Vascular Function

Question 1

Where is the blood distributed at any given time?

Answer 1

• Systemic veins: 65%
• Systemic Arteries: 13%
• Systemic capillaries: 5%
• Lungs: 10%
• Heart: 7%

Question 2

How does compliance vary between arteries and veins?

Answer 2

• Arteries are less compliant than veins. This is because veins have thin walls that distend quite easily. this means that arterial pressure is more sensitive to changes in volume than venous pressure.
• The proportion of blood in the systemic arteries would be increased by venoconstriction.
• The proportion of blood in the veins would be increased by decreased cardiac output and decreased TPR.

Question 3

What are some properties of the endothelium?

Answer 3

Produces substances that alter smooth muscle contraction
- nitric oxide(potent vaasodilators), endothelin (extremely potent vasoconstrictors that bind irreversibly), prostaglandins (mixture)

Mediates the actions of circulating substances
- angiotensin, thrombin, bradykinin (dilation; such as during insect bites)

Question 4

What does Nitric Oxide do?

Answer 4

• vasodilator
• modulated by physical stimuli (such as hitting the skin), hypoxia, circulating vasoactive factors, paracrine vasoactive factors (adjacent cells; blood cells)

Question 5

What do white blood cells do with regard to vessels?

Answer 5

• releases NO, histamines, cytokines

- vasodilators (induces warmth in acute inflammation, ensures good access by the immune system.)

Question 6

What do platelets do with regard to vessels?

Answer 6

• release thrombin, ADP, thromboxane A2

- enhance coagulation and platelet aggregation and vasoconstriction to reduce blood loss