2- Pulmonary Physiology

What is the goal of breathing?

Gas exchange

Key components of the respiratory system

1.) An air pump

2.) O2 and CO2 carriage in blood

3.) A surface for gas exchange

4.) A circulatory system

5.) A mechanism for regulating ventilation and perfusion

6.) A mechanism for centrally regulating ventilation

Upper airway consists of ____________

nose, mouth, pharynx, larynx

Nose does what?

warm and moisturize air and filter large particles

Pharynx

throat; passageway for food to the esophagus and air to the larynx

Larynx

voice box, Closes airway, Helps generate an effective cough, Makes speech possible

path of respiratory tract (lower airway)

trachea, mainstem bronchi, lobar bronchus, bronchioles, alveoli

Trachea

The windpipe; a passage through which air moves in the respiratory system.

Conduction zone

called conducting airways because they conduct air from outside to inside

Respiratory zone

-Site of gas exchange in lungs

-after the 16th generation, airways perform respiration, where gas exchange occurs

Right upper lobe of the lung begins __________

above the clavicle and extends to the fourth rib

right middle lobe of lung is where?

between 4th and 6th ribs

Type I pneumocytes

thin alveolar cells that are adapted to carry out gas exchange

Type II pneumocytes

Cells producing surfactant in alveoli

Where does gas exchange occur through?

Blood-air barrier

Alveolar ducts have __________ but alveolar sacs don’t

Smooth muscle cells

Surfactant

chemical in the lungs to maintain the surface tension of the alveoli and keep them from collapsing

Pleurae

double-layered serosal membrane that divides thoracic cavity into two pleural compartments and mediastinum

Visceral pleura

Covers the surface of each lung, is inseparable from the lung tissue

Parietal pleura does what?

Covers the inner surface of the chest’s wall and exposed portion of the diaphragm

Pleural space

The potential space between the parietal pleura and the visceral pleura. It is described as "potential" because under normal conditions, the space does not exist.

Ventilation

movement of air in and out of the lungs

Volume

Some measurable amount of air

Capacity

Two or more volumes combined

Inspiratory reserve volume (IRV)

Amount of air that can be forcefully inhaled after a normal tidal volume inhalation

Expiratory Reserve Volume (ERV)

Amount of air that can be forcefully exhaled after a normal tidal volume exhalation

Residual Volume (RV)

Amount of air remaining in the lungs after a forced exhalation

Total Lung Capacity (TLC)

maximum amount of air contained in lungs after a maximum inspiratory effort

Inspiratory Capacity (IC)

-TV + IRV

-maximal volume of air that can be inhaled

Functional residual capacity

-ERV + RV

-volume of air remaining in the lungs after a normal tidal volume expiration

Vital Capacity (VC)

-Sum of volume of air that can be inhaled and exhaled

-TV + IRV + ERV

Major difference between standing and supine is a change in _______

FRC

Factors that volume is dependent on

1. Mechanics of lungs and chest wall

2. Activity of inspiration and expiration

3. Size of lungs

4. Height, weight, body surface area

5. Age and sex

Minute Ventilation (VE)

Volume of air inspired or expired per minute

Dead space ventilation

-volume of air that DOES NOT reach the alveoli per minute

-Where there is no gas exchange

-Volume of air that is wasted ventilating dead space

Alveolar ventilation (VA)

Volume of air that reaches the alveoli and participates in gas exchange per unit of time

Tidal volume =

dead space volume + alveolar volume

Physiologic dead space

-portion of the tracheobronchial tree that doesn’t participate in gas exchange

-anatomical dead space + alveolar dead space

-the volume of gas that doesn’t eliminate CO2

Alveolar dead space is __________ but unperfused alveoli

Ventilated

Bohr's method

expired CO2 comes from alveolar gas and not dead space

Should physiologic dead space equal anatomic dead space?

yes

More dead space = _________

Less gas exchange

Is ventilation evenly distributed in the lungs?

no

Diffusion

Movement of molecules from an area of higher concentration to lower concentration

Gases move by _______ then diffusion

Mass flow

Fick's Law of Diffusion

-The rate of transfer of gas through a sheet of tissue is proportional to the surface area and the difference in gas partial pressure between the two sides

-the rate is inversely proportional to tissue thickness

Diffusing capacity

-measurement of CO2, oxygen, or nitric oxide transfer from inspired gas to pulmonary capillary blood
-reflective of the volume of a gas that diffuses through the alveolar capillary membrane each minute