784 DIRECTIONS FOB LABORATORY WORK 



IX. THE BLOOD VASCULAR SYSTEM 



(A) ARTERIES. 



(1) MEDIUM-SIZED ARTERIES (the larger peripheral arteries, e.g., 

 the carotids, femoral, radial, popliteal, etc.). Study the vessel as a 

 whole, in a stained transverse section, noting its circular outline, the 

 generally empty lumen, the corrugated inner surface, and the thickness 

 of the wall relative to the diameter of the lumen. Make a l.p. sketch 

 (142) of entire vessel, indicating the three tunics: (a) tunica interna 

 (intima) ; (b) tunica media, and (c) tunica externa (adventitia). 

 Sketch h.p. (143) a narrow segment of the wall, noting the fundamental 

 tissues of the several layers. Identify the internal and external elastic 

 (fenestrated) membranes, and the vasa and nervi vasorum of the tunica 

 externa. Which is the thickest tunic and what tissue elements does it 

 include ? 



(2) LARGE ARTERIES (e.g., the aorta). Study the wall of the 

 aorta in stained section. Sketch h.p. (144) a segment of the wall. 

 Compare with wall of medium sized artery. Note the relatively wider 

 tunica interna, the much narrower tunica externa, the apparent absence 

 of the internal and external elastic membranes, and the great abundance 

 of elastic tissue among the muscle cells of the tunica media. Study also 

 a similar section stained with some specific elastic tissue stain (e.g., 

 resorcin-fuchsin), and note the elastic fibers in the three tunics. Com- 

 pare aorta with some other large (conducting) artery, e.g., subclavian 

 and common iliac. 



(B) VEINS. 



(1) MEDIUM-SIZED VEINS .(the larger peripheral veins, e.g., exter- 

 nal jugular, basilic, median, femoral, etc.). Study the vessel as a 

 whole, in stained transverse section, and note its relatively thinner wall 

 as compared with a medium-sized artery, its generally collapsed condi- 

 tion, and its lumen frequently filled with blood. Compare in detail 

 with a medium-sized artery, noting differences in composition and rel- 

 ative thickness of the several tunics. Sketch l.p. (145) the entire vessel, 

 indicating the three tunics. Sketch h.p. (146) a narrow segment of the 

 wall, noting the fundamental component tissues in each tunic. Note the 

 delicate character of the internal and external elastic membranes. 



(2) LARGE VEINS, (a) The Inferior Vena Cava. Study the wall 

 in a stained section. Compare with aorta. Note great thickness of 



