SKELETAL CONNECTIVE TISSUES 



23 



Fie. 10. Photomicrograph of a 

 stained section of hyaline cartilage 

 from the ear of the rabbit. X 230. 

 Shrinkage of the cells make the 

 lacunae in which they lie conspicuous 

 and the quantity of matrix is rela- 

 tively small. The perichondrium ap- 

 pears at the left side. 



adding It to that already present, during embryonic growth and 

 may do so also in the adult in repair of injury. 



In the adult skeleton cartilage is present only in small amount. 

 It forms the articular surfaces of 

 joints, the ventral portions or cos- 

 tal cartilages of the ribs, and a 

 portion of the nasal septum; it is 

 also found uniting the basal bones 

 of the skull and supporting the walls 

 of the respiratory passages. In the 

 embryo, however, it forms the en- 

 tire skeleton, with the exception 

 of a small portion which, as de- 

 scribed below, is composed of 

 membrane bone. In the course of 

 development, except in the situa- 

 tions indicated, the cartilage is 

 replaced by bone. 



Vessels and nerves may be absent in cartilage, the small amount 



of material exchange re- 

 quired to maintain the life 

 of the cells taking place 

 by diffusion through the 

 ground substance. 



Bone is a compact, re- 

 sistant, but yet somewhat 

 elastic tissue, possessing 

 much greater strength than 

 cartilage, and therefore 

 forming a more perfect 

 skeletal support. As indi- 

 cated below, its appearance 

 as a tissue differs some- 

 what according to its mode 

 of formation. The more 

 typical structure (intra- 



FiG. 11. Intramembranous bone from a ground lllCmbranOUS boue) is il- 



transverse section of a radius (human). X 120. he, i- i 



Haversian canal; hi, Haversian lamella; il, inter- lustratecl m the aCCOmpaUy- 

 .stitial lamella; lac, lacuna. 



