Lecture 10 - Art-Ven-Lymph Flashcards
How do distensible arteries “even out” pressure pulsations in pulsatile blood flow?
Their distensible nature allows them to expand to the extra volume, which causes smooth velocity to blood flow.
Compare venous distention to arterial distention.
Veins are 8x more distensible (lack the smooth muscle of arteries)
Why is pulmonary vein distensibility the same as systemic arteries.
“The left heart pumps out what the right heart receives.”
Describe vascular compliance
An increase in volume over an increase in pressure. This gives the amount of blood that can be “stored” in a vessel for each mmHg rise in pressure.
Describe the concept of “elastance.”
Elastance is the ability for a deformed object to “return to normal.” For example, rubber band with high elastance will readily return to its shape.
Elastance is higher in (arteries/veins). Why?
Arteries. They contain more elastic tissue (tunica media) and can readily “snap back” to shape after distention.
Compliance is said to be the “…measure of the ease with which a hollow viscus may be _____.”
distended
Describe the changes in flow due to aortic valve stenosis.
There is decreased flow, as flow is directly proportional to a vessel’s radius
Describe how patent ductus arteriosis changes blood flow.
The opening of the ductus arteriosus forms a “shunt” from the left to right heart, reducing volume pumped with each pulse, and therefore reduces pressure wave.
Explain the incisure found in pressure pulse contour waves.
Backflow of the blood into the aortic semilunar valve cusps produces a slight “increase” in pressure contour.
The progressive reduction of pressure pulsations due to muscular arterial walls
damping
The ability for a vessel to increase its volume in response to pressure.
Vascular distensibility
The central venous pressure is measured in the _______
Right atrium
Two factors which regulate right atrial pressure
- Ability of heart to pump blood to pulmonary circuit
- Venous return to right atria
Describe factors increasing venous return
- increased blood volume
- increased peripheral venous pressures (SNS stimulation)
- dilation of arterioles
Describe the effect of increased Intra-abdominal P on venous return
The venous system must overcome the Intra-abdominal P before blood flow can resume to the heart
Explain the pathophysiology of varicose veins.
Veins have increased capacitance. However, when they are engorged with blood, the leaflets of their valves no longer prevent backflow of blood.
Describe the structure of a capillary (width, thickness, etc.)
Unicellular, thick B.M., 0.5micrometer wall, 4-9 micrometer diameter
Slit pores in capillaries allow for _______
Extravasation of water and water-soluble solutes.
Explain the role of calveolins.
Proteins similar in structure to clathrin. Allow for transcytosis.
What is the most important factor in regulating vasomotion?
Tissue [oxygen]
Describe the means of diffusion of water, oxygen, and carbon dioxide in capillaries.
These water soluble substances diffuse through the endothelial cells
Describe the diffusion of non-lipid soluble compounds in blood.
Utilize the intercellular pores
Compare water diffusion into/out of the vessel to plasma flow through the vessel.
Water diffuses 80x more rapidly
Explain how the interstitium forms a barrier to bulk flow of liquids.
Large amounts of proteoglycan fibers.
List the forces that are responsible for filtration from capillaries
Capillary pressure (out), interstitial osmotic pressure (out), plasma osmotic pressure (in), interstitial fluid pressure (in)
What is the f(x) of lympatic vessels
to return filtrate to the circulation and prevent edema
What may increase lymph flow?
Elevate capillary hydrostatic pressure, decreases plasma osmotic pressure, increased interstitial osmotic pressure, increased capillary permeability
What is the function of the lymphatic system?
To return fluid filtered from the capillaries to the circulation. If no such mechanism existed, the interstitium would become swollen (edema).
What causes lymphatic capillary collapse?
The increase of atmospheric pressure above lymphatic hydrostatic pressure
What factors increase lymph flow?
- Elevated capillary hydrostatic P
- Decreased plasma oncotic P
- Increased interstitial oncotic P
- Increased capillary permeability
How do you calculate rate of lymph flow?
Interstitial fluid P x activity of lymphatic pump
Drains right head, RUE, R axilla, R thorax
Right lymphatic duct
Drains left head, LUE, abdomen, L thorax, bilateral LE
thoracic duct
Explain the role of “anchoring filaments” in lymphatic capillary flow
Anchoring filaments connect to the capillary endothelial cells; as interstitial pressure increases, the capillaries are “compressed” inward, causing the anchoring filaments to open the valves
What two factors influence the pulse pressure?
A. Cardiac output and TPR
B. SV and Arterial compliance
C. Venous return and SNS stimulation
B. SV & Arterial compliance
How does an increase in blood volume alter blood pressure?
Initially, the increase in blood volume increases blood pressure. However, certain responses return it to normal.
1) Increased Pc forces blood out of the tissues
2) Increased Pc causes a stress-relaxation, dilating venous reservoirs to hold more blood
3) Increased TPR, decreasing venous return
