Human Anatomy: Bone Tissue

Bone Tissue

• Bone tissue is a type of connective tissue that provides structural support and protection to the body.
• It is composed of:
  • Osteocytes (mature bone cells)
  • Osteoblasts (bone-forming cells)
  • Osteoclasts (bone-resorbing cells)
  • Bone matrix (organic and inorganic components)

Bone Matrix

• Organic component (30%):
  • Collagen fibers (type I)
  • Proteoglycans
  • Glycoproteins
• Inorganic component (70%):
  • Hydroxyapatite (calcium phosphate crystals)
  • Calcium and phosphate ions

Bone Cells

Osteocytes

• Mature bone cells
• Embedded in lacunae (small cavities) within the bone matrix
• Responsible for bone maintenance and repair
• Communicate with each other through canaliculi (small channels)

Osteoblasts

• Bone-forming cells
• Derived from mesenchymal stem cells
• Responsible for bone growth and development
• Produce osteoid (unmineralized bone matrix)

Osteoclasts

• Bone-resorbing cells
• Derived from hematopoietic stem cells
• Responsible for bone remodeling and resorption
• Contain lysosomes and release acid to dissolve bone matrix

Bone Structure

• Compact bone:
  • Dense, compact layers of bone tissue
  • Found in shafts of long bones
• Cancellous bone:
  • Spongy, porous bone tissue
  • Found in ends of long bones and flat bones
• Bone surfaces:
  • Periosteum (outer layer)
  • Endosteum (inner layer)

Bone Development and Remodeling

• Bone development:
  • Intramembranous ossification (direct bone formation)
  • Endochondral ossification (bone formation through cartilage templates)
• Bone remodeling:
  • Resorption of old bone tissue
  • Formation of new bone tissue
  • Process regulated by hormones and growth factors

Bone Tissue

• Provides structural support and protection to the body
• Composed of osteocytes, osteoblasts, osteoclasts, and bone matrix

Bone Matrix

Organic Component

• 30% of bone matrix
• Consists of collagen fibers (type I), proteoglycans, and glycoproteins

Inorganic Component

• 70% of bone matrix
• Composed of hydroxyapatite (calcium phosphate crystals), calcium, and phosphate ions

Bone Cells

Osteocytes

• Mature bone cells embedded in lacunae within bone matrix
• Responsible for bone maintenance and repair
• Communicate with each other through canaliculi

Osteoblasts

• Bone-forming cells derived from mesenchymal stem cells
• Responsible for bone growth and development
• Produce osteoid (unmineralized bone matrix)

Osteoclasts

• Bone-resorbing cells derived from hematopoietic stem cells
• Responsible for bone remodeling and resorption
• Contain lysosomes and release acid to dissolve bone matrix

Bone Structure

Compact Bone

• Dense, compact layers of bone tissue
• Found in shafts of long bones

Cancellous Bone

• Spongy, porous bone tissue
• Found in ends of long bones and flat bones

Bone Surfaces

• Outer layer: periosteum
• Inner layer: endosteum

Bone Development and Remodeling

Bone Development

• Intramembranous ossification: direct bone formation
• Endochondral ossification: bone formation through cartilage templates

Bone Remodeling

• Resorption of old bone tissue
• Formation of new bone tissue
• Regulated by hormones and growth factors