Dr. Young's Anatomy Class: Lecture on Bones

Overview of Bone Function

• Protection: Skull protects the brain; less protection from long bones.
• Mineral Storage: Bones store calcium, phosphate, magnesium; 2/3 of bone is calcium.
• Blood Cell Formation: Red and white blood cells made in red bone marrow.
• Fat Storage: Yellow bone marrow stores fat.
• Movement & Support: Muscles attach to bones for movement; bones provide structural support.

Types of Bones

• Long Bones: Longer than they are wide.
• Short Bones: Include wrist (carpals) and ankle (tarsals) bones.
• Flat Bones: Ribs, some skull bones, sternum.
• Irregular Bones: Vertebrae and some skull bones; don't fit other categories.
• Sesamoid Bone: Patella; unique category due to nut-like shape.

Bone Structure

• Periosteum: Outer connective tissue; route for blood vessels and nerves.
• Diaphysis: Main shaft; filled with bone marrow (red or yellow).
• Epiphysis: Ends of bones; contains spongy bone.
• Compact Bone: Dense, strong, resists linear compression.
• Spongy Bone: Porous, lighter, at bone ends; supports joints.
• Endosteum: Inner lining of bone.
• Epiphyseal Line: Growth plate; cartilage turns to bone as you age.

Blood Supply

• Nutrient Arteries: Supply blood through nutrient foramina.
• Red Bone Marrow: Site of red blood cell production; requires good blood supply.
• Yellow Bone Marrow: Stores fat; increases with age.

Microscopic Structure

• Inorganic Matrix: Mostly calcium; provides strength.
• Organic Matrix: Collagen fibers; provides flexibility.
• Osteoblasts: Build bone, lay down bony matrix.
• Osteogenic Cells: Precursor to osteoblasts.
• Osteocytes: Mature bone cells trapped in lacunae.
• Osteoclasts: Break down bone using hydrogen ions & enzymes.

Bone Renewal

• Bones are renewed every 12-15 years.

Compact vs. Spongy Bone

• Compact Bone: Made up of osteons, arranged in circles (lamellae) with a central canal for blood vessels and nerves.
• Spongy Bone: Arranged in trabeculae; blood vessels weave through holes rather than central canals.
• Both types contain osteoblasts, osteocytes, and osteoclasts.

Visuals

• Diagrams of bone types and structure, showing periosteum, diaphysis, epiphysis, and bone marrow.
• Illustrations of osteons with central canals and trabeculae in spongy bone.