Skeletal System

• Functions of Skeletal System:

  • Support
  • Protect
  • Movement
  • Storage
  • Blood cell production
• Components of Skeletal System:

  • Bone
  • Cartilage
  • Tendons
  • Ligaments
• Components of Skeletal System

  Cartilage - reduce friction and model for bone formation
• Components of Skeletal System

  Tendons - attach bone to muscle
• Components of Skeletal System

  Ligaments - attach bone to bone
• Proteoglycans - large polysaccharides attached to proteins that is a part of ground substance and stores water
• Bone’s extracellular matrix is collagen and minerals (flexible and able to bear weight)
• Cartilage’s extracellular matrix is collagen and proteoglycans (good shock absorber)
• Tendons and ligaments’ extracellular matrix is collagen (very tough)
• Classification of Bones

  Based on shape:

  • Long
  • Short
  • Flat
  • Irregular
• Classification of Bones

  Type of bone tissue:

  • compact
  • spongy (cancellous)
• Long Bone Structures

  • Diaphysis
  • Epiphysis
  • Articular cartilage
  • Epiphyseal plate
  • Medullar cavity
  • Periosteum
  • Endosteum
• Long Bone Structures

  Diaphysis:

  • shaft
  • compact bone tissue (on outside)
• Long Bone Structures

  Epiphysis:

  • ends
  • spongy bone tissue
• Long Bone Structures

  Articular cartilage:

  • covers epiphyses
  • reduces friction
• Long Bone Structures

  Epiphyseal plate:

  • site of growth
  • between diaphysis and epiphysis
• Long Bone Structures

  
  

  Medullary cavity:

  • center of diaphysis
  • red or yellow marrow
• Long Bone Structures

  Periosteum:

  • membrane around bone’s outer surface
• Long Bone Structures

  Endosteum:

  • membrane that lines medullary cavity
• Compact Bone Tissue - outer part of diaphysis (long bones) and thinner surfaces of other bones
• Parts of Compact Bone Tissue

  • Osteon
  • Lamella
  • Lacunae
  • Canaliculus
  • Central canal
• Compact Bone Tissue

  Osteon:

  • structural unit of compact bone
  • includes lamella, lacunae, canaliculus, central canal, osteocytes
• Compact Bone Tissue

  Lamella:

  • rings of bone matrix
• Compact Bone Tissue

  Lacunae:

  • spaces between lamella
• Compact Bone Tissue

  Canaliculus:

  • tiny canals
  • transport nutrients and remove waste
• Compact Bone Tissue

  Central canal:

  • center of osteon
  • contains blood vessels
• Spongy Bone Tissue - also known as "cancellous bone" and is located in the epiphyses of long bones and center of other bones; no osteons.
• Trabeculae - interconnecting rods, spaces contain marrow
• Bone Cells

  • Osteocytes
  • Osteoblasts
  • Osteoclasts
• Bone Cells

  Osteocytes - maintain bone matrix
• Bone Cells

  Osteoblasts - build bone
• Bone Cells

  Osteoclasts - carve bone
• Bone Formation

  Ossification - process of bone formation (occurs in utero)
• Bone Formation

  Osteoblast’s role:

  • build bone
  • after an osteoblast becomes surrounded by bone matrix it becomes an osteocyte
• Bone Formation

  Ossification center - where bone formation begins
• Bone Formation

  Primary ossification center:

  • where bone 1st begins to appear
  • forms diaphyses
• Bone Formation

  Secondary ossification center - forms epiphyses
• Intramembranous Ossification - bone formation within connective tissue membranes where osteoblast build bone (Ex. Skull bones)
• Endochondral Ossification - bone formation inside cartilage where cartilage models are replaced by bone (All bones, except skull)
• Steps in Endochondral Ossification

  1. Chondroblasts build a cartilage model, the chrondroblasts become chondrocytes.
  2. Cartilage model calcifies (hardens).
  3. Osteoblasts invade calcified cartilage and a primary ossification center forms diaphysis.
  4. Secondary ossification centers form epiphysis.
  5. Original cartilage model is almost completely ossified and remaining cartilage is articular cartilage.