BONE 07 



fibers, extciuling from the periosteum into the bony matrix ht)l(i 

 the two tightly together. 



Each epii)hysis is larger than the shaft in diameter and has a 

 very thin jjeripheral layer of hard, compact bone enclosing a mass 

 of spongy bone between whose spicules is red marrow. Among 

 the constituents of red marrow are: a small anioimt of loose fibro- 

 elastic connective tissue and some fat cells; reticular tissue; erythro- 

 cytes; and a variety of cells in different phases of differentiation from 

 primitiAc blood cells to both red and white blood cells; blood vessels; 

 lymphatics; and nerve fibers. 



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Haversian ^^^^^;^>^ 



InfersLHial-%_:'l 1^^^^ •^^^J^^'^-J^f' 



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Fig. 38. — Diagram of cross-section of shaft of a long bone. 



The diaphysis has four systems of lamella^. (Fig. 38.) Imme- 

 diately })elow the periosteum are several periosteal lamella^ encircling 

 the shaft, these are called the external circumferential lamelhv. 

 Internally, adjacent to the marrow cavity, a few similarly disposed 

 endosteal lamellse occur and are described as internal circumferential 

 lamella?. Between these outer and inner lamelUe are arranged sys- 

 tems of Haversian lamellse. Portions of Haversian lamell* left 

 over from earlier Haversian systems are called interstitial lamella^ 

 and occur between complete later Ha^'ersian systems. Attention has 

 already been called to the lacuntt^ and canaliculi occupied by the 



