Lecture Notes: Structure of Long Bones

Overview

• Long Bones: Composed of compact bone on the outside and spongy bone on the interior.
• Example: The humerus is a long bone used for demonstration.

Key Structures

Diaphysis

• Definition: The long shaft of a long bone.

Epiphysis

• Proximal Epiphysis: Closest to the attachment point.
• Distal Epiphysis: Furthest from the attachment point.

Epiphyseal Plate/Line

• Epiphyseal Plate: Present during early development between the epiphysis and diaphysis; made of hyaline cartilage.
• Epiphyseal Line: Develops once growth has ceased; formerly the epiphyseal plate.
• Growth Plate: Another term for epiphyseal plate.
• Note: Weak spot during development, prone to fractures.

Medullary Cavity

• Location: Inside the diaphysis.
• Contents: Contains yellow marrow (lipid or fat).
• Red Marrow: Found in spongy bone, responsible for bone cell formation.

Membranes

Periosteum

• Location: Covers the outer surface of the bone.
• Structure: Dense irregular connective tissue, very strong.
• Components: Contains osteoblasts, osteoclasts, nerves, lymphatic vessels, and blood vessels.
  • Sharpies Fibers: Collagen fibers that attach the periosteum to the bone; difficult to peel off.

Endosteum

• Location: Lines the medullary cavity and spongy bone trabeculae.
• Components: Similar to periosteum, contains osteoblasts and osteoclasts.

Additional Notes

• Sharpies Fibers: Also known as perforating fibers; a case study will be discussed.
• Membrane Functions: Both periosteum and endosteum have similar purposes in covering and containing bone-related cells.