Mechanic of Movement

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Mechanic of Movement

• Tissues and Structures Involved
• Muscle
• Nerve
• Bone
• Cartilage
• What are Tendons Ligaments?
• Types of Joints
• Mechanics of Joints

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Nerve and Muscle--the Motor Unit

• Motor Unit is one motor neuron plus the muscle
  cells it synapses
• Action potential--controlled conduction of
  electrical messages in neurons and muscle by
  depolarization of cell membrane

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Neuro-Muscular Junction
Action potential in nerves triggers chemical
release at synapse which triggers action
potential in muscle
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Bone and Cartilage

• Bone as tissue
• Bones as structures formed from bone, cartilage
  and other tissues
• Location of cartilage in skeleton and relation to
  joints

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HOW DOES MOVEMENT HAPPENS?
Muscles Pull on Tendons to Move Bones at
Connections called Joints or Articulations
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Tendons

• Tendons are structures that connect bone to
  muscle, muscle to muscle, or bone to bone

• Made up of tendon tissue (connective tissue)
• Can have various shapes
• Typical is cord-like tendon of biceps

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Ligaments

• Ligaments connect bone-to-bone or reinforce
  joints--they are made up of tendinous tissue as
  well
• Typical are knee ligaments

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Joints or Articulations

• Connections between bones
• Usually, but not always allow for movement
• Formed from various connective tissues
• Fibrous
• Cartilaginous
• Synovial (most complex--typical limb joints)
• Functions of joints
• Hold bones together
• Allow for mobility
• Ways joints are classified
• Functionally
• Structurally

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Functional Classification The amount of movement
the joint allows

• Synarthroses
• immovable joints
• Amphiarthroses
• slightly moveable joints
• Diarthroses
• freely moveable joints

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Structural Classification

• Fibrous joints
• Generally immovable
• Fibrous tissue separate the boney region at the
  joint
• Cartilaginous joints
• Immovable or slightly moveable
• Cartilage separates the boney regions at the
  joint
• Synovial joints
• Freely moveable
• The boney regions of the joint are separated by a
  space

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Fibrous Joints

• Bones united by fibrous tissue synarthrosis or
  largely immovable.

• Skull
• Bones tightly bound by minimal fiber

• Syndesmoses
• Longer connecting fibers
• Joint has more give

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Cartilaginous Joints

• Mostly amphiarthrosis
• Bones connected by cartilage

• Pubic symphysis
• Intervertebral joints
• Hyaline cartilage unites bones
• Epiphyseal growth plates
• Costal cartilage-sternum

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Synovial Joints

• Diarthroses movable joint
• Most common joint in the body

• Articulating ends of bones are covered with
  hyaline cartilage
• Enclosed by a capsule of fibrous connective
  tissue lined with synovial membranes
• Joint cavity is filled with synovial fluid for
  lubrication
• Ligaments reinforce the joint

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Typical Synovial Joint
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Structures Associated with the Synovial Joints

• Bursae flattened fibrous sacs
• Lined with synovial membranes
• Filled with synovial fluid
• Not actually part of the joint
• Tendon sheath
• Elongated bursa that wraps around a tendon

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Types of Synovial Joints
The type of joint, in part, determines the range
and direction of movement
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Types of Synovial Joints
The type of joint, in part, determines the range
and direction of movement
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HOW DOES MOVEMENT HAPPEN? The elbow joint - a
hinge joint allowing movement in 1 plane
The Capsule. Holds the bones of the joint in
place.
The synovial membrane. Secretes synovial fluid
The synovial fluid. Lubricates the movement of
the cartilage surfaces against each other
reducing friction and preventing arthritis
(inflammation and joint damage).
Cartilage. Lubricates the movement of the
cartilage surfaces against each other reducing
friction and preventing arthritis (inflammation
and joint damage).
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HOW DOES MOVEMENT HAPPEN? The elbow joint - how
the bicep and triceps control movement
When the biceps contracts the elbow joint flexes
(its joint angle decreases).
humerus
biceps (flexor muscle), contracts
When the triceps contracts the elbow joint
extends (its joint angle increases).
Triceps (extensor) relaxes
The biceps and triceps are called antagonistic
muscles because they have the opposite effect on
the same joint.
radius
ulna
Remember that for this to work properly the
biceps must relax when the triceps contracts, and
vice versa.
THE BICEPS AND TRICEPS ARE AN ANTAGONISTIC PAIR
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Inflammatory Conditions Associated with Joints

• Bursitis inflammation of a bursa usually caused
  by a blow or friction
• Tendonitis inflammation of tendon sheaths
• Arthritis inflammatory or degenerative diseases
  of joints
• Over 100 different types
• The most widespread crippling disease in the
  United States

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Clinical Forms of Arthritis

• Osteoarthritis
• Most common chronic arthritis
• Probably related to normal aging processes
• Rheumatoid arthritis
• An autoimmune disease the immune system attacks
  the joints
• Symptoms begin with bilateral inflammation of
  certain joints
• Often leads to deformities

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X-ray of hand affected by arthritis
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Artificial Hip Joint
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Lots of problems with joints result from sports
injuries
What can go wrong with joints