Respiratory Physiology

Question 1

Outline the Processes of external respiration and specify driving pressure and physical mechanism responsible for each process

Answer 1

Steps of external respiration:

1. ventilation btw atmosphere and alveoli
2. exchange O2 and CO2 between air in alveoli and blood in pulmonary capillaries
3. transport O2 and Co2 by blood btw lungs and tissues
4. exchange O2 and CO2 btw blood in systemic capillaries and tissue cells (cellular respiration)

Direction movement = high to low pressure
bulk flow: large distances ventilation/breathing driven by air pressure gradient

Blood gas transport driven by bp gradient
Diffusion: short distances, Gas exchange driven by partial pressure gradient of gases.

Question 2

describe role of upper airways in air conditioning, airway patency, and in OSA (obstructive sleep apnea)

Answer 2

uvula: inhibit nasal regurgitation
epiglottis: direct food into esophagus
vocal chord: allow phonation, prevent aspiration food

Patency: over 20 muscles control position of tissues in upper airway. dilator muscles help keep airway open

OSA: decrease in genioglossus dilator muscle activity –> airway obstruction as tongue falls back, stops airflow

air conditioning: during inspiration, mucosal lining loses heat & moisture. during expiration, partial recovery of heat & moisture lost by mucosa from expired air. remaining recovery from blood.
** need humidifier for ventilation

Question 3

outline functional differences btw conducting and respiratory zones of tracheobronchial tree

Answer 3

conducting (0-16): BULK FLOW-requires energy
muscles activity alters thoracic volume, changes thoracic pressure relative to atmosphere driving movement of air

Respiratory (17-23): diffusion- no energy. individual gases diffuse across alveolar-capillary membrane driven by their pressure.

Question 4

describe functional significance of alveolar cell types and structural layers of alveolar-capillary membrane

Answer 4

Type 1 pneumocyte: flat squamous epithelium. 95% of alveolar surface area. thin

type 2 granular pneumocyte/septal cell: cuboidal shape. contains laminar inclusion bodies that store surfactant (reduce tension bc of DPPC in it)

type 3 alveolar macrophage/dust cell: extracellular lining of alveolar surface. migratory and phagocytic defends against pathogens

alveolar interstitium:

1. joins/support structural elements, contributes to its compliance allowing airway to expand and spring back
2. fluid space in series with lymphatic system, drainage

as go from trachea –> alveolus, lose cartilage, glands, SM

Question 5

describe airway clearance mechanisms,

Answer 5

particles >10 microns are filtered/trapped by nasal hairs. irritant receptor initiate sneeze

particles 2-10 microns: MCC system lining airways proximal to terminal bronchioles, irritant receptors –> cough
MCC system has 2 layers: GEL mucus, sticky. and SOL aqueous periciliary (PCL)- low viscosity facilitate cilia

Question 6

describe role alveolar macrophage in airway clearance and in lung scarring (pulmonary fibrosis)

Answer 6

particles < 2 microns reach alveoli.
macrophages engulf, degrade.
non-degradable particles (i.e. silica dust, asbestos) injure epithelium resulting in inflammation, scar (collagen deposition) and PF.

Question 7

outline examples of mucociliary transport impairment

Answer 7

smoking: decrease ciliary length, number, motility, increase mucus production
pathogenic microbes: release substances that paralyze, slow ciliary motion (i.e. HIV)
Primary ciliary dyskinesia: decrease ciliary motility
CF: increase mucus viscosity, reduces clearance in lungs & pancreatic ducts.