CH. IT.] 



ELASTIC TISSUE 



43 



FIG. 64. Elastic fibres from the 

 ligamenta subflava. x 200. 

 (Sharpey.) 



Elastic Tissue. 



This is a form of connective tissue in which the yellow or elastic 



fibres predominate. The yellow fibres are larger than those found in 



areolar tissue (see fig. 64), and are bound 



into bundles by areolar tissue. It is found 



in the ligamentum nuchae of the ox, horse, 



and many other animals ; in jthe liga- 

 menta subflava of man ; in the arteries 



and veins, constituting the fenestrated coat 



of Henle; in the lungs and trachea; in 



the stylo-hyoid, thyro-hyoid, and crico- 



thyroid ligaments; and in the true vocal 



cords. 



Elastic tissue occurs in various forms, 



from a structureless, elastic membrane to 



a tissue whose chief constituents are bundles 



of fibres crossing each other at different 



angles ; when seen in bundles elastic fibres 



are yellowish in colour, but individual 



fibres are not so distinctly coloured. The 



larger elastic fibres are often transversely 



marked, indicating their mode of origin 



(see p. 41), and on transverse section are seen to be angular 



(fig. 65). 



Elastic tissue, being extensible and elastic (i.e., recoiling after it 

 has been stretched), has a most important use 

 in assisting muscular tissue in a mechanical 

 way, and so lessening the wear and tear of such 

 an important tissue as muscle. Thus, in the 

 ligamenta subflava of the human vertebral 

 column it assists in the maintenance of the 

 erect posture; in the ligamentum nuchae in 

 the neck of quadrupeds it assists in the raising 

 of the head and in keeping it in that position. 

 In the arterial walls, and in the air tubes and 

 lungs, it has a similar important action, as we 

 shall see when discussing the subjects of the 

 circulation and respiration. 



We now come to those forms of con- 

 nective tissue in which the cells rather than the fibres are most 



prominent. 



Adipose Tissue. 



In almost all regions of the human body a larger or smaller quantity 

 of adipose or fatty tissue is present ; the chief exceptions being the 



FIG. 65. Transverse section 

 ofaportionoflig.nucha;, 



showing the outline of 



the fibres. (After Stohr.) 



