Respiratory Physiology Flashcards
(27 cards)
What are the 3 different zones in the respiratory tract, and their components?
- Upper respiratory tract
- nasal and oral cavities
- pharynx
- larynx - Lower respiratory tract (conducting zone)
- trachea
- bronchi and bronchioles (excepting respiratory bronchioles) - Lower respiratory tract (respiratory zone)
- respiratory bronchioles
- alveolar sac and alveoli
What are the different areas of the pharynx?
Nasopharynx (behind nose)
Oropharynx (behind mouth)
Laryngopharynx (behind larynx)
What are the epithelial types in the conducting zone of the respiratory tract?
Trachea and bronchi:
- psuedostratified ciliated columnar epithelium
Terminal bronchioles:
- cuboidal epithelium
Alveoli:
- squamous epithelium
Which parts of the respiratory tract have cartilaginous walls?
Trachea: cartilaginous rings
Bronchi: irregular cartilaginous plates
Bronchioles: no cartilage (elastic fibres provide structure)
What is the respiratory membrane?
The membrane between alveoli and capillaries where gas exchange occurs
- formed by the fused basement membranes of the squamous epithelial cells of alveoli and capillaries
What are the 2 types of alveolar cells?
Type 1:
- squamous epithelium
- most of alveolar wall
Type 2:
- cuboidal epithelium
- secrete surfectant that reduces the surface tension of alveolar fluid
How does gas exchange occur at the respiratory membrane?
O2 and CO2 are both lipid soluble and diffuse directly through respiratory membrane (moving from area of higher concentration to area of lower concentration)
What is respiration?
The processes involved in supplying the body with oxygen and disposing of carbon dioxide
What are the 4 components of respiration?
- pulmonary ventilation (inspiration and expiration)
- external respiration (exchange of gases at the respiratory membrane)
- gas transport
(movement of gas through the bloodstream) - cellular respiration
(aerobic metabolism within cells)
What are the 3 pressures in the lungs?
- Intra-pulmonary / intra-alveolar
- pressure within the alveoli
- decreases in inspiration (as alveoli expand)
- increases in expiration (as alveoli contract) - Intrapleural
- pressure within pleural cavity
- always negative to intrapulmonary pressure (so that lungs are coupled to thoracic wall) - Transpulmonary
- difference between intrapulmonary and intrapleural pressures
What is Boyle’s Law?
Pressure decreases when volume increases, and vice versa
How does Boyle’s Law work in inspiration?
- Tx cage expands and volume increases
- intrapulmonary pressure decreases as alveoli expand
- air flows into lungs (area of lower pressure) until intrapulmonary pressure equals atmospheric pressure
How does Boyle’s Law work in expiration?
- Tx cage constricts and volume decreases
- intrapulmonary pressure increases as alveoli constrict
- air flows out of lungs (from higher pressure to lower atmospheric pressure) until intrapulmonary pressure equals atmospheric pressure
Which factors affect the body’s ability to achieve ventilation?
- Lung compliance
(ability of lungs to expand)
- incapacity of Tx cage to expand - Airway resistance
- restriction, occlusion or resistance to air flow within respiratory tract
What are examples of restrictive pulmonary disease (lungs unable to expand)?
Intrinsic:
- pneumonia
- cancer
Extrinsic:
- pleural effusion
- obesity
- scoliosis / kyphosis
What are examples of obstructive pulmonary disease (obstruction of airways)?
- COPD
- asthma
- cystic fibrosis
What is Henry’s Law?
Gas at higher pressure is more soluble, and will dissolve towards areas of lower pressure
What is Dalton’s Law?
Partial pressure = pressure exerted by each individual gas within the overall pressure of the sum of gases
What is Fick’s Law?
Describes the rate of gas diffusion across a membrane, dependent on:
- solubility of gas
- surface area for diffusion (larger area = faster diffusion)
- difference in partial pressure on each side of barrier (gas will move from high to low pressure)
- thickness of barrier to diffusion (thinner = faster)
What are the 3 laws governing gas diffusion at the respiratory membrane and in microcirculation, and what do they relate to?
- Dalton’s Law (partial pressure of gases)
- Henry’s Law (gas moves from high pressure to low pressure)
- Fick’s Law (factors affecting rate of diffusion)
How is oxygen transported in the blood?
- 98.5% in bound to haem groups in haemoglobin
2. 1.5% dissolved in plasma
How is CO2 transported in the blood?
- 70% as carbonic acid in plasma
- 25% bound to haemoglobin
- 5% as dissolved CO2 gas in plasma
What are the 3 factors affecting oxygen saturation in the blood?
- local availability of O2
- local presence of CO2 or H+
(increased levels weaken Hb-O2 bond and enhance O2 offloading) - temperature
(increased temperature decreases Hb affinity for O2)
What are the respiratory centres?
There are 3 altogether - 2 medullary and 1 pontine
Medullary:
- VRG (Ventral Respiratory Group), rhythm generation via phrenic & intercostal nerves
- Dorsal respiratory, modifies rhythms set by VRG
Pontine:
- interact with medullary centres to fine tune respiratory patterns
