Gross Anatomy of a Bone

Overview

• Bones are considered organs due to being composed of multiple tissue types.
• They consist of several structures with different functions and are classified as long bones in this context.

Structure of Long Bones

Major Parts

1. Epiphyses (Ends of the Bone)

   • Proximal Epiphysis: Closest to the trunk's attachment point.
   • Distal Epiphysis: Farther away from the trunk.
   • Contains spongy bone (also known as woven or cancellous bone).
   • Interaction points with other bones; covered by articular cartilage for protection and shock resistance.

2. Diaphysis (Middle Portion of the Bone)

   • Long axis of the bone with a central cavity.
   • Made of compact bone which is denser and supports more weight than spongy bone.

3. Epiphyseal Plate

   • Separates epiphyses and diaphysis.
   • Made of a disc of hyaline cartilage.
   • Facilitates bone growth and elongation by pushing new chondrocytes into the diaphysis.
   • Fuses into bone in early adulthood, affecting height.

Membranes and Fibers

• Periosteum: Membrane covering the bone surfaces except at articular cartilage points.
  • Attached to bone via Sharpey’s fibers (perforating fibers made of collagen).
• Endosteum: Inner surface lining the medullary cavity within the diaphysis.

Nutrient Supply

• Nutrient Arteries: Supply blood, nutrients, and assist in new tissue growth.

Bone Cavity and Marrow

• Medullary Cavity
  • Located within the diaphysis.
  • Stores yellow bone marrow (fat tissue).
• Spongy Bone
  • Main site for hematopoiesis (production of blood cells).
  • Contains trabeculae: thin filaments in spongy bone.
  • Spaces in trabeculae house red bone marrow.

Articular Cartilage

• Located at the surfaces of epiphyses.
• Protects bones and facilitates movement.

Conclusion

• Understanding the gross anatomy of bones includes recognizing different sections, functions, and their roles in overall bone physiology and development.
• Important for identifying how bones function as part of the skeletal system.

• Review this material for a better understanding of bone structures and their growth mechanisms. Further exploration of osteons and the Haversion system will be covered in future lessons.