Vessels Flashcards
- Contrast arteries, veins, capillaries, arterioles, and venules.
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.
- Name the 3 layers in the wall of an artery or vein.
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.
- Describe the wall and function of a capillary.
3.One cell layer. Diffusion
- Describe the differences in blood velocity in large vs small blood vessels.
4.Velocity is speed, and is slowest in capillaries.
- Explain what causes a pulse.
5.As heart has systole/diastole, this force can be felt in arteries carrying blood away from the heart.
- Define blood flow, blood pressure, and resistance.
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.
- Name some factors that effect resistance.
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
- Name the vessel that is most important in determining resistance to blood flow.
8.arteriole
- Describe the relationship of blood flow to pressure and resistance.
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).
- Describe the relationship of mean arterial pressure, cardiac output, and total peripheral resistance.
10.MAP = CO x TPR
All direct relationships
- List the neural factors that influence arterial pressure and describe how they function.
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.
- Describe the effects of angiotensin, epinephrine, and ADH on arterial pressure.
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.
- Describe the renin-angiotensin-aldosterone interaction.
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.
- Describe how blood volume influences arterial pressure and describe the factors that influence blood volume.
14.Increased blood volume leads to increased arterial pressure.
- Describe the measurement of blood pressure. What does systolic pressure correspond to? Diastolic 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.
