HBSHBS Project ProjectThe Respiratory System and The Respiratory System and

Gas ExchangeGas Exchange

Melia Ungson, Kioma Palkhivala, Aviva Prager, Carina Coffey

Gas Gas ExchangeExchange

Gas exchangeGas exchange is the uptake of molecular oxygen from the is the uptake of molecular oxygen from the environment and the discharge of carbon dioxide to the environment and the discharge of carbon dioxide to the environment.environment.

After oxygen is diffused across the respiratory surface, the After oxygen is diffused across the respiratory surface, the molecules travel throughout an organism via the transport molecules travel throughout an organism via the transport system.system. cellular respiration and ATP productioncellular respiration and ATP production

It involves:It involves:– Respiratory MediumRespiratory Medium - water or air- water or air– Respiratory SurfaceRespiratory Surface - Skin, trachea, gills, lungs- Skin, trachea, gills, lungs

Must be a Must be a thin, moist, large surface areathin, moist, large surface area

Gas Gas ExchangeExchange - In - In Aquatic AnimalsAquatic Animals

RespiratoryRespiratory Surface: Gills Surface: Gills Respiratory Medium: Respiratory Medium:

WaterWater Advantages: easily stays Advantages: easily stays

moistmoist Disadvantages: water has Disadvantages: water has

a low oxygen a low oxygen concentrationconcentration Must use Must use ventilationventilation

—increasing the flow —increasing the flow of the respiratory of the respiratory medium over the medium over the respiratory surfacerespiratory surface

Countercurrent Countercurrent ExchangeExchange Enhances gas exchangeEnhances gas exchange

– Blood flows in Blood flows in opposite direction opposite direction as the water moving as the water moving past the gillspast the gills

– It is of adaptive It is of adaptive value because it is a value because it is a very efficient very efficient process that greatly process that greatly reduces the energy reduces the energy cost of ventilation cost of ventilation alone and yields alone and yields more oxygen more oxygen because diffusion because diffusion across the across the membrane is always membrane is always favoredfavored

In Insects and In Insects and Terrestrial Animals Terrestrial Animals

Respiratory Medium: AirRespiratory Medium: Air Advantages:Advantages:

Much higher concentration Much higher concentration of oxygenof oxygen

Less ventilation required Less ventilation required More energy efficientMore energy efficient

Disadvantages:Disadvantages: Respiratory surface Respiratory surface

constantly loses water by constantly loses water by evaporationevaporation

Respiratory surface is Respiratory surface is folded into the body folded into the body to reduce loss of to reduce loss of water in terrestrial water in terrestrial animalsanimals

Tracheal System: In Tracheal System: In InsectsInsects

Air tubes branch throughout the Air tubes branch throughout the body and the largest tracheal body and the largest tracheal tubes opening to the outsidetubes opening to the outside

Gas is exchanged by diffusion Gas is exchanged by diffusion across epithelium lining ends of across epithelium lining ends of systemsystem Open circulatory system not Open circulatory system not

involvedinvolved

Lungs- In Many Lungs- In Many Terrestrial AnimalsTerrestrial Animals

Size and complexity Size and complexity correlated with metabolic correlated with metabolic raterate

Restricted to one locationRestricted to one location Circulatory system must Circulatory system must

be involved with gas be involved with gas exchangeexchange

Have a dense net of Have a dense net of capillaries under capillaries under epithelium that epithelium that transports gases transports gases between lungs and rest between lungs and rest of the bodyof the body

Mammalian Respiratory Mammalian Respiratory System System

Mammalian Respiratory Mammalian Respiratory System- ContinuedSystem- Continued

Alveoli are the air sacks at the tips of bronchiolesAlveoli are the air sacks at the tips of bronchioles Capillaries cover each alveolus and gas diffuses Capillaries cover each alveolus and gas diffuses

across epitheliaacross epithelia Oxygen diffuses across the alveoli epithelia into Oxygen diffuses across the alveoli epithelia into

the surrounding capillariesthe surrounding capillaries Carbon Dioxide diffuses the opposite direction, Carbon Dioxide diffuses the opposite direction,

from capillaries into the alveolifrom capillaries into the alveoli

Lung Ventilation – Lung Ventilation – BreathingBreathing

Alternate inhalation Alternate inhalation and exhalation of and exhalation of air air AmphibianAmphibian

Positive pressure Positive pressure breathingbreathing

– Pushes air down Pushes air down tracheatrachea

Breathing in MammalsBreathing in Mammals Negative pressure breathingNegative pressure breathing

Pulls air down tracheaPulls air down trachea (Inhalation) - (Inhalation) - Diaphragm contracts, lung Diaphragm contracts, lung

volume increasesvolume increases Gas flows from a region of higher pressure Gas flows from a region of higher pressure

to a region of lower pressure, so air to a region of lower pressure, so air rushes into the body and down to the rushes into the body and down to the alveolialveoli

((Exhalation) – Exhalation) – Diaphragm relaxes, Diaphragm relaxes, decreasing lung volume and increasing decreasing lung volume and increasing pressure inside alveolipressure inside alveoli

Forces air out of the lungs and out of the Forces air out of the lungs and out of the body body

Breathing in Mammals- Breathing in Mammals- ContinuedContinued

Tidal Volume – volume of air Tidal Volume – volume of air inhaled and exhaled with each inhaled and exhaled with each breathbreath

Vital Capacity – maximum tidal Vital Capacity – maximum tidal volume during forced breathingvolume during forced breathing

Residual Volume – the air Residual Volume – the air remaining in the lungs after remaining in the lungs after exhaling as much as possibleexhaling as much as possible

Lungs do not empty and Lungs do not empty and refill completely with each refill completely with each breath so inhaled air mixes breath so inhaled air mixes with residual airwith residual air

Breathing of BirdsBreathing of Birds Parabronchi – tiny Parabronchi – tiny

channels that air channels that air flows through in only flows through in only one direction (instead one direction (instead of dead-ended of dead-ended alveoli)alveoli)

Air sacs in addition to Air sacs in addition to lungs to keep air lungs to keep air flowing through lungsflowing through lungs

Completely renews Completely renews air in lungs with air in lungs with every exhalationevery exhalation Maximum lung Maximum lung

oxygen oxygen concentration is concentration is higher higher

High altitude High altitude (migration over (migration over mountains)mountains)

Control of Breathing – Control of Breathing – HumansHumans

Breathing Control Centers-Breathing Control Centers- PonsPons

Moderate medulla’s basic Moderate medulla’s basic rhythm, smoothing out rhythm, smoothing out transitions between transitions between exhalations and inhalationsexhalations and inhalations

Medulla OblongataMedulla Oblongata Sets basic breathing rhythmSets basic breathing rhythm Responds to pH changes Responds to pH changes

determined by amount of determined by amount of carbon dioxide in blood carbon dioxide in blood (and cerebrospinal fluid (and cerebrospinal fluid surrounding brain)surrounding brain)

Sends impulses to Sends impulses to diaphragm and rib muscles, diaphragm and rib muscles, stimulating contraction, stimulating contraction, which causes inhalationwhich causes inhalation

Control of Breathing in Control of Breathing in Humans- ContinuedHumans- Continued

Carotid arteriesCarotid arteries Signal medulla to increase breathing when oxygen Signal medulla to increase breathing when oxygen

levels severely lowlevels severely low Detect changes in blood pH and send nerve impulses Detect changes in blood pH and send nerve impulses

to medulla to medulla AortaAorta

Sends alarm signals to control centers when oxygen Sends alarm signals to control centers when oxygen level is too lowlevel is too low

Sends impulses to medulla when blood pH change is Sends impulses to medulla when blood pH change is detecteddetected

DiaphragmDiaphragm Contracts/relaxes to draw in or push out airContracts/relaxes to draw in or push out air

Partial Pressure Partial Pressure GradientsGradients

Partial Pressure – differences in quantity of a gasPartial Pressure – differences in quantity of a gas Gasses diffuse from a region of higher partial pressure to Gasses diffuse from a region of higher partial pressure to

lower partial pressurelower partial pressure Blood arriving at lungs from pulmonary arteries has Blood arriving at lungs from pulmonary arteries has

lower Po2 and a higher Pco2 than air in alveolilower Po2 and a higher Pco2 than air in alveoli Po2 of blood is raised and Pco2 lowered Po2 of blood is raised and Pco2 lowered Blood returns to heart to be pumped through Blood returns to heart to be pumped through

systemic circuitsystemic circuit

Respiratory Pigments Respiratory Pigments proteins that bind to and transport oxygen and circulate with proteins that bind to and transport oxygen and circulate with

the blood – increase amount of oxygen that can be carried in the blood – increase amount of oxygen that can be carried in bloodblood This is crucial because oxygen has a low solubility in water This is crucial because oxygen has a low solubility in water

and bloodand blood

Oxygen TransportOxygen Transport

HemocyaninHemocyanin In arthopods and In arthopods and

mainly mollusksmainly mollusks Uses copper to Uses copper to

bind oxygen, bind oxygen, results in bluish results in bluish bloodblood

HemoglobinHemoglobin In erythrocytes of In erythrocytes of

most vertebrates most vertebrates and many and many invertebratesinvertebrates

Has 4 subunits with Has 4 subunits with iron atom at center iron atom at center to bind oxygento bind oxygen

Oxygen Transport- Oxygen Transport- ContinuedContinued

Dissociation CurvesDissociation Curves Hemoglobin Hemoglobin

Dissociation with Po2 Dissociation with Po2 – a small drop in Po2 – a small drop in Po2 causes a large causes a large increase in the increase in the amount of oxygen amount of oxygen unloaded (in active unloaded (in active tissues) – oxygen tissues) – oxygen saturation in saturation in hemoglobin is hemoglobin is greater than that of greater than that of resting tissues, so resting tissues, so oxygen still leaves oxygen still leaves hemoglobin if tissues hemoglobin if tissues are not active, just are not active, just at a lesser rateat a lesser rate

Hemoglobin Hemoglobin Dissociation with Dissociation with pH – drop in pH pH – drop in pH lowers affinity of lowers affinity of hemoglobin for hemoglobin for oxygen – oxygen – Bohr Bohr Shift Shift – which – which increases increases oxygen oxygen released, which released, which supports cellular supports cellular respirationrespiration

More Oxygen Transport

Carbon Dioxide TransportCarbon Dioxide Transport HemoglobinHemoglobin – transports carbon dioxide – transports carbon dioxide

as well as oxygenas well as oxygen Aides in buffering – preventing harmful Aides in buffering – preventing harmful

changes in blood pHchanges in blood pH1.1. Carbon dioxide produced by body tissues diffuses Carbon dioxide produced by body tissues diffuses

into plasma and interstitial fluidinto plasma and interstitial fluid

2.2. Most of the carbon dioxide diffuses into red blood Most of the carbon dioxide diffuses into red blood cells, small percent stays in plasma as dissolved cells, small percent stays in plasma as dissolved carbon dioxidecarbon dioxide

3.3. Some of CO2 in blood transported by hemoglobinSome of CO2 in blood transported by hemoglobin

4.4. Most CO2 reacts with water in red blood cells to Most CO2 reacts with water in red blood cells to form carbonic acid (H2CO3)form carbonic acid (H2CO3)

Carbon Dioxide Carbon Dioxide Transport- ContinuedTransport- Continued

5.5. Carbonic acid dissociates into bicarbonate ion and Carbonic acid dissociates into bicarbonate ion and hydrogen ionhydrogen ion

6.6. Hemoglobin binds most of the hydrogen ion, Hemoglobin binds most of the hydrogen ion, preventing acidic pH change in blood (and Bohr preventing acidic pH change in blood (and Bohr Shift)Shift)

7.7. Most of the bicarbonate ion diffuses into red blood Most of the bicarbonate ion diffuses into red blood cells from plasma, combines with released cells from plasma, combines with released hydrogen ions reforming carbonic acidhydrogen ions reforming carbonic acid

8.8. Converted back into carbon dioxide and water Converted back into carbon dioxide and water 9.9. Carbon dioxide unloaded from hemoglobin and Carbon dioxide unloaded from hemoglobin and

diffused into interstitial fluid diffused into interstitial fluid 10.10. Diffuses into alveolar space, exhaled out of bodyDiffuses into alveolar space, exhaled out of body11.11. Reduction of carbon dioxide concentration in Reduction of carbon dioxide concentration in

plasma stimulates break down of carbonic acid into plasma stimulates break down of carbonic acid into carbon dioxide and water in red blood cellscarbon dioxide and water in red blood cells

Evolutionary Adaptations Evolutionary Adaptations in Animalsin Animals

1.1. Endurance Runners Endurance Runners (Pronghorn)(Pronghorn)

2.2. Diving Mammals (Weddell Diving Mammals (Weddell Seal)Seal)

a.a. Higher concentration Higher concentration of myoglobin – of myoglobin – oxygen storing oxygen storing protein -- in musclesprotein -- in muscles

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