What is the structure and function of the compact bone?

Compact bone, also known as cortical bone, is one of the two main types of bone tissue found in the human skeleton, the other being cancellous bone (spongy bone). Compact bone forms the outer layer of bones and provides strength, support, and protection to the body.

Structure of Compact Bone:

Osteons: Compact bone consists of cylindrical structures called osteons or Haversian systems. Each osteon is composed of concentric rings of bone tissue known as lamellae, surrounding a central canal called the Haversian canal. The Haversian canal contains blood vessels, nerves, and connective tissue.

Lamellae: Lamellae are thin layers of mineralized matrix composed mainly of collagen fibers and calcium phosphate. These layers are arranged parallel to the long axis of the bone and are responsible for the strength and rigidity of compact bone.

Lacunae: Between the lamellae, small spaces called lacunae are present. Lacunae house bone cells called osteocytes, which maintain the bone tissue and participate in metabolic activities.

Canaliculi: Radiating from the lacunae, small channels called canaliculi connect neighboring lacunae and form a network. These canaliculi facilitate the exchange of nutrients, waste products, and cell-to-cell communication between osteocytes.

Function of Compact Bone:

Support and Protection: Compact bone provides structural support to the body and protects vital organs. It forms the dense outer layer of bones, giving them strength and resistance to external forces.

Load Transmission: Compact bone helps distribute the weight and forces applied to the bone throughout its structure, allowing efficient load transmission and reducing the risk of fractures.

Mineral Storage: Compact bone serves as a reservoir for essential minerals, particularly calcium and phosphorus. These minerals can be released into the bloodstream when needed for various physiological processes.

Hematopoiesis: Although hematopoiesis (the production of blood cells) primarily occurs in the bone marrow of cancellous bone, certain types of blood cells can be produced in the Haversian canals of compact bone.

Metabolic Activity: Osteocytes embedded within compact bone participate in bone remodeling, a process that involves the continuous resorption and deposition of bone tissue. This remodeling helps maintain bone strength, repair micro-damage, and regulate mineral balance in the body.

Overall, compact bone is responsible for the mechanical integrity and stability of the skeletal system, playing a crucial role in supporting the body's structure and protecting vital organs.