CV - Vessels

Question 1

At any given moment, where is the majority of blood volume stored?

Answer 1

The blood volume in venules and veins comprises the majority of total blood volume. This is why the venous system can be thought of as a blood resevior.

Question 2

What is the relationship between blood pressure, blood flow, and fluid resistance?

What is the mathematical formula that relates these three variables?

Answer 2

Ohm’s Law: BP = F x R

BP = Blood Pressure
F = Flow
R = Peripheral Resistance

• Cardiovascular homeostasis is mainly dependent on
  blood flow, but blood flow is hard to measure.
• Blood pressure is easier to measure, and related to blood flow

Question 3

What is MAP, and what is its clinical relavance?

Answer 3

Mean arteriole pressure (MAP) = diastolic BP + 1/3 (systolic BP – diastolic BP)

The definition of mean arterial pressure (MAP) is the average arterial pressure throughout one cardiac cycle, systole, and diastole. MAP is influenced by cardiac output and systemic vascular resistance, each of which is influenced by several variables

https://www.ncbi.nlm.nih.gov/books/NBK538226/

Question 4

What is Poiseuille’s Law?

Answer 4

Poiseuille’s law relates the resistance to flow using the cross sectional radius of a blood vessel, the blood’s viscosity, and the lenght of the vessel.

R = 8ηl/(πr⁴)

Question 5

If a given blood vessel diameter is decreased, how is fluid resistance impacted?

Answer 5

Fluid resistance will increase by a factor of four (Poiseuille’s law: R = 8ηl/(πr⁴))

Question 6

What are some factors that can increase the viscosity of blood?

Answer 6

Dehydration, increased RBC production, abnormal clotting factors, specific medications (blood thinners - i.e. warfarin)

Question 7

Why is it that obesity tends to be comorbid with hypertension?

Answer 7

Becuase adipose tissue is vascularized with new blood vessels, increasing the total length of the vessel system. According to Poiseullie’s law, increasing the length of the vessel will increases resistance to flow, which will cause and increase in BP to compensate.

R = 8ηl/(πr⁴)

Question 8

How can we calculate cardiac output given venous return?

Answer 8

Becuase venous return is defined as “the volume of blood returning to the heart from the veins,” VR = CO.

Question 9

Venous return is a passive process compared to the intense pressures experience in the major arteries, what helps blood flow back towards the heart in the venous system?

Answer 9

• Pressure gradients
• Venous valves (one-way)
• Venoconstriction
• Skeletal muscle pumps
• Respiratory pumps

• The skeletal muscle pump uses the action of muscles to milk
  blood in and upward direction.
• The respiratory pump uses the negative pressures in the
  thoracic and abdominal cavities generated during inspiration to
  pull venous blood towards the heart.

Question 10

Define anastomosis

Answer 10

onnection or joining of vessels that is artery to artery or vein to vein the general purpose of these connections is to provide alternate pathways for the flow of blood if one vessel becomes obstructed.