ANP2 - Ch. 21 - Blood Vessels

*Identify and explain the factors that determine vascular resistance.

1. size of lumen - smaller the lumen, the greater its resistance to blood flow. 2. viscosity - the higher the blood's viscosity, the higher the resistance. 3. total bv length - the longer the bv, the greater the resistance

*Briefly describe the distribution of the blood in the body.

9% - Vessels (Pulmonary) 7 - Heart 13 - Arteries and Arterioles (systemic) 7 - Capillaries (systemic) 64 - Veins and Venules (blood reservoirs)

*Compare and contrast the function of the following: arteries, arterioles, capillaries, venules, and veins.

Arteries Carries blood away from heart (usually O2-rich) Diameter decreases as move away from heart Arterioles (100s of millions) Smallest branches of arteries Capillaries (10s of billions) Smallest blood vessels, size of RBC Location of exchange between blood and interstitial fluid Venules Collect blood from capillaries Veins Returns blood to heart (usually O2-poor) Diameter increases as get closer to heart

*Compare and contrast the structure and function of arteries and veins.

Arteries - carries blood away from heart Veins - return blood to heart

*Compare the location and function of baroreceptors and chemoreceptors.

Baroreceptors - monitor changes in pressure and stretch in the walls of blood vessels. Chemoreceptors - monitor chemical concentrations in the blood.

What is the main pressure promoting reabsorption of fluid?

Blood Colloid Osmotic Pressure

What is BCOP?

Blood Colloid Osmotic Pressure a force caused by the colloidal suspension of these large proteins in plasma Pulls fluid INTO capillaries from interstitial spaces

What is BHP?

Blood Hydrostatic Pressure the pressure generated by the pumping action of the heart and interstitial fluid osmotic pressure. Within vessels, the hydrostatic pressure is due to the pressure that water in blood plasma exerts against blood vessel walls Pushes fluid OUT of capillaries into interstitial fluid

What are the main pressures promoting filtration of fluid?

Blood Hydrostatic Pressure and Interstitial Fluid Osmotic Pressure

*Compare and contrast the following: blood flow, blood pressure, systolic blood pressure, diastolic blood pressure, and mean arteriole pressure.

Blood flow - the volume of blood that flows through any tissue in a given time period. (Total blood flow is Cardiac Output.) Blood Pressure - hydrostatic pressure exerted by blood on the walls of a blood vessel; generated by the contraction of the ventricles. Systolic BP - highest pressure attained in arteries during systole. Diastolic BP - the lowest arterial pressure during diastole. Mean arteriole pressure - the average blood pressure in arteries; roughly 1/3 between diastolic and systolic pressures. ex: in BP 110/70, MAP = 83

BHP IFHP BCOP IFOP NFP

Blood hydrostatic pressure - Pushes OUT Interstitial fluid hydrostatic pressure - Pushes IN Blood colloid osmotic pressure - Pulls IN Interstitial fluid osmotic pressure - Pulls OUT Net filtration pressure

*Describe the structure and function of a capillary bed (be sure to note the difference between continuous capillaries and fenestrated capillaries).

Capillaries form extensive branching networks Increase surface area for rapid material exchange Capillary Bed - a network of 10-100 capillaries - arise from a single metarteriole

*Explain how capillary exchange occurs.

Capillary exchange - the movement of substances between blood and interstitial fluid. The mission of the cardiovascular system is to keep blood flowing through capillaries for this exchange. Methods by which substances enter and leave capillaries: Diffusion Transcytosis - pinocytic vesicles move across the cell and exit with large, lipid-insoluble molecules via exocytosis. Bulk flow - passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction. Move further along together than alone. Continues as long as high-low pressure differences exist.

*Define edema and explain how it develops.

Edema - an abnormal increase in interstitial fluid volume. Results if filtration > reabsorption.

*Elastic arteries

Elastic arteries aka Conducting arteries largest arteries in the body -- garden size hose (aorta and pulmonary trunk) to finger size (branches of aorta) thin vessel walls internal and external elastic laminae thick tunica media dominated by elastic fibers - elastic lamellae ex: two major trunks of the heart, aorta's major branches (brachiocephalic, subclavian, common carotid, common iliac arteries) fx: propel blood onward while the ventricles are relaxing. A pressure reservoir.

*Define and explain the importance of bulk flow (be sure you understand the difference between filtration and reabsorption).

Filtration - pressure-driven movement of fluid and solutes from blood capillaries *INTO* INTERstitial fluid - promoted by blood hydrostatic pressure (BHP) - pressure generated by pumping of the heart and interstitial fluid osmotic pressure. Reabsorption - pressure-driven movement from interstitial fluid *INTO* BLOOD capillaries. - promoted by Blood Colloid Osmotic Pressure Net filtration pressure balance of these two pressures

What is IFHP?

Interstitial Fluid Hydrostatic Pressure Pushes fluid INTO capillaries from interstitial spaces. Is close to zero and difficult to measure.

What is IFOP?

Interstitial Fluid Osmotic Pressure Pulls fluid OUT of capillaries out of interstitial fluid

*Describe how the CV center affects CO and blood pressure.

It regulates heart rate and stroke volume.

*Muscular arteries

Muscular arteries aka Distributing arteries Medium sized Tunica media contains more smooth muscle and fewer elastic fibers than elastic arteries Capable of greater vasoconstriction and vasodilation fx: distribute blood to ea organ vascular tone - ability to contract and maintain partial contraction. stiffens vessel walls and maintains vessel pressure and efficient blood flow.

What determines whether the volumes of blood and interstitial fluid remain steady or change?

NFP - Net filtration pressure

What is NFP?

Net Filtration Pressure the balance of these pressures (blood hydrostatic pressure and interstitial fluid osmotic pressure) determines whether the volumes of blood and interstitial fluid remain steady or change.

What is vascular resistance?

The opposition to blood flow due to friction between blood and the walls of blood vessels. Depends on: 1. size of lumen 2. viscosity 3. total bv length

T/F - The difference in osmotic pressure across a capillary wall is due almost enterily to the presence of plasma proteins in blood, which are too large to pass through fenestrations or gaps.

True

T/F - Blood hydrostatic pressure pushes fluid out of capillaries.

True (aka Filtration)

T/F - Blood colloid osmotic pressure pulls fluid into capillaries.

True (aka Reabsorption)

*Describe the structure and function of the blood vessels walls (3 layers).

Tunica interna (intima) - epithelial inner lining - has direct contact with blood - contribute to thickness of vessel wall - smooth luminal surface facilitates efficient blood flow by reducing surface friction - lumen Tunica media - elastic CT - regulates the diameter of the lumen (opening) -- a decrease in diameter = vasoconstriction -- an increase in diameter = vasodilation Tunica externa (adventitia) - CT, elastic and collagen fibers - numerous nerves - anchors vessels to surrounding tissues (vaso vasorum - vessels to the vessels found here)

*Define vasomotion, explain why it is important.

Vasomotion - An intermittent contraction and relaxation, which may occur 5-10 times per minute. Typically, blood flows intermittently through capillaries due to alternating contraction and relaxation of the smooth muscle of metarterioles and the precapillary sphincters.

*Describe the major differences between veins and arteries.

Veins - return blood to heart - range from .5mm - 3cm in diameter - no internal or external elastic lamina - tunica media - thinner than arteries - tunica externa - thickest of three layers Arteries - tunica interna - well defined and elastic lamina - tunica media - thick and mostly elastic fibers; external elastic lamina - tunica externa - thinner than media - Elastic -- conduct blood from heart to muscular arteries -- Largest arteries in the body - Muscular -- distribute blood to arterioles -- Medium sized arteries

*Explain the relationship between velocity of blood flow and cross sectional area of the vessel lumen.

Velocity of blood flow is inversely related to the cross-sectional area. Velocity of blood flow is slowest in the capillaries because they have the largest total cross-sectional area. Each time an artery branches, the total cross-sectional area of all of its branches is greater than the cross-sectional area of the original vessel, so blood flow becomes slower as it moves away from the heart. Slowest in the capillaries.

*Explain how the skeletal muscle pump and respiratory pumps help facilitate vascular return.

When muscular or abdominal (respiratory) veins are compressed, a greater volume of blood moves from the compressed area to decompressed areas and into the proximal valve (muscular) or the right atrium (respiratory).

*Explain how hydrostatic and osmotic pressures determine net fluid movement across the walls of capillaries. (Hint you should be able to define the following NFP; BHP; IFHP; BCOP; IFOP).

Whether fluids leave or enter capillaries depends on the balance of pressures. if pressures that push fluid out of capillaries > pressures that pull fluid into capillaries, fluid will move from capillaries into interstitial spaces = filtration. if pressures that push fluid out of interstitial spaces into capillaries > pull, fluid will move from interstitial spaces into capillaries = reabsorption.

*What is total peripheral resistance, why must it be overcome - explain. Identify and explain the factors that affecting total peripheral resistance.

aka Systemic Vascular Resistance (SVR) Refers to all of the vascular resistances offered by systemic blood vessels. p. 742

*Which of the above vessels is the site of diffusion between the tissues and the blood?

capillaries

*Briefly describe the effect of the following hormones on CO and blood pressure: ADH, RAA and angiotensin II, EPO, Epinephrine and NE, and ANP.

p. 744

What is venous return?

the volume of blood flowing back to the heart through the systemic veins. occurs due to the pressure generated by contractions of the heart's left ventricle