6. Respiration I - Alveolar and Systemic Gas Exchange Flashcards
what is the name for ALVEOLI CELLS
PNEUMOCYTES
what type of cells are TYPE 1 ALVEOLAR CELLS / PNEUMOCYTES
SQUAMOUS EPITHELIAL
- THIN, FLATTENED
- large, thin cytoplasm
- central nucleus (fried egg appearance)
what type of cells are TYPE 2 ALVEOLAR CELLS / PNEUMOCYTES
CUBOIDAL EPITHELIAL CELLS
- distinct apical MICROVILLI
- LARGE nucleus
- abundant cytoplasm with MITOCHONDRIA, extensive ER, GOLGI
- SECRETORY CELLS
what do TYPE 2 PNEUMOCYTES do
SECRETE SURFACTANT
(Secretory Cells)
TYPE 2 PNEUMOCYTES are HIGHLY METABOLIC so have important roles in:
- SURFACTANT PRODUCTION
- SURFACTANT HOMEOSTASIS
- REPAIRING ALVEOLI (upon injury)
TYPE 1 PNEUMOCYTES contribute to the..
AIR-BLOOD BARRER
Overlies capillaries on alveolar wall
which PNEUMOCYTE comprises 90% of the ALVEOLAR WALL
TYPE 1
TYPE 1 play a role in
GAS EXCHANGE
(PASSIVE role)
what is the DISTANCE of GAS EXCHANGE
0.1 - 1.5 μm
(MAX 1.5)
- SHORT DISTANCE for maximum EFFICIENCY
what is the ROLE of SURFACTANT (from Type 2 pneumocyte)
REDUCE SURFACE TENSION
how does SURFACTANT REDUCE SURFACE TENSION (what happens without)
SURFACE TENSION created by FLUID LINING ALVEOLI
- H20 COHESION (attract to each other/stick)
tension pulls alveolar walls inwards causing COLLAPSE
SURFACTANT MOLECULES INTERPOSE between H20 MOLECULES
- have HYDROPHILIC and HYDROPHOBIC Regions
- interfere with H BONDING between H2O molecules
by REDUCING SURFACE TENSION what are the 3 MAIN FUNCTIONS of SURFACTANT
- INCREASE LUNG COMPLIANCE
facilitate changes in volume/expansion of lungs - STABILISING ALVEOLAR SIZE
LAPLACE LAW - keeping LUNGS DRY / PREVENT FLUID ACCUMULATION
surface tension would draw in fluid from interstitium
how does SURFACTANT STABILISE ALVEOLAR SIZE
- LAPLACE LAW
1. what would happen without
2. what does surfactant do
- without:
SURFACE TENSION REDUCES ALVEOLI SIZE
SMALLER alveoli have HIGH PRESSURE
air moves from high to low pressure, from small alveoli into large alveoli
therefore Small ALVEOLI COLLAPSE - smaller size alveoli have MORE DENSE SURFACTANT
- STABILISES SIZE
- REDUCES PRESSURE
- PREVENT COLLAPSE
what is INFANT RESPIRATORY DISTRESS SYNDROME
- LACK OF SURFACTANT
fetus starts to produce surfactant 24-28 WEEKS GESTATION
if born premature/before 35 weeks, may have insufficent
- ALVEOLI COLLAPSE
what does DALTON’S LAW state
the TOTAL PRESSURE is EQUAL to the SUM of the PARTIAL PRESSURES
OXYGEN and CARBON DIOXIDE MOVE DOWN..
GRADIENTS of PARTIAL PRESSURE
between Alveoli and Pulmonary Capillary Blood
and between Systemic Capillary Blood and Interstitial Fluid
what does HENRY’S LAW state
the SOLUBILITY of a GAS IN A LIQUID is
PROPORTIONAL to its PARTIAL PRESSURE Above the Liquid and the SOLUBILITY COEFFICIENT of the GAS In the Liquid
what does FICK’S LAW state
the AMOUNT of GAS DIFFUSING IN unit time through the resistance of a barrier is
INVERSELY PROPORTIONAL to the THICKNESS of the BARRIER
and
DIERECTLY PROPORTIONAL to the SURFACE AREA of the BARRIER, DIFFUSION CONSTANT (D), and PARTIAL PRESSURE DFFERENCE (GRADIENT) on each side
(INCREASE THICKNESS BARRIER, DECREASE AMOUNT DIFFUSION)
(INCREASE SURFACE AREA, INCREASE DIFFUSION
INCREASE DIFFUSION CONSTANT, INCREASE DIFFUSION
INCREASE PRESSURE DIFFERENCE, INCREASE DIFFUSION)
what does GRAHAM’S LAW state
the RATE of DIFFUSION is
DIRECTLY PROPORTIONAL to the SOLUBILITY COEFFICIENT
and
INVERSELY PROPORTIONAL to the SQUARE ROOT of its MOLECULAR WEIGHT
(INCREASE SOLUBILITY, INCREASE RATE)
(INCREASE SIZE, DECREASE RATE
smaller size faster diffusion)
properties that MAXIMISE GAS EXCHANGE
- LARGE SURFACE AREA (70m^2) (300-600 million alveoli)
- DENSE NETWORK CAPILLARIES
- THIN Alveolar-Capillary MEMBRANE
- SURFACTANT production to REDUCE SURFACE AREA and facilitates EXPANSION of LUNGS (further increases Surface Area)
SURFACE AREA of GAS EXCHANGE surface
70 m^2
does CO2 or O2 DIFFUSE FASTER and why
CO2 20X FASTER than o2
- MORE SOLUBLE
CO2 MORE SOLUBLE so what does this mean
20X FASTER DIFFUSION RATE
does NOT NEED as big PARTIAL PRESSURE GRADIENT/DIFFERENCE to DIFFUSE
from blood (45 mmHg) to Alveoli (40mmHg)
OXYGEN NEEDS BIG GRADIENT
Alveoli (104 mm Hg) to Blood (40 mm Hg)
when does DIFFUSION CAPACITY INCREASE
during EXERCISE
- LARGER TIDAL VOLUMES - inflate alveoli, INCREASES SURFACE AREA
more pulmonary capillaries perfused
increased PAO2 due to increased ventilation
INCREASED PARTIAL PRESSURE GRADIENT
