Bone Types

Bone types can be classified based on the structures, maturity and shape of the bones. The human body consists of 206 mature bones that give the body the shape, protection and support.

Bone types can be classified based on the structures into:

• Cortical bones.
• Cancellous bones.

Bone types based on maturity are:

• Lamellar or mature bone: which is the normal bone.
• Woven bone: it is either immature bone or pathologic bone.

Bone types based on the shape of the bones are:

• Long bones.
• Flat bones.

See Also: Bone Cells

Bone types based on Shape:

The bone can be divided based on the shape into:

• Long bone: such as femur, tibia, humerus, and forearm bones
• Flat bones: such as skull, pelvis and scapula.

Long bone has three anatomic area:

• The diaphysis: it’s the central part of the bone that surrounds the central canal of bone . It has a thick cortical bone and covered with periosteum. The inner aspect of the cortical bone is called the endosteal surface, while the outer region is called the periosteal surface.
• The metaphysis: the region between the diaphysis and epiphysis, it has a thin cortical bone. Most of it is a cancellous bone.
• The epiphysis: the ends of bone that has an articular surface. It has the growth plate that permits the longitudinal growth of bone.

Periosteal surface is covered by the periosteal membrane, which is composed of an outer layer of fibrous connective tissue and an inner layer of undifferentiated, osteogenic progenitor cells.

See Also: Bone Metabolism

Bone Types based on the Structures:

Cortical bone:

Cortical bone is found in almost 80 % of the skeleton. In the metaphysis and epiphysis, cortical bone serves as a border to Cancellous bone. It Consists of tightly packed osteons or Haversian systems.

Haversian systems are Connected by Haversian or Volkmann canals. Haversian canals are oriented along long axis of bone, while Volkmann canals are oriented transversely to long axis of bone. Cortical bone contains arterioles, venules, capillaries, nerves possibly lymphatic channels.

Cortical bone is characterized by:

• Slow turnover rate,
• Higher Young’s modulus of elasticity,
• More stiffness.

Osteons or Haversian systems: is the Fundamental Functional Unit of the cortical bone. Cement lines define the outer border of an osteon. Between osteons there are Interstitial lamellae.

Cancellous bone:

Cancellous bone is spongy or trabecular bone that is found in the metaphyseal region of long bone and in the core of the vertebral body. It is composed of a loose network of bony struts (rods and plates). It’s Less dense, and more remodeling according to lines of stress (Wolff’s law).

Cancellous bone is characterized by:

• High turnover rate
• Smaller Young’s modulus of elasticity
• More elasticity.

Young’s modulus of elasticity E: it is a mechanical property that measures the tensile stiffness of a solid material. It quantifies the relationship between tensile stress (force per unit area) and axial strain (proportional deformation) in the linear elastic region of a material.

See Also: Bone Formation

Bone types based on Maturity:

Lamellar Bone:

Lamellar Bone is the mature form of the bone (Normal Bone). It’s secondary bone that results from the remodeling of woven bone into an organized bone tissue. Its collagen is organized and is stress oriented.

Lamellar bone can be cortical bone or cancellous bone.

Woven bone:

Woven bone is the immature form of bone or it could be pathologic bone. It is primary bone that is characterized by random orientation of collagen and mineral and it is not stress oriented.

References & More

• Campbel’s Operative Orthopaedics 12th edition Book.
• Millers Review of Orthopaedics -7th Edition Book.
• Cowan PT, Kahai P. Anatomy, Bones. [Updated 2022 Jul 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537199/
• Umadevi, N. and S.N.Geethalakshmi. “A Brief Study on Human Bone Anatomy and Bone Fractures.” viXra (2012): n. pag.