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Updated: May 17, 2025
The arrangement of the compact and spongy substance varies with the different bones. Surface layer of bone. 2. Deeper portion. 3. Haversian canals from which pass the canaliculi. 4. A lacuna. Observe arrangement of lacunæ at surface and in deeper portion.
How may the per cent of animal and of mineral matter in a bone be determined? What properties are given the bones by the animal matter? What by the mineral matter? Locate the bone cells. What is their special function? State the plan by which nourishment is supplied to the bone cells in different parts of the bone. Give the uses of the periosteum. State the purpose of the Haversian canals.
Lymph from these vessels is conveyed to the cells through the canaliculi that connect with the Haversian canals. *Plan and Purpose of the Skeleton.*—The framework of the body is such as to adapt it to a movable structure. Obviously the different parts of the body cannot be secured to a foundation, as are those of a stationary building, but must be arranged after a plan that is conducive to motion.
These Haversian canals are supplied with tiny blood-vessels, while the lacunæ contain bone cells. Very fine branches from these cells pass into the canaliculi. Thus bones are not dry, lifeless substances, but are the very type of activity and change.
His experimental observations appear to show that new bone is exclusively formed by the cellular elements or osteoblasts: these are found on the surface of the bone, lining the Haversian canals and in the marrow.
The new bone is laid down on the surface, in the Haversian canals, or in the cancellous spaces and medullary canal, or in all three situations.
*The Bone Cells.*—Surrounding the Haversian canals are thin layers of bone substance called the laminæ, and within these are great numbers of irregular bodies, known as the lacunæ. The walls of the lacunæ are hard and dense, but within each is an open space.
When the new bone is laid down in the Haversian canals, cancellous spaces and medulla, the bone becomes denser and heavier, and is said to be sclerosed; in extreme instances this may result in obliteration of the medullary canal.
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