Blood Supply, Gas Exchange, Ventilation & Perfusion

Question 1

Describe Bronchial Circulation

Answer 1

1) 1% cardiac output from the aorta travels in the bronchial arteries and supplies oxygenated blood to the lung tissue, smooth muscle and nerves
2) Bronchial veins carry deoxygenated blood to SVC/IVC

Question 2

Describe Pulmonary Circulation

Answer 2

1) Left and Right Pulmonary arteries carry deoxygenated blood away from right ventricle to the lungs and return oxygenated blood to the left atrium and ventricle of the heart via the pulmonary vein
2) Supplies the dense capillary network surrounding the alveoli

Question 3

Rules of Diffusion (6)

Answer 3

Directly proportional to the partial pressure gradient
Directly proportional to gas solubility
Directly proportional to the available surface area
Inversely proportional to the thickness of the membrane
Most rapid over short distances
CO2 is much more soluble in water than O2 therefore it diffuses faster than expected despite the small partial pressure gradient

Question 4

Effect of emphysema on diffusion

Answer 4

Loss of surface area for gas exchange

Question 5

Effect of fibrosis on diffusion

Answer 5

Thickened alveolar membrane slows down rate of gas exchange and reduced lung compliance and ventilation

Question 6

Effect of pulmonary oedema on diffusion

Answer 6

Fluid in interstitial space increases diffusion distance

Question 7

What is the relationship between ventilation and perfusion

Answer 7

Ventilation (air getting to the alveoli L/min) compliments Perfusion (local blood flow L/min) through pulmonary capillaries

Question 8

Describe the relationship between the ventilation and perfusion in the base of the lungs

Answer 8

Blood flow is higher than ventilation because the the arterial pressure is greater than the alveolar pressure and the alveoli are compressed

Question 9

Describe the relationship between the ventilation and perfusion in the apex of the lungs

Answer 9

Blood flow is low because arterial pressure is less than alveolar pressure and the arterioles are compressed

Question 10

Ratio at Apex

Answer 10

Ventilation>Perfusion > 1.0

Question 11

Ration at Base

Answer 11

Perfusion>Ventilation < 1.0

Question 12

Where does the majority of mismatch occur

Answer 12

Apex

Question 13

What is a Shunt

Answer 13

Passage of blood through poorly ventilated areas

Question 14

What is Alveolar Dead Space

Answer 14

Alveoli that are ventilated but not perfused

Question 15

Anatomical Dead Space

Answer 15

Parts of the respiratory tract that are ventilated but not perfused and do not take part in gas exchange. This includes the trachea, bronchi and bronchioles

Question 16

How much is the anatomical dead space each time we take a breath

Answer 16

1/3 (150)

Question 17

Causes of Shunts

Answer 17

Collapse of alveoli
Pneumonia and Pulmonary Oedema
Tissue trauma (alveolar swelling)
Mucous plugging
Pulmonary Arteriovenous Fistula (abnormal connection between vein and artery in lung)