4.6 Bones

4.6.1 Major boney structures examined in this course

@Bartel2006 @OpenStaxAnatomy2020

The human body is shown in anatomical position in an (a) anterior view and a (b) posterior view. The regions of the body are labeled in boldface.

  • There are typically 206 bones in the human body (+4 sesamoid bones in the foot)
  • Can be categorized into roughly 4 groups
    • Long bones (femur, tibia, humerus, etc)
      • Long in one direction, tubular cross sections
    • Short bones (wrist, ankle, hand, foot, etc)
      • Have similar dimensions in all directions
    • Flat bones (scapula, skull, pelvis, etc)
      • Are short in one dimension relative to the others
    • Irregular
      • Those that don’t easily fit into the other categories

4.6.2 Bone tissue types

Femoral head with metastasis

Femoral_head_with_bone_metastasis

  • There are two types of bone tissue
    • Cortical (compact) bone
      • Dense, stiff, strong
      • Load carrying bone
    • Cancellous (trabecular) bone
      • Less dense, less stiff
      • What functions does it serve?

4.6.3 Long bone

@Bartel2006

The shaft (diaphysis) grows from its ends at growth plates (physis)

  • The shaft has a medullary cavity filled with yellow marrow (fat and primitive blood cells)
  • The proximal humerus and femur have red marrow within their cancellous bone tissue. (Red blood cells are made here)
  • The medullary cavity serves no structural purpose in normal bone
  • Implants often interface with the medullary cavity as a means of attachment (ie intramedullary nail)
  • The epiphysis (bone end) grows from separate ossification centers at the end of the bone
  • Metaphysis is the region between the diaphysis and the epiphysis

4.6.4 Anatomy of a Long Bone

@OpenStaxAnatomy2020 Ch. 6

A typical long bone shows the gross anatomical characteristics of bone.

(slide credit: @OpenStaxAnatomy2020 Ch. 6)

4.6.5 Periosteum and Endosteum

@OpenStaxAnatomy2020 Ch. 6

The periosteum forms the outer surface of bone, and the endosteum lines the medullary cavity.

(slide credit: @OpenStaxAnatomy2020 Ch. 6)

4.6.6 Anatomy of a Flat Bone

@OpenStaxAnatomy2020 Ch. 6

This cross-section of a flat bone shows the spongy bone (diploë) lined on either side by a layer of compact bone.

(slide credit: @OpenStaxAnatomy2020 Ch. 6)

4.6.7 Bone Features

@OpenStaxAnatomy2020 Ch. 6

The surface features of bones depend on their function, location, attachment of ligaments and tendons, or the penetration of blood vessels and nerves.

(slide credit: @OpenStaxAnatomy2020 Ch. 6)