Structure of a Long Bone

Structure of a Long Bone

Overview of Long Bone Anatomy

Long bones are a type of bone found in the limbs and are characterized by a central shaft and two ends. They play a crucial role in movement, support, and blood cell production. The image provided shows a longitudinal section of a long bone, highlighting its internal structure.

• Diaphysis: The shaft or central part of the long bone, composed mainly of compact bone that provides strength.

• Epiphysis: The expanded ends of the bone, consisting mostly of spongy (cancellous) bone, which contains red bone marrow.

• Medullary (Marrow) Cavity: The central cavity within the diaphysis, containing yellow bone marrow in adults (primarily fat storage).

• Periosteum: A dense, fibrous membrane covering the outer surface of the bone, except at the joints. It contains nerves and blood vessels that nourish the bone.

• Endosteum: A thin membrane lining the medullary cavity, involved in bone growth, repair, and remodeling.

• Articular Cartilage: A smooth, white tissue covering the ends of bones where they form joints, reducing friction and absorbing shock.

• Nutrient Foramen: An opening in the bone through which blood vessels enter to supply the bone tissue.

Bone Marrow

Bone marrow is a soft tissue found within the cavities of bones. There are two types:

• Red Bone Marrow: Found mainly in the spongy bone of the epiphyses; responsible for hematopoiesis (production of blood cells).

• Yellow Bone Marrow: Found in the medullary cavity of long bones in adults; primarily stores fat.

Blood Supply to Bone

Bones are highly vascularized structures. The nutrient artery enters the bone through the nutrient foramen and branches within the medullary cavity to supply the bone tissue.

• Nutrient Artery: Main blood vessel supplying the diaphysis and medullary cavity.

• Periosteal Vessels: Supply the outer compact bone.

• Metaphyseal and Epiphyseal Vessels: Supply the ends of the bone.

Summary Table: Major Parts of a Long Bone

Part	Description	Main Function
Diaphysis	Shaft of the bone, composed of compact bone	Provides strength and support
Epiphysis	Ends of the bone, composed of spongy bone	Houses red marrow, forms joints
Medullary Cavity	Central cavity within diaphysis	Contains yellow marrow (fat storage)
Periosteum	Outer fibrous covering	Protection, nourishment, attachment for tendons/ligaments
Endosteum	Inner lining of medullary cavity	Bone growth and remodeling
Articular Cartilage	Cartilage covering epiphyses	Reduces friction at joints

Additional info:

• The image likely represents the femur, the longest bone in the human body, but the structure is typical for all long bones.

• Long bones are essential for movement as they act as levers and provide attachment points for muscles.