Lecture Notes on the Skeletal System

Functions of the Skeletal System

• Structural Framework: Supports soft tissues like skin and provides attachment points for tendons of most skeletal muscles.
• Protection:
  • Skull protects the brain.
  • Rib cage protects the heart and lungs.
• Movement:
  • Muscles attach to bones; muscle contraction pulls on bones to create movement at joints.
• Mineral Storage: Stores important minerals such as calcium and phosphorus.
• Blood Cell Production:
  • Red bone marrow produces red blood cells, white blood cells, and platelets.
• Fat Storage: Yellow bone marrow stores triglycerides (fats).

Types of Bones

• Long Bones:
  • Greater length than width (e.g., femur, fingers, and toes).
  • Support body weight and facilitate movement.
• Flat Bones:
  • Thin, composed of parallel layers of compact and spongy bone.
  • Protect organs and provide muscle attachment surfaces (e.g., skull, sternum, rib cage, pelvis).
• Irregular Bones:
  • Complex shapes, often protect internal organs (e.g., vertebrae).
• Sesamoid Bones:
  • Develop in tendons, protect tendons from wear, change tendon pull direction (e.g., patella).
• Short Bones:
  • Cube-shaped, provide stability and limited movement (e.g., carpals, tarsals).

Importance of Long Bones

• Contain both red and yellow bone marrow.
• Facilitate body movement through muscle attachment.

Structure of a Long Bone

• Diaphysis:
  • The long cylindrical shaft of the bone.
• Epiphyses:
  • Two ends of the bone, proximal (closer to point of attachment) and distal (farther from point of attachment).
• Metaphyses:
  • Located between diaphysis and epiphyses.
  • Contains epiphyseal plate (growth plate) allowing bone growth in length.
  • Epiphyseal line forms when bone stops growing.
• Articular Cartilage:
  • Layer of hyaline cartilage at bone ends; reduces friction and absorbs shock at joints.
• Periosteum:
  • Tough connective tissue layer surrounding the bone, except at joints.
  • Contains cells for growth, protects, nourishes, and provides attachment points for ligaments and tendons.
• Endosteum:
  • Thin membrane lining inner bone surface; contains bone-forming cells.
• Medullary Cavity:
  • Hollow space within diaphysis; stores yellow marrow, reduces bone weight.

Bone Tissue Types

• Compact Bone:
  • Dense tissue forming outer bone layer.
• Spongy Bone:
  • Porous, sponge-like tissue found at bone ends.