Respiratory 6 Flashcards
What are the non respiratory functions of the lungs?
- Defense mechanisms of respiratory system
- Pulmonary fluid exchange
-production of lymphatic & pleural fluid - Metabolic functions
-remove & inactivate hormones & toxins
-platelet biogenesis
Describe examples of defense mechanisms of the respiratory system.
- Organic dust = plants/animals
- Infectious agents = bacteria/virus
- Allergens = spores/pollen
- Others = endotoxins
Describe the nonspecific defenses/innate immunity of the defense mechanism.
-immediate protection from inhaled substances
>mucociliary system
>cough
>resident phagocytic cells in alveoli
>TLRs on surface of cells
—production of pro inflammatory cytokines
Describe the specific defenses/adaptive immunity of the defense mechanisms.
-immune system
-directed against specific injurious agents (ex. Bacteria)
-days to be activated
-immune memory against future attacks of same organism
What does the particle deposition onto the mucocilliary system depend on?
-particle size
-occurs by: impaction, sedimentation, diffusion
-particles & aerosols (collection of particles or liquid droplets)
>removed from air when in contact w the moist epithelial surface of tracheobronchial tree
Describe large particles in particle deposition.
(>5um)
-contact airway wall by inertial impaction
-impaction occurs where airway direction changes
>small particles = less inertia & carried around corners & continue in path of airflow
-sites of inertial impaction = lymphoid tissue to start immune response
>EX: tonsils & bronchus lymphoids
Describe small particles in particle deposition.
(1-5um) inhaled drugs are this size
-contact airway wall by sedimentation or diffusion
-airflow rate diminish deeper in lung = smaller particles settle onto walls
>smallest particle reach peripheral airways & alveoli
>contact wall by diffusion or exhaled again
What is the deposition of particles in the respiratory tract influenced by?
-pattern of breathing
-size of airway lumen
1. Slow, deep breathing = transport particles deep into lungs
2. Rapid shallow = enhances inertial deposition in larger airways
3. Bronchoconstriction = enhances deposition of particles in more central airways
4. Bronchodilation = peripheral distribution
How are particles deposited on the epithelial surface transported?
-mucocillary system -> pharynx -> swallowed
Describe the mucocilliary system.
-mucocilliary system = mucus + watery layers overlying epithelial cells
1. Watery layer (SOL)
>low-viscosity
>cilia beat
>bathes surface of epithelial cells
2. Mucus layer (GEL)
>entrap inhaled particles
*extended cillium propels particles to tracheobronchial system or through nasal cavity
Describe where the respiratory tract mucus originates from.
- Bronchioles = Clara cells
- Large airways = goblet cells
- Bronchial mucosa = bronchial glands
*changes in amount, composition, & viscosity of mucus happen in response to stimuli & can be cause/result of respiratory disease
Describe the normal airway epithelia.
-regulate rate of Na absorption & Cl secretion to regulate depth of mucus layer
-imp for optimal ciliary function
>changes in depth/viscosity of sol layer = impairs ciliary function
>changes in viscoelastic property of gel layer = change clearance rates
—bacterial infections increase viscoelasticity & decrease clearance bc increase amount of bacteria & neutrophil DNA in mucus
—mucus clearance affected by gravity
EX: horses prevent from lowering head = decrease mucociliary clearance & increase pneumonia risk
Describe coughing.
-clearance mechanism
-stimulation of sub epithelial irritant receptors
>mechanical deformation (ex. Foreign body)
>a lot of material on epithelial surface (ex. Mucus)
-more numerous in larger bronchi
-cough reflex hyperresponsive when airways are inflamed & respiratory tract epithelium is injured
>EX: viral infection
*cough reflex dont assist in removing mucus from peripheral bronchi or bronchioles
Describe alveolar macrophages.
-look for particles deposited on alveolar surface
-majority of cells in alveolar lining fluids
>principle resident phagocytes in lung
>originate in bone marrow as monocytes & differentiate during passage from blood to alveolus
>recruited from blood also
-surfactant proteins, complement, opsonins, & lysosomes in respiratory tract secretion assist macrophages in killing & removal of particles
>macrophages function as APCs (immune response)
*can damage lung tissue during disease
What happens when the lung is injured by infectious agents?
-allergic response or toxic particles = inflammatory process begins
-cytokines & chemokines = proteins that are made & released by macrophages, lymphocytes, epithelial cells, endothelial cells, etc
>molecules attract inflammatory cells to site = communication between cells
>tissue remodeling & healing
Describe the role of PAMPs & DAMPs in the defense mechanisms.
-signals from commensal microbes/respiratory pathogens (PAMPs) & generated from cell stress/death (DAMPs) = recognized via membrane or cytosolic receptors in respiratory epithelial cells
-binding of ligands to receptors = activate signaling pathways (via MAPK, IRFs, ROS & NF-kB) & production of cytokines, chemokines, & antimicrobial proteins
-recruit & activate cells of innate & adaptive immune system = regulate barrier function
-stimulate autophagy, phagocytosis & clearance of necrotic cells & pathogens
