Lecture 16 - Respiratory Physiology I Volumes and pressures Flashcards Preview

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Flashcards in Lecture 16 - Respiratory Physiology I Volumes and pressures Deck (47):
1

What is the main function of the respiratory system?

 

Provide oxygen and remove carbon dioxide

 

2

What are the steps in respiration ?

 

1.    Ventilation: Exchange of air

between atmosphere and alveoli

2.    Exchange of O2 and CO2 between alveolar air and blood in lung capillaries by diffusion

3.    Transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow

4.    Exchange of O2 and CO2 between blood in tissue capillaries and cells in tissues by diffusion

5.    Cellular utilization of O2 and production of CO2

 

 

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3

How many lobes do the lungs have ?

 

 

Right lung has 3 lobes and left lung has 2, each can function independently

 

 

4

What are the two groups of the respiratory tract, and which parts are in them?

 

Upper respiratory tract:

Nasal cavity

Nostril

Mouth

Pharynx

Larynx

Lower respiratory tract:

Trachea

Right main bronchus 

Right lung

Left main bronchus

Left lung

Diaphragm

 

 

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5

What are the functions of the upper respiratory tract

 

Filtration

An important defence mechanism against infection with 10-15,000L of air passing through the nose/day.

Inhaled particles are trapped by hair and mucus in nasal passages.

Particles activate irritant receptors triggering sneezing reflex.

Excess mucus also passes back to pharynx to be removed by swallowing, or is expulsed through nose.

Conditioning of air

Air passing through nasal cavity is warmed and humidified. This is necessary for optimal gas exchange in the alveoli. Nasal passages have a rich blood supply for this purpose

Speech

Larynx contains vocal cords: two folds of elastic tissue stretched across its lumen. These vibrate as air flows across them, producing sound.

 

 

 

6

How much air passes through the nose each day?

 

10 - 15,000 L

 

7

What are the two zones of the lower respiratory tract and what are their functions ?

 

The lower respiratory tract is divided into the conducting zone and the respiratory zone.

Conducting zone:

Provides a low-resistance pathway for airflow. Resistance is physiologically regulated by changes in contraction of bronchiolar smooth muscle and by physical forces acting upon the airways.

Defends against microbes, toxic chemicals, and other foreign matter. Cilia, mucus, and macrophages perform this function.

Warms and moistens the air.

Phonates (vocal cords)

 

Trachea and bronchi:

Low resistance pathway for air flow.

C-shaped bands of rigid cartilage keep airways open.

Trachealis muscle spans gaps between ends of cartilage bands. Contracts to aid expulsion of blockages, eg. coughing reflex

 

Bronchioles:

No cartilage.

Smooth muscle bundles. Normally relaxed, allowing air to reach alveoli.

Contraction prevents irritants and particles from entering alveoli.

 

Respiratory zone: 

Respiratory bronchioles:

Minimal actual gaseous exchange. They branch into individual alveoli or alveolar ducts.

 

Alveolar ducts and alveolar sacs (~50 alveoli in each sac):

Site of gaseous exchange. Extensive blood supply, surrounded by capillaries.

 

 

 

 

 

 

8

What are the two types of pneumocytes(alveolar cells)?

 

Type I and Type II

Type I:

Flattened epithelium (gaseous exchange)

Type II:

Thicker cells (secrete surfactant)

 

9

Pores ?

 

gaps between alveoli. Allow entry of air even if duct is blocked and equalise pressure.

 

10

Lungs contain ~300x106 alveoli what are their diameter?

 

~0.2mm

 

Very high surface area of ~85m2 and very thin walls of ~0.2µm, maximises gaseous exchange.

 

11

Summary of Functions of the Lungs?

 

Provides oxygen & removes carbon dioxide

Form speech sounds (phonation)

Protection from microbes & other foreign matter

 

Regulates blood hydrogen ion concentration (pH)

 

Removal of micro-thrombi arising in systemic veins

 

Removal or deactivation of circulating vasoactive hormones

5-hydroxytryptamine (serotonin)

bradykinin

noradrenaline

prostaglandins

 

Activation of angiotensin II:

Angiotensin converting enzyme (ACE) on surface of pulmonary endothelium converts angiotensin I into angiotensin II.

Angiotensin II = vasoconstrictor, triggers release of aldosterone from adrenal cortex

 

 

12

In normal steady quiet breathing, the volume of air inspired is

equal to the volume expired. What is this called and what is the volume?

 
 

It's called the Tidal volume (VT)

500 mL

 

Lung volumes vary between individuals: Influenced by age, gender and height.

Values quoted here are for an average young adult male

 
 

13

What is the maximum amount that lung volume can be increased above Vcalled? and what is the volume ?

 
 

Inspiratory Reserve Volume (IRV).

3000 mL

 

Lung volumes vary between individuals: Influenced by age, gender and height.


Values quoted here are for an average young adult male
 

14

After expiring VT, a further maximal exertion of the expiratory muscles a further volume can be expired. What is this called and what is the volume ?

 
 

This is the Expiratory Reserve Volume (ERV).

1200mL

 

Lung volumes vary between individuals: Influenced by age, gender and height.


Values quoted here are for an average young adult male
 

15

Even after maximal expiratory effort, the lungs cannot be completely emptied, a sizeable volume always remains. What is this called and what is the volume?

 

This the Residual Volume (RV).

1200 mL

 

Lung volumes vary between individuals: Influenced by age, gender and height.


Values quoted here are for an average young adult male

 

16

What is the sum of Inspiratory Reserve Volume (IRV) and Tidal Volume (VT) called ?

 
 

Inspiratory Capacity (IC)

 

 
 

17

The sum of two or more ‘volumes’ are known as ??

 

‘Capacities’

 

18

What is the sum of The sum of IRV+VT+ERV called?

 

The Vital Capacity (VC).

 

19

What is the sum of ERV+RV called?

 

the Functional Residual Capacity (FRC).

 

20

What is the sum of all four volumes (IRV+VT+ERV+RV) called?

 

The Total Lung Capacity (TLC).

 

21

 

 

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Inspiratory reserve volume

 

22

 

 

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Tidal volume

 

23

 

 

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Expiratory reserve volume 

 

24

 

 

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Residual volume

 

25

 

 

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Functional residual capacity

 

26

 

 

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Vital capacity

 

27

 

 

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Inspiratory capacity

 

28

 

 

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Total lung capacity 

 

29

Exchange of air between atmosphere and the alveoli??

 

Ventilation

 

30

Total ventilation per minute?

 

Minute Ventilation (VE).  

 

31

Volume of fresh air reaching alveoli per minute?

 

Alveolar Ventilation (VA).

 

 

32

How is minute ventilation (VE) calculated?

 

If respiratory rate (R) = 12 breaths/min and tidal volume (V ) = 500ml.

Then: VE = 500 x 12 = 6000 ml/min, or 6.0 L/min.

 

 

33

Is VA different from VE?

 

Yes, because gaseous exchange occurs primarily in alveoli and minimally in respiratory bronchioles, while pharynx and conducting zone of lower respiratory tract do not contribute at all to this.

 

The volume from the top of the pharynx down to terminal bronchioles is known as the Anatomical Dead Space.

 

 

 

In adults this is fixed and is ~150 ml.

 

34

150 ml of air remains in conducting zone from previous breath.

Of the 500 ml tidal volume, 350 ml will reach the alveoli for gaseous exchange, while 150 ml will remain in the conducting zone and not be absorbed.

How do you calculate VA?

 

Alveolar vent. (VA) = minute vent. (VE) - dead space vent.

= (500 x 12) – (150 x 12) = 4200 ml/min

 

 

35

Although anatomical dead space is fixed, Physiological Dead Space is not, how does this work ?

 

In healthy lungs: Anatomical Dead Space = Physiological Dead Space.

However, If some alveoli are poorly perfused, then no gas exchange occurs in those areas.

This is the Alveolar Dead Space.

Physiological Dead Space = Anatomical Dead Space + Alveolar

Dead Space

 

 

36

How does ventilation occur ?

 

Air moves from a region of high pressure to a region of low pressure. This can be defined by the equation

Flow (F) = difference of pressure ∆P or P1-P2 / Resistance R (to the flow)

In ventilation, important pressures are atmospheric pressure (Patm) and alveolar pressure (Palv)

F = Palv – Patm / R

Movement of air into and out of lungs occurs when Palv becomes smaller or larger than Patm, respectively

So, in between breaths, when Palv is the same as Patm, there is no flow of air.

 

 

37

Boyles law?

 

The pressure (P) of a fixed amount of a gas (at a constant temperature) is inversely proportional to the volume (V) of the container in which it is placed.

 

P1V1=P2V2

 

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38

At __________ (end of normal breath out), all respiratory muscles are relaxed and __________ is balanced by ________ of chest wall.

 

At Functional Residual Capacity (end of normal breath out), all respiratory muscles are relaxed and inward recoil of lungs is balanced by outward recoil of chest wall.

 

39

What is the difference between alveolar pressure and intrapleural pressure (PIP)?

 
 

Transpulmonary pressure (PTP).

PTP = Palv – PIP

 
 

40

Sequence of events in inspiration?

 

Nerves stimulate diaphragm and other inspiratory muscles to contract, expanding the chest wall

¯

Intrapleural pressure falls – (becomes more negative -0.7 kPa)

¯

Alveoli are expanded (due to increased PTP causing increased pressure gradient across alveoli)

¯

Pressure in Alveoli falls (Boyles Law)

¯

Air drawn into lungs (increased pressure gradient from mouth to alveoli)

 

41

Sequence of events in normal expiration?

 

Nerves decrease firing to diaphragm and intercostals, muscles relax

¯

Expanded chest wall recoils inward

¯

Intrapleural (PIP) pressure goes back towards pre-inspiration level

Transpulmonary pressure decreases to pre-inspiration level

¯

Expanded lungs which have a greater elastic recoil, reduce in size

¯

Air in alveoli gets compressed (Boyles Law)

¯

Air flows out of lungs

 

In forced expiration or high ventilation: abdominal muscles increase recoil of diaphragm and speed shrinkage of chest wall and lungs. INTRAPLEURAL PRESSURE MAY BE POSITIVE.

 

 

42

Volume/pressure relationships during breathing?

 

1. Palv = Patm and there is no airflow

2. Mid-inspiration. Expanding chest wall lowers PIP, making PTP more positive (Palv - PIP). This expands the lung, making Palv negative and results in inward airflow

3. End of inspiration. Chest wall no longer expanding, but has yet to passively recoil. Palv = Patm and there is no airflow

4. Mid-expiration. Lung is collapsing, compressing alveolar gas. So Palv becomes positive relative to Patm, causing outward airflow

1 . Cycle starts over again

 

 

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43

Dry air = mixture of gases, primarily N2 and O2. What are the fractional concentrations?

 

FN2 + inert gases = ~0.79 (79%)

FO2 = ~0.21 (21%)

FCO2 = <0.0004 (0.04%)

 

Humidified Air: presence of water vapour alters relative

concentrations of other gases

 

44

Pressure exerted by a gas is directly proportional to ??

 

Temperature + number of gas molecules in a given volume (concentration)

 

 

 

45

In dry air, if Patm = 101.3 kPa and FO2 is 0.21

what is PO2 ?

 

 PO2 = 101.3 x 0.21 = 21.2 kPa

 

46

In aerobic respiration, cells require O2 and produce CO2

O2 must be absorbed from the air and transported to cells

CO2 must transported from cells and released into the air

At rest:

250 ml O2 is consumed by tissues per min

so 250ml O2 is extracted from blood per min

 

200 ml CO2 is produced by tissues per min

so 200ml CO2 is expired in lungs per min

 

Why are the volumes different ??

 

 

Oxidation of organic fuel produces H2O as well as CO2

CO2 produced/O2 consumed = respiratory quotient = 0.8

 

 

 

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