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Anatomy > Gas Exchange > Flashcards

Gas Exchange Flashcards

1
Q

how does gas exchange occur in the lungs?

A

due to differences in the partial pressure of gases

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2
Q

what is the atmospheric (barometric) pressure at sea level?

A

760 mmHg

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3
Q

Dalton’s Law of Partial Pressures

A

in a mixture of gasses, each gas will contribute to the total pressure of the system in direct proportion in the mixed gas;
[Pressure] x [Gas %] = Partial pressure of gas

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4
Q

what is the significance of partial pressures of gas?

A

direction of diffusion is determined by partial pressure of the gas (gas movement from high to low pressure); the only reason oxygen comes from alveolus into blood and deposit into tissue is b/c there is a [ ] gradient for O2 extremely high in the atmosphere and lowest at the tissues

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5
Q

partial pressure gradient - as atmospheric air enters the alveoli:

A

partial pressure of O2 decreases due to increase in p.p. of H2O and CO2 (p.p. CO2 increases due to addition from blood)

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6
Q

partial pressure gradient - as air moves from alveoli to atmosphere:

A

p.p. of O2 increases due to mixing w/ dead space air, p.p. CO2 decreases due to mixing w/ dead space air

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7
Q

what is the significance of CO2 being more soluble than O2?

A
  • there is a tight range for CO2 b/c of carbonic acid equation; small changes in CO2 levels also change pH of body
  • the partial pressure of CO2 is not as affected by diffusion
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8
Q

what is the effect of blood flow on gas exchange?

A

as blood flows past alveoli, and there is time, pressures will equilibriate

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9
Q

what is the effect of increased diffusion barrier on gas exchange?

A

due to pulmonary edema

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10
Q

ventilation-perfusion mismatch

A

sometimes there are regions of the lung where there is an imbalance b/w how well it is ventilated and how well it is perfused - this is described as an abnormal V/Q ratio

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11
Q

high V/Q ratio

A

there is not enough perfusion of a well-ventilated area:

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12
Q

low V/Q ratio

A

not enough ventilation of a well-perfused area:

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13
Q

how to correct for a V/Q mismatch

A
  • pulmonary arterioles relax if PaCO2 is low or PaO2 is high

- pulmonary arterioles constrict if PaCO2 is high or PaO2 is low

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14
Q

how do the pulmonary arteries respond when moving to higher elevation?

A
  • airways wide open for ventilation but oxygen levels are low: sensed by pulm.
  • arterioles and constrict to shunt blood to other areas getting good adequate oxygenation (unable to) → pulm.
  • hypertension
  • can lead to right sided heart failure
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15
Q

what would happen to pulmonary arteriolar pressures in COPD?

A
  • issues w/ airway ventilation due to collapsed airways and low O2 levels in alveoli = all the pulmonary vessels start to constrict the arterioles
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16
Q

CO2 transport in the blood

A

carried in the blood dissolved, as bicarbonate, or bound to hemoglobin as carbamino-Hb

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17
Q

carbonic anhydrase

A

enzyme that catalyzes the reaction between carbon dioxide and water to form carbonic acid

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18
Q

O2 transport in the blood

A

carried in the blood dissolved or bound to hemoglobin (majority)

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19
Q

hemoglobin

A

iron containing protein:
heme - reversibly binds oxygen in relation to partial pressure, higher affinity for CO
globin - globular protein chains (2 alpha, 2 beta)

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20
Q

forms of hemoglobin

A

adult, fetal and sickle

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21
Q

cooperativity

A

after Hb binds one oxygen, it becomes easier to bind the next three (this results in a non-linear O2-Hb dissociation curve)

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22
Q

flat top dissociation curve

A

the flat top allows lots of oxygen pick up with respiratory failure, and the steep portion allows tissue to pull off as much oxygen as needed

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23
Q

steep slope dissociation curve

A

hemoglobin is normally 100% saturated; at rest 25% oxygen is released from Hb to tissues(65% during exercise)

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24
Q

right-shifted dissociation curve

A

this is due to tissues with high-metabolism due to increased PCO2, increased temperature and decreased pH

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25
Q

what is the purpose of breathing control?

A

to ensure that alveolar ventilation is at an appropriate level for the amount of tissue respiration occurring at any given time (maintain ABG levels)

26
Q

breathing components of medulla

A

ventral and dorsal RG

27
Q

dorsal respiratory group (DRG)

A

pacemaker cells

28
Q

ventral respiratory group (VRG)

A

sends outputs to accessory muscles during forced breathing

29
Q

what influences the smoothness, intensity, and frequency of the respiratory groups in the medulla?

A

the pontine respiratory group

30
Q

respiratory inputs to the pons and medulla

A

cerebral cortex, hypothalamus, peripheral chemoreceptors, baroreceptors, muscle & joint receptors lung stretch & irritant receptors

31
Q

cerebral cortex

A

voluntary control of breathing

32
Q

hypothalamus

A

breathing influenced by stress, emotion and pain

33
Q

role of peripheral chemoreceptors in breathing control

A

responsible for fine control of breathing

34
Q

baroreceptors

A

changes in BP during respiratory cycle

35
Q

muscle and joint receptors

A

when activity increases, breathing increases

36
Q

lung stretch receptors

A

prevents over inflation of lungs when breathing

37
Q

irritant receptors

A

triggers the cough reflex

38
Q

central chemoreceptors

A

located on the ventral surface of the medulla and sense CSF levels; monitors PaCO2 via H+ (CO2 + H2O <=> HCO3- + H+) (chemoreceptors provide input to maintain constant PaCO2 of 40mmHg)

39
Q

peripheral chemoreceptors

A

located in the carotid and aortic bodies; monitor PaCO2, decrease in arterial pH and decrease of PaO2; disturbances are restored by increasing ventilation

40
Q

80% of our atmosphere is what?

A

nitrogen

41
Q

20% of our atmosphere is what?

A

oxygen and carbon dioxide

42
Q

does PO2 decrease or increase as we inhale?

A

decreases

- increase in PH20 in water and PCO2

43
Q

Does PCO2 increase or decrease as we inhale?

A

increase

- due to addition from blood

44
Q

Does PO2 increase as we exhale air?

A

increases

- mixes with dead space

45
Q

Does PCO2 increase or decrease as we exhale?

A

decreases

- mixing with dead space

46
Q

Where is PO2 higher?

A

in the alveoli than blood, higher in blood than tissues

47
Q

Where is PCO2 higher?

A

higher in the tissues than blood, higher in blood than alveoli

48
Q

How is elastic tissue around the lobule supplied?

A

bronchial arteries supply, drained by pulmonary veins

49
Q

pulmonary vein does what?

A

collects oxygen rich blood

- called arteriole blood b/c it goes to arteries and service tissues to provide them with oxygen

50
Q

pulmonary artery does what?

A

bring up physiologically venous blood

  • collects blood from right side of the heart which comes back from tissue
  • deoxygenated blood
51
Q

venous blood is

A

spent

52
Q

pulmonary edema

A
  • extra fluid coming in from vascular space ending up in alveoli
  • oxygen doesnt dissolve well in the water
  • partial pressure of oxygen is reduced by half of the time it gets to the tissue
  • becomes cyanotic
53
Q

Where does high ventilation of perfusion ratio occur?

A

at the apex of the lung and due to pulmonary embolism

54
Q

Where does low ventilation of perfusion ratio occur?

A

at the base of the lung and due to asthma or lung cancer

55
Q

High ventilation to perfusion ratio

A
  • high O2 making smooth muscle relax

- more blood flow going across alveoli that is well ventilated

56
Q

Low ventilation to perfusion ratio

A
  • Low O2 making smooth muscle in arterioles to constrict

- reduces blood flow to the alveolus and shunts to others getting fresh air

57
Q

How does CO2 dissociate?

A

high conc in tissue to low conc in the blood

58
Q

What is the gas exchange membrane lining the alveolus?

A

type one pneumocyte

59
Q

When does CO2 have a high concentration?

A

in the blood and low conc in alveoli

60
Q

How much O2 is dissolved and how much is carried by hemoglobin?

A

dissolved (1.5%)

bound (98.5%)

Anatomy (14 decks)

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