Bone Marrow Location: Not in the Epiphysis

Bone marrow is not located in the epiphysis. This is a common anatomical misconception.

Where Bone Marrow Is Found

• Medullary (central) cavity of long bones (diaphysis/shaft) – contains yellow marrow (adipose tissue) in adults.
• Trabecular (cancellous/spongy) bone spaces of:
  • Epiphyses (ends of long bones)
  • Flat bones (skull, ribs, sternum, pelvis, vertebrae)
  • Short bones (carpals, tarsals)
• These spaces contain red marrow (hematopoietic tissue) in adults—primary site of blood cell production.

Epiphysis Structure

• The epiphysis is the expanded articular end of a long bone.
• It is composed of a thin outer shell of compact (cortical) bone and an interior of spongy (cancellous) bone.
• The spongy bone spaces within the epiphysis contain red marrow—this is the correct relationship.
• The epiphysis is covered by articular (hyaline) cartilage at the joint surface.

Developmental Note

• In infants/children, red marrow fills nearly all bone cavities (including diaphyses).
• With age, diaphyseal marrow converts to yellow (fatty) marrow; red marrow retracts to axial skeleton and proximal epiphyses (femur, humerus).

Summary: The epiphysis contains spongy bone that houses red marrow—it is not "filled with marrow" as a distinct cavity. The marrow resides in the trabecular spaces of the epiphysis and other cancellous bone, not in the epiphysis as a separate compartment.