Cartilage

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Cartilage

• A non-vascular structural material found in
  various parts of the body.
• Forms most of the skeleton in infants.
• Replaced by bone through ossification during the
  maturing process.

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Cartilage Classified by Its Change During
Maturation

1. Temporary Cartilage Cartilage which is
   naturally replaced by bone during ossification.
2. Permanent Cartilage Cartilage which is designed
   to remain largely unossified throughout life.

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Types of Cartilage

1. Hyaline Cartilage
2. Elastic Cartilage
3. Fibrocartilage

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TYPES OF CARTILAGE

• Hyaline Cartilage
• A gristly mass of firm consistency
• Considerably elastic
• Covered by a fibrous membrane called the
  perichondrium which provides its source of
  nutrition
• PERICHONDRIUM NOT PRESENT IN ARTICULAR CARTILAGE

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TYPES OF CARTILAGE (continued)

• Elastic Cartilage
• Yellowish in color
• More flexible or rubbery than other types of
  cartilage
• Contains elastic fibers imbedded in the cartilage
  matrix

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TYPES OF CARTILAGE (continued)

• Fibrocartilage
• A mixture of white fibrous tissue and
  cartilaginous tissue
• Flexibilty comes from the fibrous tissue
• Toughness comes from the cartilaginous tissue

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TYPES OF FIBROCARTILAGE

• connecting fibrocartilage
• intervertebral joints (vertebral symphysis) and
  pubic symphysis
• adheres to opposing surfaces
• found in joints which admit only slight mobility

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Vertebrae Cross Section
intervertebral discs
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TYPES OF FIBROCARTILAGE (continued)

• interarticular fibrocartilage
• menisci of knee
• also found in temporomandibular,
  sternoclavicular, acromioclavicular and wrist
  joints
• free on both surfaces - held in place by
  ligaments
• Found in joints subject to frequent movement and
  high impact

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Menisci Top View
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TYPES OF FIBROCARTILAGE (continued)

• circumferential fibrocartilage
• labrum in shoulder and hip
• deepens the joint to increase stability and
  contact area

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Hip Cross Section
articular cartilage
pelvis
labrum
articular cartilage
femur
labrum
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TYPES OF FIBROCARTILAGE (continued)

• 4. stratiform fibrocartilage
• forms a thin coating where tendons pass through
  grooves in the skeleton
• develops in the tendons of some muscles where
  they glide over bones (examples Peroneus Longus
  and Tibialis Posterior)

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SITES OF STRATIFORM FIBROCARTILAGE
Right Leg Lateral View
Right Ankle Medial View
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ANATOMICAL PRESENCE OF CARTILAGE

1. JOINT CARTILAGE
2. STRUCTURAL CARTILAGE
3. ELASTIC CARTILAGE
4. BONE CARTILAGE (TEMPORARY CARTILAGE)

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A. JOINT CARTILAGE

• 1. Articular cartilage - surrounds ends of bones
  at articulations
• formed by hyaline cartilage
• assists in shock absorption - compression
• increases contact area
• low friction surface
• High in proteoglycans, some TypeII collagen

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A. JOINT CARTILAGE (continued)

• 2. Fibrocartilage
• Assists in shock absorption
• Promotes a "tight fit in the joint
• Made of proteoglycans, Type I and II collagen

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B. STRUCTURAL CARTILAGE

• Performs a supportive structure like bones
• Made of hyaline cartilage
• Costal cartilage (continuation of the ribs)
• Also found in nose, larynx, xiphoid process and
  most of the trachea

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Thoracic Skeleton
Costal Cartilage
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C. ELASTIC CARTILAGE

• Shapes or supports structures needing flexibility
  and elasticity
• Found in external ear, Eustachian tube,
  epiglottis and parts of the larynx

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D. BONE CARTILAGE

• The temporary cartilage that ossifies during the
  maturing process.
• Largely responsible for the structural
  differences between the bones of children and
  adults.
• Because of the high cartilage content, childrens
  bones
• have lower strength
• are less stiff
• have lower energy to failure
• have larger strain to failure
• are subject to greenstick fractures

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Susceptibility to Injury

• Due to its lack of direct blood supply, cartilage
  has very limited ability for repair.
• Susceptible to "wear and tear" injuries
• Cushioning effect decreases with age

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Joint Cartilage

• ANISOTROPIC (has different structural properties
  in different directions)
• High resistance to COMPRESSION
• NOT to tension or shear
• reduces stress by decreasing impact forces and
  increasing area of contact

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Synovial Fluid

• Secreted by synovial membrane
• Lubricant in freely moveable (synovial) joints
  (i.e., reduces friction in joint while moving)
• Not an oil! Composed of water, hyaluronic acid,
  glycoproteins (lubricin)
• Most effective with healthy cartilage
• The faster the joint is articulating (increased
  angular velocity) the greater the lubricating
  effect
• Temperature dependent (Becomes less viscous with
  increased temperature)

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Basic Synovial Joint