Answer:
vasodilation
Step-by-step explanation:
Vasodilation is a physiological process that consists in the enlargement of the transverse diameter of the arteries and arterioles in order to increase the blood flow to a specific region of the organism or, failing that, decrease blood pressure.
The arteries are like "pipes" where blood flows from the heart to the lungs (pulmonary arterial system). From these back to the heart through the pulmonary veins and from there to the rest of the body through the systemic arteries. It is a closed circuit where blood leaves the heart through the arteries and returns through the veins.
The stimuli that can induce vasodilation are many, but of all these one of the most potent is hypoxia (lack of oxygen in the tissues).
When the concentration of oxygen decreases in a given area - such as a leg during physical exercises - a series of chemical mediators are generated that, by joining the artery receptors that go to that area with hypoxia, induce that it is dilated, all in order to get more blood to the area and, therefore, more oxygen.