respiratory physiology basics CPBC

Question 1

List the structures of the respiratory system from proximal to distal

Answer 1

nasal chambers, pharynx, larynx, trachea, primary bronchi, secondary bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs

Question 2

what respiratory system structures take part in the gas exchange

Answer 2

respiratory bronchioles, alveolar ducts, alveolar sacs

Question 3

what are club cells

Answer 3

• make glycosaminoglycans –> protects the bronchioles
• surfaces stem cells –> produce more bronchiole cells

Question 4

what mediates the contraction or expansion of the lungs?

Answer 4

• collagen and elastin from fibroblasts
• no muscles

Question 5

what is the ratio when comparing the thickness of RBCs and alveolar walls

Answer 5

alveolar walls are significantly thinner –> RBCs 7 times thicker

Question 6

what are goblet cells

Answer 6

• produce mucous to catch unwanted material that is then brought up by cilia
• decrease in number from proximal to distal

Question 7

what are the pores of Kohn?

Answer 7

interalveolar clefts –> allow fluid and cells to come in and out of alveoli

Question 8

what are the 3 major cell types in the alveoli

Answer 8

• type I pneumocytes
• type II pneumocytes
• phagocytes (macrophages)

Question 9

what is the main function of type I pneumocytes?

Answer 9

• most important for gas exchage

Question 10

what is the main function of type II pneumocytes?

Answer 10

secrete surfactant to lower surface tension

Question 11

what is the role of nitrogen in the lungs?

Answer 11

gaseous skeleton in small airways –> important for stability –> can be washed out when patient is placed on 100% oxygen

Question 12

how does the pressure of pulmonary arteries compare to systemic pressure

Answer 12

only 1/6th of systemic pressure

Question 13

what causes peribronchial cuffing

Answer 13

dilated lymphatics at junction between alveolar and extra-alveolar spaces

Question 14

what is hypoxic vasoconstriction in the lungs?

Answer 14

closing of precapillary sphincters –> terminal bronchioles can go straight to postcapillary venule (=shunt)

Question 15

what could open precapillary sphincters in the lungs?

Answer 15

higher O2 demand, e.g., exercise

Question 16

explain the forces creating centripetal pressure in alveoli

Answer 16

• forces of attraction between molecules of liquid lining alveoli
• proposing forces of water and interface of alveoli –> inward collapsing pressure –> elastic recoil

Question 17

Explain the Law of Laplace

Answer 17

collapsing pressure = 2x surface tension / radius

P = 2T/r

–> the greater the radius the smaller the collapsing pressure

Question 18

what are the effects of surfactant?

Answer 18

• prevents transudation of fluid from capillaries to alveolar space
• prevents small alveoli emptying (air flow from small to larger alveoli)

prevents collapse of alveoli

reduces work of breathing (due to less negative pressure necessary to move air into alveoli)

Question 19

what are the partial pressures of O2 and CO2 in the alveolus?

Answer 19

• PO2 = 100 mm Hg
• PCO2 = 40 mm Hg

Question 20

what are the partial pressures of O2 and CO2 in the afferent alveolar capillaries?

Answer 20

PO2 = 40 mm Hg

PCO2 = 45 mm Hg

Question 21

what are the partial pressures of O2 and CO2 in the efferent alveolar capillaries

Answer 21

• PO2 = 100 mm Hg

PCO2 = 40 mm Hg

Question 22

what are the partial pressures of O2 and CO2 in the resting tissue cells/leaving systemic capillaries?

Answer 22

PO2 = 40 mm Hg

PCO2 = 45 mm Hg

Question 23

what is Fick’s Law

Answer 23

gas movement across membrane proportional to transfer surface area and inversely proportional to thickness of membrane

–> large and thin alveolar wall enables more gas exchange than short and tick

Question 24

what is the thickness of alveolar membranes?

Answer 24

1/3 micrometer

Question 25

what is the equation for Fick’s law of diffusion?

Answer 25

Diffusion = SA x D x (P1-P2) / T

SA = surface area

D = diffusion constant of the particular gas

P1 and P2 pressures of the gas on either side of the membrane

T = thickness

Question 26

Describe Boyle’s Law

Answer 26

P1V1 = P2V2

i. e., decreasing the volume will increase the pressure and increasing the volume will decrease the pressure
e. g., breath: increase volume –> decrease pressure –> negative pressure –> airflow into lungs

Question 27

Describe Dalton’s Law

Answer 27

P_total = P1 + P2 + P3 …

i.e., within the alveolus the total pressure in the alveoli is the total sum of partial pressures

Question 28

Describe Henry’s Law

Answer 28

C_Gas ~ P_Gas

i.e., at a constant temperature the concentration of a gas is going to be proportional to the pressure of the gas

Question 29

how much ml of O2 does one gram of hemoglobin contain if it is 100% saturated?

Answer 29

~ 1.36 ml of O2

Question 30

what is the normal Hg concentration of blood?

Answer 30

~ 15 g/dL

15 x 1.36 (ml/g O2) = 20 –> 20 ml/dL O2 in blood bound to Hg

Question 31

what is the amount of dissolved O2 in blood per PaO2?

Answer 31

0.003 mL/dL/mm Hg PaO2

Question 32

what is the amount of O2 in arterial blood, how much is dissolved and how much bound to Hg?

Answer 32

arterial blood ~ 19.8 mL/dL, 0.29 in solution and 19.5 bound to Hg

Question 33

what is the venous Hg O2 saturation?

Answer 33

75%

Question 34

what is the total O2 content of venous blood?

Answer 34

15.2 mL/dL

Question 35

what is the P50 of the oxygen-hemoglobin saturation curve in dogs?

Answer 35

28.8

means at 28.8 pO2 –> 50% of Hg will be saturated with O2

Question 36

what is the P50 of the oxygen-hemoglobin saturation curve in cats?

Answer 36

means at 36 pO2 –> 50% of Hg will be saturated with O2

Question 37

what does a right shift of the oxygen-hemoglobin curve mean?

Answer 37

O2 is less Hg bound/ affinity of O2 to Hg decreases –> more O2 released from Hg to tissues

Question 38

What is the mechanism of hypoventilation causing hypoxemia?

Answer 38

hypoventilation –> pACO2 goes up –> pAO2 must go down because sum of pressures must be constant –> if pACO2 goes up pAO2 goes down –> paO2 goes down –> Dalton’s law

Question 39

How do you calculate alveolar pO2 (P_AO2)

Answer 39

PAO2 = PIO2 - (PACO2 / R)

R = respiratory quitient –> fraction of CO2 produced to O2 consumed –> influenced by factors like diet

at sea level:

PAO2 = 150 - (PACO2 / 0.8)

Question 40

when can you not use the formula PAO2 = 150 - (PACO2 / 0.8)?

Answer 40

when you’re not at sea level

use:

PiO2 (150 at sea level) = FiO2 (barometric pressure - water vapor pressure)

= FiO2 (PB - PH2O)

Question 41

what is the equation for PiO2 when not at sea level?

Answer 41

PiO2 (150 at sea level) = FiO2 (barometric pressure - water vapor pressure)

= FiO2 (PB - PH2O)

Question 42

in high altitude what happens to PaO2, A-a gradient and effect of supplemental oxygen?

Answer 42

PaO2 decreased

A-a gradient normal

O2 supplementation improves oxygenation

Question 43

during hypoventilation what happens to PaO2, A-a gradient and effect of supplemental oxygen?

Answer 43

PaO2 decreased

A-a gradient normal

O2 supplementation improves oxygenation

Question 44

during diffusion defect what happens to PaO2, A-a gradient and effect of supplemental oxygen?

Answer 44

PaO2 decreased

A-a gradient decreased

supplemental O2 will improve oxygenation

Question 45

during V/Q defect what happens to PaO2, A-a gradient and effect of supplemental oxygen?

Answer 45

PaO2 decreased

A-a gradient increased

O2 supplementation will improve oxygenation

Question 46

during R to L shunt what happens to PaO2, A-a gradient and effect of supplemental oxygen?

Answer 46

PaO2 decreased

A-a gradient increased

O2 supplementation will not improve oxygenation