Lec 1 Flashcards
What is the normal function of the respiratory system?
gas exchange [warm/humidify and filter/protect air]
acid-base
phonation
metabolism of endogenous substances
What is the main function of lung?
gas exchange = remove CO2 and replenish O2
How long does gas exchange take in the lungs?
0.25 seconds
How long does it take for entire blood volume [5 L] to pass through the lungs?
one minute
What is the main difference between bronchi and bronchioles?
bronchi have cartilage
bronchioles lack cartilage
Do terminal bronchioles participate in gas exchange?
nope!
they are part of conducting zone of lungs; they branch into respiratory bronchioles that do gas exchange
What is the pulmonary acinus?
functional unit of lung = the portion of lung distal to terminal bronchiole including respiratory bronchioles, alveolar ducts, and alveoli
What parts of lung are part of the conducting zone?
- trachea
- bronchi
- bronchioles
- terminal bronchioles
What parts of lung are part of respiratory zone?
respiratory bronchioles
alveolar ducts
alveolar sacs
What is the function of conducting zone of the lung?
funnel gas to respiratory unit of lung
What is the function of the airways?
- serve as conduit of air
- provide evacuation of foreign material
- immuno and protective function
- warm and humidify air
What is normal tidal volume?
500 cc
How much of tidal volume remains in conducting portion of lungs and does not participate in gas exchange?
1/3 of tidal volume = 150 CC
What type of epithelium lines airways?
pseudostratified columnar epithelium with cilia
What other histo findings in large airway or bronchus?
bronchial cartilage
submucosal mucinous glands
How do you distinguish bronchus from bronchiole histologically?
bronchiole = smaller diameter, epithelium, then thin layer of connective tissue then smooth muscle
bronchus = cartilagenous
What is width of blood-air barrier at its thinnest point?
~0.15 microns
What aspects of lung design make it ideal for gas exchange?
- large surface area
- short diffusion path [thin barrier]
- concentration gradients of Co2/O2
How does hemoglobin aid in gas exchanges?
binds O2 so ddecreases concentration of available O2 in blood –> increases driving force for gas exchange
What aspects of blood-brain barrier make it ideal for diffusion?
- thin cycoplasm of typ I pneumocyte
- fused basement membranes of capillary and alveolus
What is important about the interstitium between epithelial basement membrane and vascular basement membrane?
there is continuity of interstitium around bronchovascular bundles, alvoelar walls, interlobular septa, pleura
What are type I pneumocytes?
- very flat cells
- cover most of avlvoelus but only account for about 40% of the cells
- cannot divide
- participate in gas exchange
What are type 2 pneumocytes?
- more cuboidal cells
- only cover about 5% of alveolar surface but account fro 60% of cells
- divide to replace injured Type ! cells
What 3 factors can cause abnormal lung function?
- impaired gas-exchange in alveolar spaces
- increased resistance to air flow in bronchioles
- altered pulmonarymechanics
What 2 mech of impaired gas exchange?
- ventilation perfusion mismatch
- diminished diffusion capacity
What are some possible etiologies of airway obstruction that can lead to ventilation-perfusion mismatch?
- neoplasm
- mucus plug, foreign object
- COPD; emphysema; chronic bronchitis
- fluid or inflammatory cells in alveolar space [pneumonia]
What 2 chronic diseases associated with increased airflow resistance in airways?
chronic bronchitis
bronchial asthma
= like backup in an expressway; alveoli might be perfectly normal but the air can’t get there
What possible etiologies of alveolar filling that prevent access to areas of gas exchange?
pneumonia
edema
What are some possible etiologies of obstacles to perfusion?
- destruction of alveolar capillaries
- alteration of pulm blood flow [HTN]
- obstruction of flow [pulm embolus/thrombus, compression]
What are the 2 circulations of pulm vasculature? function? resistance?
pulmonary arteries: low pressure, involved in gas exchange
bronchial arteries: systemic pressure, nutrient vessels, supply bronchial tissue with nutrients
What is normal relationship PA pressure to systemic pressure?
PA pressure is 1/6th that of systemic
How do PA vessels differ from systemic counterparts?
thinner walls
wider vessels
What happens to pulm vessels wtih pulmonary HTN?
thickening of blood vessels due to pressure –> decrease lumen size –> decreased blood flow to gas exchange areas
What are some ways diffusion capacity can be impaired?
- loss of alveolar or endothelial area [emphysema]
- thickening of alveolar wall [fibrosis]
What is mech in fibrosis of V-Q mismatch?
thickened alveolar wall = less diffusion capacity
What is mech in emphysema of V-Q mismatch?
- loss of alveolar or endothelial area
- desturction of alveolar surface
- airway obstruction
- less surface area for diffusion –> less gas exchagne
What 2 anatomic factors determine diffusion capactiy?
- alveolar surface area
- thickness of air-blood barrier
What types of abnormalities can alter pulmonary mechanics?
- anything that changes the lung
- airway obstruction, vascular abnormalities, fibrosis
- cardiac abnormalities
- chest wall abnormalities
What structures in the lungs designed for protection?
- nasal hairs
- branching airways
- muco-ciliary escalaotr = cilitaed epithelium and mucus layer trap particles and sweep them out
- alveolar macrophages
What size particles trapped in each part of lung?
> 10 microns = in nose/nasopharynx
5-10 microns = in mucous coated airways
< 2 microns = reach alveoli
