Why does pain occur in the heart or legs in vascular occlusion?

The aorta, which extends from the heart to distribute clean blood to the body, extends its branches to the brain and arms and then moves down by extending many branches to the spinal cord, liver, spleen, kidneys, intestines which are respectively fed from the aorta. The aorta, which is divided into two major branches as right and left iliac arteries in the abdomen, is very prone to vascular stiffness starting from this separation point to the legs. When strictures turn into obstructions over time, pain and dysfunction in the organ that cannot be fed are very common. The main symptom in the legs is pain. Because when the blood does not flow, oxygen cannot reach the legs. Normally, energy in the body is obtained through oxygen. We call this aerobic respiration, but when there is no oxygen, cells use backup energy paths, these paths do not use oxygen to produce energy, but there is a price for this pathway to accumulate waste products. Lactic acid accumulates in the body, just like the embers left over from the coal stove. Lactic acid is literally acid, it damages when it accumulates like every acid and we feel this damage as pain in our body; if this pain is in the heart, it is called angina pectoris, if it is in the leg, it is called intermittent claudication. The pain lasts until the lactic acid is removed from the area. For this reason, after walking a certain amount, pain typically occurs in the in the leg vein in the calf and when patients cease resting and walk again when the pain is gone, this pause-rest character of the pain also causes the patients to move hesitantly as if they were window shopping, thus colloquially giving intermittent claudication the name of “window shopping disease". If left untreated, there will be pain and small wounds in the leg when resting and these wounds gradually grow and become gangrene, thus leading to limb losses, injuries and deaths.​