i _><; 



MICROSCOPIC ANATOMY OF THE ORGANS. 



tinct coats: the intima, media, and adventitia. The intima 

 consists of a thin connective-tissue layer immediately surround- 

 ing the endothelial tube, and Henle's fenestrated membrane or 

 the elastica interna. Around this is a thick layer, the media, 

 consisting largely of smooth muscle, but containing as well 



IlllillHl 



FIG. 90. 



Media 



_Endothelinin 



Coiiitcctire tissue 



111' I III I Hill 



Elastic tissue 



\Smooth muscle 



/ cell* 



iictei of smooth 



nxcle cells 





Adventiti 



bre* 

 Connective tissue 



Part of a cross-section of the aorta of a dog. X 140. 



many white fibrous and elastic connective-tissue strands. The 

 rnu.<clo runs circularly, and is arranged in layers separated by 

 connective tissue in the form of concentric bands of elastic 

 ti.-sue (Fig. 89). There are often seen longitudinal strands of 

 muscle between the circular layers. The outermost sheath, the 

 adventitia, is composed largely of connective tissue and muscle. 



