Respiration Flashcards
What is the process underlying respiration in humans?
- Both ventilation (breathing) and transport of blood gases in the blood stream are accomplished by convection (bulk flow) and depend on a difference in total pressure
- Gas exchange at the lungs and at the level of tissues/cells is accomplished by diffusion and depends on the difference in the partial pressure of a given gas
What are the four basic steps of respiration?
- Ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs
- Exchange of O2 and CO2 between air in the alveoli and the blood in the pulmonary capillaries
- Transport of O2 and CO2 by the blood between the lungs and the tissues
- Exchange of O2 and CO2 between the blood in the systemic capillaries and the tissues
What is the CO2 production of a normal individual at rest?
200ml/min
What is the O2 consumption of a normal individual at rest?
250ml.min
What is the respiratory quotient (RQ)?
the ratio of CO2 produced to O2 consumed = 0.8 = 8 molecules of CO2 produced for every 10 molecules of O2 consumed
What is gas exchange at the lungs and at the level of tissues/cells accomplished by? What does it depend on?
diffusion
- depends on difference in the partial pressure of a given gas
what are ventilation and transport of blood gases in the blood stream accomplished by? What do they depend on?
convection
- depend on a difference in total pressure
What are the major structures in the upper airways?
- nose, mouth, pharynx (throat), larynx(vocal cords)
Excluding the structures of the upper airway, what are the other respiratory airway structures?
- Trachea, right bronchus, carina, left bronchus, and the diaphragm
What is the upper airway?
a multipurpose passage for air, solid and liquid food and a common structure for breathing, digestion and phonation
What is the function of the Uvula?
closes the naso-pharynx during swallowing and inhibits nasal regurgitation
What is the function of the epiglottis?
movement of hyoid bone during swallowing brings it down stopping food from entering the trachea and directs food into the esophagus
What are the vocal cords/vocal folds and what are their function?
folds of mucous membrane that lie across the laryngeal opening and allow for phonation and prevent aspiration of food
How many muscles control the position of the 4 structures of the airway in order to keep it closed during swallowing and open during breathing? (upper airway dilators)
20 muscles
What are the 4 structures whose positions are regulated by the 20 upper airwayd dilators?
- soft palate
- tongue
- hyoid apparatus
- pharyngeal wall
What happens during obstructive sleep apnea with regards to the airway dilators?
decreased genioglossus muscle activity leads to obstruction of the airway by the tongue
What are the functions of the upper airway mucosal lining?
to heat and humidify the inspired air
How does the mucosal lining of the upper airway effect inspiration?
heat and moisture from the mucosal lining heats and humidifies the inspired air to 37 degrees, saturated water vapor
How does the mucosal lining of the upper airway recover from the heat and moisture lost during inspiration?
air releases heat and moisture during exhalation, partially warming and humidifying the mucosa. the remaining is from the systemic blood supplying the airways
What happens to the regulation of heat and moisture in a patient with a tracheostomy?
the trach tube usually has heating and humidifying functions, otherwise air would be cold and dry
How many lobes do the left and right lung have?
left = 2 lobes right = 3 lobes
What are the structures involved in the tracheobronchial tree?
- trachea, carina, left primary bronchus, right primary bronchus
What is a characteristic of the tracheobronchial tree in terms of branching?
every parent structure has two or more daughter structures (usually 2 but sometimes more)
What structures are part of the conducting zone?
trachea, bronchi, bronchioles and terminal bronchioles
What structures are part of the transitional and respiratory zones?
respiratory bronchioles, alveolar ducts and alveolar sacs
What happens as the diameter of the airways gets smaller?
the number of them increases
What function does cartilage serve in the airways?
prevents/resists collapse
What is the structure of the tracheal cartilage?
U shaped cartilage completed into A ring by the trachealis smooth muscle
What is the structure of the bronchi cartilage?
Cartilage plates interspersed within the bronchial smooth muscle ring
Which airways have no cartilage?
bronchioles, terminal bronchioles, respiratory bronchioles, and alveolar ducts
What are bronchioles mainly composed of?
smooth muscle
What is the function of the terminal bronchioles?
conducting function
What is an additional function of the respiratory bronchioles and why?
gas exchange due to presence of alveoli
What are the walls of the alveolar ducts covered in and what do they terminate in?
covered with alveoli and terminate in alveolar sacs
What are the three types of airflow in the airways?
turbulent, laminar and transitional
What is turbulent flow?
axial and radial in direction, noisy and rapid in speed
Where does turbulent flow occur?
in larger diameter airways where speed of air molecules is fast
- upper airways
- trachea during quiet breathing (at rest) and bronchi during exercise
What does turbulent flow depend on?
density of air
What is air composed of?
about 80% nitrogen and 20% oxygen
What would happen if you replaced the regular composition of air with a lighter gas mixture? Why might yu do this?
it would reduce turbulent flow in the airways and make laminar flow more likely
- can help patient who is having trouble breathing (don’t lose any energy)
What is laminar flow?
streamline (parabolic profile), silent and slow
- air molecules int he center are moving fastest
Where does laminar flow occur>
in the smaller airways (<2mm diameter) where speed of air molecules is slow
What are the characteristics of transitional flow?
intermediate between laminar and turbulent
Where is transitional flow present?
throughout most of the tracheo-bronchial tree
In general, what is the composition of the airway wall lining?
a gradual transition from proximal to distal airways to thinner epithelium with loss of mucous glands and cartilage
What are the two separate blood supplies?
- conducting zone by the bronchial circulation (part of systemic circulation)
- Respiratory zone (alveoli) by the pulmonary circulation
What are pores of Kohn?
collateral ventilation aids in introducing fresh air into an obstructed airway
How many alveoli are in contact with 100s of pulmonary capillaries?
300 million
What three cell types are the alveolus composed of?
- Type 1 Pneumocyte
- Type 2 Grandular Pneumocyte (AKA alveolar septal cell)
- Type 3 Alveolar Macrophage “dust cell”
What is the structure of a type 1 pneumocyte? How much surface area do they cover?
composed of flat squamous epithelium and covers 95% of the alveolar surface area
- thin
What is the structure of type 2 granular pneumoctyes?
Cuboidal in shape and contain lamellar inclusion bodies that store pulmonary surfactant
What is pulmonary surfactant?
a surface active agent that reduces alveolar surface tension
- mixture of lipids (mostly) and proteins
What is the key surface tension reducing agent in pulmonary surfactant?
Diphosphatidylcholine (DPPC)
Where are type 3 alveolar macrophages found?
at the extracellular lining of the alveolar surface
What is the function of a Type 3 alveolar macrophage?
It migrates and is phagocytic (defends against forgeign particles)
Starting at the blood plasma, what are the layers of the air-blood barrier or alveolar capillary membrane?
blood plasma, capillary endothelium, interstitium, alveolar epithelium, surfactant, air
What is the alveolar interstitium?
a fluid space between air and blood barrier in series with the lymphatic system allowing excess fluid drainage into the lymphatic system
What does the alveolar interstitium do?
joins and supports the structural elements via an elaborate fiber system (collagen and elastin fibers)
How is airway clearance of particles that are >10um in diameter achieved?
- filtered and trapped by nasal hairs
- irritant receptors lining the nasal passages initiate the sneeze reflex –> removal of particles
How is airway clearance of particles that are 2-10um in diameter achieved?
- mucociliary transport system lining the airways proximal to the terminal bronchioles
- irritant receptors in airway lining –> cough –> removal of particles
What is the structure of the mucociliary transport system?
mucous blanket with 2 layers: gel or mucus layer and a sol or aqueous periciliary layer
How is the mucociliary escalator and airway clearance achieved?
cillia with tip claws beat in a path or unified motion to push material upwards
What impaires the mucociliary transport system? How?
- smoking ( decreased ciliary motion and increased mucus production)
- Pathogenic microbes (release substances that paralyze ciliary motion)
- Primary ciliary dyskinesia (cilia dysfunction due to a structural defect - inherited disease)
- Cystic fibrosis (defective chloride channels involved in transport of water and sodium across the epithelium result in formation od viscous sticky mucus hard to clear from the lungs and pancreatic ducts - inherited disease)
What happens if particles <2um in diameter reach the alveoli?
- migrating and phagocytic macrophages engulf forgien particles on alveolar surface and degrade them
- non-degradable particles with sharp profiles injure alveolar epithelium and the alveolar macrophages leading to inflammation, scar formation (collagen deposition) and in turns pulmonary fibrosis
The lungs and chest wall both have what properties?
elastic
At full respiratory capacity (FRC) the outward recoil of the chest wall is equal in magnitude but opposite in direction to what?
the inward recoil of the lungs
Where is the pleural cavity?
in between the lungs and the chest wall
What do the cohesive forces of the pleural fluid do?
- attach the two compartments to each allowing the lungs to inflate and deflate with the movements of the chest wall
- Reduce friction as the lung tissue glides past the chest wall
What is the pleural pressure(Ppl)? Where is it?
-5cmH2O, in the pleural cavity
What is the alveolar pressure (Pa)? Where is it?
0cmH2O, in the lungs