46 ANATOMY FOR NURSES [Chap. IV 



stance of the bone is penetrated by intercommunicating channels, 

 antl the nutrient matters and mineral salts from the blood in the 

 Haversian canals can find their way to every part. 



Function of periosteum in growth of bone. — In the embryo 

 the toiindation of the skeleton is laid in cartilage, or in primitive 

 connective tissue, ossification of the bones occurring later. The 

 hardening or ossification of the bones is accomplished by the 

 penetration of blood-vessels and bone-cells, called osteoblasts, 

 from the periosteum. As they penetrate into the cartilaginous 

 or membranous models, they absorb the cartilage and connective 

 tissue and deposit the true bone tissue at various points until they 

 form the i)articular bony structure with which we are familiar. 



Regeneration of bone. — A fracture is usually accompanied 

 l)y injur\- to the periosteum and tissues. This results in inflam- 

 mation, which means an increased amount of blood is sent to the 

 part. The plasma and white blood corpuscles from the blood 

 exude into the tissues and form a viscid substance, which sticks the 

 ends of the bone together, and is called callus. Usually bone-cells 

 from the periosteum and lime salts are gradually deposited in the 

 callus, which eventually becomes hardened and forms new bone. 

 Occasionally the callus does not ossify and a condition known as 

 fibrous union results. The periosteum is largely concerned in this 

 process of repair ; for if a portion of the periosteum be stripped ofl"', 

 the subjacent bone will be liable to die, while if a large part or the 

 whole of a bone be removed, and the periosteum at the same time 

 left intact, the bone will wholly or in a great measure be regen- 

 erated. 



SUMMARY 



CONNECTIVE TISSUE — A tissue of cells with a great deal of inter- 

 ccUular substance, which is derived from the cells. 



1. Resemble each other in function. 

 Reasons for Classification { 2. Resemble each other in origin. 



3. Resemble each other in structure. 

 Areolar, Reticular, 

 Fibrous, Lymplioid, 

 Elastic, Cartilage, 

 Adipose, Bone. 

 Areolar tissue. — Formed hy interlacing of wavy bundles of white fibres 



and some straight elastic fil)res with cells lying in the spaces. 

 Fibrous tissue. — Formed of wavy bundles of white fibres only, with cells 

 in rows between bundles. \'ery strong and tough but pUant. 



Classification 



