Chapter 6

• Three types of skeletal cartilage:

  • Hyaline cartilage: provides support with flexibility and resilience; found in the nose, trachea, and larynx
  • Elastic cartilage: maintains the shape of a structure while allowing flexibility; found in the external ear and epiglottis
  • Fibrocartilage: highly compressible and great tensile strength; found in the menisci of the knee and intervertebral discs
• Axial bones of the skeleton include the skull, vertebral column, and rib cage

  Appendicular bones of the skeleton include the upper and lower limbs, shoulder, and hip
• Shape classes of bones:

  • Long bones: longer than they are wide (e.g., femur)
  • Short bones: roughly cube-shaped (e.g., wrist bones)
  • Flat bones: thin, flattened, and usually curved (e.g., sternum)
  • Irregular bones: complicated shapes that do not fit into other classes (e.g., vertebrae)
• Functions of bones:

  • Support
  • Protection
  • Movement
  • Mineral storage
  • Blood cell formation
  • Triglyceride storage
• Common types of bone markings:

  • Projections: sites of muscle and ligament attachment
  • Depressions and openings: allow the passage of blood vessels and nerves
• Anatomical structure of bones:

  • Long bones: shaft with heads at both ends (e.g., femur)
  • Short bones: cube-shaped (e.g., carpals)
  • Flat bones: thin, flattened, and usually curved (e.g., sternum)
  • Irregular bones: complicated shapes that do not fit into other classes (e.g., vertebrae)
• Locations of red bone marrow:

  • Infants: found in the medullary cavity and all areas of spongy bone
  • Adults: found in the diploe of flat bones and the head of the femur and humerus
• Anatomy of compact and spongy bone:

  • Compact bone: dense outer layer that looks smooth and solid
  • Spongy bone: honeycomb of trabeculae with red bone marrow filling the spaces
• Organic and inorganic composition of bone:

  • Organic: includes cells and osteoid (collagen and ground substance); provides flexibility and tensile strength
  • Inorganic: mineral salts (calcium phosphate); provides hardness and resistance to compression
• Intramembranous ossification: bone develops from a fibrous membrane; forms flat bones like the skull

  Endochondral ossification: bone forms by replacing hyaline cartilage; forms most bones in the body
• Processes of lengthwise bone growth:

  • Epiphyseal plate allows for lengthwise growth until closure in early adulthood

  Growth in width: osteoblasts beneath the periosteum add bone matrix to the diaphysis
• Effects of growth hormone, testosterone, and estrogen on bone growth:

  • Growth hormone: stimulates epiphyseal plate activity
  • Testosterone and estrogen: promote adolescent growth spurts and end growth by inducing epiphyseal plate closure
• Hormonal mechanism controlling bone remodeling:

  • Parathyroid hormone (PTH): stimulates osteoclast activity to release calcium ions into the blood
  • Calcitonin: inhibits osteoclast activity, decreasing blood calcium levels
• Role of mechanical stress on bone remodeling:

  • Mechanical stress stimulates bone growth and remodeling to become stronger and more resistant to stress
• Types of bone fractures:

  • Closed (simple) fracture
  • Open (compound) fracture
  • Greenstick fracture
  • Comminuted fracture
  • Spiral fracture
  • Impacted fracture
  • Depressed fracture
• Events of bone repair:

  • Hematoma formation
  • Fibrocartilaginous callus formation
  • Bony callus formation
  • Bone remodeling