Bone Cells and Bone Structure

Key Bone Cells

Osteogenic Cells

• Precursor cells that differentiate into other bone cells.
• Considered stem cells.

Osteoblasts

• Known as "bone builders."
• Responsible for secreting osteoid, which creates bone matrix.
• Transforms into osteocytes once buried in osteoid.

Osteocytes

• Mature bone cells.
• Maintain bone tissue.
• Reside in lacunae (small spaces in bone).

Osteoclasts

• Known as "bone destroyers" or "bone eaters."
• Break down bone material.
• Important for bone remodeling and removing unnecessary bone material.

Bone Structure

Periosteum

• Location where osteoblasts and osteoclasts are active.
• Involved in adding or removing bone matrix on the bone's surface.

Bone Markings

• Projections: Bony extensions that serve for muscle attachment or articulation.
  • Examples include the trochanters (muscle attachment) and the head of the femur (fits into the acetabulum).
• Depressions and Openings: Indentations or holes allowing for better bone fit or passage for nerves and blood vessels.

Bone Types and Components

Compact Bone

• Contains structures called osteons, visible as concentric circles surrounding a central canal.
• Osteons are the structural units of compact bone.
• Lamellae are layers of the osteon made of collagen fibers, alternating in direction.
  • This structure provides strength and resistance to twisting forces.

Spongy Bone

• Less dense, supports the compact bone.

Compact Bone Structures

Osteons

• Concentric layers (lamellae) around a central canal (Haversian canal).
• Central canal contains blood vessels and nerves.

Haversian Canal

• Central channels within osteons, containing blood supply and nerves.

Canaliculi

• Tiny canals connecting lacunae to each other and the central canal.
• Allow osteocytes to exchange nutrients and waste.

Perforating (Volkmann's) Canals

• Horizontal canals to the Haversian canals.
• Allow blood vessels and nerves to penetrate the bone tissue from the periosteum.

Study Tips

• Be prepared for test questions on bone markings, including projections and depressions.
• Understand the role and transformations of each bone cell type, particularly osteoblasts and osteoclasts.
• Familiarize yourself with the structure and function of osteons and associated canals in bone tissue.