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

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

The bones of the human skeleton space classified by their shape: lengthy bones, quick bones, flat bones, sutural bones, sesamoid bones, and also irregular skeleton (Figure 19.16).

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

Long bones are much longer than they are broad and have a shaft and two ends. The diaphysis, or central shaft, contains bone marrow in a marrow cavity. The rounded ends, the epiphyses, are covered with articular cartilage and also are filled with red bone marrow, i m sorry produces blood cell (Figure 19.17). Many of the body bones are long bones—for example, the femur, tibia, ulna, and also radius. Exception to this encompass the patella and also the skeleton of the wrist and ankle.

Figure 19.17. The long bone is extended 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 same width and also length, providing them a cube-like shape. For example, the bones of the wrist (carpals) and also ankle (tarsals) are brief bones (Figure 19.16).

Flat bones room thin and fairly broad bones the are discovered where substantial protection of organs is required or where vast surfaces that muscle attachment room required. Instances of flat bones room the sternum (breast bone), ribs, scapulae (shoulder blades), and the roof of the skull (Figure 19.16).

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

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

Figure 19.18. The patella that the knee is an example of a sesamoid bone.
Figure 19.19. Compact bone tissue consists of osteons that space aligned parallel to the lengthy axis that the bone, and also the Haversian canal that contains the bone’s blood vessels and also nerve fibers. The inner class of bones is composed of spongy bone tissue. The little dark ovals in the osteon represent the life osteocytes. (credit: change of work-related by NCI, NIH)

whereas compact bone tissue forms the outer layer of every bones, spongy bone or cancellous bone develops the inner class of every bones. Spongy bone organization does no contain osteons that constitute compact bone tissue. Instead, it consists of trabeculae, which are lamellae that space arranged as rods or plates. Red bone marrow is found in between the trabuculae. Blood vessels within this tissue provide nutrients to osteocytes and also remove waste. The red bone marrow of the femur and also the inner of other big bones, such as the ileum, develops blood cells.

Spongy bone reduces the density of bone and allows the ends of long bones come compress as the result of stresses applied to the bone. Spongy bone is prominent in areas of bones that room not greatly stressed or wherein stresses arrive from many directions. The epiphyses the bones, such together the neck the the femur, room subject to stress from countless directions. Imagine laying a hefty framed photo flat ~ above the floor. You might hold up one next of the picture with a toothpick if the toothpick was perpendicular to the floor and also the picture. Now drill a hole and stick the toothpick into the wall surface to hang up the picture. In this case, the function of the toothpick is to transmit the downward push of the snapshot to the wall. The force on the picture is directly down to the floor, but the force on the toothpick is both the snapshot wire pulling down and the bottom of the hole in the wall surface pushing up. The toothpick will break off ideal at the wall.

The neck that the femur is horizontal like the toothpick in the wall. The weight of the human body pushes that down near the joint, yet the vertical diaphysis the the femur pushes it up at the other end. The neck of the femur should be solid enough to transport the downward pressure of the body load horizontally to the vertical column of the femur (Figure 19.20).

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Figure 19.20. Trabeculae in spongy bone room arranged such the one next of the bone bear tension and also the other withstands compression.