Answers, BIO 2320, Blood Vessels

Objectives – 2, BIO 2320, Blood VesselsAnswers


1.Arteries carry blood away from the heart and have oxygenated blood (except the pulmonaries); veins carry blood toward the heart and have deoxygenated blood (except the pulmonaries); capillaries are thin-walled vessels and link the arterial system with the venous system; arterioles are tiny arteries, and venules are tiny veins.

2.Tunica interna is smooth endothelium; tunica media is smooth muscle and tunica externa may have elastic fibers in an artery. The wall of artery is much thicker than vein. The lumen of vein can therefore expand more.

3.One cell layer. Diffusion

4.Velocity is speed, and is slowest in capillaries.

5.As heart has systole/diastole, this force can be felt in arteries carrying blood away from the heart.

6.The volume of blood flowing through a vessel is flow and it is directly related to pressure (ie. larger pressure leads to more flow) and indirectly related to resistance that blood may encounter along its way (more resistance, less flow) F = P/R. Pressure is highest in the vessels closest to the pump. Aorta has highest pressure, less in arterioles, less in capillaries, less in venules and the very least in the veins.

7.A longer vessel has more resistance, but this isn’t something we can change. The thicker the blood the more resistance, so a dehydrated person would have more viscous blood leading to less blood flow. Most important is the radius or diameter of the blood vessel. As the smooth muscle contracts, a vessel can get smaller and smaller which increases resistance and therefore decreases flow. Arterioles can get so small that they can actually close causing a LOT of resistance and no flow and therefore are sometimes called the ‘resistance’ blood vessel


9.Flow and pressure are directly related (one goes up, so does other…) and flow and resistance are indirectly related (one goes up, the other goes down).

10.MAP = CO x TPR

All direct relationships

11.Vasomotor fibers of the sympathetic nervous system can result in vasodilation (larger diameter vessel) or vasoconstriction (smaller diameter vessel). The brainstem has a vasomotor center that regulates these sympathetic fibers. Baroreceptors and chemoreceptors also provide input to the vasomotor center.

12.Angiotensin is a potent vasoconstrictor causing increase in arterial pressure. Epinephrine also increases overall blood pressure; ADH causes increased volume in your bloodstream which also causes increased blood pressure.

13.If not enough blood is going to the kidneys due to low blood pressure, the kidneys release renin. This enzyme converts inactive angiotensinogen to angiotensin. Angiotensin is a strong vasoconstrictor bringing blood pressure back up. Also, angiotensin causes the adrenal cortex to release aldosterone which indirectly raises blood pressure by causing sodium and water reabsorption at the kidney.

14.Increased blood volume leads to increased arterial pressure.

15.The measurement is on your brachial artery. The systolic pressure is representative of the force coming from your heart during systole and the diastolic pressure is representative of the force during diastole. Of course, due to the elastic nature of arteries, the pressure does not go to zero during diastole, as it does in the ventricle. As the tight cuff cuts of blood flow down the brachial artery, you hear no sounds distal to the cuff, as no blood is passing. As you slowly release the cuff pressure, you will reach a point where during systole there is enough force to push blood past the squished artery but during diastole there is not enough force and the blood flow stops again. (the first time blood can get through the artery is your systolic pressure) This turbulent blood flow can be heard through the stethoscope and seen as the needle bounces on the sphygmomanometer. Finally, you release enough pressure on the cuff that blood can flow unimpeded whether the heart is in diastole or systole and this is your diastolic pressure.

16.Blood returning to right atrium through systemic veins. F = P/R determines venous return and gravity plays a role, causing blood to pool inferiorly.

17.Veins have valves to prevent blood back flow. Also, there is very little resistance (but poor pressure) in veins. The best way blood moves through veins is by skeletal muscles contracting, thus squeezing the blood through the vein. So, movement promotes venous return.

18.When you first stand up, gravity does pull blood towards the ground. You might feel light headed, until the baroreceptors in your neck note a drop in blood pressure, which cause compensatory vasoconstriction and increased heart rate. Also, as you take a step, your skeletal muscles will “milk” the blood from your feet back toward your heart.

19.Increased HR, SV, CO, Arterial blood pressure, Increased venous return, vasoconstriction to skin and visceral blood vessels, yet vasodilation to skeletal muscle blood vessels.

20. Inferior/Superior Vena cava –>RA–>Tricuspid valve–>RV–>Pulmonary semilunar valve –>pulmonary trunk and arteries –>lungs for oxygen –>pulmonary veins –>left atrium –> bicuspid valve –>left ventricle –>aortic semilunar valve –>aorta

21.Systemic is whole body & provides circulation to all of body besides that pulmonary circuit in number 20.



24.Filter digestive blood through the liver

25. Umbilical Vein

26.See diagram. Fetal lungs are bypassed via foramen ovale which shunts blood from RA to LA or through the ductus arteriosus which shunts blood from pulmonary trunk to the aorta. The liver is bypassed via the ductus venosus.