Systemic Circuit Blood Pressure

Consider/Assume/Remember

That you have to remember when considering the cardiovascular systemThe organ system that includes the heart and blood vessels, responsible for circulating blood and ox. I say cardiovascular system because you need to remember aspects of the heart. You should also remember the blood vessels and the blood itself. Number one if your blood is not in your vessels you should see a doctor. Your vascular system is a closed system. This means that the only input and outputs occur through the walls of the blood vessels. #2 most of your blood is in your veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge.  #3 your heart is the pump that is forcing the blood through your vessels. This means that the heart’s contractilityThe ability of muscle tissue to shorten with force. provides the force that moves your blood through the vessels. #4 your heart also provides the volume of blood that is entering all of your vessels. This volume of blood is equal to the cardiac output. And last but not least, #5 only your arteriolesSmall arteries that regulate blood flow into capillaries through vasoconstriction and vasodilation are the resistanceThe opposition to airflow in the respiratory tract, influenced by airway diameter. vessels. They provide the afterload that pushes back against your aortic valve.

As you travel from Aorta to Vena Cava

There are other things you have to remember as you travel from aorta to vena cava. We know the sequence of blood vessels starts with elastic arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr. Then it moves to muscular arteries and arterioles. Finally, it reaches the capillary beds where exchange happens. Then you will drain those capillary beds into larger veins and ultimately the vena cava. This is the sequence of vessels for the systemic circuitThe part of the circulatory system that carries oxygenated blood from the heart to the body and retu. This circuit is the example we use to talk about blood pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange..

As you travel…

People can be afraid of graphs but these graphs just tell you things that you pretty much already know. First, let’s take the graph on the left. It is showing us the diameter of vessels as we travel from the aorta to the vena cava. Down on the bottom of the graph is the X axisSecond cervical vertebra; has the odontoid process (dens) for pivoting head (“no” motion).. It shows the sequence of vessels I just verbalized in the previous slide. D aorta is large capillariesThe smallest blood vessels where gas, nutrient, and waste exchange occurs between blood and tissues. are small the vena cava is also large. This accounts for this U-shaped line that you see representing the diameter of vessels from aorta to vena cava.

The graph over here on the right has the same setup. We are considering the average blood pressure as we travel from the aorta to the vena cava. This time there is a steadily decreasing line. This signifies a trend in the systemic circuit. As we travel from the heart and back to the heart, blood pressure increasingly lowers. The graph on the left shows that the vena cava has a higher vessel diameter than capillaries. However, this graph here shows that the vena cava has a lower blood pressure than capillaries. Right about here is where this line is the steepest. And the slope of the line indicates that arterials are the major cause of resistance and therefore blood pressure.