Components of a Long Bone

Components of a Long Bone

• Long bones consist of the humerus, radius, ulna, fibula, tibia and femur
• Diaphysis: is the shaft of the bone composed of compact bone.
• Medullary cavity of the diaphysis: contains red bone marrow in children and yellow bone marrow in adults. Contains fat and is lined by endosteum
• Epiphysis: are the proximal and distal ends of the bone
• Epiphyseal plate: composed of hyaline cartilage and is the site of bone growth in length (endochondral ossification)
• Epiphyseal line: replaces the epiphyseal plate when growth is complete, appears as a line between diaphysis and epiphysis
• Endosteum: delicate connective tissue lining internal bone surfaces and canals, contains osteoblasts and osteoclasts
• Periosteum membrane: double membrane covering entire bone surface except joints, outer layer of dense irregular connective tissue and inner layer is osteogenic (contains osteoblasts and osteoclasts)
• Articular cartilage: hyaline cartilage on epiphyseal surfaces preventing friction

Tissues of the Skeletal System

• Bone: can be compact or spongy and contains osteoprogenitor cells which give rise to osteoblasts, osteocytes and osteoclasts
  • Osteoblasts: build the matrix
  • Osteocytes: maintain the matrix
  • Osteoclasts: resorb (breakdown) the matrix
• The matrix of bone connective tissue consists of:
  • Collagen fibers for flexibility
  • Ground substance: hydroxyapetite crystals for strength (made of calcium phosphate salts)
  • Water

Types of Bone

• Compact bone: found on exterior surfaces of all bones, structurally composed of osteons (Haversian Systems)
  • Osteons: contain:
    • Osteocytes: found in lacunae
    • Lamellae: concentric rings of bone matrix with osteocytes between them
    • Canaliculi: connect cells and blood vessels
    • Haversian Canals: contain blood vessels and nerves, lined with endosteum
    • Volkmann’s Canals: run perpendicular to Haversian canals, connect periosteum to endosteum, providing blood supply
• Spongy bone: not organized into osteons, contains trabeculae (irregularly arranged lamellae with osteocytes)
  • Found in the epiphyses of long bones and flat bones (skull, ribs)
  • Spaces contain red bone marrow – produces blood cells and supplies blood to developing osteocytes

Hyaline Cartilage

• Contains chondrocytes (cells of cartilage) found in lacunae
• The matrix is composed of:
  • Collagen fibers
  • Ground substance: chondroitin sulfate and hyaluronic acid
  • Water
• Avascular tissue

Articulations and Joints

• Points of contact between two or more bones, classified by structure or function
• Functional classification: based on degree of movement
  • Synarthrotic: immovable joints, e.g., sutures
  • Amphiarthrotic: slightly moveable joints, e.g., pubic symphysis
  • Diarthrotic: freely moveable joints, e.g., hip, knee, elbow, shoulder
• Structural classification: based on presence/absence of a joint cavity and the connecting tissue type
  • Fibrous Joints: no joint cavity, composed of fibrous connective tissue, e.g., sutures
  • Cartilaginous joints: no joint cavity, composed of cartilage, e.g., pubic symphysis and intervertebral disks
  • Synovial joints: contain a joint cavity filled with synovial fluid, bones held together by a joint cavity and ligaments, all diarthrotic joints are synovial, e.g., knee, shoulder, hip, elbow

Synovial Joints

• All synovial joints contain:
  • Articular cartilage: hyaline cartilage on bone ends, reduces friction
  • Joint cavity: contains synovial fluid
  • Joint capsule: outer fibrous connective tissue layer attached to periosteum, inner synovial membrane secretes synovial fluid

Types of Synovial Joints

• Classified by shape of articulating bones
  • Gliding (plane): flat surfaces, e.g., sacroiliac joint
  • Hinge: concave and convex surfaces, e.g., elbow, knee
  • Pivot: e.g., odontoid process of the axis
  • Ball and socket: head of femur and acetabulum (hip), head of humerus and glenoid fossa (shoulder), allows large freedom of movement

This quiz covers the essential components of long bones, including their structure and function. Learn about the diaphysis, epiphysis, and various membranes involved in bone tissue. Perfect for students studying anatomy or related fields.