Short answers, pulled from the story.
Blood pressure is the force exerted by circulating blood against the walls of blood vessels. It is usually expressed as systolic pressure over diastolic pressure in millimetres of mercury or kilopascals.
Healthcare workers traditionally measure blood pressure non-invasively by auscultation listening through a stethoscope for sounds in an arm's artery. Auscultation remains generally considered the gold standard of accuracy for non-invasive readings in clinic settings.
Fully automated oscillometric measurement has been available since 1981 and this principle has recently been used to measure blood pressure with a smartphone. Modern devices validated to international standards achieve an average difference of 5 mmHg or less between standardized reading methods.
The most important arterial baroreceptors are located in the left and right carotid sinuses and in the aortic arch. These receptors adjust mean arterial pressure by altering both the force and speed of the heart's contractions as well as systemic vascular resistance.
The blood pressure in the fetal aorta is approximately 30 mmHg at 20 weeks of gestation and increases to approximately 45 mmHg at 40 weeks of gestation. The average blood pressure for full-term infants ranges from 65, 95 mmHg systolic and 30, 60 mmHg diastolic.