And this usually takes place within days of the clamping process. So following birth, the duct that's venosis also constricts and eventually diminishes in size to a non functional structure. Now, what about the doctor's arteriosis? Remember, the doctor's arteriosis connects the pulmonary trunk to our aorter. So what happens as soon as we take the first breath? Well, when we take the first breath, we have more blood flowing into the lungs, and the lungs decrease in pressure.