Lecture 25 : Cardiovascular 8

Question 1

What is generic circulation?

Answer 1

Each organ and tissue receives a blood supply that flows through a circuit
- Blood leaves heart to each organ
- Deliver 02/remove CO2
- Blood returns to heart

Question 2

What is generic circulation blood flow regulated by?

Answer 2

1. Myogenic control (resistance vessels)
2. Neural control
3. Metabolic requirements

Question 3

What are the 2 main specialised regional blood flows?

Answer 3

1. Fetal circulation
2. Pulmonary blood flow

Question 4

What are the roles of the placenta?

Answer 4

1. INtestine (nutrient upatke
2. Kidney - remove waste
3. Lungs - Uptake of O2
4. Recieves large fraction of CO2 - low resistance circuit

Question 5

What is the distribution of blood flow in a fetus?

Answer 5

• Dependent of local requirements
• Organs not yet active e.g. lungs are by-passed

Question 6

Where is fetal blood oxgenated?

Answer 6

Site of placenta via the maternal blood supply
- Relatively hypoxic = 80% saturated

Question 8

In which part of fetal circulation is SO2 highest?

Answer 8

Placental arterial blood - low compared to adult

Question 9

Describe the blood flow through fetal circulation:

Answer 9

• By-pass liver to inferior vena cava
  – Slightly contaminated with circulating placental venous blood
  – SO2 = 67%
• Flow is laminar!
• This projected blood flow “crosses” pathways with venous blood from superior vena cava to right ventricle

Question 10

What is the role of the folds in the vena cava?

Answer 10

“Guide” blood flow
through:
1. Right atrium
2. Foramen Ovale
3. Left atrium

Question 12

What inspiratory motions begin after birth?

Answer 12

Generate -ve thoracic pressure
-> draws blood out of placenta
-> inflates lungs (VE)
-> decrease pulmonary vascular resistance which increases systemic resistance
-> blood flows into lungs

Question 15

How much of cardiac output does pulmonary circulation receive?

Answer 15

100%

Question 16

Compare the resistance of systemic vs pulmonary circulation:

Answer 16

Pulmonary has 10-15 fold lower resistance than systemic

Question 17

What are the 3 characteristics of the pulmonary circulation?

Question 18

What happens if pulmonary pressure increases?

Answer 18

Can lead to:
1. Impaired ejection of blood (increased afterload)
2. Right heart failure
3. Pulmonary edema

Question 19

Name the 4 regulators of pulmonary blood flow:

Answer 19

1. Gravity
2. Hypoxia (low O2)
3. Endothelial control
4. Sympathetic nervous system

Question 20

How is gravity a regulator of pulmonary blood flow?

Question 21

How is hypoxia a regulator of pulmonary blood flow?

Question 22

How does endothelial control regulate pulmonary blood flow?

Question 23

How is the sympathetic nervous system a regulator of pulmonary blood flow?

Answer 23

Via α-adrenoreceptors and β-adrenoreceptors
- They negate each otehr therefore, SNS has minor role in regulating pulmonary blood flow

Question 24

How do α-adrenoreceptors

Question 25

How do β-adrenoreceptors