Anatomy, Physiology, Investigations Flashcards
Anatomical definitions of: nasopharynx, oropharynx, laryngopharnyx
Nasopharynx = posterior to choanae to dorsal aspect soft palate Oropharynx = soft palate to superior border of epiglottis Laryngopharynx = superior border of epiglottis to inferior border of cricoid (C6)
role of intrinsic vs extrinsic laryngeal muscles
- Intrinsic – function in speech
2. Extrinsic (infrahyoid group) – elevate larynx during swallowing
VC abduction vs adduction produces what kind of sound?
- When cords adducted, vibration causes high pitched sound
- When cords abduction, lower pitch sounds
cell lining of trachea
Pseudostratified columnar epithelium, with goblet cells, cilia and basal stem cells
right lung vs left lung: # of lobes, and fissures
right lung: 3 lobes. horizontal above and oblique fissure below
left lung: 2 lobes with lingula, oblique fissure only
aspirated contents most likely to go into which lobe? why?
apical segment of RLL
RMB more vertical and larger
compare the conducting vs gas exchange zone of the lungs
conducting zone: up to terminal bronchioles (dead space). low surface area, high resistance / turbulence
gas exchange zone: generation 16 to alveoli, high surface area, low resistance / turbulence
what is the bronchopulmonary segment vs pulmonary lobule?
bronchopulmonary segment: portion of lung supplied by each tertiary bronchus
pulmonary lobule: portion of lung ventilated by one bronchiole
types of alveolar cells
1) type 1 (95% SA): squamous, rapid gas exchange
2) type 2 (5% SA, though more in number): cuboidal, repair alveolar epithelium and secerete surfactant
3) alveolar macrophages
normal pulmonary pressure at alveoli
10mmHg - keeps alveoli dry
what is the respiratory membrane and what is it made of?
barrier between alveolar air and blood made of: 1) squamous alveolar cell 2) shared basement membrane 3) squamous endothelial cell of pulmonary capillary
surfactant:
- produced by what
- production starts when
- type II alveolar cells (present at 20-24 weeks)
- surfactant secretion starts at 30 weeks
alveolar development:
- starts when
- when does most of it occur
- starts week 24
- true alveoli seen by week 32
- most alveolar development is postnatal (85%)
- exponential until 2yo, and develops until 8yo
how many alveoli at birth vs adult?
term: 15 mil
adult: 300-600 mil
outline process of development of airways
embryonic - 3 weeks: bud from primitive foregut
pseudoglandular at 3 – 16 weeks: bronchial tree
cannicular at 16 – 24 weeks: beyond 16 generations (small airways), thinning, surfactant
saccular at 24 – 36 weeks: gas exchange stuff
birth – 3 years: alveoli inc number
3-8yo: inc zize and complexity of alveoli, pores of Kohn
central vs peripheral chemoreceptors
- where
- what they respond to
Central chemoreceptors
- ventral surface of medulla, surrounded by CSF
- Respond to CSF [H+]: ↑ PaCO2 → ↑ CSF [H+] → ↑ ventilation
Peripheral chemoreceptors
- bifurcation of common carotid arteries in neck, and aortic bodies around arch of aorta
- Respond to ↓ PaO2, ↓ pH, ↑ PaCO2 → ↑ ventilation
what is the herring-breuer reflex?
excessive inflation triggers pulmonary stretch receptors to feedback via vagus to medulla inspiratory centre, inhibiting further inspiration
lung elastance vs compliance
Reciprocals of one another:
elastance = amount of pressure takes to expand the lung unit
compliance = amount of lung volume expanded per pressure unit
lung physiology: describe resistance
amount of pressure required to generate flow of gas across the airways
compare elastic vs resistive work of breathing
Elastic work (work required to overcome lung and chest wall elastance) = tidal volume Resistive work (work required to overcome airway and tissue resistance) = respiratory rate
what is the concept of time constant?
time constant = amount of time it takes for alveoli to equilibriate with Patm = compliance x resistance
poiseuille’s law for resistance across airways
R= (8xlength) / radius^4
which is active in quiet breathing: inspiration or expiration? why?
inspiration is active - need to contract diaphragm and intercostals to create negative intrapleural and intrathoracic pressure (cf Patm) to get airflow in. Need to overcome:
A) elastic resistance (65%)
B) airway resistance (35%)
examples of extrathoracic, intrathoracic and extrapulmonary, and intrapulmonary airway obstructions
extrathoracic: croup, choanal atresia etc.
intrathoracic/extrapulmonary: vascular ring, tumour etc.
intrapulmonary (distal to main bronchi): asthma, bronchiolitis
what tends to happen with resp sounds as obstructions move from extrathoracic to intrapulmonary?
extrathoracic: more stridor and retractions, less wheeze / grunting
intrapulmonary: more wheeze / grunting, less stridor.
essentially, how does surfactant work?
exerts smaller attracting forces for liquid molecules therefore lower surface tension
what is the primary component of surfactant?
surfactant is 90% lipid: Dipalmitoyl phosphatidyl choline (DPPC)
at which level of airway is resistance highest? why?
highest at 4th-8th generation - bc so many small airways that in total, resistance is low
how many ml is normal anatomical dead space?
150ml
4 factors affecting alveolar gas exchange
1) pressure gradient of the gases
2) Gas co-efficient = Weight and solubility of gases in water to travel across membrane
3) membrant thickness and SA
4) V/Q matching
*only
which is more soluble in water - CO2 or O2?
CO2, so:
A) CO2 diffusion limitation only occurs with severe AC problems
B) even though pressure gradient of oxygen much greater than carbon dioxide, equal amounts of the two gases are exchanged because CO2 is so much more soluble and therefore diffuses quicker
what is the normal V/Q ratio?
V = 4L/min Q = 5L/min
therefore 0.8 i.e. more blood flow, less ventilation
how is most CO2 transported around the body?
90% as carbonic acid:
CO2 + H2O –> H2CO3 –> HCO3 + H+
where in the lungs are V and Q greatest?
LOWER lobes - ventilation 3x more, perfusion 12x more
where is V/Q ratio highest and why?
highest at apex because:
V > Q at apex
Q > V at base
what happens in pulmonary shunting?
Right to left: blood that enters arterial system without going through ventilated areas of the lung
4 pulmonary factors causing hypoxemia vs hypercapnea
hypoxemia: hypoventilation, diffusion limitation, shunting, v/q mismatch
hypercapnoea: hypoventilation and v/qmismatch