Bone Tissue Structure

Overview

This lecture covers the structure and composition of bone tissue, explaining the differences between spongy and compact bone and detailing the organization of osteons.

Bone Composition

• All bones contain connective tissue made of bone cells (osteocytes) and an extracellular matrix.
• The extracellular matrix consists of collagen, ground substance, and calcium phosphate.

Types of Bone Tissue

• Bone tissue includes spongy bone (cancellous bone) and compact bone.
• Spongy bone has a mesh-like network called trabeculae with bone marrow filling the gaps.
• Compact bone makes up the outer layers of bone and provides strength and support.
• The internal layers of bone are made of spongy bone.

Structure of Compact Bone

• Compact bone is organized into structural units called osteons or Haversian systems.
• Osteons run parallel to the long axis of long bones.
• Each osteon contains a central canal (Haversian canal) with blood vessels and nerves.
• Perforating (Volkmann's) canals branch out from central canals at right angles to connect to the periosteum.
• Osteons are surrounded by concentric layers called lamellae.

Bone Cell Organization

• Lacunae are small spaces within lamellae that house osteocytes (bone cells).
• Canaliculi are tiny tunnels that connect lacunae, allowing communication between osteocytes.

Key Terms & Definitions

• Osteocyte — a bone cell embedded in the matrix.
• Extracellular Matrix — the material outside bone cells, including collagen, ground substance, and minerals.
• Spongy (Cancellous) Bone — bone tissue with a mesh-like structure called trabeculae.
• Compact Bone — dense bone forming the outer layer of bones.
• Osteon (Haversian System) — the basic structural unit of compact bone.
• Haversian Canal — central channel in an osteon containing blood vessels and nerves.
• Perforating (Volkmann's) Canal — canals running at right angles, connecting Haversian canals to the periosteum.
• Lamellae — concentric rings of bone matrix around an osteon.
• Lacuna — small cavities in bone that house osteocytes.
• Canaliculi — small channels connecting lacunae for cell communication.

Action Items / Next Steps

• Review the structural differences between compact and spongy bone.
• Study diagrams of osteon and bone tissue organization.