Lecture Notes: Classifying Bones

Ways to Classify Bones

• Gross Anatomy and General Features
• Regional Classification
  • Apendicular Skeleton: bones of the limbs (e.g., arms, legs, and girdles)
  • Axial Skeleton: bones along the central axis (e.g., skull, vertebrae, thoracic cage)
• Shape Classification

Bone Classification by Location

• Axial Skeleton
  • Examples: Skull, vertebrae, ribs, sternum
  • Located along the midline or central axis of the body
• Apendicular Skeleton
  • Examples: Limbs, pectoral girdle (clavicle and scapula), pelvic girdle (ilium, ischium)
  • Includes limb bones and girdles attaching limbs to the body

Bone Classification by Shape

• Long Bones

  • Characteristics: Longer than they are wide
  • Examples: Femur, humerus, phalanges
  • Function: Movement and locomotion, contains marrow cavity

• Short Bones

  • Characteristics: Cuboidal, as wide as they are tall
  • Examples: Carpals (wrist), tarsals (ankle), calcaneus (heel)
  • Function: Provide stability, tightly knit with ligaments

• Flat Bones

  • Characteristics: Thin, often curved
  • Examples: Skull, ribs, scapula
  • Function: Protection of delicate viscera, site of hematopoiesis throughout life

• Sesamoid Bones

  • Characteristics: Embedded within soft tissue
  • Example: Patella (knee cap)
  • Function: Alleviate stress and friction on tendons

• Irregular Bones

  • Characteristics: No defined shape
  • Example: Sphenoid bone (in the cranial region)
  • Function: Protection, support, can be pneumatic (contain air pockets)

Fusion of Bones

• Humans start with approximately 300 bones, reduced to 206 in adults due to fusion, especially in the skull and appendicular skeleton.

External and Internal Structure of Long Bones

• External Features

  • Regions: Proximal epiphysis, metaphysis, diaphysis, distal epiphysis
  • Coverings: Articular cartilage (joint areas), periosteum (remainder)

• Internal Features

  • Diaphysis: Contains marrow cavity (red or yellow marrow)
  • Osteons: Found in compact bone, resist torsion

Red and Yellow Marrow

• Red Marrow: Produces blood cells, found in young individuals or adults with high oxygen demand
• Yellow Marrow: Contains adipose tissue, found in normal adults

Additional Concepts

• Ligaments: Connect bone to bone
• Tendons: Connect muscle to bone
• Hematopoiesis: Production of blood cells, occurring in flat bones throughout life
• Pneumatic Bones: Bones containing air pockets for reduction in weight and sound resonance.

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These notes highlight the classification, structure, and function of different types of bones, providing a comprehensive overview suitable for review and study.