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BDS1 BAMS: Respiratory System > Respiratory Gas Transport > Flashcards

Respiratory Gas Transport Flashcards

1
Q

What direction do carbon dioxide and oxygen move in the respiratory system?

A

CO2 transported from tissues to lungs, and O2 transported from lungs to tissues

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2
Q

Describe the unique anatomical and physiological properties that the respiratory and circulatory systems contain to facilitate gas diffusion

A
  1. Large surface area for gas exchange (alveolar sacs)
  2. Large partial pressure gradients (gases moving from high to low gradients encourages the diffusion of gases)
  3. Gases with advantageous diffusion properties
  4. Specialised mechanisms for transporting O2 and CO2 between lungs and tissues
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3
Q

Why does oxygen move from alveoli to pulmonary artery?

A

Because it moves from a high concentration (100 mmHg) in the alveoli to a low concentration (40 mmHg) in the pulmonary artery

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4
Q

What is partial pressure?

A

The pressure a gas exerts within a mix of gases

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5
Q

What needs to be taken into account when calculating the partial pressure of O2 in the body?

A

Water vapour
Has its own partial pressure (47 mmHg)
Humidifies the air, impacts the partial pressure of O2

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6
Q

What are the 2 forms that oxygen is carried in the blood?

A
  1. Dissolved within blood plasma

2. Bound to haemoglobin

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7
Q

The amount of dissolved O2 in blood is proportional to what?

A

Partial pressure

For each mmHg of PO2, there is 0.003ml O2/100ml blood

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8
Q

What volume of O2 is present in the dissolved form in 1 litre of arterial blood?

A

PO2 = 100 mmHg
0.3 ml/100ml of blood
3ml O2/litre of blood

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9
Q

What is the major transport system for O2 in blood?

A

Haemoglobin

Transport of O2 in dissolved form is not adequate

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10
Q

What are haemoglobin molecules compose of?

A

4 proteins chains: 2 alpha and 2 beta chains
Joined to a globin protein
Each chain contains a haem group

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11
Q

What is a haem group?

A

Iron porphyrin compounds

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12
Q

How many molecules of haemoglobin are present in a red blood cell?

A

280 million Hb molecules per RBC

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13
Q

How quickly does binding and dissociation of O2 with Hb occur?

A

In milliseconds (to facilitate transport - red blood cells are only in capillary for 1 second)

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14
Q

What does the oxyhaemoglobin dissociation curve illustrate?

A

The relationship between PO2 in blood and the number of O2 molecules bound to Hb

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15
Q

Describe the flat portion of the oxyhemoglobin curve

A

Drop in PO2 from 100 to 60 mmHg has minimal effect on Hb saturation

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16
Q

Describe the steep portion of the oxyhemoglobin curve

A

Large amount of O2 is released from Hb with only a small change in PO2, facilitating release into tissues

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17
Q

How many oxygen atoms can each molecule of Hb bind?

A

4

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18
Q

What is SaO2?

A

O2 saturation: the amount of O2 bound to haemoglobin relative to maximal amount that can bind

19
Q

1g Hb binds with 1.39ml of O2. Normal blood has 15g Hb/100ml of blood. What is the O2 capacity per 100ml of blood?

A

15g x 1.39 ml

= ~20.8ml O2/100ml of blood

20
Q

Which factors can shift the oxyhemoglobin dislocation curve?

A

pH and temperature

21
Q

Describe the effects of pH on the oxyhemoglobin dissociation curve

A

Overheating: curve shifts to the right
Start to dissociate O2 from haemoglobin much earlier
Lower temperature: curve shifts to the left

22
Q

Describe the effects of temperature on the oxyhemoglobin dissociation curve

A 
Higher pH (alkaline): curve shifts to the left 
Lower pH (acidic): curve shifts to the right
23
Q

What device can be used to measure O2 saturation?

A

Pulse oximeters

Measure the ratio of absorption of red and infrared light by oxyHb and deoxyHb

24
Q

What volume of CO2 is typically excreted during rest? (in ml/min)

A

200ml/min

25
Q

What is the respiratory exchange ratio (RER)?

A

The ratio of expired CO2 to O2 uptake

26
Q

What is the ratio of expired CO2 to O2 uptake known as?

A

Respiratory Exchange Ratio

27
Q

What is the respiratory exchange ratio in normal conditions?

A

0.8 (80 CO2 to 100 O2)

28
Q

What are the 3 forms that CO2 is carried in the blood?

A

1) Dissolved
2) Bound to haemoglobin
3) As bicarbonate

29
Q

What happens to the RER during strenuous exercise?

A

RER will become greater than 1. Produce more CO2 molecules compared to amount of O2 molecules taken in

30
Q

What percentage of CO2 is dissolved in the plasma?

A

7%

31
Q

What percentage of CO2 binds to Hb forming carbaminohaemoglobin?

A

23%

32
Q

What percentage of CO2 is converted to carbonic acid by carbonic anhydrase?

A

70%

33
Q

What does carbonic acid (H2CO3) dissociate into?

A

H+ and HCO3-

hydrogen ions and bicarbonate

34
Q

What is HCO3- important for?

A

Chloride shift

35
Q

Which pathway plays a critical role in regulation of H+ ions and in maintaining acid-base balance in the body?

A

The CO2 to HCO3- pathway

36
Q

What is the direction and speed of the CO2-HCO3 pathway determined by?

A

The concentration gradients

37
Q

Changes in bicarbonate concentrations can be used to stabilise pH. What type of reaction is this?

A

Buffer reaction

38
Q

How can acidity of the blood be regulated?

A
  • Using ventilation to adjust PCO2

- By using the kidneys to regulate the bicarbonate concentration

39
Q

What is the major transport system for O2?

A

Within red blood cells bound to haemoglobin

40
Q

What shape is the oxy-haemoglobin curve?

A

Sigmoidal (‘S’ shaped)

41
Q

What shape is the oxy-haemoglobin dissociation curve?

A

Sigmoidal (‘S’ shaped)

42
Q

Which pathway plays a critical role in the regulation of H+ ions and in maintaining the acid-base balance in the body?

A

CO2 to HCO3- pathway

43
Q

Which parameters are on the x and y axes of the oxyhemoglobin dissociation curve?

A

X axis = PO2

Y axis = Percent Hb saturation

BDS1 BAMS: Respiratory System (8 decks)

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