Skeletal System Lecture

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Skeletal System Lecture Day 2 Joints,
Fractures, and the Healing Process
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• Joints hold bones together, giving stability,
• yet at the same time, give our skeleton
  mobililty.
• There are three types of joints
• Fibrous bones connected by fibrous tissue (no
  movement)
• Cartilaginous bones connected by cartilage
  (slightly movable)
• Synovial articulating bone ends are separated by
  a joint cavity
• and inside is synovial fluid (allows for
  more movement)

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Examples of Fibrous joints
Bones of skull
Pelvic bones
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Examples of Cartilaginous joints
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Examples of Synovial joints
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• Synovial joints are found in all limbs and allow
  for various movements.
• There are 6 main types of synovial joints
• Plane joints (gliding movements i.e. in wrist)
• Hinge joints (uniaxial movement i.e. in elbow)
• Pivot joints (rotation movements i.e. radioulnar
  joint)
• Condyloid joints (some sideways movements i.e. in
  metacarpels)
• Saddle joints (slight rotation sideways
  movements i.e. in thumb)
• Ball and socket joints (uniaxial movements full
  rotation i.e. in hip and shoulder)

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Bone Fractures Healing
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Although bones are strong, they are susceptible
to breaks (fractures) all throughout life. The
most common times in life for fractures to occur
are during youth (due to excessive activity,
sports, and bad judgement) and in the elderly
(due to bone thinning and weakening, often due to
osteoporosis).
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• Six most common types of fractures
• Comminuted
• Compression
• Depressed
• Impacted
• Spiral
• Greenstick

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Comminuted fractures bone breaks in many
fragments.
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Compression fractures bone is crushed.
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Depressed fractures bone is pressed inward.
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Impacted fractures broken bone ends are forced
into each other.
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Spiral fractures ragged break occurs during
twisting.
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Greenstick fractures bone breaks incompletely
(like a young twig).
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• The process of fracture/bone healing
• A hematoma is formed. Blood vessels are ruptured
  when bone breaks. As a result, a blood-filled
  swelling forms. Bone cells are deprived of
  nutrition and die.

hematoma (swelling)
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2) The break is splinted by a fibrocartilage
callus. Connective tissue cells of various types
form a mass of repair tissue called
fibrocartilage callus (containing cartilage
matrix, bony matrix, and collagen fibers) which
act to splint the broken bone, closing the gap.
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3) A bony callus is formed. Osteoblasts and
osteoclasts migrate to the area and multiply.
Thus the fibrocartilage callus is
gradually replaced by one made of spongy bone,
known as the bony callus.
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4) Lastly, bone remodeling occurs. Over the next
few weeks to months, the bony callus is remodeled
in response to mechanical stresses placed on it,
so that it forms a strong permanent (bone) patch
at the fracture site.
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The end!