Chapter 42

Respiratory Systems

Qualifying Respiration

Gas Exchange

Cellular Respiration

Organismal levelO2 in CO2 out via

diffusion

Cellular levelUse O2 and

produce CO2 and

ATP

Respiratory Medium

WaterMembranes always moist

AirHigh concentration of oxygenLess denseO2 and CO2 diffuse faster in air than water

Respiratory Surface Requirements

ThinDiffusion distance

MoistPM stability

LargeSA to volume ratio

Fick’s LawR = D x A ( p/d)

Altitudes and OxygenAir is a fixed ratio of

gasesEach contributes a

partial pressure to the atmospherePN2

, PO2, PCO2

, and

other gasesAir thins with

increasing altitudeGas 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 organizationMovement of water

across gills

Inefficient of landDesiccationTissue mass

Countercurrent Exchange

Exchange between two opposite flowing fluidsMaximum efficiency

Concentration gradient favors O2 diffusion from H2OAlways slightly more

in bloodCompare with

concurrent

Tracheal System

Most terrestrial animals (insects)

Internal branched tubesConnect all cells to

environmentClose 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

vertebratesVariations between

phyla

Terrestrial VertebratesAmphibians

Obtain O2 via positive pressure

Skin for exchangeBirds

1 way flow2 cycles to complete

MammalsNegative pressureIncomplete removal

each cycleMyoglobin varies with

environment

Mammalian Respiratory System

Respiratory Cycle

Boyle’s Law: increased volume, decreases thoracic pressure

Control of Human BreathingMedulla establishes rhythm Pons sets rateMost is involuntary

Holding breathSensors in carotid arteries

and aortapH of CSF reflects [CO2] in

bloodMust correlate with

circulationExercise or baby’s first

breath

Gas ExchangePO2

and PCO2 vary

within the circulatory system

Pressure gradient facilitates gas exchange in tissue capillariesLungs: O2 into blood,

CO2 into alveoliBody tissues: O2 out

of blood, CO2 in

Respiratory Pigments

Protein bound to a metalHemoglobin increases O2 carrying capacity

Increase PO2 increase

Increase PCO2 increase dissociation = H+ binding to buffer

bloodpH increase Temperature decrease

Respiratory Problems

Alveoli of ciliated epitheliumTraps contaminantsSwept out in mucus

Alveoli highly susceptible to contaminantsMacrophages patrol

COPD, pnemonia, Black lung

Surfactants keep alveoli openFetal development at 33

weeks