1 - The Organization of the Respiratory System and Principles of Ventilation

Cellular respiration Definition

Intracellular metabolic processes that uses O2 and produces CO2

External respiration (pulmonary physiology) Definition

All the events involved in the exchange of O2 and CO2 between the external environment and tissues

Parts of Upper airways or respiratory tract

Larynx and above (nose, nasal cavity, pharynx, larynx)

Parts of Lower airways or respiratory tract

Trachea and below

Two sections of the respiratory tract

1. Conducting zone

2. Respiratory zone

Parts of the conducting zone

Trachea to terminal bronchioles

Parts of respiratory zone

Respiratory bronchioles to alveolar sacs

Function of respiratory zone

Have at least one alveolus on the wall

Gas exchange

What are the functions of the conducting zone

• Conduit for air movement

• Humidify the air

• Warm the air

• Remove particulate material

Components of the respiratory epithelium (6)

• Periciliary fluid layer (Watery fluid)

• Lumen

• Epithelial cell

• Cilia

• Goblet cell

• Mucus layer

How does the conducting zone of the lower respiratory tract (and the nasal cavity) help remove inhaled particulate material (dust, pollutants, microbes, etc)?

Mucus traps foreign particles

Cilia beat and move the mucus and trapped particles toward the throat

What happens to any particulate material that escapes being cleared by the respiratory epithelium and gets into the alveoli?

Phagocytosed by macrophages in the alveoli

Alveolar sacs are in which part of the respiratory tract?

A. Conducting zone of the upper respiratory tract

B. Conducting zone of the lower respiratory tract

C. Respiratory zone of the upper respiratory tract

D. Respiratory zone of the lower respiratory tract

D. Respiratory zone of the lower respiratory tract

Cystic fibrosis is caused by mutations in a Cl- channel that results in a decreased ability to secrete Cl-, which enhances Na+ and water absorption by airway epithelial cells, causing a reduction in the volume of periciliary fluid. This will most likely cause: (pick 2)

A. A more watery mucus layer

B. A more viscous mucus layer

C. Reduced mucociliary transport

D. Enhanced mucociliary transport

B. A more viscous mucus layer

C. Reduced mucociliary transport

A smoker develops a lower respiratory tract infection and has been coughing up mucus. What put him at risk for this infection?

A. Recruitment and increased activity of lung macrophages

B. Decreased mucus production

C. Increased activity (more contraction) of bronchiolar smooth muscle

D. Paralysis or decreased activity of the cilia in the respiratory epithelium

E. Increased production of watery fluids by the respiratory epithelium

D. Paralysis or decreased activity of the cilia in the respiratory epithelium

What aspect of an alveoli facilitates gas exchange? (2)

• Thin wall

• Alveoli are close to the capillaries

Type I and Type II cells

• Type I cell - Makes up most of the alveolar wall

• Type II cell - Produce surfactant

Functions of the intrapleural fluid (3)

1. Lubrication

2. Holds the parietal and visceral pleural membranes together

3. It has an intrapleural pressure (Pip) which is needed for ventilation

What are the 2 phases of ventilation or breathing?

Inspiration and expiration

What causes air to flow into and out of the lungs?

Pressure gradient

What prevents or resists flow?

Resistance of conducting airways

What is the Flow formula for airflow?

Flow = (Palv-Patm)/R

(Palv-Patm) = Pressure gradient

Patm value

Atmospheric pressure (760 mm Hg at sea level, but we will set it at zero)

Fill out the table

Ptp equation

Pressure difference between the alveolus and intrapleural fluid

Ptp= Palv - Pip

Pip definition

Pip - Elastic recoil of the lung and chest wall

Ptp relationship to elastic recoil

Ptp is equal and opposite to the elastic recoil of the lungs

Before insp (Ptp= Palv - Pip)

4 = 0 - -4

If just Pip changes (Ptp= Palv - Pip)

5 = 0 - -5

If both Palv and Pip changes (Ptp= Palv - Pip)

5 = -1 - -6

What happens with a pneumothorax/ collapsed lung

• If the pleura is punctured, air can enter the pleural cavity.

• The pressure in the pleural cavity will then be equal to atmospheric pressure (Pip will be 0)

• Transpulmonary pressure will then be 0

• There isn’t anything to oppose the elastic recoil of the alveoli and they collapse

In order for inspiration and expiration to occur, the volume of the thoracic cavity needs to change. What causes this change in volume?

Muscle contraction and relaxation

muscles of inspiration

Diaphragm

More muscles recruited during labored breathing

Muscles of expiration

Only used during forced expirations (labored breathing)

How does muscle contraction during inspiration affect the size (i.e. volume) of the thoracic cavity, and how does this affect Pip?

Contraction of inspiratory muscles causes:

• Volume of thoracic cavity will increase

• Pip will be More negative (Creating a larger vacuum)

During inspiration (mid inspiration), how does the change in Pip, affect Ptp, and lung or alveolar volume?

Pip is more negative

Ptp increases (Greater than elastic recoil)

Alveolar volume increases

During inspiration (mid inspiration), if alveolar volume increases, what happens to Palv?

Palv more negative (or < 0

During inspiration (mid inspiration), what happens to air?

Flows from an area of higher pressure (atmospheric pressure outside the body) to an area of lower pressure (alveolar pressure)

DRAW THIS OUT using numbers

What happens to Pip, Ptp, alveolar volume and Palv during expiration (mid expiration)?

Pip becomes less negative

Ptp decreases

Alveolar volume decreases

Palv increases

Air flows out (From high to low pressure)

Take home message: When breathing in (mid inspiration)

Thoracic cavity and alveoli get bigger

Both Pip and Palv become more negative (same direction)

Take home message: When breathing out (mid expiration)

Thoracic cavity and alveoli get smaller

Both Pip and Palv become more positive (same direction)

Pressure at the end of an unforced expiration

• Air movement

• Alveolar pressure

No movement of air

Alveolar pressure = atmospheric pressure

Pressure During inspiration when Inspiratory muscles contract (7)

1. Diaphragm

2. Ribs

3. Thorax

4. Alveolar volume

5. Alveolar pressure

6. Air movement

1. Diaphragm moves down to make chest cavity bigger

2. Ribs move up and out

3. Thorax expands (more of a vacuum = decreased Pip)

4. Alveolar volume increases

5. Alveolar pressure is less than atmospheric pressure

6. Air moves inward

Pressure at the end of inspiration

• Air movement

• Alveolar pressure

• No air movement

• Alveolar pressure = atmospheric pressure

Pressure During expiration

1. Diaphragm

2. Inspiratory muscles

3. Thorax

4. Alveolar pressure

5. Alveolar volume

6. Air movement

1. Diaphragm relaxes and moves up

2. Inspiratory muscles relax/ recoil

3. Thorax - less of a vacuum in thoracic cavity = increased IP

4. Alveolar pressure greater than atmospheric pressure

5. Alveolar volume decreases

6. Air moves outward

A person started choking and was administered the Heimlich maneuver (you do an abdominal thrust or push on their abdomen). Why did this work to expel the food out of the throat?

A. There is an increase in Palv without affecting Pip

B. Pip becomes more positive leading to a decrease in Palv

C. Pip becomes more positive leading to an increase in Palv

D. Pip becomes more negative leading to an increase in Palv

E. Pip becomes more negative leading to a decrease in Palv

C. Pip becomes more positive leading to an increase in Palv

In order for air to enter the lungs during inspiration, what needs to happen to Palv and Pip? Compared to at the end of an unforced expiration:

A. There is no change in Palv or Pip

B. Palv needs to be more positive and Pip need to be more negative

C. Palv needs to be more negative and Pip need to be more positive

D. Both Palv and Pip need to be more positive

E. Both Palv and Pip need to be more negative

E. Both Palv and Pip need to be more negative

A person has a stab wound to the chest which causes their lungs to collapse (pneumothorax). What happened to Pip?

A. Pip > 0

B. Pip < 0

C. Pip = 0

C. Pip = 0

This causes the transpulmonary pressure gradient (P tp) to be lost

Besides the transpulmonary pressure (Ptp), what else affects the change in volume (i.e. size) of the lungs or alveoli when breathing?

A. Lung compliance

B. Airway resistance

A. Lung compliance

Lung compliance definition

How well the lungs (alveoli) can stretch

change in lung volume produced by a given change in Ptp

Airway resistance defintion

Resisting flow in the tube → Viscosity of air, length of tube, radius of the tube

What 2 factors determine the compliance of the lungs?

The ability of the lung tissue to stretch

Surface tension of the liquid on the alveolar wall

What is the purpose of surfactant production?

Acts like a detergent which lowers surface tension

What is the benefit of surfactant? (2)

It increases compliance

Don’t need as great of an increase in Ptp to expand the lungs with inspiration

Benefit of surfactant when Pip decreases

Ptp increases

Alveoli stretch

Much easier to do with surfactant

Now let’s look at airway resistance. How can the body change the resistance of the airways? By changing the:

A. Size of the alveoli

B. Compliance of the alveoli

C. Viscosity of the air

D. Radius of the tube (trachea, bronchi, bronchioles)

E. Length of the tube (trachea, bronchi etc)

D. Radius of the tube (trachea, bronchi, bronchioles)

Purpose of trachea, bronchii

Cartilage keep the airways open

Purpose of bronchioles

Smooth muscle/ no cartilage
The same forces that open up alveoli, open up bronchioles!

can also contact and relax the smooth muscle

There are several hormones (e.g. epinephrine), neurotransmitters (e.g. acetylcholine), paracrine factors (e.g. histamine, leukotrienes) that affect airway resistance. For example, epinephrine decreases airway resistance by activating:

A. a1 receptors which relaxes bronchiolar smooth muscle

B. B2 receptors which contracts bronchiolar smooth muscle

C. a1 receptors which contracts bronchiolar smooth muscle

D. B2 receptors which relaxes bronchiolar smooth muscle

D. B2 receptors which relaxes bronchiolar smooth muscle

NO SYMPATHETIC INERVATION

Respiratory distress syndrome of the newborn occurs in premature infants (< 37 weeks gestation) in which the alveoli collapse. Which of the following contributes to this lung collapse?
A. Decreased lung compliance

B. Excessive production of surfactant by type II alveolar cells

C. Increased lung resistance

D. Decreased lung resistance

E. Deceased surface tension in the alveoli

A. Decreased lung compliance

What happens with less surfactant?

The force to keep alveoli open and expand the lungs during inspiration needs to be greater

Asthma is an inflammatory disease. But, during an attack, one reason why a person has difficulty breathing is because smooth muscle in the lungs is hyperactive with excessive broncho constriction. How will this affect respiration

A. Decrease lung compliance

B. Decrease airway resistance

C. Increase elastic recoil

D. Increase lung compliance

E. Increase airway resistance

E. Increase airway resistance

The increased airway resistance makes it difficult to exhale.

Draw and lable

During exercise, which of the following changes occur? (select all that are correct)

A. Tidal volume increase

B. Tidal volume stays the same

C. Inspiratory reserve volume increases

D. Inspiratory reserve volume decreases

E. Expiratory reserve volume decreases

F. Expiratory reserve volume stays the same

G. Residual volume decrease

H. Residual volume stays the same

A. Tidal volume increase

D. Inspiratory reserve volume decreases

E. Expiratory reserve volume decreases

H. Residual volume stays the same

What is vital capacity?

Maximum amount that you can expel from the respiratory tract after a maximum inspiration

How is vital capacity measured?

Inhale maximally, then exhale maximally into a spirometer as fast as possible

• Forced expiratory vital capacity (FVC)

• Forced expiratory volume in 1 second (FEV1)

What is Forced expiratory vital capacity (FVC)? What is Forced expiratory volume in 1 second (FEV1)?

How much you can inhale

How fast or easy it is to exhale

A person has muscular dystrophy where their diaphragm is weak. How will this effect their vital capacity?

C. No effect

D. Increased

E. Decreased

E. Decreased

Reduced compliance can also reduce vital capacity

A person has emphysema. (with emphysema the elastic recoil of the lungs is reduced). How will this affect their FEV1?

A. Not have any effect

B. Decreased

C. Increased

B. Decreased

FEV1 can also be reduced by asthma/ bronchoconstriction