CIRCULAR DISTURUANCKS. 133 



Microscopic, the blood vessels are practically empty and the 

 tissue cells are more or less shriveled as a result of insufficient 

 moisture. 



Effects.— The outcome of ischemia is determined by the 

 length of time it exists and the degree of completeness of the 

 condition. Temporary, partial ischemia usually terminates in 

 complete recovery. Continued partial ischemia is a frequent 

 cause of atrophy. Complete absence of blood for a considerable 

 time results in necrosis. 



HYPEREMIA. 



DEFrNITION. 

 ETIOLOGY. 



Enfeebled eireulatioii, 



Mcelianieal interference. 

 APPEARANCE. 



Maeruseopie, bluish, cold ckininiy. 



Microsco/^ie, enc/ort/ed z'Cins. dciieiierntion. 

 EFFECTS— -Depend upon cause, duration, degree and location and ina\ be 

 fibrosis, oedema, titronibosis, necrosis and recovery. 



Hyi-ercmia is a condition in which there is an increased 

 ciuantity of blood in a part. The condition is practically local 

 for an increased total amount of blood could not be retained in 

 the general circulation without increasing the general blood 

 pressure wdiich would result in an increased production of Ivmpli 

 and hence diminish the volume of blood. Physiologic hvperemia 

 is evident whenever an organ or part is active. Local patho- 

 logic hyperemia mav be passive (venous) or active (arterial). 



P.vssivi-: OR A'lixous Hvpi-:ri-:.mi.\. 



Passive or venous hyperemia is a condition in which there 

 is a normal quantitv of blood constantly flowing into an organ 

 or part, but a diminished quantity flowing out. An excess of 

 venous blood consequently accumulates in the part. 



Etiology. — Passive hyperemia is caused bv enfeebled circu- 

 lation due to weak heart, biscuspid and tricuspid insufficiency or 

 stenosis, or diseased vessels and bv pressure upon the outg(Mng 

 vessels by ligatures, bandages, neoplasms, dislocations, fractures, 

 etc. 



Appearance.. Macroscopic. — The affected tissues are bluish 

 in color and usually feel spongy, cold and moist when palpated. 



Microscopic. — A tissue affected with venous hyperemia has 

 distended capillaries and venules, the lymph spaces are engorged 

 with lymph and the cells are swollen and their protoplasm cloudy. 



