Unit 2 Lecture 6: Intro to Vascular

Question 1

Functions of the Vascular System?

Answer 1

1. Transport of O2
2. Removal of CO2
3. Nutrient Delivery
4. Removal of Waste
5. Distribution of Hormones
6. Transport of Immune Cells
7. Temperature Control

Question 2

What does selective distribution of the vascular system mean?

Answer 2

The vascular system does not distribute blood equally to every organ/system

Even bones need a blood supply as they can become brittle without any blood flow

Question 3

What are the two systems of circulation & what can they be further broken down into?

Answer 3

Pulmonary & Systemic Circulation (Lungs vs all other tissue)
* Further broken into Arterial and Venous circulation

Arterial circulation is distinguished as blood moving away from the heart
Venous circulation is distinguished as blood moving towards the heart

Question 4

What is Macro vs. Micro Circulation? Give examples of both

Answer 4

Macro: Takes blood to or from organs
* The Aorta (Large artery) or Systemic veins are apart of macro circulation
Micro: Distributes blood within each organ
* The venules, arterioles & capillaries are examples of micro circulation

Question 5

What is common about all blood vessels?

Answer 5

Endothelial cells form the inner layer of all of them (even capillaries)

Question 6

Differentiate between Artery & arterioles

Answer 6

• Both contain an endothelium
• Both have basement membrane (adhesive layer)
• Both have smooth muscle
• Arteries have elastic fibres (allow for stretch from high pressure)
• Both contain connective tissue

Arteries are macro circulation
Arterioles are micro circulation

Question 7

Distinguish between Veins and capillaries

Answer 7

Veins are apart of macro circulation while capillaries are apart of micro circulation

• Capillaries only have a basement membrane and endothelial inner layer
• Veins have endothelial layer, basement membrane, smooth muscle & elastic fibre layer & finally a connective tissue layer

• Veins are a low pressure system but can direct blood flow via venous valves
• Smooth muscle layer contracts differently from arterial smooth muscle
• Veins are a blood reservoir (when you’re sitting blood mostly stays in the veins)

Question 8

What is the formula for cardiac output relating to atrial pressure & total peripheral resistance?

Answer 8

CO = Mean arterial pressure - right atrial pressure / TPR
or
CO = Mean arterial pressure/TPR

Right atrial pressure is basically 0 because when the atria is being filled with blood there is no valve between it and the vena cava resisting flow

Question 9

What is mean arterial pressure? What is Total Peripheral Resistance?

Answer 9

Mean arterial pressure: Average pressure in the arteries during a cardiac cycle (left ventricle to the entire systemic circulation)
Total Peripheral Resistance: Total resistance to blood flow in the systemic circulation; Blood vessels contribute to this

Question 10

What is the formula to calculate pressure gradient?

Answer 10

ΔP = P1-P2

Can vary based on resistance but generally pressure gradient along a tube will determine blood flow

Question 11

What is the main idea behind effect of pressure gradients in blood vessel?

Answer 11

The pressure gradient along the length of the tube determines blood flow
ABSOLUTE VALUE DOES NOT

Question 12

If diastolic blood pressure is 80mmHg in a systolic heart failure patient, what would be the pressure gradient in the aorta if the systolic blood pressure reached 80mmHg? Explain how you got your answer?

Answer 12

0mmHg (80-80 = 0)
* There won’t be any blood flow
* In order for the semilunar valve (aortic and pulmonary) to open, you must exceed 80mmHg in order for blood flow to occur systolically through the aorta to the rest of the body, if not then there won’t be any blood flow

Question 13

In the left ventricle, systolic pressure shoots up to 120 but diastolic pressure stays at 0. What is the reason behind this?

Answer 13

Since it is the left ventricle, systole is related to ventricular contraction & ejection which means that the blood is being emptied out & therefore no blood left

Question 14

In the aorta (large arteries) we see systolic pressure reaches 120 but diastolic pressure does not reach 0. What is the reason for this?

Answer 14

• 120 systolic pressure is due to the pressure generated by the left ventricle
• Diastolic pressure not reaching 0 is due to there always being blood in the aorta; it is a closed system so you cannot get rid of the blood in the systemic circulation

Question 15

Why is pressure gradient in systemic circulation oscillatory flow?

Answer 15

It is oscillatory flow because the flow of blood is going up and down; with each heart beat blood is being pushed & in between heart beats blood is not being pushed

Increased flow = increased pressure
Decreased flow = decreased pressure

Question 16

When does oscillatory flow become steady flow?

Answer 16

At the distal end of the arterioles going down to the venules and veins

Question 17

Where does the greatest pressure drop in the systemic circulation occur?

Answer 17

Arterioles; blood flow slows down and pressure drops as we expand into more arterioles and capillaries and venules

As we move from large arteries the branches of the arterioles, capillaries and veins create a vast environment allowing pressure to evenly spread out

Question 18

In systemic circulation if Cardiac output is 5L/min what is venous return?

Answer 18

5L/min; systemic circulation occurs in a closed system so whatever you pump out you get that much back