Human Skeleton Lecture Notes

Categories of Bones

• Total Bones: 206 bones in the human skeleton.
• Axial Skeleton: Forms the long axis of the body, consisting of:
  • Skull
  • Vertebral column
  • Rib cage
  • Found in the midline of the body.
• Appendicular Skeleton:
  • Comprises the appendages (upper and lower limbs).
  • Girdles attach these limbs to the axial skeleton.

Classification of Bones by Shape

1. Long Bones:
   • Longer than they are wide.
   • Examples: Femur, Tibia, Fibula, Phalanges (fingers).
2. Short Bones:
   • Look like small lumps of clay.
   • Examples: Wrist bones (Carpals), Ankle bones (Tarsals), Patella.
3. Flat Bones:
   • Thin, flat, slightly curved.
   • Examples: Sternum, Skull bones, Rib bones.
4. Irregular Bones:
   • Complex shapes that don't fit into other categories.
   • Examples: Vertebrae, Pelvis.

Bone Markings

• Purpose: Sites for muscle attachments, ligament attachments, and tendinous attachments on the bone's external surface.
• Types of Bone Markings:
  1. Projection:
     • Outward bulge of bone.
     • Examples: Tuberosity, Crest, Trochanter, Line, Tubercle, Epicondyle, Spine, Process.
  2. Depression:
     • Shallow groove or bowl-like cutout.
     • Examples: Groove, Fossa.
  3. Opening:
     • Hole or canal in a bone.
     • Examples: Fissure, Foramen, Meatus, Sinus.

Detailed Examples of Bone Markings

• Tuberosity: Large, rounded projection, often roughened (e.g., Deltoid tuberosity on Humerus).
• Crest: Narrow ridge of bone (e.g., Iliac crest of the Pelvis).
• Trochanter: Large, blunt, irregularly shaped process found only on the Femur.
• Line: Narrow ridge of bone, less prominent than a crest (e.g., Linea Aspera on the Femur).
• Tubercle: Small, rounded projection (e.g., Rib tubercle).
• Epicondyle: Raised area on or above a condyle (e.g., Medial and lateral epicondyles of the Elbow).
• Spine: Sharp, slender, pointed projection (e.g., Spine of the Scapula).
• Process: Any bony prominence (e.g., Spinous process of the Vertebrae).
• Head: Bony expansion on a narrow neck (e.g., Head of the Rib).
• Facet: Smooth, nearly flat articular surface (e.g., Facets on the Spine).
• Condyle: Rounded articular projection (e.g., Mandibular condyle).
• Ramus: Arm-like bar of bone (e.g., Ramus of the Mandible).

Depressions and Openings

• Groove: Furrow for blood vessels or nerves.
• Fissure: Narrow, deep groove or slit.
• Foramen: Round or oval hole for blood vessels and nerves.
• Notch: Indentation at the edge of a structure.
• Meatus: Canal-like passageway (e.g., External auditory meatus).
• Sinus: Cavity within a bone, filled with air, lined with mucus.
• Fossa: Shallow depression in a bone, often serving as an articular surface.

Summary

These bone classifications and markings provide the foundation for studying the appendicular and axial skeleton in greater detail, understanding how bones grow, and recognizing sites of muscle, ligament, and joint connections.