Respiratory System Flashcards
Describe the role of upper airways in air conditioning
Upperairways: nasal passages, mouth, pharynx, larynx
key role of upper airway mucosal lining
- conditioning inhaled gasses (warming. humidifying, and filtering air)
Distinguish between conducting and respiratory zones of the Tracheobrchonial Tree (TBT)
Conducting zone:
- trachea, main bronchus, bronchiole, terminal bronchiole
- mvmt of air = bulk flow
- requires ATP (respiratory muscle contraction creates pressure difference between airway and atmosphere to result in air flow)
Respiratory zone
- respiratory bronchiole, alveoloar duct, alveolar sac
- mvmt of air = diffusion
- air flow is result of partial pressure gradient of individual gases
Specify the structural changes in the airway from the trachea to the alveoli (2)
- decreases in epithelial height
- loss of cartilage, smooth muscle, mucous glands
Describe the structure and function of the alveolar cell types and the composition of pulmonary surfactant
- Type I Pneumocyte
- flat, squamous epithilum (fried egg whites) and thick nucleus center (fried egg yolk)
- covers 95% of alveolar surface area(80 - 200 m^2)
- thin 0.1 to 0.3 microns in width
- Type II Pneumocyte / Granular pneumocyte
- cuboidal shape
contains lamellar inclusion bodies that store pulmonary surfactant
Pulmonary surfactant
- mixture of lipids and proteins that reduces alveolar surface tension
- Alveolar Macrophage (dust cell)
- migratory and phagoxytic (defends against foreign invaders)
Describe airway clearance mechanisms and provide examples of their impairment
- Particles > 10 um in diameter
- filter and trap via nasal hairs
- irritant receptors lining nasal passages initiate squeeze reflex –> removes particles - Particles 2 - 10 um in diameter
- mucociliary clearnace (MCC) system lining airways proximal to terminal bronchioles
- irritant receptors in airway lining –> initiate cough reflex - Particles < 2um diameter
- migrating and phagocytic macrophages engulf particles and degrade them
- non-degradable particles w/ sharp profiles can injudry teh alvolar epithelium and alvolar macrophages –> inflammation, scar formation / pulmonary fibrosis
Outline the elastic recoil properties of the lungs and the chest wall at FRC
FRC –> (end of quiet breath) = functional residual capacity / FRC
outward recoil of chest wall is equal in mag but opp in dir to inward recoil of lungs
Explain the mechanism behind the changes in alveolar and intra-plerual pressures, airflow, and lung volume during a normal quiet breath
Inspiration
- inspiratory muscles contract (active process)
- chest wall expands (thoracic volume increases and intra-thoracic pressure decreases)
- Ppl (decreases by 3cm H2O)
- Pa (decreases by 1cm H2O) - air flows into lungs (atmospheric pressure > alveolar pressure)
Exhalation
- inspiratory muscles stop contracting (passive)
- lungs recoil inward (reduces thoracic volume and increases intra-throacic pressure)
- Ppl increases
- Pa increases - air flows out of lungs (alveolar pressure > atmospheric pressure)
Describe the 4 static lung volumes, their relationship to the 4 lung capacities, and the key factors that impact them
Static lung volumes
1. Inspiratory reserve volume (IRV)
2. Tidal volume (VT)
3. Expiratory Reserve volume (ERV)
4. Residual volume (RV)
Lung capacities
1. Total lung capacity
- sum of all static lung volumes
- Inspiratory Capacity
- sum of IRV and VT - Functional residual capacity
- sum of ERV and RV - Vital Capacity
sum of IRV, VT, and ERV
Explain the use of forced VC maneuver in diagnosising obstructive and restrictive ventilatory defects
FEV = forced expiratory volume
FVC = forced vital capacity
Obstructive defects
- FEV / FVC is decreased
Restrictived defects
- FEV / FVC is increased
Dscribe the role of ventilation-perfusion mismatch/inequality on partial pressure of respiratory gases in the arterial blood
Key concept:
- alveolar ventilation and perfusion must match to control the partial pressures of O2 and CO2 in arterial blood
Result:
- gas exchange occurs such that the PO2 and PCO2 at the capillary blood are in equilibrium with the PO2 and PCO2 in the alvoli
Specify the partial pressures of O2 and CO2 in the arterial and mixed venous blood and determine the drive pressure (pressure gradient) for their diffusion at the lungs and tissues
Across pulmonary capillaries
PO2 gradient (avloli to blood) = 60 mmHg
PCO2 gradient (blood to alvoli) = 6 mmHg
Across tissue capillaries
PO2 gradient (blood to tissue) = 60 mmHg
PCO2 gradient (tissue to blood) = 6 mmHg
Define pulmonary transit time (PTT)
PTT (pulmonary transit time) is the time it takes for blood to go through the alveolar-capillary system
Explain why gas exchange is complete during PTT in healthy individuals at rest and in exercise
PTT takes 3/4 sec
but gas exchange only needs 1/4 sec
therefore, even in exercise, gas exchange is complete
Explain why gas exchange is incomplete, resulting in hypoxemia in elite athletes during intense exercise and in patients when pulmonary fibrosis during exercise
PTT can be < 1/4 sec
- due to intense exercise and high cardiac output
Results in hypoxemia
- due to inadequate oxygen exchange at lungs and low artieral PO2
Explain the regional difference in ventilation (V) and perfusion (Q) in the lungs
The different V/Q ratios
- “shunt like” V/Q ratio = 0
- no transport of gases - Ideal V/Q ratio = 1
- Dead space V/Q ratio = inf
- no blood flow
Ventilation regional differences
1. top of lungs
- more neg intrapleural pressure
- large, less compliant alveoli
- less ventilation
- bottom of lungs
- less neg intrapleural pressure
- small, more compliant alveoli
- greater ventilation
Perfusion regional differences
1. Top of lungs
- low intravascular pressure (pleural pressure > arterial pressure > venous pressure)
- higher resistance / less blood flow
- middle of lungs
(arterial pressure > pleural pressure > venous pressure) - Bottom of lungs
- greater intravascular pressure (arterial pressure > venous pressure > pleural pressure)
- lower resistance / greater blood flow
Summary:
- both V and Q increase as you go down the lung
- but V/Q decreases as you go down the lung b/c Q increases more than V
Explain how surface area and thickness impact gas exchange
Improved gas exchange:
- increase surface area (of both alveoli and capillaries)
- decrease alveolar thickness
Decreased gas exchange
- destruction of alveolar walls –> increased lung compliance and decreases area for gas exchange (emphysema)
- collagen deposition in alveolar walls –> decreased lung compliance and increased thickness (pulmonary fibrosis)
