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Updated: May 18, 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.
Around these are arranged rings of bone, with little black bodies in them, from which radiate fine, dark lines. These openings are sections of canals called Haversian canals, after Havers, an English physician, who first discovered them. The black bodies are minute cavities called lacunæ, while the fine lines are very minute canals, canaliculi, which connect the lacunæ and the Haversian canals.
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.
*Minute Structure of Bone.*—A microscopic examination of a thin slice of bone taken from the compact substance shows this to be porous as well as the spongy substance. These serve the general purpose of distributing nourishment through the bone. They extend lengthwise through the bone. The canaliculi are channels for conveying lymph.
Of the canaliculi. Give functions of the spinal column. Name the different materials used in the construction of a joint and the purpose served by each. Name four mechanical devices, or machines, found in the skeleton and state the purpose served by each. Name one or more of the body machines not located in the skeleton. Of what advantage is the peculiar shape of the lower jaw? Of the ribs?
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.
This passes through the canaliculi to the cells in the different parts of the bone, as follows: 1. The cells in the surface layer of the bone receive lymph from the capillaries in the periosteum. It gets to them through the short canaliculi that run out to the surface. The cells within the interior of the bone receive their nourishment from the small blood vessels in the Haversian canals.
They pass out from the Haversian canals at right angles, going to all portions of the compact substance except a thin layer at the surface. In the surface layer of the bone the canaliculi are in communication with the periosteum. Arterial capillary. 2. Venous capillary. 3. Nerve fibers. 4. Lymph vessel.
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