Bone growth

• We have a cartilage and after 6 weeks, bones have ossified and grew to form into bones. This is called endocondral ossification.
• Outside the cartilage is the osteoblast
• 1. The blood pushes themselves inside
  2. Once inside, they turn cartilage into bone tissue
• Primary ossification centres is the first place into forming a bone.

  We start in the middle of it, calling it the shaft. The epiphysis remains as a cartilage for a little longer.
• The secondary ossification is after the diaphysis -> epiphysis (end of the bone).

  The blood vessel will travel to the centre part and will turn it into bone tissue until the ends fill up, but the epiphyseal plate will not turn into cartilage yet.

  The diaphysis and epiphysis are seperated by the growth plate.
• We keep the growth plates as we're growing older for it to get longer. When the bone finishes growing, it will ossify.
• Growth in Width is called appositional growth
• Appositional growth


  Growing outwards and we use osteoblasts.

  We use lamallae that wraps around the bone to make it wider to make it more heavy.

  However, by making it heavy, we have to hollow out the bone.

  We do this by using osteoclasts that breaks down the bone from inside
• Joints

  Our bones articulate at the joints. Out joints allow our bones to hold together, bone ends (touch each other), soft tissues allow for attachment, and to control movement
• Key soft tissues: surrounded by a matrix

  1. Cartilage
  2. DFCT = dense fibre connective tissue = packed closely together
• The cartilage contains a fibrocartilage and hyaline - found in articulating surfaces
• DFCT are packed closely together to creat ligaments, tendons and joint capsules
• If we have osteocytes in cartilage, they are called Chondrocytes.
• Chondrocytes sit in little lakes in little spaces. They make extracellular matrix on the cartilage. In the matrix, the gel like substance is ground substance where collagen fibres are embedded into dense strong ropes.
• Avascular tissue is where we have no blood vessels. This is a consequence because we need nutrients. The nutrients diffuse through the matrix and go through the process of joint loading.
• At the ends of the bones is cartilage, next to it is fluid that has nutrients. When movement occurs, the fluid is squished into the cartilage and gives it the nutrients it needs.
• Hyaline resists compression by having water molecules in the extracellular matrix
• Hyaline is moulded to the surfaces of the bones where they articulate. They add pressure and adds friction as they move.
• Fibrocartilage resists compression and tension because it has more collagen fibres than hyaline. We arrange the collagen fibres into bundles along the lines of stress (pull)
• We arrange collagen into bundles along the lines of stress because it acts as a shock absorber - distributing force all over the area. if they are too heavy, they break.
• DFCT

  • made by fibroblasts
  • have collagen fibres to resist tension
  • have elastin forces to stretch
  • tightly packed together
• ligaments connect bone to bone and made out of collagen and elastin . Their job is to resist movement away from themselves.
• Tendons connect muscle to bone and have less elastin than ligaments. their job is to facilitate and control movements. it the muscle movement contracts, the tendon pulls on the bone to the joint = contraction of muscle movement to bone.
• Bony Congruence 


  Some bone surfaces that form an articulation and have less congruence lead to soft tissues to support.
• Joint Classifictations

  • Fibrous - least amount of movement
  • Cartilaginous - some movement
  • Synovial - most amount of movement
• Fibrous joints


  Tissue: DFCT

  Structure: ligament

  Function: It limits movements, which provides most stability.
• Cartilaginous joints

  Tissues: fibrecartilage

  Structure: varies

  Function: some movement and the bones are connected entirely
• Synovial joints

  Tissues: Many

  Structure: Many

  Function: allows a lot of movement