Bone, or osseous tissue, is a connective organization that constitutes the endoskeleton. It contains specialized cells and also a matrix of mineral salts and collagen fibers.

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The mineral salts primarily encompass hydroxyapatite, a mineral created from calcium phosphate. Calcification is the procedure of deposition of mineral salts on the collagen fiber matrix that crystallizes and also hardens the tissue. The procedure of calcification just occurs in the visibility of collagen fibers.

The bones of the human skeleton are classified by your shape: lengthy bones, short bones, flat bones, sutural bones, sesamoid bones, and irregular bones (Figure 19.16).

Figure 19.16. Displayed are different types of bones: flat, irregular, long, short, and sesamoid.

Long bones are longer than castle are vast and have actually a shaft and two ends. The diaphysis, or main shaft, has bone marrow in a marrow cavity. The rounded ends, the epiphyses, are covered through articular cartilage and are filled with red bone marrow, which produces blood cells (Figure 19.17). Many of the body bones are lengthy bones—for example, the femur, tibia, ulna, and radius. Exceptions to this include the patella and the skeletal of the wrist and ankle.

Figure 19.17. The long bone is covered by articular cartilage at either end and also contains bone marrow (shown in yellow in this illustration) in the marrow cavity.

Short bones, or cuboidal bones, space bones that room the exact same width and length, giving them a cube-like shape. Because that example, the bones of the wrist (carpals) and ankle (tarsals) are brief bones (Figure 19.16).

Flat bones are thin and fairly broad bones the are uncovered where extensive protection of offal is forced or where vast surfaces of muscle attachment space required. Examples of level bones are the sternum (breast bone), ribs, scapulae (shoulder blades), and the roof of the skull (Figure 19.16).

Irregular bones room bones with complicated shapes. These bones may have actually short, flat, notched, or ridged surfaces. Examples of rarely often rare bones are the vertebrae, i know good bones, and also several skull bones.

Sesamoid bones space small, level bones and also are shaped likewise to a sesame seed. The patellae space sesamoid skeletal (Figure 19.18). Sesamoid bones build inside tendons and also may be discovered near joints at the knees, hands, and feet.

Figure 19.18. The patella of the knee is an instance of a sesamoid bone.
Figure 19.19. Compact bone tissue consists of osteons that space aligned parallel to the lengthy axis of the bone, and the Haversian canal that includes the bone’s blood vessels and also nerve fibers. The inner layer of bones consists of spongy bone tissue. The small dark ovals in the osteon represent the living osteocytes. (credit: modification of job-related by NCI, NIH)

vice versa, compact bone tissue creates the external layer of all bones, spongy bone or cancellous bone forms the inner great of all bones. Spongy bone organization does not contain osteons that constitute compact bone tissue. Instead, it is composed of trabeculae, which space lamellae that room arranged together rods or plates. Red bone marrow is found in between the trabuculae. Blood vessels in ~ this tissue provide nutrients to osteocytes and remove waste. The red bone marrow the the femur and the internal of other big bones, such together the ileum, develops blood cells.

Spongy bone reduce the thickness of bone and enables the end of lengthy bones come compress as the an outcome of stresses applied to the bone. Spongy bone is influential in locations of skeletal that room not heavily stressed or wherein stresses arrive from countless directions. The epiphyses the bones, such together the neck that the femur, are subject to anxiety from numerous directions. Imagine laying a heavy framed photo flat ~ above the floor. You could hold increase one next of the snapshot with a toothpick if the toothpick was perpendicular come the floor and also the picture. Now drill a hole and stick the toothpick into the wall to cave up the picture. In this case, the duty of the toothpick is come transmit the downward push of the photo to the wall. The pressure on the snapshot is straight down to the floor, yet the force on the toothpick is both the snapshot wire pulling down and the bottom the the feet in the wall pushing up. The toothpick will break off best at the wall.

The neck the the femur is horizontal choose the toothpick in the wall. The load of the body pushes the down near the joint, but the vertical diaphysis that the femur pushes it up in ~ the various other end. The neck that the femur must be solid enough to deliver the downward pressure of the body weight horizontally to the vertical tower of the femur (Figure 19.20).

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Figure 19.20. Trabeculae in spongy bone space arranged such that one next of the bone bears tension and the other withstands compression.