Unit 2.1 Joints

• Cartilage


  Ground substance has a lot of PGs and water, helps cartilage act as a CUSHION
• Cartilage


  • Fibers provide toughness and support
• Types of cartilage


  • Hyaline
  • Elastic
  • Fibrocartilage
• Hyaline cartilage


  Tough with a small amount of flexibility
• Hyaline cartilage locations

  • Articular cartilages (synovial joints)
  • Costal cartilages (important for respiration!)
  • Larynx cartilages (respiratory system)
  • Nasal cartilages (respiratory system)
• Elastic cartilage


  Tons of elastic fibers, super flexibility
• Elastic cartilage locations found in epiglottis and outer ear
• Fibrocartilage


  Very tough, found in areas of pressure and stretch
• Cartilage is generally found in areas that need cushioning, shock absorption, flexibility
• Cartilage growth


  1. Appositional growth: New cartilage formed on the edges

  2. Interstitial growth: New cartilage is formed from within
• Joints are the weakest part of the skeleton but they do a pretty good job
• Articulation


  Joint = a site where 2 bones meet, this doesn't mean they have to be mobile
• Classifications of joints


  • Bony
  • Fibrous
  • Cartilaginous
  • Synovial
• Bony joints


  • Two bones ossify together, immobile
• Bony joint example


  • Coxal bone made of ilium, ischium, pubis
• Fibrous joints


  • Collagen fibers cross from one bone to the other, little to no movement
• Fibrous joint examples


  • Suture (bones of skull)
  • Gomphosis (teeth in socket)
  • Syndesmosis (distal fibula and tibia)
• Cartilaginous joints


  • Synchondrosis (made of hyaline cartilage, e.g. long bone contains epiphyseal plate)
  • Symphysis (made of fibrocartilage, e.g. pubic symphysis), slight mobility
• Synovial joints


  • Complex structure, hyaline cartilage, viscous lubricating fluid, secretes synovial fluid, attaches bone to bone
• Accessory structures of synovial joints


  • Capsule
  • Ligaments
  • Bursae
• Menisci


  Serve as shock absorbers and improve the fit of the bones, made of fibrocartilage
• Articular discs


  Similar in structure to menisci, found in jaw and a few other places
• Ligaments in the tibiofemoral (knee) joint


  • Collateral ligaments (prevent rotation when joint is extended)
  • Tibial collateral ligament (MCL)
  • Fibular collateral ligament (LCL)
  • Anterior cruciate ligament (ACL) (prevents hyperextension)
  • Posterior cruciate ligament (PCL) (prevents sliding of femur off of tibia)
• Muscles associated with the knee flexion: hamstring, short head and long head of biceps femoris, semitendinosus, semimembranosus
• Knee flexion


  Muscles contract and shorten, pull tibia and fibula to flex knee
• Knee extension


  Muscles contract and shorten, pull tibia and fibula to extend knee
• Patella


  Extends length of moment arm (lever) of the quadriceps muscle allowing for greater knee extension (less force required)
• Popliteus


  Unlocks the knee prior to flexion
• Common joint issues


  • Osteoarthritis
  • Rheumatoid arthritis
• Rheumatoid arthritis


  Autoimmune disease where rheumatoid factor attacks synovial membranes, causing chronic inflammation and loss of cartilage
• Ankylosis


  Abnormal stiffening and immobility of a joint, starts with inflammation and erosion, loss of cartilage and damage to bone
• Osteoarthritis


  Degeneration of articular cartilage, "wear and tear", common in aging, can lead to swelling, pain, reduced mobility
• Muscles associated with knee extension: quadricep, rectus femoris, vastus intermedius, vastus medialis, vastus lateralis