TRANSVERSE SECTION OF COMPACT BONE 



39 



Transverse Section of Compact Bone (Fig. 4). The osseous tissue consists of cells, 

 osteoblasts, and intercellular substance arranged in lamellae. In the osseous tissue are 

 found Haversian systems, lacunae, canaliculi, and osteoblasts. In the middle of long bones 

 is a space, the marrow cavity, containing the marrow. 



There are four varieties of lamella?: (1) The periosteal, peripheral, circumferential, or 

 external; (2) the Haversian, or concentric; (3) the interstitial, ground, or intermediate; 

 and (4) the perimedullary, or internal. The periosteal lamella* are sometimes called primary, 

 as they are the first to appear, and are formed by the direct transformation of the inner layer 

 of the periosteum into bone. In the shaft of a long bone there are several layers of periosteal 

 lamella?, but no one layer is extensive enough to surround the bone completely. Lacuna 1 and 

 canaliculi are present. 



In the outer surface of the layer of periosteal lamella? depressions exist that are known as 

 Howship's foveolae, or lacunae. These depressions are made by large cells, called osteoclasts, 

 which destroy bone. There are no Haversian cabals in this outer layer, but there are some 

 laro-e channels, Volkmann's canals, that convey bloodvessels into the bone and run at right 

 angles to the periosteal surface. Many small arteries from the periosteum enter the periphery 

 both of the shaft and of the epiphyses. 



The Haversian or concentric lamellae 

 are circular layers arranged around a 



ntral space, or canal, known as the 

 Haversian canal. There is no fixed 

 number of these layers, there being 

 usually from five to ten. The layers of 

 each system are parallel to one another, 



FIG. 5. --Nucleated bone cells and their pro- 

 cesses, contained in the bone lacuna^ and their 

 canaliculi respectively. From a section through 

 the vertebra of an adult mouse. (Klein and 

 Noble Smith.) 



FIG. 6. Combined transverse and longitudinal section of 

 compact bone. CH. Longitudinal Haversian canal and 

 anastomosing canals, o. Communicating with medullary 

 cavity. Si. Intermediate systems. Spe. Circumferential 

 lamellae. .Spi. Perimedullary lamelke. os. Osteoblasts. 

 (Poirier and Charpy.) 



but the layers of different systems cross at various angles. Between these layers are small, irreg- 

 ular spaces called lacunae; and extending radially out from the lacunfe and piercing the various 

 lamella? are delicate canals known as canaliculi, which connect the lacunae. The lacuna nearest 

 to the Haversian canal communicates with it by means of canaliculi; and canaliculi also com- 

 municate with other Haversian systems. The Haversian canal contains bloodvessels an artery 

 or a vein, or both and a nerve. The vessel in the canal is covered with endothelial cells, and the 

 canal itself is lined with them. The space thus formed is a lymph channel, and into these chan- 

 nels the canaliculi empty. Beneath the periosteum and at the periphery of the medullary cavity 

 there are lymph spaces that are in direct communication with the canaliculi of the Haversian 

 systems. In each lacuna is a bone cell a corpuscle that almost fills the space, and sends arms, 

 or processes, out into the canaliculi (Fig. 5). This bone cell is an osteoblast. 



The interstitial or intermediate lamellae occupy the spaces l>etween the Haversian systems. 

 They represent the remains of peripheral lamella 3 . They are usually short and very irregular, 

 but possess lacuna? and canaliculi, which are arranged as in the Haversian systems. 



The perimedullary lamellae are irregular and few in number. They surround the marrow 

 cavity, and in areas may be interrupted. Lacuna?, canaliculi, and osteoblasts are present. 



Lining the marrow cavity surface of the bone is a membrane, the endosteum, that resembles 

 the periosteum in structure, but is not quite so prominent. 



The osteoblasts are irregular, flattened, stellate masses of protoplasm, possessing a number 

 of processes. The protoplasm is granular, and each cell contains a large and distinct nucleus. 



