Essay On Bone Tissue

Bone tissue is the subject of Chapter 7. It covers the tissue and organs of the skeletal system, the histology of osseous (bone) tissue, the development of bone, physiology of osseous tissue and disorders of the bone.

The skeletal system provides support to the internal structures of the body. It allows us to sit, stand, walk and even talk. It provides protection for such vital organs as the brain, heart and lungs, the marrow of bone produces new blood cells, and it aids the body in balancing acid and electrolytes.

Bone is a connective tissue with a hardened matrix that is developed from calcium phosphate deposits. Calcification is the process that creates the hard tissue of bones. They come in various shapes and sizes, from flat bones

Compact bone matrix has concentric lamellae, which resemble the layers of an onion and surround a haversian canal. The layers are connected by canaliculi. Spongy bone contains spicules (rods or spines) and trabeculae (thin plates). Marrow is contained within the medullary cavity and is a soft tissue.

Skull bones and much of the clavicle are flat bones produced by intramembranous ossification, a process by which a membrane of soft tissue becomes ossified, subsequently producing another membrane which becomes ossified, which gives flat bones their layered appearance. Endochondral ossification is a process of bone development that begins in a fetus of about 6 weeks old and lasts until more than 20 years after birth.

Bones grow both in length and width. An increase in height is an indication of the growth of bone in length. The growth of bones in width or diameter is called appositional growth. In this process, osteoblasts deposit new tissue on the inside of the periosteum which calcifies. At the same time, osteoclasts dissolve the surface of the inner bone, widening the medullary cavity. This simultaneous building and destroying of bones cells is called bone remodeling. Mineral deposition is the deposit of calcium, phosphate and other ions into bone tissue through blood plasma. This is a process that begins in a fetus and does not end until the end of life. Mineral resorption is performed by osteoclasts

Maintaining proper levels of calcium and phosphate are essential to bone development. Calcium deficiency (hypocalcemia) can cause muscle spasms. Consequently, hypercalcemia (excessive calcium) can cause nervous system suppression, muscle weakness and cardiac arrest. To prevent either of these occurrences, the body uses calcitrol, calcitonin and parathyroid hormone. Calcitrol is a product of Vitamin D and helps to raise the level of calcium and phosphate in the blood. Calcitonin is produced by the thyroid gland and, when secreted, lowers the level of calcium in the blood. Parathyroid hormone is, of course, secreted by the parathyroid glands when the calcium or phosphate level in the blood is too