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Lung Defense + Pulmonary Ventilation (Mucus (Surfactant protein A…
Lung Defense + Pulmonary Ventilation
Nasal cavity defence
Posterior 2/3rds cavity lined pseudostratified columnar ciliated epithelium
Goblet cells: secrete mucus
Mucus acts physical barrier infection athogens: sticky + traps harmful substances
Cilia in epithelium create motions drain mucus from nasal passages to throat
Swallowed and digested
Airway defence
Particles reach trachea: cough reflex triggered, remove debris + infected mucus
Trachea + terminal bronchioles lined pseudostratified columnar epithelium
Goblet cells + submucosal glands secretes gel like mucus floats on a more fluid sol phase (pericilary liquid)
Sol phase allows cilia beat gel phase towards mouth: synchranous beating :
MUCOCILIARY ESCALATOR
15 mins clear airway
Sol phase and gel phase together form
AIRWAY SURFACE LIQUID
(7nm thick)
Homeostasis ASL
CFTR (cystic fibrosis transmembrane conductance regulator)
Process stopped through secretion chlorine to surface through CFTR
Channels break on ENaC, prevents further fluid absorption
ENaC (epithelial sodium channel)
Normally active
Draws sodium from surface, draws H2O from ASL: get pumped out of cell from the bottom
DECREASING VOLUME ASL, INCREASES VISCOSITY
Mucus
Surfactant protein A
Enhances phagocytosis through opsonisation
Lysozomes
Antifungal and antibacterial properties
Lysozymes degrade a glycosidic linkage of bacterial membrane peptidoglycans
Anti-proteases
Inhibits actions of trypsin, proteases and elastase (released by bacteria)
IgA
Restricts adherance of microbes to mucosa
Opsonizes antigenic particles
Alveolar defence
Alveolar epithelium no cilia, alveolar macrophages key
Type 2 pneumocytes: antimicrobial activites
Major source of surfactant
Surfactant proteins a and d opsonizes bacteria promoting phagocytosis by macrophages
Macrophages
Macrophages active boundary body and outside world
Phagocytosing bacteria + dust particles
Antigen presenting cells
Secrete anti-inflammatory cytokines (IL-10)
Secrete chemoattractants promote neutrophil infiltration from plasma (e.g. IL-8 and leukotriene B4)
Asthma immune resposne
Smooth muscle contraction
Inflammation thickening airway wall
Mucus and exudate in airway lumen
Capillary leakage
Type 1 hypersensitivty
Breathlessness
Wheezing
Chest tightness
Cough
Pulmn ventilation
Quiet vs Forced respiration
Quiet Inspiration
Diaphragm tenses + increases height thoracic cavity
Quiet Expiration
Driven by effects of surface tension on alveolar volume
Passive: elastic recoil
Forced Respiration
Expiration
Abdominal muscles (rectus abdominis, transverse abdominis, internal obliques)
Internal intercostals pull ribs downward and inwards
Push diaphragm up
Inspiration
Scalenes raise first 2 ribs
Sternocleidomastoid raises sternum
External intercostals raise ribs
Along with diaphragm
Nervous control breathing
Autonomic contrrol
Sympathetic
Mediated
inhibiting Ach + noradrenaline
: activates beta 2 receptors: bronchodialtion
Parasympathetic
Mediated by
Ach
, bind to M3 receptors: maintains bronchoconstriction
Breathing control
Medulla brain
Dorsal (inspiratory) Ventral (expiratory)
Control: CO2, O2, irritants, stretch receptors + H) conc + emotions (hypothalamus)
Key defintions
Air flow
Air flow
Flow of air per unit of time
Determined by pressure gradient + resistance (Ohms law)
Flow rate
:(ml/min)
Change in pressure (mmHg)/ airway resistance (L/sec)
Resistance
Resistance
Resistance of resp tract to airflow
Determined by airway length, density of air + diameter of airway (poiseuilles law)
Greater diameter, less resistance
Diameter of each bronchioles much less than trachea, combined diameter = greater
A-a gradient
Difference between alveolar oxygen pressure and arterial oxygen pressure:
optimally = 0
Ideally, equilibrium is always reached between alveolar spaces and capillary blood
Norm grad 5-15mmHg
Gradient increased: hypoxemic (pulm fib, oedema, shunt, thicken alveolar membrane)
Partial pressures mmHG
Atmospheric: 160
Alveolar air: 100
Venous blood: 40
Arterial blood: 100
Tissues at rest: 40
Lungs + heart work together
Ventilation perfusion ratio
Zone 1
Highest V/Q ratio, ventilation low, blood flow even lower: vasculature being compressed
Zone 3
Lowest V/Q ratio: Alveoli compressed and will ventilate well upon inspiration, Pulmonary perfusion quite high
Max flow rate here
Zone 2
Moderate V/Q ratio: better ventilation + more rapid blood flow
Factors affecting
Airway obstruction
Blood flow obstruction