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Gas Exchange Flashcards

1
Q

What is the pulmonary circulation?

A

pathway that carries blood through lungs

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2
Q

Functions of pulmonary circulation:

A
  • re-oxygenate blood and remove CO2

- exchange metabolic products to and from lungs

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3
Q

Pulmonary vessels are ___ flow, ___ pressure, and ____ resistance

A
  • high flow
  • low pressure
  • low resistance
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4
Q

Arteries in pulmonary vessels have less…

A

smooth muscle than systemic arteries of the same size

  • high compliance needs lower pressure for flow
  • lowers workload of R ventricle
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5
Q

At rest, what percentage of pulmonary circulation is in the capillaries?

A

15%

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6
Q

During exercise, what percentage of pulmonary circulation is in the capillaries?

A

25%

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7
Q

Function of alveolar-capillary network:

A

where exchange of gases occurs

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8
Q

Layers of respiratory membrane:

A
  • alveolar epithelium: has type 1 cells
  • fused basement membranes: CT
  • capillary endothelium: squamous cells
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9
Q

Capillary endothelium has…

A

angiotensin converting enzyme (ACE), which converts angiotensin 1 to angiotensin 2

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10
Q

Function of capillary endothelium:

A

inactivates or removes vasoactive substances

  • bradykinin
  • serotonin
  • prostaglandins
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11
Q

Exchange of O2 and CO2 is governed by what type of forces?

A

Starling

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12
Q

Pulmonary arterial pressure is much lower than…

A

arteries in the systemic system

  • systolic: 25 mmHg
  • diastolic: 10 mmHg
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13
Q

At rest, what happens to the capillaries at the base and apex of the lung?

A

difference due to gravity

  • base: most capillaries are open and have rapidly flowing blood
  • apex: few capillaries are open and blood flow is slow
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14
Q

During exercise, distribution of blood flow would be…

A

more uniform due to increased cardiac output and increased pulmonary arterial pressure

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15
Q

Function of auxiliary drainage system of the lungs:

A
  • remove excess fluid in ISF

- drains fluid into systemic veins

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16
Q

Failure of the auxiliary drainage system results in…

A

pulmonary edema

  • fluid accumulation overcomes removal by lymph system
  • increases diffusion distance
  • decreases exchange of gases
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17
Q

What is the Va/Q ratio?

A
  • Va: alveolar ventilation
  • Q: flow of blood through capillaries
  • major determinant of normal gas exchange
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18
Q

Va/Q ratio of a resting, upright individual?

A
  • average: 0.8

- air flow greatest at apex and lowest in base

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19
Q

At apex of the lung, there can be a condition called…

A

regional hypoxia: groups of alveoli with low O2

  • higher ventilation and lower perfusion
  • decrease in V and even bigger decrease in Q
  • increase in O2
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20
Q

At the base of the lung, there can be a condition called…

A

hypoxemia: reduction of O2
- lower ventilation and higher perfusion
- increase in V and even bigger increase in Q
- decrease in O2

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21
Q

Pulmonary arterioles control ____ and aids…

A
  • blood flow into capillaries by altering diameter

- aids in balancing perfusion of blood

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22
Q

Decreased arterial PO2 produces…

A

hypoxic vasoconstriction

  • resistance to blood flow increases
  • blood flows to areas with lower resistance
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23
Q

What happens if all regions of the lungs become hypoxic?

A
  • all arterioles constrict
  • resistance to blood flow increases
  • pulmonary arteriole pressure rises (pulmonary hypertension)
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24
Q

What is the predominant means for movement of gases?

A

simple diffusion
- moves along their own concentration gradient, which is determined by partial pressure of gas in alveoli and capillary blood

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25
What are the pressures of H2O, CO2, and O2 at alveolus?
- pH2O: 47 mmHg - pCO2: 40 mmHg - pO2: 104 mmHg
26
What are the pressures of CO2 and O2 in pulmonary arteries?
blood going to lungs - pO2: 40 mmHg - pCO2: 46 mmHg
27
What are the pressures of CO2 and O2 in pulmonary veins?
blood leaving lung with oxygenated blood - pO2: 100 mmHg - pCO2: 40 mmHg
28
O2 gradient diffuses from _____ into ____
alveolus into capillary | - from 104 mmHg to 40 mmHg
29
CO2 gradient diffuses from ____ into ____
capillary blood into alveolus | - 46 mmHg to 40 mmHg
30
What happens during hyperventilation?
increased ventilation by increasing tidal volume and frequency (exercise) - increases alveolar pO2 - decreases pCO2 - improves gradients for both
31
What happens during hypoventilation?
decreased ventilation - decreases alveolar pO2 - increases pCO2 - decreases gradients for both
32
What is the arterial oxygen pressure?
100 mmHg
33
How does O2 get transported in the blood?
- binds to hemoglobin in RBC | - minimal amount of O2 is dissolved in gaseous state in plasma
34
Exchange of gases occur between...
blood and tissues | - diffuse through endothelial cells
35
What is the oxyhemoglobin dissociation curve?
graph that shows O2 saturation of blood - shows how many hemoglobin binding sites are filled with O2 - dependent on partial arterial pressures of O2 in blood
36
Definition of O2 carrying capacity:
max amount of O2 that can be carried by 100mL of blood
37
Definition of O2 content:
amount of O2 actually bound to hemoglobin
38
Definition of O2 content/O2 carrying capacity x 100:
percent of hemoglobin saturated with O2
39
As pO2 rises, what happens to the % of binding sites on hemoglobin for O2?
increases
40
The oxyhemoglobin dissociation curve begins to plateau at _____ and flattens at ____
- plateau: 50 mmHg | - flatten: 70 mmHg
41
What happens when the oxyhemoglobin dissociation curve shifts to the right?
- decreased affinity of hemoglobin for O2 | - increased dissociation from hemoglobin
42
What happens when the oxyhemoglobin dissociation curve shifts to the left?
- increased affinity of hemoglobin for O2 | - decreased dissociation from hemoglobin
43
What factors affect the oxyhemoglobin dissociation curve?
- pH and CO2 - temperature - 2,3 diphosphoglycerate (DGP) - CO
44
How does pH and CO2 affect the oxyhemoglobin dissociation curve?
- decrease in pH shifts it to the right because CO2 generates H+ ions - increases in pH when CO2 is released and shifts curve to the left
45
How does temperature affect the oxyhemoglobin dissociation curve?
- increase in temp = curve shifted to the right b/c it facilitates O2 release to tissues - decrease in temp = curve shifted to the left b/c O2 release inhibited
46
How does 2,3 DPG affect the oxyhemoglobin dissociation curve?
competes directly with O2 at binding site of hemoglobin | - causes right shift
47
How does CO affect the oxyhemoglobin dissociation curve?
- binds to same site as O2 - has a higher affinity - shifts curve to the left
48
CO2 diffuses from...
tissue to plasma | - some stay in plasma but mostly into RBC
49
Removal and uptake of CO2 from blood is directly related to...
pCO2
50
RBC has what enzyme?
carbonic anhydrase, which catalyzes the reaction of CO2 and H2O to make bicarb - decreases pH of tissues
51
CO2 is predominately transported via...
bicarb
52
Structure of erythrocytes (RBC):
- biconcave - no nucleus or organelles needed for cell maintenance - cytoplasm filled with hemoglobin
53
Function of RBC:
carry blood gasses
54
Life cycle of RBCs:
1. created from hematopoietic stem cells in bone marrow (erythropoiesis), which is stimulated by erythropoietin 2. circulate in blood for 4 months 3. removed by macrophages in spleen, liver, and marrow
55
Erythropoietin is secreted by...
kidneys in response to decreased O2
56
Structure of hemoglobin:
4 non-protein heme groups and 4 polypeptide chains (2 alpha and 2 beta chains)
57
What happens to iron at the heme groups?
gets reduced to ferrous Fe2+ | - that's the site where O2 binds
58
Where does CO2 bind to on hemoglobin?
polypeptide chains
59
Functions of hemoglobin:
- O2 transport (up to 4) - CO2 transport - H+ transport
60
Hemoglobin in the blood is directly proportionate to...
% blood volume occupied by RBC (hematocrit)
61
What is myoglobin?
O2 carrying and storage protein in muscle tissues
62
What is anemia and its symptoms?
- abnormally low O2 carrying capacity of the blood - shortness of breath - physical weakness
63
When do you think anemia occurs in a person?
- decreased number of circulating RBC (hematocrit < 37%) | - abnormal or low hemoglobin
64
Types of anemia caused by decreased number of RBCs:
- megalobastic: decreased folic acid and or cobalamin (vitamin b12) - pernicious: autoimmune disease and causes lack of IF (reduces b12 absorption) - aplastic: abnormal decrease in production of RBCs
65
Illnesses caused by abnormal hemoglobin:
- sickle cell anemia: glutamine to valine | - thalassemias: defective chains
66
What is methemoglobinemia?
alteration in iron state - iron converted to ferric (Fe3+) instead of ferrous (Fe2+) - causes abnormal hemoglobin levels
67
What is iron deficiency anemia?
- associated with internal blood loss | - comes from inadequate absorption of iron

Physiology (33 decks)

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