physiology Dar. Butcher quiz 2

how many circulations do the lung have?

2

• bronchial and pulmonary circulation

bronchial artery circulation

• high pressure, low flow circulation

• gives arterial blood to the tracheal and bronchial tree

  • contains oxygenated blood, empties out to the pulmonary veins

    • 1-2% greater blood volume enters left ventricle

pulmonary artery

• low pressure, high flow circulation

• has the pulmonary artery

  • its where deoxygenated blood from body to alveolar capillaries for gas exchange, returned by pulmonary veins to the heart

special characteristics of pulmonary vessels

• pulmonary arteries and lymphatics

pulmonary arteries

• typically slightly smaller than aorta and shorter than most arteries

• arterioles are also typically larger than what are seen systematically

• thin walled and distensible

• large compliance- accommodates the stroke of right ventricle

whats complaince

how easily the lungs stretch/expand when pressure is applied

lymphatics

• found in the supportive tissue of the lungs

• empty into the right thoracic lymph duct

• removed particulate matter and plasma protein leaking from lung capillaries

how does Oxygen move

• diffusion

why s oxygen exchange necessary

• O2 is the final electron acceptor in cellular respiration

• Food + oxygen →ATP

rates of diffusion are dictated by the size of the __________ ___________

concentration gradient

• Concentration is typically used to describe diffusion within a single aqueous solution (one phase)

Problem: O2 and CO2 diffuse between a gas mixture and aqueous solution; how do we fix

• partial pressure

The partial pressure and the concentration of a gas in an aqueous solution are

proportional to each other

3 important characteristics to know about partial pressure

• solubilities of different gases are different, specifically CO2 is higher than O2 and N2

• solubilities of gases in aqueous solutions decrease strongly with increasing water temp

• solubilities of gases in aqueous solutions decrease with increasing salinity

law of diffusion: what is it, when is it true, when is it not true

gases diffuse from areas of relatively high partial pressure to areas of relatively low partial pressure

• This is true within gas mixtures, within aqueous solutions, and across gas–water interfaces

• Does NOT necessarily mean that diffusion occurs in the direction of the concentration gradient

so ex.

Beetle has consumed 50% of the oxygen in the bubble

Higher concentration of oxygen compared to water

Lower concentration of partial pressure compared to water

Thus, oxygen diffuses into the bubble

equilibrium is always attained with respect to

any given gas when the partial pressure of the gas is uniform everywhere in a system

Krogh diffusion coefficient describes

gas permeability of the tissue

• Diffusion through water can meet O2 requirements of living tissues only if the distance covered is < 1 mm

Gases diffuse easier thru air than________

water

which gas mol. contribute to partial pressure of gas?

Only gas molecules that exist as free gas molecules contribute to the partial pressure of a gas

Pulmonary arterial pressure, Pulmonary capillary pressure, Left atrium/pulmonary vein pressure

• Pulmonary arterial pressure < 30 mmHg

• Pulmonary capillary pressure is ~ 7 mmHg

• Left atrium/pulmonary vein pressure is ~ 2 mmHg

zones of pulmonary blood flow

• zone 1: no blood flow- alveolar air pressure > local alveolar capillary pressure during any part of the cardiac cycle

• zone 2: intermittent blood flow- alveolar pressure sometimes > local alveolar capillary pressure

  • During diastole

• Zone 3: Continuous blood flow - alveolar air pressure < local alveolar capillary pressure

Capillary Exchange of Fluid in the Lungs:

1. Forces tending to cause movement of fluid outward from the capillaries and into the pulmonary interstitium:

2. Forces tending to cause absorption of fluid into the capillaries:

3. alvelolar structure?

4. how is fluid carried away>

1. Pulmonary capillary pressure is low (+7)

   1. Interstitial fluid colloid osmotic pressure (+14)

   2. Negative interstitial fluid (-8)

   3. Total = 29 mmHg

2. • Colloid osmotic pressure (-28)

3. Alveolar walls extremely thin

4. Fluid in the alveoli is sucked mechanically into lung interstitium and carried away in lymphatics

exercise does what to the lung?

• increases blood flow in all parts of the lung

• Pulmonary vascular pressure rise to convert lung apices from zone 2 to zone 3

increased cardiac output does NOT mean

large increases in pulmonary artery pressure

• capillary recruitment

• distension of capillaries

• increasing pulmonary pressure

what are lungs basically

basically a blood reservoir

• roughly 9% of blood volume

• in normal circumstances (at rest, healthy)

in the lungs why is blood flow at that rate?

its matched for optimal blood exchange

• Hypoxia (not enough oxygen to tissues)→ increase in vascular resistance→ diverts blood flow (opposite of systemic vessels)

• Lungs are better aerated

Which pulmonary circuit is low-pressure, high flow circulation?

Bronchial arteries

Pulmonary Artery

All of the above

Pulmonary Artery

What characteristic of gases and partial pressure is NOT true?

Solubilities of different gases are different

The solubilities of gases in aqueous solutions decrease strongly with increasing water temperature.

The solubilities of gases in aqueous solutions decrease with increasing salinity.

All of the above are true

All of the above are true

If atmospheric oxygen has a higher concentration and a higher atm than inside the lung, which direction with it diffuse?

It will diffuse into the lungs

It will diffuse out of the lungs

It will not diffuse at all, because it is already at equilibrium

Not enough info given

• It will diffuse into the lungs

What are the force(s) that cause fluid absorption into the capillaries?

Low pulmonary capillary pressure

Negative interstitial fluid

Capillary osmotic pressure

A and B

• Capillary osmotic pressure

The blood vessels of pulmonary and systemic vessels behave in a similar fashion with hypoxia. • True • False

False

Compositions of Alveolar Air and Atmospheric Air are Different: what are they

• Alveolar air is only partially replaced by atmospheric air with each breath

• Oxygen is constantly being absorbed into pulmonary blood

• Carbon dioxide is constantly diffusing from the pulmonary blood

• Dry atmospheric air is humidified well before it reaches the alveoli

atmospheric air has almost no water vapor?

Yes

water vapor dilutes________?

other gases

what is alveolar air slowly renewed by?

atmospheric air

• 15% of alveolar air os replaced with each breath

• functional residual capacity of the lungs (the volume of air remaining in the lungs at the end of normal expiration)

why is alveolar air replaced by atmospheric air

• Helps Stabilize Respiratory Control

  • Prevents sudden changes in gas concentrations

  • Prevent excessive increases and decreases in tissue oxygenation, tissue CO2 concentration, and tissue pH when respiration is temporarily interrupted

  • • What can you infer about animals with higher respiratory rates?

O2 concentration in the alveoli, as well as its partial pressure, is controlled by

• The rate of absorption of O2 into the blood

• The rate of entry of new O2 into the lungs by the ventilatory process

• Take home from graph:

• During exercise→ alveolar ventilation must increase by 4-fold to max normal alveolar PO2

• Even with extreme alveolar ventilation, alveolar PO2 won’t increase above 149 mmHg in normal atmospheric air at sea level

Respiratory unit or respiratory lobule?

• respiratory bronchiole, alveolar ducts, atria, and alveoli

• Couple hundred million

• alveolus has an average diameter of about 0.2 millimeter

Respiratory plexus described as

sheet of flowing blood

Components of the respiratory membrane

1. A layer of fluid containing surfactant that lines the alveolus and reduces the surface tension of alveolar fluid

2. The alveolar epithelium, composed of thin epithelial cells

3. An epithelial basement membrane

4. A thin interstitial space between the alveolar epithelium and capillary membrane

5. A capillary basement membrane that in many places fuses with the alveolar epithelial basement membrane

6. The capillary endothelial membrane

Average diameter of capillary

5 Um

• RBC’s squeeze thru, literally touching capillary wall

Factors Affecting Rate of Gas Diffusion Through the Respiratory Membrane

1. Thickness of the membrane

   1. Diseases; edema build-up in interstitial space, fibrosis

2. Surface area of the membrane

   1. Decreased by: lung removal, emphysema

3. Diffusion coefficient of the gas in the substance of the membrane

4. Partial pressure difference of the gas between the two sides of the membrane

Alveolar air is diluted compared to atmospheric air • True • False

True

An animal is experiencing hyperventilation, increases respiratory rate. What is this doing to their alveolar air turn-over?

Alveolar air turn-over is not influenced by respiratory rate

Alveolar air turn-over is increased

Alveolar air turn-over is decreased

Not enough information given

• Alveolar air turn-over is increased

What controls O2 concentration and partial pressure in the alveoli?

The rate of absorption of O2 into the blood

The rate of entry of new O2 into the lungs by the ventilatory process

Both A and B

• Both A and B

If you want to measure the alveolar concentration of gases, what part of exhalation would you collect?

• First 25% •

First 50% •

Last portion after forced expiration

All of expiration

• Last portion after forced expiration

Of the 6 components of the respiratory membrane, which one is first on the alveolar side (lowers the surface tension)?

• Surfactant

partial pressure of gaseous O2 in alveolus? in venous blood entering pulmonary capillary at arterial end (lung)?

in venous blood entering pulmonary capillary at arterial end: 40 mmHg

in alveolus: 104mmHg

• 64 mmHg difference, blood enters lungs with low partial pressure of O2

  • diffusion moves O2 into blood quickly, before blood has moved 1/3 of the way through the capillary its at 104mmHg

• blood stays in blood capillary 3x longer than needed (safety factor)

  • if something slows down oxygen transfer, we still have extra capillary time

Uptake of oxygen by the pulmonary blood during exercise?

• need way more O2, can require up to 20x the normal amount along with increased cardiac output

  • reduces time blood remains in the blood capillary

safety factor during exercise

• capillary recruitment in zone 1 or 2 to increase surface area

• capillary distension meaning capillaries become wider and open up

• all the above provides bandwidth to allow for full blood oxygen to occur

How much blood passes thru the alveolar capillaries?

98%

what is shunt flow? partial pressure of O2 there?

blood bypassing the gas exchange areas

• P O2 of 40 mmHg

describe graph

Venous admixture of blood causes PO2 to fall to 95 mmHg

How does interstitial PO2 increase?

blood flow

explain this

• 40 mmHg → 60 mmHg needs 400x blood flow (A →B, red line)

• Conversely, if blood flow decreases, PO2 decreases (C) • Increasing tissue metabolism decreases interstitial PO2

why is intracellular P O2 variable? whats the intracellular P O2 range then?

• because of the distance between capillaries and tissues

• ranges from 5-40 mmHg, averaging 23 mmHg

  • 1-3 mmHg needed for full support of chemical processes

Diffusion of CO2

• directly opposite of O2 diffusion

• only difference is that CO2 can diffuse

Effect of Tissue Metabolism and Tissue Blood Flow Rate on Interstitial PCO 2

• Tissue capillary blood flow and tissue metabolism affect the PCO2 in ways exactly opposite to their effect on tissue PO2

• Specific highlights:

  • 25% decrease in blood flow (A →B) results in 15 mmHg elevation of PCO2

  • Increasing blood flow 6x (A→C) reduces PCO2 to 40 mmHg

  • 10x increase in metabolism elevates interstitial PCO2 at all rates of blood flow

how is oxygen transported under normal circumstances

• 97% of oxygen is transported by chemical combination with hemoglobin in RBC’s

• 
  

function of RBC

• Primary function is to transport hemoglobin

  • Some animals and invertebrates use free hemoglobin

  • 4 Heme chains → iron + 4 pyrrole rings

• Carbonic anhydrase

• Diameter averages 7.8 um, thickness 2.3 um but 1 um in middle

  • Highly deformable

• Iron oxidation state

  • Ferrous state (Fe2+)

what happens when PO2 is high?

oxygen binds to heme and vise versa- when PO2 is low, oxygen is released

• 1.34 mL of O2/1 gram of hemoglobin

hemoglobin’s relationship

loosely bond

• reversible

percent saturation of hemoglobin

• 97% leaving the lungs

• 76% returning from tissue

• 
  

utilization coefficient

• percentage of the blood that gives up its O2 as it passes through the tissue capillaries

• Normal value = 25% •

• can go up to 75-85%

what causes the graph to shift to the right and down? what does it mean?

• increased H+, CO2, temp, BPG (upregulated with high altitude, chronic hypoxia/anemia, pregnancy)

• means more O2 is offloaded given the same PO2

hemoglobin as a buffer

• is a tissue oxygen buffer

• during heavy exercise, extra amounts of O2 (up to 20x) must be delivered from hemoglobin to tissues, but van be achieved with little decrease in tissue PO2 bc steep disassociation curve

• Thus, a very small fall in PO 2 causes large amounts of extra O2 to be released from hemoglobin. Hemoglobin in the blood automatically delivers O2 to the tissues at a pressure that is held rather tightly between about 15 and 40 mm Hg.

• Consequently, the level of alveolar O2 may vary greatly, from 60 to more than 500 mm Hg PO 2, and still the PO 2 in the peripheral tissues does not vary more than a few milliliters from normal, demonstrating the tissue “oxygen buffer” function of the blood hemoglobin system

• high PO2= hemoglobin holds o2

• low Po2= hemoglobin lets go of PO2

In a normal resting pulmonary capillary, how long will it take for the blood to be saturated with oxygen?

33%

50 %

75%

All the way thru

33%

Why does the systemic PO2 average 95 mmHg and not the 104 mmHg of atmospheric air?

Diffusion distance is too small

Surface area is too large

Blood flow is too slow thru capillaries

Systemic blood is a venous admixture

• Systemic blood is a venous admixture

What is typical venous PO2 in a dog? •

04 mmHg

95 mmHg

40 mmHg

15 mmHg

• 40 mmHg

CO2 does not need the partial pressure differences of O2 because it diffuse faster

True

False

Capillary osmotic pressure

A and B

True

What is the effect of increased blood flow on PCO2 in interstitial fluid? -

• Increases it

• Decreases it

• Doesn’t change it

• Not enough information given

• Decreases it

What are the function(s) of RBC’s?

Transport hemoglobin

Enzymatic action of carbonic anhydrase

Serve as immune cells

A and B

A and B

Given a PO2 of 40 mmHg, what would oxygen saturation be?

90%

75%

20%

None of the above

75%

An animal is heavily exercising but cannot increase their blood flow to those muscles. Assuming everything else is healthy, which statement is correct?

• Oxygen delivery would decrease without increased blood flow

• Hemoglobin saturation would remain the same

• The fall in interstitial PO2 would cause increased offloading of oxygen from hemoglobin

• All of the above

The fall in interstitial PO2 would cause increased offloading of oxygen from hemoglobin

What are the force(s) that cause a rightward and downward shift of the hemoglobin/oxygen dissociation curve?

Increased H+

Increased BPG

Increased CO2

Decreased Temperature

• everything except Decreased Temperature

Hemoglobin does not act a buffer, which we can derive as the variation in alveolar PO2 is mimicked in the PO2 of the tissues.

True • False

F

interpret

Movement of Carbon Dioxide – RBC’s

• Co2 can typically be transported in far greater quantities than O2

• Under normal resting conditions, an average of 4 ml of CO 2 are transported from the tissues to the lungs in each 100 ml of blood.

• Steps of CO2 removal from tissue

  • Dissolves easily in molecular form from cells

  • Upon entering capillaries, most of carbon dioxide undergoes instantaneous physical and chemical reactions

Acetazolamide

is a diuretic and antiglaucoma agent

• t is also a carbonic anhydrase inhibitor

• Can lead to hyperchloremic metabolic acidosis and potential acidemia in dogs

Movement of Carbon Dioxide – Carbaminohemoglobin

• In addition to reacting with water, CO2 reacts directly with amine radicals of the hemoglobin molecule

  • Forms carbaminohemoglobin (CO2Hgb)

  • A small amount of CO2 also reacts in the same way with the plasma proteins in tissue capillaries.

• Taken together, the RBC’s are generally responsible for CO2 transport, with 70% being via carbonic anhydrase and 23% being Hb itself (bottom right of figure)

interpret

haldane effect

• reverse of bohr effect (where increasing CO2 in blood displaces O2 from hemoglobin)

• The binding of O2 with hemoglobin tends to displace CO2 from the blood

• occurring in the lungs

• 
  

interpret this

respiratory exchange ratio

• The ratio of CO2 output to O2 uptake

  • aka RER

    • changes under metabolism conditions

    • carbs drive RER toward 1

    • fats drive RER toward 0.7

Diffusion limited

cells are rarely more than 50 um from a capillary to avoid this condition, usually occurs in pathological states

Blood-flow limited

if blood flow rate falls to zero, available o2 also falls to zero

interpret

Displacement of Oxygen from Hemoglobin – Carbon Monoxide: Interpret

What is the rate limiting step in healthy animals for rate of oxygen usage?

ATP

ADP

AMP

Carbonic anhydrase

ADP

Why does carbon monoxide displace oxygen from hemoglobin? •

Higher affinity

Loosens oxygen bonds to hemoglobin

Binds to a different binding site than oxygen

All of the above

• Higher affinity

What is the primary mechanism whereby carbon dioxide is transported?

Dissolved in molecular form

Converted by carbonic anhydrase

Bound to hemoglobin

None of the above

• Converted by carbonic anhydrase

What is the term used to describe that binding of O2 with hemoglobin tends to displace CO2 from the blood?

Bohr Effect

Boring effect

Haldane Effect

Shunt effect

• Haldane Effect