Respiration 1

Question 1

What are the 5 stages of respiration?

Answer 1

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 utilisation of O2 and production of CO2

Question 2

What parts make up the upper and lower respiratory tract?

Answer 2

Upper: nasal cavity, nostril, mouth, pharynx, larynx
Lower: Trachea, lungs, bronchi, diaphragm

Question 3

Explain the structure of the trachea&bronchi

Bronchioles?

Answer 3

trachea&bronchi = low resistance pathway for air flow, C-shaped bands of rigid cartilage keep airways open, trachealis muscle spans between ends of cartilage bands (contracts to aid expulsion of blockages - when coughing and sneezing)

bronchioles = no cartilage, smooth muscle bundles, these are normally relaxed (allowing air to reach alveoli), contraction prevents irritants and particles from entering alveoli

Question 4

How many division are there of the bronchi in humans?

Answer 4

up to 8 divisions

Question 5

What are the conducting zones?

Answer 5

Region of the lower respiratory tract which carries air to the alveoli. It has too many layers for gas exchange to occur.

Question 6

Give features of bronchioles

Answer 6

No cartilage.
Smooth, muscle bundles - normally air to reach alveoli.
Contraction prevents irritants and particles from entering alveoli.

Question 7

What forms the respiratory zone?

Answer 7

Respiratory bronchioles
Alveolar ducts
Alveoli

Question 8

What are the functions of the lower respiratory tract?

Answer 8

Gas Exchange:

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

Alveolar duct and sacs:
Site of gaseous exchange. Extensive blood supply, surrounded by blood capillaries.

Question 9

What two things in the lungs maximise gas exchange?

Answer 9

• High surface area

- Very thin walls

Question 10

What are the two types of alveolar cells and give details on each?

Answer 10

Both pneumocytes

Type 1 flattened epithelium (for gaseous exchange)
Type 2 thicker cells (secrete surfactant).

Question 11

What is the purpose of the pores between alveoli?

Answer 11

Allow entry of air even if alveolar ducts are blocked.

Question 12

What are the 4 main functions of the lungs?

Answer 12

• Provide oxygen and remove carbon dioxide
• Form speech sounds
• Protection from microbes and other foreign matter
• Regulates blood hydrogen ion concentration

Question 13

Define each of these lung volume:

1. Tidal volume
2. Inspiratory reserve volume
3. Expiratory reserve volume
4. Residual volume

Give approx male values

Answer 13

1. In normal steady breathing, the volume of air breathed in per breath
2. Maximum amount that lung volume can be increased above tidal volume
3. A further maximal exertion of the expiratory muscles after tidal volume
4. Even after maximal expiratory effort, the volume of air left in the lungs
5. 500ml
6. 3000ml
7. 1200ml
8. 1200ml

Question 14

What is the functional residual volume?

Answer 14

What is left in the lungs after a normal breath

- expiratory reserve & residual volume

Question 15

What are lung capacities?

Give some examples of them

Answer 15

Sum of two or more volumes

Inspiratory capacity = tidal volume + inspiratory reserve
Vital capacity = inspiratory reserve volume, tidal volume, expiratory reserve
Functional Residual capacity = expiratory reserve + reserve volume

Sum of inspiratory reserve, expiratory reserve, tidal volume and residual volume = total lung capacity.

Question 16

Explain what ventilation is and hence minute ventilation calculation

How is this different from alveolar ventilation?

Answer 16

Ventilation is exchange of air between the atmosphere and the alveoli.

Minute ventilation - total ventilation per minute
This is respiratory rate X tidal volume.

Alveolar Volume = volume of fresh air reaching alveoli per minute.
This is different because gaseous exchange occurs primarily in alveoli and minimally in respiratory bronchioles, while pharynx and conducting zone do not contribute. Alveolar V will be less as less air is getting to the alveoli than is breathed in.

Question 17

What is the volume from the top of the pharynx down to the terminal bronchioles called?

What is this fixed value for humans?

Where is anatomical dead space found?

Answer 17

Anatomical dead space

150ml

Conducting zone

Question 18

Work out alveolar ventilation knowing tidal volume is 500ml and dead space is 150ml

Respiratory rate is 12

Answer 18

500-150=350ml reaching alveoli

Tidal volume = alveolar ventilation and alveolar dead space

Alveolar vent = minute ventilation - dead space ventilation

(500x12) - (150x12) = 4200ml/min

Question 19

What is alveolar dead space and hence physiological dead space?
Are they fixed?

Answer 19

Alveolar dead space = alveoli are poorly perfused with blood, then no gas exchange occurs in those areas.

Physiological dead space = anatomical dead space + alveolar dead space

Anatomical dead space is fixed (150ml) but physiological dead space is not as alveolar dead spaces changes.

Question 20

Explain how and why ventilation occurs

What is the equation for flow of air?

Answer 20

Air moves from a region of high pressure to a region of low pressure.
Flow = difference in pressure / resistance

The pressures here are atmospheric pressure - alveolar pressure (the difference between pressure inside and outside lung).

Question 21

What pressure changes causes air to move into and out of the lungs?

When is there no pressure change?

Answer 21

Atmospheric pressure is higher than alveolar pressure means airs move in.

Vice versa for air to move out.

In between breaths.

Question 22

How does Boyles law explain air flow?

Answer 22

Pressure in a gas is inversely proportional to volume.

Diaphragm goes down in inspiration, increases volume, decreasing pressure so air flows into lungs as pressure is lower in lungs.

Question 23

What is occurring in the lung at functional residual capacity?

Answer 23

at the end of normal breathing out…

respiratory muscles are relaxed and inward recoil of lungs is balanced by outward recoil of chest wall

Question 24

What are the two pressures in the lung?

What is the difference between the two?
When is this value higher?

Answer 24

Intrapleural (pressure between two membranes. This is usually slightly negative as lungs recoil inwards and chest wall recoils outwards)

Alveolar pressure

Difference: alveolar - intrapleural is called trans- pulmonary pressure.

Higher after breathing in as intrapleural pressure decreases.

Question 25

Give the 5 events in inspiration

Answer 25

1. Nerves stimulate diaphragm and other inspiratory muscles to contract, expanding the chest wall 2. Intrapleural pressure falls – (becomes more negative -0.7 kPa) 3. Alveoli are expanded (due to increased PTP causing increased pressure difference across alveoli) 4. Pressure in Alveoli falls (Boyles Law) 5. Increased pressure difference from mouth to alveoli - air flows into lungs

Question 26

What are the sequences of events in normal expiration? What happens in forced expiration?

Answer 26

1. Nerves decrease firing to diaphragm and intercostals, muscles relax 2. Expanded chest wall recoils inwards 3. Intrapleural pressure goes back towards pre-inspiration level. Transpulmonary pressure decreases to inspiration level. 4. Expanded lungs which have a greater elastic recoil, decrease in size 5. Air in alveoli gets compressed (Boyles Law) 6. Air flow out of lungs Forces expiration: abdominal muscles increases recoil of diaphragm and speed shrinkage of chest wall and lungs. Intrapleural pressure may be positive.

Question 27

What happens to the pressures during inspiration?

Answer 27

Expanding chest wall lowers intra-pleural pressure, making transpulomary pressure more positive. This expands the lung and makes alveolar pressure negative and results in inward airflow.

Question 28

What happens to the pressures during expiration? Between breaths?

Answer 28

Lung is collapsing, alveolar pressure is higher than atmospheric causing air outflow. Chest wall isnt expanding. Alveolar pressure is the same as atmospheric pressure so there is no airflow.

Question 29

What causes resistance in the upper and lower airways?

Answer 29

Upper = congestion in nose, pharynx and larynx Lower = middle order bronchi mainly cause this. Bronchioles have a smaller diameter but there are more of them so total resistance is very low.

Question 30

Explain the difference in air flow in quiet breathing and high ventilation

Answer 30

Quiet - flow is usually laminar: gas particles move parallel to the walls with a higher velocity at centre of tube High - turbulent, noisy flow

Question 31

Explain how obstructive lung disease (asthma or bronchitis) affects air flow

Answer 31

Narrowing of lumen, airway resistance increased, airflow decreased, decreased gaseous exchange Asthma: smooth muscle is hypersensitivity to constrictors, causes thickening and inflammation Chronic bronchitis: glands produce excess mucus, with inflammation

Question 32

How does resistance affect air flow? What other things affect radius of bronchi?

Answer 32

Flow = difference in pressure / resistance. Resistance is inversely proportional to the 1/r^4. Radius of tube has the most affect on resistance of the airflow. A small change in radius gives us a large change in resistance. - Chemical and neural factors (dilators and constrictors) - Physical factors. Beginning of inspiration (lateral traction exerted by connective tissue increases airway radius, aiding lung expansion). Forced expiration (dynamic compression of airways increases resistance considerably).

Question 33

What is lung compliance?

Answer 33

Change in lung volume / change in trans-pulmonary pressure. It measures how easily lungs are expanded by a given change in pressure which determines the amount of work that has to be done by reparatory muscles. Trans-pulmonary pressure cannot be measured directly. Subject needs to inhale in step and hold breath at each step and the volume each time inspired is measured.

Question 34

What determines lung compliance?

Answer 34

Forces that inspiratory muscles have to overcome to make lungs expand 1.Resistance of tissues to stretch influenced by composition of extracellular matrix. Elastin is stretchable, but requires work, collagen is not Too much = fibrosis (low compliance). (amount of elastin affecting the expansion of alveoli) Not enough = emphysema (high compliance) 2. Resistance due to Surface Tension at air/water interface in alveoli

Question 35

What does a decreased compliance suggest? Increased compliance?

Answer 35

Work of breathing increased. Suggests lung fibrosis (restrictive lung disease) Suggests lung emphysema. Tissue destruction causes alveoli to fuse forming large air-sacs. Bronchioles tens to collapse more easily upon expiration.

Question 36

How does surface tension affect lung compliance?

Answer 36

Surface tension is caused by water molecules attracting each other. Wall tension is a fixed value so if pressure changes, radius has to change also. Different alveoli have different radius and hence different pressure.

Question 37

A small alveoli next to a large one will tend to collapse. How is this prevented?

Answer 37

Surface tension is the same in both. Higher pressure in smaller one so air flow from smaller to larger will collapse smaller. Surfactant changes the surface tension so the pressure difference is normalised and air will not flow from smaller to larger alveoli, More surfactant in smaller alveoli to prevent the collapse. Tension is reduced more in smaller alveoli. Prevents the difference in pressure.

Question 38

What things can be seen in obstucture and resistive dieases?

Answer 38

Obstructive - unable to force out 75% volume but lung volume is okay. Restrictive - may force out more than 75% but unable to expand lung in all.