muscle Basics to Remember

• 3 Types Skeletal, Cardiac, Smooth
• Origin vs. Insertion
• Direct vs. Indirect Attachments
• direct right onto bone
• indirect via tendon/aponeurosis
• more common
• leave bony markings tubercle, crest, ridge,
  etc.
• Sometimes attach to skin

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Functional Muscle Groups

• Agonist primary mover of a muscle, major
  response produces particular movement
• (eg) biceps brachii is main flexor of forearm
• Antagonists oppose/reverse particular movement,
  prevent overshooting agonistic motion
• (eg) triceps brachii is antagonist to biceps
  brachii

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Functional Muscle Groups

• Synergists muscles work together, adds extra
  force to agonistic movement, reduce undesirable
  extra movement
• (eg) muscles crossing 2 joints
• Fixators a synergist that holds bone in place
  to provide stable base for movement
• (eg) joint stablilizers

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Naming Muscles

• Location (eg) brachialis arm
• Shape (eg) deltoid triangle
• Relative Size (eg) minimus, maximus, longus
• Direction of Fascicles (eg) oblique, rectus
• Location of Attachment (eg) brachioradialis
• Number of Origins (eg) biceps, quadriceps
• Action (eg) flexor, adductor, extensor

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Arrangement of Muscle Fibers

• Parallel long axis of fascicles parallel to axis
  of muscle straplike (eg) biceps,
  sternocleidomastoid
• Convergent O broad, I narrow, via tendon
  fan or triangle shaped (eg) pectoralis major
• Circular fascicles arranged in concentric
  circles sphincter (eg) around mouth

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Arrangement of Muscle Fibers

• Pennate fascicles short attached obliquely to
  tendon running length of muscle featherlike
• Unipennate fascicles insert on only 1 side
• (eg) flexor pollicis longus
• Bipennate fascicles insert both sides
• (eg) rectus femoris
• Multipennate many bundles inserting together
• (eg) deltoid

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Arrangements of Muscle Fascicles
pg 269
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STOP
More on Levers on the following pages
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First Class Lever

• Effort at 1 end
• Load at other end
• Fulcrum in middle
• (eg) scissors
• (eg) moving head up and down

pg 267
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Second Class Lever

• Effort at 1 end
• Fulcrum at other end
• Load in middle
• (eg) wheelbarrel
• (eg) standing on tip toes (not common in body)

pg 267
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Third Class Lever

• Load at 1 end
• Fulcrum at other end
• Force in middle
• (eg) using a tweezers
• (eg) lifting w/biceps

pg 267
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Mechanical Advantage

• When the load is close to the fulcrum, effort is
  applied far from fulcrum
• Small effort over large distance move large
  load over short distance
• (eg) Using a jack on a car

pg 266
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Mechanical Disadvantage

• When the load is farther from the fulcrum than
  the effort, the effort applied must be greater
  than the load being moved
• Load moved quickly over large distance
• (eg) using a shovel

pg 266