Bone Marrow

Bone marrow is a general term for soft tissue that occupies the medullary cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger central canals. There are three kinds of marrow—red, yellow, and gelatinous. We can best appreciate their differences by considering how marrow changes over a person's lifetime.

In a child, the medullary cavity of nearly every bone is filled with red bone marrow (myeloid tissue). This is a hemopoietic18 (HE-mo-poy-ET-ic) tissue—that is, it produces blood cells. Red bone marrow looks like blood but with a thicker consistency. It consists of a delicate mesh of reticular tissue saturated with immature blood cells and scattered adipocytes.

In young to middle-aged adults, most of this red marrow turns to fatty yellow bone marrow, like the fat at the center of a ham bone. Yellow bone marrow no longer produces blood, although in the event of severe or chronic anemia, it can transform back into red marrow. In adults, red marrow is limited to the vertebrae, ribs, sternum, part of the pelvic (hip) girdle, and the proximal heads of the humerus and femur (fig. 7.6). By old age, most of the yellow bone marrow has turned to a reddish jelly called gelatinous bone marrow.

Before You Go On

Answer the following questions to test your understanding of the preceding section:

  1. Suppose you had unlabeled electron micrographs of the four kinds of bone cells and their neighboring tissues. Name each of the four cells and explain how you could visually distinguish it from the other three.
  2. Name three organic components of the bone matrix.
  3. What are the mineral crystals of bone called, and what are they made of?
  4. Sketch a cross section of an osteon and label its major parts. 10. What are the three kinds of bone marrow? What does hemopoietic tissue mean? Which type of bone marrow fits this description?

1eAlfred Volkmann (1800-1877), German physiologist

Saladin: Anatomy & I 7. Bone Tissue I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

224 Part Two Support and Movement

Circumferential LamellaeImages Osteon Bone

Circumferential lamellae Concentric lamellae

Osteon -

Central canal

Periosteum

Perforating fibers

Blood vessel

Endosteum

Perforating canal

- Collagen fibers

Osteon -

Central canal

Periosteum

Perforating fibers

Blood vessel

Endosteum

Perforating canal

Compact Bone Tissue Label

Figure 7.4 The Histology of Bone. (a) Compact and spongy bone in a frontal section of the shoulder joint. (b) The three-dimensional structure of compact bone. (c) Microscopic appearance of a cross section of compact bone.

Which type of bone, spongy or compact, has more surface area exposed to osteoclast action?

- Collagen fibers

Shoulder Physiology

Figure 7.4 The Histology of Bone. (a) Compact and spongy bone in a frontal section of the shoulder joint. (b) The three-dimensional structure of compact bone. (c) Microscopic appearance of a cross section of compact bone.

Which type of bone, spongy or compact, has more surface area exposed to osteoclast action?

Saladin: Anatomy & 7. Bone Tissue Text © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 7 Bone Tissue 225

Spongy Bone Cross Section
Figure 7.5 Spongy Bone Structure in Relation to Mechanical Stress. In this frontal section of the femur (thighbone), the trabeculae of spongy bone can be seen oriented along lines of mechanical stress applied by the weight of the body.
Distribution Red Marrow

Figure 7.6 Distribution of Red and Yellow Bone Marrow. In an adult, red bone marrow occupies the medullary cavities of the axial skeleton and proximal heads of the humerus and femur. Yellow bone marrow occurs in the long bones of the limbs. What would be the most accessible places to draw red bone marrow from an adult?

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Responses

  • crispus proudfoot
    What does yellow bone marrow look like?
    7 years ago
  • asmarina yonatan
    Which type of bone, spongy or compact, has more surface area exposed to osteoclast action?
    7 years ago
  • makda amanuel
    Is red bone marrow in the heads of the femur and humerus?
    6 years ago
  • JULIA
    What would be the most accessible places to draw red bone marrow from an adult?
    3 years ago

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