CIRCULAR DISTl'RliAN'CKS. 



IJb 



ACTIVE OR ARTERTAI. IIVrEREMIA. 

 ETIOLOGY. 



Increased calibre of arteries. 



Stniiiilalion of I'aso-dilator iierz'es. 

 Inhibition of z'oso-coiistrictor nerves. 

 Paralysis of 'I'esscI musculature. 

 Collateral isclieiuia. 

 I^iniinished pressure. 

 APPEARANCE. 



Macroscopic, red, hot, szvollen. 

 Microscopic, enqorqed arteries and capillaries 

 EFFECTS. 



Hypertrophy, hyperplasia, inflaninuition. recoz'ery. 



Active or arterial liyperemia is a conditinn in which there 

 is an increased inilow of l^lood to a part or organ without an 

 equally increased outflow. 



Etiology. — Arterial hyperemia is caused bv an increase 

 in the calibre of the supplying arteries, by collateral ischemia 

 and bv diminished external pressure. The calibre of the supply- 

 ing arterv ma\' be increased bv stimulation of the vaso-dilator 

 nerves, by heat, chemicals, etc., bv inhibition of the vaso-con- 

 strictor nerves, and bj^ paralysis of the muscular tunic of the 

 artery. 



The calibre of the surface vessels is in part the result of ex- 



-,.b 



Fig 86 — Hyperemia, hemurrhagr and ordema of intestine of a 

 'a .Surtac- exudate. t. Area ot oedema. . 



h Engorged vessels. d. Subsurface liemorrhas 



