14. Chapter 17- Mechanics of Breathing

Question 1

What are the 4 primary functions of the respiratory system?

Answer 1

1. Exchange of gases between atmosphere and blood
2. Homeostatic regulation of body pH
3. Protection from inhaled pathogens and irritating substances
4. Vocalization

Question 2

What is the four step process of external respiration?

Answer 2

1. Exchange I - atmosphere to lung (ventilation)
2. Exchange II- lung to blood
3. Transport of gases in the blood
4. Exchange III- blood to cells
   Requires coordination between respiratory and cardiovascular systems
   Slide 6 Jan 4

Question 3

What are the 3 structures involved in ventilation and gas exchange?

Answer 3

1. Conducting system of airways
2. Alveoli
3. The bones and muscles of the thorax (chest cavity)

Slide 7 Jan 4

Question 4

What is the structure of the lungs?

What is the pleural sac and it’s two types?

Answer 4

The lungs are composed of light spongy tissue whose volume is occupied mostly by air filled spaces
Right lung is slightly larger than the left

Each lung is surrounded by s double walled pleural sac that hold lungs to thoracic wall and makes slippery surface
Visceral pleural is connected to outside surface of the lungs
Parietal pleural is connected to the inside surface of the thoracic cavity
Slides 8-9 Jan 4

Question 5

What is the pharynx, larynx, and trachea?

Answer 5

Pharynx- air enters through the nasal cavity and or the mouth
Larynx- from the pharynx air flows through these vocal cords to the trachea
Trachea- semi flexible wind pipe held open with cartilage rings

Slide 10 Jan 4

Question 6

What are the 3 roles of the upper airways and bronchi?

Answer 6

1. Warming the air to body temp
2. Adding water vapor
3. Filtering out foreign material

More efficient with nose breathing since nasal cavity has large surface area, rich blood supply and nasal hair

Air is filtered in trachea and bronchi

Question 7

How is air filtered in the trachea and bronchi?

Answer 7

Saline is produced by epithelial cells and overtop saline is a layer of mucus made by goblet cells
Mucus contains immunoglobulins
The epithelial cells also contain cilia which push the mucus towards the pharynx

Slide 12-13 Jan 4

Question 8

What are alveoli?

Answer 8

Site of gas exchange
Study picture on slide 15 Jan 4
300-600 million alveoli in adult respiratory system
Clustered at the ends of bronchioles
Study picture slide 16 Jan 4 (type I cells most common)

Question 9

How does blood go through pulmonary circulation?

How is the pressure and flow rate?

Answer 9

Deoxygenated blood returns through systemic circuit and enters right atria with low O2 but high CO2, then ventricle then is ejected through pulmonary trunk and transported to lungs where oxygen is added in alveoli
CO equal in pulmonary and systemic circuit

Low pressure due to low resistance (shirt length circuit lungs close to heart) high flow of blood

Question 10

Similarities between blood flow in cardiovascular system and air flow in the respiratory system?

Answer 10

Pressure gradients created to cause flow (flow down pressure gradients)
Both are fluids (substance that continually deforms under applied shear stress, gas/liquid)
Both measured in mmHg

Question 11

What is Dalton’s law and the equations for partial pressures and flow using alveoli pressure and atmospheric pressure?

Answer 11

Dalton’s law is the total pressure exerted by a mixture of gases is the sum of the pressure exerted by each gas
Partial pressure on S7 Jan 7

Flow=ΔP/R= Palveoli - Patm /R
R=resistance
Patm is 0 at sea level

Inspiration= lower pressure in alveoli causes air to flow down pressure gradient into cell
Expiration= increase pressure in alveoli drives air down pressure gradient out of cell

Jan 7 S8

Question 12

What is Boyle’s law?

Answer 12

P1V1=P2V2
Make container larger, makes more space to move same number of particles so ,over amount of pressure
Make container smaller, less space for particles to move and bump into each other and walls more increasing pressure
Jan 7 S9-10

Question 13

What are the 4 lung volumes?

What is total pulmonary ventilation (equation)?

Answer 13

1. Tidal volume- ~500mL total ventilation during rest is product of tidal volume and frequency of breaths (volume you breath in and out during quiet breathing)
2. Inspiratory reserve volume- ~3000mL amount of air you can inspire beyond tidal volume (max air you can inhale)
3. Expiratory reserve volume- ~1100mL the air that remains in the lungs at the end of quiet expiration that can be exhaled
4. Residual volume- ~1200mL air that always remains in the lungs even with maximal expiratory effort (prevents airway collapse and allows continuous exchange of gases) can’t measure this
   These DO NOT overlap

Total pulmonary ventilation= tidal volume x frequency of breaths

Jan 7 S12-13

Question 14

What are the 4 lung capacities?

Answer 14

1. Total lung capacity- the sum of all 4 volumes
2. Functional residual capacity- capacity of air remaining in the lungs after quiet expiration, sum of expiratory reserve volume and residual volume
3. Inspiratory capacity- sum of inspiratory reserve volume and tidal volume (max amount of air someone can inspire
4. Vital capacity- sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume (max achievable tidal volume, max you can inspire followed by max you can expire)

Question 15

Look at pulmonary function test Jan 7 S15

Answer 15

Okayyyyyyyyyy

Question 16

What causes 60-75% of inspiratory volume change?

What accounts for the rest?

Answer 16

Diaphragm contracts and flattens (for expiration it relaxes)
Jan 9 S5
movements of the rib cage accounts for the rest (25-40%)
External intercostals of upper ribs and scalenes cause pumps handle motion (for expiration these relax as well)
Jan 9 S6-8

Question 17

What are 3 additional accessory or secondary muscles that become activated during forced inspiration?

Answer 17

1. Sternocleidomastoids- lift sternum upwards, adds to water pump effect
   2- neck and back muscles- elevate pectoral girdle increasing thoracic volume and extend back
   3- upper respiratory tract muscles- decrease airway resistance

Jan 9 S9

Question 18

What a re the 3 accessory muscles of forced expiration?

Answer 18

1. Abs
2. Internal intercostals and triangularis sterni
3. Neck and back muscles
   Jan 9 S10

Question 19

Is the lungs connected to the diaphragm or thoracic wall?

Answer 19

No
Inspiratory muscles pull parietal layer of pleura away from visceral layer, increasing volume of the intrapleural cavity and decreasing intrapleural pressure

Jan 9 S11-13

Question 20

At rest what is the intrapleural pressure (negative or positive)?

Answer 20

Negative intrapleural pressure due to the elastic recoils of the lung inwards and chest wall outwards

Inspiratory muscles contract and pull pleural layers away from one another (decrease in intapleural pressure pulls alveoli open decreasing alveolar pressure and air flows in, as alveoli fill with air pressure begins to match atmospheric pressure and air flow into the alveoli stops)

Jan 9 S15

Question 21

What is pneumothorax?

What a re the 2 types?

Answer 21

Collapsed lung that is the result of an interruption of intrapleural pressure
Traumatic pneumothorax- parietal pleura
Spontaneous pneumothorax- lung and visceral pleura ruptures

Jan 9 S16

Question 22

What is lung compliance and elastance?

Answer 22

Compliance- stretchability of the lungs given any change in P 
Decreased compliance (a lot of effort to fill lungs with air) means high levels of elastance and vice versa

Elastance- reciprocal of compliance (elastic recoil is ability to resist being deformed

Scientists initially assumed elasticity of pulmonary cells and extracellular matrix determined lung compliance and lung recoil but this is only the case for diseased individuals not healthy ones

Graph on slide 3 Jan 11

Question 23

What is pulmonary fibrosis and emphysema?

Answer 23

Pulmonary fibrosis- formation or development of excess fibrous connective tissue in the lungs cause by inhilation of pollutants (metals asbestos etc)

Emphysema- reduced elasticity of the lungs caused by proteolytic enzymes secreted by leukocytes attacking alveolar tissue (results in alveolar merge which is loss of capillaries and reduction of surface area) cigarette smoking

Jan 11 S4-5

Question 24

What is surface tension in the lungs?

How is radius and inward pressure in surface tension related?

Answer 24

Determinant of compliance and major determinant of the lungs elastic recoil at the air water interface of airways
Measure of force acting to pull a liquids molecules together at an air water interface
Holds water together put pressure inward
The smaller the radius the larger the inward pressure is with surface tension

Jan 11 S8-9

Question 25

What is surfactant?

What are the 2 things it does?

Answer 25

Detergent like molecule secreted by type II alveolar cells (detergent in soap acts to break up surface tension at air water interface like surfactant)
90% phospholipids
10% protein

1. Increases compliance (reduces elasticity)
2. Ensures alveoli of all size inflate

Smaller alveoli, more surfactant and vice versa for equal inflation

Jan 11 S10-12

Question 26

What is airway resistance equation?

Answer 26

R=8nl/πr^4

F=ΔP (πr^4/8nl)

Question 27

What is bronchoconstriction/dilation?

Answer 27

Paracrine control CO2
High levels= dilation
Low levels= constriction

Histamine released from mast cells bronchoconstricts
Parasympathetic nerves innervate bronchiole smooth muscle and activate PLC-IP3 pathway via M3 muscarinic receptor
Jan 11 S15

Question 28

What is asthma?

Answer 28

Chronic inflammation of the airways, recurring and varying amounts of bronchoconstriction

Infrequent attacks β2-adrenergic agonist
Frequent attacks- weekly inhaled corticosteroid

Question 29

How is the effectiveness of ventilation determined?

Answer 29

Determined by total pulmonary ventilation: volume of air moved into and out of the lungs each minute
Normal rate: 12-20 breaths/min tidal volume:500mL
TPV=ventilation rate x tidal volume
Alveolar ventilation= ventilation rate x (tidal volume-dead space)
Jan 11 S17-19

Question 30

What determines the rate of O2 and CO2 diffusion between alveoli and capillaries?
How does PCO2 and PO2 change during quiet respiration?

Answer 30

Gas composition in the alveoli

PCO2 and PO2 remains relatively constant during quiet respiration

O2 entering=O2 uptake

Jan 14 S6 graph

Question 31

How is blood flow related to O2 pickup?

How does gravity affect it?

Answer 31

Bringing O2 from atmosphere into alveoli is only first step of external respiration
Blood flow must be high enough to pick up the available O2
More negative intrapleural pressure due to gravity at apex which means alveoli are partially open and filled even at rest and therefore do not take in much air during ventilation
Gravity causes similar regions of lung to receive matching ventilation and perfusion
Jan 14 S7

Question 32

What are the pulmonary arterioles primarily influenced by?

Answer 32

The decreasing O2 levels around them
Decreases in O2 cause constriction, opposite of systemic CV system (presence of O2 sensitive K+ channels)
Jan 14 S9

Question 33

When PCO2 and PO2 increase or decrease, do the bronchioles, pulmonary arteries, and systemic arteries constrict or dilate?

Answer 33

PCO2 increase- B- dilate PA- constrict SA- dilate
PCO2 decrease- B- constrict PA- dilate SA- constrict
PO2 increase- B- constrict PA- dilate
SA- constrict
PO2 decrease- B- dilate PA- constrict SA- dilate

PCO2 increase and PO2 decrease are same
PCO2 decrease and PO2 increase are same