Thyroxin from the thyroid gland causes a sustained increase in heart rate, leading to damage from hyperthyroidism. Blood pressure is the pressure of blood against the walls of blood vessels, measured with a sphygmomanometer. Blood pressure drops with increasing distance from the left ventricle. The velocity of blood flow is driven by the blood pressure in the arteries. The movement of blood in veins and venules is due to contraction of skeletal muscles.
Valves prevent blood backflow.
The pulmonary veins return oxygenated blood to the heart. The systemic circuit includes blood vessels that leave the left ventricle, distribute blood throughout the body, and return blood to the right atrium. The hepatic portal system begins with a set of capillaries leaving the small intestine with nutrient-rich blood from digestion, continues with the hepatic portal vein leading to the liver, and ends with the capillaries of the liver. Smoking, drug abuse, and obesity all lead to cardiovascular disease. A healthy diet and exercise can prevent cardiovascular disease.