It is after all in the arterioles and smaller arteries that the lesions of arteriosclerosis do the most damage.
It will be recalled that there is relatively much more muscle tissue in the arterioles than in the large arteries.
The arterioles are thickened, the sclerosis being either of the intima or media or of both.
It would appear that rise of blood pressure tends to throw increased work upon the musculature of the arterioles.
For blood tension to be raised all over the body, conditions must favor the generalized contraction of a large area of arterioles.
The diastolic pressure is determined by the tone in the arterioles and is under the control of the vasomotor sympathetic system.
Any agent which acts to produce thickening of the walls of the arterioles, narrowing their lumina, produces the same effect.
Also the arterioles show extensive intimal thickening, fibrous in character, with occasional obliterating endarteritis.
Hemorrhages of this kind are due to two causes—to the disorganization of the blood, and to fatty degeneration of the arterioles.
The pressure then in these arterioles is practically the same as the diastolic pressure.