Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Respiratory System > Blood Gas Transport > Flashcards

Blood Gas Transport Flashcards

1
Q

How are blood gases transported around the body?

A

Gases carried in the blood, first dissolve in the plasma before mostly being transported in other forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the route O₂ takes from lungs to tissues

A 
O₂  exchange at the lung 
↓
O₂ dissolves in plasma 
↓
O₂ binds to Hb 
↓
Redissolves in plasma 
↓
O₂ diffuses into tissues
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the transport of CO₂ from tissues to lungs

A 
CO₂ produced by tissues
↓
CO₂ dissolves in plasma
↓
CO₂ transported as HCO₃⁻ or bound to Hb
↓
CO₂ redissolves in plasma 
↓
CO₂ exchanged at the lungs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe how much % CO₂ is transported out the body in the different ways

A

HCO₃⁻ = 70%
HbCO₂ = 23%
Dissolved CO₂ = 7%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the % O₂ transported out the body bound to Hb and dissolved?

A

HbO₂ = 98%

Dissolved O₂ = 2%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the significance of Hb?

A
  • Hb is critical for O₂ transport
  • Hb presence overcomes need for high alveolar PO₂
  • Vast majority of O₂ transported by blood is bound to Hb
    >98%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why is Hb critical for O₂ transport?

A

O₂ has low solubility in plasma (0.225 ml/L/kPa)
in order to dissolve a sufficient amount of O₂ needed to supply tissues, an impossibly high alveolar PO₂ would be required
Binding to Hb enables O₂ to be concentrated in blood
(increases carrying capacity) at gas exchange surfaces and is released at respiring tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is the oxygen content of blood defined?

A
  • O₂ partial pressure (PaO₂) is expressed as kPa
  • Total O₂ content (CaO₂) is expressed as ml of O₂ per L of
    blood (ml/L)
  • O₂ saturation (SaO₂) and SpO₂ (estimated by pulse
    oximetry) is expressed a s a%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does O₂ partial pressure mean?

A

This is the partial pressure of O₂ within a gas phase (at a gas-liquid interface) that would yield this much O₂ in plasma at equilibrium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define what is meant by the total O₂ content

A

Volume of O₂ being carried in each litre of blood, including O₂ dissolved in plasma and bound to Hb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the % O₂ saturation of blood?

A

% of total available Hb binding sites occupied by O₂

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the role of the oxygen-haemoglobin dissociation curve?

A

The relationship between [O₂], partial pressure, and saturation is shown by the Oxygen Dissociation Curve

The curve shifts to offload O₂ to demanding tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is Hb so effective at transporting O₂ around the body?

A

The structure of Hb produces high O₂ affinity
∴ a high level of Hb-O₂ binding (and saturation) is
achieved at a relatively low PaO₂

[heme] group and Hb contained in RBCs enables a high carrying capacity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the O₂ carrying capacity?

A

O₂ carrying capacity total = 200 ml/L

  • 3 ml/L = Plasma
  • 197 ml/L = Hb
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does Hb-O₂ affinity change?

A

Hb O₂ affinity changes depending on the local environment, enabling O₂ delivery to be coupled to demand
Also enables decreased PvO₂ and more oxygen delivery per unit pf blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the PO₂ and O₂ saturation in the lungs

A

In lungs:

  • High PO₂
  • Low PCO₂ = high pH
  • High O₂ saturation
17
Q

Describe the PO₂ and O₂ saturation in resting tissue

A

In resting tissue:

  • low PO₂
  • low O₂ saturation
  • O₂ moves from Hb to tissue
18
Q

What is the PO₂ and O₂ saturation in working tissue?

A
  • v. low PO₂
  • Anaerobic resp. and hypoxia produce H+, lactate, CO₂
    and 2,3-DPG, increasing O₂ demand
  • high CO₂ = low pH and 2,3-DPG
  • low Hb-O₂ affinity and binding
  • low O₂ saturation
  • Increased O₂ moving form Hb to tissues
19
Q

What is the role of Myoglobin?

A

Myoglobin acts as an O₂ reservoir

only releases O₂ at low PO₂

20
Q

What is the difference between foetal and adult Hb-O₂ affinity?

A

Foetal Hb has a higher O₂ affinity and effectively steals O₂ from maternal Hb

21
Q

What colour does oxyhaemoglobin appear?

A

Hb-O₂ oxyhaemoglobin appears red

22
Q

What is the colour of deoxyhaemoglobin?

A

Hb deoxyhaemoglobin appears blue

23
Q

What is Cyanosis and why does it occur?

A

Purple discolouration of the skin and tissue, occurring when [deoxyhaemoglobin] becomes excessive

24
Q

Describe the features of Central cyanosis

A
  • bluish discolouration of core, mucus membranes and
    extremities
  • Inadequate oxygenation of blood
  • e.g. hypoventilation, V/Q mismatch
25
Q

Describe the pathological features of peripheral cyanosis

A
  • Bluish colouration confined to extremities (e.g. fingers)
  • Inadequate O₂ supply to extremities
  • e.g. small vessel circulation issues
26
Q

Why does insufficient Hb anaemia (hypoxia) occur?

A

Hypoxia can occur despite adequate ventilation and perfusion, if blood isn’t able to carry sufficient O₂ to meet tissue demands

27
Q

What are the causes of insufficient RBCs/Hb anaemia?

A 
Iron deficiency (decreased production)
Haemorrhage (increased loss)
28
Q

Why is more CO₂ dissolved in plasma?

A

CO₂ has a higher H₂O solubility than O₂ ∴ a greater % of CO₂ is transported dissolved in plasma
(7% compared to 1% of O₂)

29
Q

How can you calculate the [CO₂] dissolved in plasma?

A

concentration = partial pressure x solubility

30
Q

Why is less CO₂ transported bound to Hb?

A

CO₂ has different (lower affinity) Hb binding sites to O₂

CO₂ binds to R-NH₂ residues at the end of peptide chains, forming carbamino-Hb (R-NHCOOH)
- lower % of CO₂ is transported like this (23%)

31
Q

How is the majority of CO₂ transported?

A

CO₂ reacts with water to form carbonic acid, which accounts for the majority (70%) of CO₂ transport:

CO₂ + H₂O ⇋ H₂CO₃ ⇋ H⁺ + HCO₃⁻

32
Q

What is the haldane effect?

A

Principle that venous blood carries more CO₂ than arterial blood

33
Q

Explain how CO₂ is transported to tissues

A
  1. CO₂ produced by respiring cells, dissolves in plasma to
    enter RBCs
  2. CO₂ + H₂O ⇋ H₂CO₃ occurs within RBCs catalysed by
    carbonic anhydrase
  3. Effective removal of CO₂ via H₂CO₃ production,
    enabling more CO₂ to diffuse into RBCs
  4. H₂CO₃ ⇋ H⁺ + HCO₃⁻ occurs. RBC membrane is
    impermeable to H⁺, so H⁺ can’t leave
  5. Accumulation of H⁺ in cell so cessation of H₂CO₃
    production is prevented by deoxy-Hb acting as a buffer
    and binding H⁺, causes movement of O₂ into tissues
    from RBCs

Increased [deoxy-Hb] enables more CO₂ to be transported

34
Q

How is CO₂ transported to the lungs?

A
  1. Low PaCO₂ creates gradient;
    CO₂ diffuses out of blood -> airspace
  2. Increased PaO₂ leads to Hb-O₂ binding. Hb-O₂ binds
    less H⁺ than deoxy-Hb, increasing free [H⁺]
  3. Increased free [H⁺], leads to increased H₂CO₃ and
    ultimately CO₂ which contributes to [CO₂] plasma
  4. The changing equilibrium of the carbonic acid rxn
    -> decreased [HCO₃⁻] as it binds to free H⁺, creating a
    diffusion gradient, allowing HCO₃⁻ to enter RBCs in
    exchange fro Cl⁻

Net result: Haldane effect
Deoxygenated blood carries more CO₂
Oxygenated of blood causes CO₂ removal

Respiratory System (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions