Long Bone Structure

As shown in Figure 45-4, a long bone consists of a porous central cavity surrounded by a ring of dense material. The bone's surface is covered by a tough membrane called the periosteum (PER-ee-AHS-tee-uhm). This membrane contains a network of blood vessels, which supply nutrients, and nerves, which signal pain.

Femur (long bone)

figure 45-4

Long bones, found in the limbs of the body, are hollow and cylindrical. The outer shell of hard compact bone consists of closely packed rings of minerals and protein fibers. Narrow canals running through these rings contain blood vessels and nerves. Spongy bone is found in small flat bones and in the ends of long bones. The central shaft of the long bone contains marrow and blood vessels.

Femur (long bone)

Periosteum

Haversian canal

Periosteum

Haversian canal

Bone marrow

Haversian canal

Mineral rings (lamellae)

Spongy bone

Mineral rings (lamellae)

Spongy bone

Haversian canals

Periosteum

Haversian canals

Under the periosteum is a hard material called compact bone. A thick layer of compact bone enables the shaft of the long bone to endure the large amount of stress it receives during activities such as jumping. In the cross section shown in Figure 45-5a, notice that compact bone is composed of cylinders of mineral crystals and protein fibers called lamellae. In the center of each cylinder is a narrow channel called a Haversian (huh-VER-shuhn) canal, as shown in Figure 45-5b. Blood vessels run through interconnected Haversian canals, creating a network that carries nourishment to the living bone tissue. Several layers of protein fibers wrap around each Haversian canal. Embedded within the gaps between the protein layers are bone cells called osteocytes (AHS-tee-uh-SIETS).

Beneath some compact bone is a network of connective tissue called spongy bone. Although its name suggests that it is soft, this tissue is hard and strong. As shown in Figure 45-4, spongy bone has a latticework structure that consists of bony spikes arranged along points of pressure or stress, making bones both light and strong.

Sirens Sleep Solution

Sirens Sleep Solution

Discover How To Sleep In Peace And Harmony In A World Full Of Uncertainty And Dramatically Improve Your Quality Of Life Today! Finally You Can Fully Equip Yourself With These “Must Have” Tools For Achieving Peace And Calmness And Live A Life Of Comfort That You Deserve!

Get My Free Ebook


Post a comment