Transcript Gas Exchange

Respiratory Systems
Chapter 42
Qualifying Respiration
Gas Exchange
 Organismal level
 O2 in CO2 out via
diffusion
Cellular Respiration
 Cellular level
 Use O2 and
produce CO2 and
ATP
Respiratory Medium
 Water
 Membranes always moist
 Air
 High concentration of oxygen
 Less dense
 O2 and CO2 diffuse faster in air than water
Respiratory Surface Requirements
 Thin
 Diffusion distance
 Moist
 PM stability
 Large
 SA to volume ratio
 Fick’s Law
 R = D x A ( p/d)
Altitudes and Oxygen
 Air is a fixed ratio of gases
 Each contributes a partial
pressure to the atmosphere
 PN2, PO2, PCO2, and other
gases
 Air thins with increasing
altitude
 Gas in same ratio, but less of
‘Skin Breathers’
 Earthworms and
some amphibians
 Skin is respiratory
surface
 Moist
environments
Gill Systems
 Extensions of body surface
(pink)
 Ventilation adaptations
varies organization
 Movement of water across
gills
 Inefficient of land
 Desiccation
 Tissue mass
Countercurrent Exchange
 Exchange between two
opposite flowing fluids
 Maximum efficiency
 Concentration gradient
favors O2 diffusion from
H2O
 Always slightly more in
blood
 Compare with concurrent
Tracheal System
 Most terrestrial animals
(insects)
 Internal branched tubes
 Connect all cells to
environment
 Close to retain moisture
 Open circulatory system role?
 Body movements in larger and
more active species
Lungs
 Internal sacs with moist
epithelium
 Extensive inner branching
 Closed circulatory system
role?
 Book lungs in spiders (open)
 Most terrestrial vertebrates
 Variations between phyla
Terrestrial Vertebrates
 Amphibians
 Obtain O2 via positive pressure
 Skin for exchange
 Birds
 1 way flow
 2 cycles to complete
 Mammals
 Negative pressure
 Incomplete removal each cycle
 Myoglobin varies with
environment
Mammalian Respiratory System
Respiratory Cycle
Boyle’s Law: increased volume, decreases thoracic pressure
Control of Human Breathing
 Medulla establishes rhythm
 Pons sets rate
 Most is involuntary
 Holding breath
 Sensors in carotid arteries and
aorta
 pH of CSF reflects [CO2] in
blood
 Must correlate with circulation
 Exercise or baby’s first breath
Gas Exchange
 PO2 and PCO2 vary within
the circulatory system
 Pressure gradient facilitates
gas exchange in tissue
capillaries
 Lungs: O2 into blood,
CO2 into alveoli
 Body tissues: O2 out of
blood, CO2 in
Respiratory Pigments
 Protein bound to a metal
 Hemoglobin increases O2 carrying capacity
 Increase PO2 increase
 Increase PCO2 increase dissociation = H+ binding to buffer blood
 pH increase
 Temperature decrease
Respiratory Problems
 Alveoli of ciliated epithelium
 Traps contaminants
 Swept out in mucus
 Alveoli highly susceptible to
contaminants
 Macrophages patrol
 COPD, pnemonia, Black lung
 Surfactants keep alveoli open
 Fetal development at 33 weeks