Arthrology

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Arthrology

• Chapter 9

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Arthrology Is

• Study of joints
• Joints are defined as places where the rigid
  elements of the skeleton meet.
• HOWEVER, joints can be between the soft parts
  of the skeleton.

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Classification of Joints

• 2 Methods of Classification
• Functional Classification
• focuses on the amount of movement
• allowed.
• Structural Classification
• focuses on the material that binds
  
• the joint together.

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ARTHROLOGY

• Types of Joints
• 1. SYNOSTOSIS
• - called a synarthrosis or
  syndesmosis
• - is a bone to bone union
• - begins as a joint where there is a
  fibrous membrane between the two bones. They are
  sometimes called FIBROUS JOINTS or LIGAMENTOUS
  UNIONS.
• - These are NON-MOVEABLE
• - Fontanelles are examples

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• AMPHIARTHROSIS (cartilagenous joints)
• - moveable and immoveable
• - cartilage between two bones
• - these joints allow some movement while
  still providing protection.

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• DIARTHROSIS (synovial joints)
• - allow for free movement
• - have three characteristics
• 1. synovial membrane
• - a serous membrane that
  produces synovial fluid which reduces friction
  and absorbs shock.
• 2. articular cartilage
• 3. capsule
• -dense connective tissue
  covering the joint

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Summary of Joint Classes
Structural Class Characteristics Types Mobility
Fibrous Bones united by collagen fibers Suture Syndesmosis gomphosis Immobile (synarthrosis) Slightly moveable (amphiarthrosis) Immobile
Cartilaginous Bone ends united by cartilage Synchondrosis (hyaline) Symphysis (fibrocartliage) Immobile Slightly moveable
Synovial Bone ends covered with articular cartilage and enclosed within a capsule lined with a synovial membrane Plane Hinge Pivot Condyloid Saddle Ball and socket Freely moveable (diarthrosis) which depends on joint design
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• The synovial fluid helps reduce friction,
  disipate heat, and absorb shock.
• The articular cartilage acts similarly to
  teflon, which helps reduce friction and
  pressure.
• The joint capsule covers and protects the
  synovial membrane.

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• There are several ligaments that help hold the
  portions of the joint together.
• Intracapuslar Ligament hold the bones together.
  Not found in every joint.
• Extracapsular Ligament called the collateral
  ligament. It is a single band that is actually a
  thickening of the joint capsule.

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• The synovial membrane is 3-dimensional, like a
  knee support enclosing the entire joint. It is
  NOT found between the bones. It produces the
  synovial fluid.
• BURSAE are found between the muscle and tendons
  and the bone/joint. These are fluid filled sacs
  that reduce friction. In some cases they are
  extensions of the synovial sac. When they become
  tubular, they can envelope the tendons and become
  a SYNOVIAL SHEATH. When these bursa become dry,
  friction and inflammation result, causing
  BURSITIS.

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• We can increase the surface area of a joint by
  having a MENISCUS. The knee has this sort of
  anatomy.
• This type of cartilage can be torn by torque.
  Meniscal cartilage cannot heal itself.

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How Do Muscles Act on Bones?

• Flexion vs. Extension
• Dorsiflexion vs. Plantarflexion
• Abduction vs. Adduction
• Circumduction
• Rotation
• Pronation vs. Supination
• Protraction vs. Retraction
• Elevation vs. Depression
• Inversion vs. Eversion

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Types of Joints (Articulations)

• Ball and Socket Joint
• - allow for the most freedom of
  movement
• - triaxial movement flexion,
  extension, abduction, adduction, circumflexion,
  and rotation
• Hinge Joint
• - uniaxial allows movement in only
  one direction. Back and Forth
• - allows only flexion and extension in
  one plane (sagittal)
• - many times the articular surfaces
  will have a distinct shape (ie spool shaped
  trochlear surface of the humerus)

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• Pivot Joint
• - allows rotation (uniaxial)
• - rounded, pointed, or conical surface
  on one bone that fits into a ring of bone on
  another.
• Saddle Joint
• - biaxial
• - allows flexion, extension, abduction,
  adduction, and circumduction.
• - surfaces are inverted relative to
  each other.

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• Condyloid Joint
• - biaxial
• - one bone is concave (hollowed out
  depression) and the other is convex (rounded or
  elliptical).
• - allows flexion, extension,
  abduction, and adduction.
• - NO ROTATION

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• Sliding or Gliding Joint
• - biaxial
• - side to side, back and forth
• - two flat surfaces that slide over
  each other
• - NO ANGULAR MOTION
• Tongue and Groove (Mortise and Tenon)
• - uniaxial
• - one side is a slot, the other side
  is an extension that fits into the slot.
• - NO SIDE TO SIDE MOVEMENT
• - Allows flexion and extension

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Introduction to Myology and Movement

• Human motion and walking is due to a system of
  levers that are made from bones and muscles.
• A lever has a fulcrum, or pivot point a force,
  or energy that has to be applied and a
  resistance, or opposition to movement.
• A wheel is a lever with the pivot in the center.

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3 Types of Human Levers Systems

• Class 1 Fulcrum is between the force and load.

Force
load
fulcrum
This type of lever pulls our head into an
extended position once flexed.
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• Class 2 The load is between the force and
  fulcrum.

The muscles that elevate us to our tip toes
plantarflexion of the foot on the leg.
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• Class 3 Lever
• The load is opposite the fulcrum.

Examples of this type of lever are muscles that
move the forearm.
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Requirements For Movement

• An alive muscle
• A stimulus
• - nerve impulse
• At least 2 bones
• - diarthrosis
• - the joint must allow for movement in
  plane that the muscle shortens.
• - the muscle must be able to pull the
  load
• - force must be greater than the
  resistance

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• Muscles that stabilize a limb so it can move is a
  FIXATOR.
• For example, the trapezius stabilizes the
  clavicle and scapula so we can move the arm but
  not have the head of the humerus become
  deflected in any direction.
• A muscle that provides most of the force for a
  particular movement is the PRIME MOVER. For
  example, the deltoid is the prime flexor of the
  arm on the shoulder.

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• Muscle pairs must work together
• AGONIST assists movement
• ANTAGONIST resists movement
• For example The triceps surae (gastrocnemius
  and soleus complex) plantarflexes the foot on the
  leg. This is the plantarflexory agonist. The
  muscles that work against the triceps are the
  dorsiflexory muscles (tibialis anterior and long
  extensors).
• The opposite is also true The plantarflexors
  are the antagonists to the dorsiflexors.

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SYNOVIAL JOINTS

• Occurs at ends of bones
• Articular cartilage enclosed within an articular
  capsule and lined with a synovial membrane.
• All freely moveable (diarthrosis)
• Type of movement depends on the shape and design
  of the joint.
• 6 Types
• 1. Plane 4. Condyloid
• 2. Hinge 5. Saddle
• 3. Pivot 6. Ball and Socket

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Part of a Synovial Joint

• Joint Cavity fluid filled potential space.
• Articulating surfaces
• simple joint 2 articulating surfaces
• compound joint - gt2 articular surfaces
• Articular Cartilage hyaline cartilage. Spongy
  cushions absorb compression
• Articular Capsule
• 2 layers
• 1. fibrous capsule outside, dense
  irregular CT that is continuous with the
  periosteum.
• 2. synovial membrane loose CT. Makes
  synovial fluid for protection.

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• Synovial Fluid
• viscous fluid resembling raw egg whites.
• filtrate of blood
• contains glycoproteins
• Reinforcing Ligaments
• bands that hold the joint together.
• Extracapsular outside the capsule
• Intracapsular internal to the capsule
• Neurovascular Bundle
• Nerves and Blood Vessels
• Detect pain when joint is disrupted (ie
  sprains,
• dislocations)

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• Synovial joints have lubricating devices to allow
  the bones to move across one another with minimal
  friction.
• Synovial joints are subject to compression.
  Compression occurs when muscles that hold the
  bones together contract.
• Lubricating fluid is squeezed out of the joint
  onto the opposing surfaces. When pressure on the
  joint ceases, the fluid rushes back into the
  articular cartilage. The fluid is absorbed back
  into the cartilage ready for the next compressive
  force. This is called weeping lubrication.

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MOVEMENTS OF SYNOVIAL JOINTS

• Movement caused by muscular contraction.
• 3 Types of Movments
• 1. Gliding sliding of flat surfaces
  across each other. Found mainly between the
  carpals and between the tarsals.
• 2. Angular increase or decreases the
  angle between the two bones
• 3. Rotation movement of bone around its
  long axis.

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SYNOVIAL JOINTS ARE CLASSIFIED BY SHAPE

• The shapes of the articulating surfaces determine
  the movement allowed at a joint.
• Types of synovial joints
• 1. plane flat articular surfaces. Short
  gliding movements are allowed.
• 2. hinge cylindrical end of one bone fits
  into the trough of another bone. Angular
  movement is in one plane. Uniaxial joint along
  one plane.
• 3. pivot rounded end of one fits into a
  ring formed by another bone.

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• 4. Condyloid egg shaped articular surface fits
  into the oval concavity in another.
• 5. Saddle Joint has both convex and concave
  areas.
• 6. Ball and Socket spherical head of one bone
  fits into a round socket in another.

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Disorders of Joints

• Injury
• 1. Sprain
• - stretching or tearing of a ligament
• 2. Dislocation
• - joint alignment is interrupted
• - Subluxation is a partial or
• incomplete dislocation of a
• joint.

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• Inflammatory Conditions
• Bursitis
• - inflammation of a bursa
• - Bursae are sacs of fluid that serve to
• protect boney prominences.
• Tendinitis
• - inflammation of a tendon sheath

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• Osteoarthritis
• - most common type of arthritis
• - degenerative condition of the
• articular cartilage
• - Enzymes wear down the cartilage
• matrix due to wear and tear
• Rheumatoid Arthritis
• - inflammation of the synovium
• - autoimmune in origin
• - often results in ankylosis of the
  joint