Chapt 48 Respiratory Lecture

8/3/2019 Chapt 48 Respiratory Lecture

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CHAPTER 48

RESPIRATORYSYSTEMS

Prepared by

Brenda Leady, University of Toledo


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Gas exchange moves carbon dioxide and

oxygen between the air and blood and betweenblood and cells


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Gases Air is

21% oxygen

78% nitrogen

Less than 1% carbon dioxide and other gases

Nitrogen gas usually ignored because it is

not part of the respiratory process


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Gas pressure Atmospheric pressure pressure exerted

by the atmosphere on the body surfaces of

animals

Measure in mmHg or kPa

1kPa = 7.5 mmHg

Sea level = 760 mmHg

Atmospheric pressure decreases at higher

elevations


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Atmospheric pressure is the sum of the partialpressure (pressures exerted by each gas in air)

in proportion to their amounts

PO2 = 0.21 x 760 mmHg = 160 mmHg

Percentage of gases remain the same

regardless of altitude, but lower atmospheric

pressure results in lower partial pressures

Diffusion is driven by partial pressure gradients Rate of oxygen diffusion into blood is lower at

higher elevations


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Solubility of gases Gases dissolve in solution fresh water,

sea water or body fluids

Most gases dissolve poorly in water

Factors influencing solubility in water

Higher pressures will result in more gas in

solution up to a limit for each gas Cold water holds more gas than warm water

Other solutes decrease the amount of gasthat dissolves into solution


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Types of respiratory organs Few mechanisms for gas-exchange

Across the body surface

Across specialized organs like gills,

tracheae, or lungs

Ventilation is the process of bringing

oxygenated water or air into contact with a

gas-exchange surface


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Adaptations for gas exchange

All respiratory organs share certaincommon features

Moist surfaces in which gases dissolveand diffuse

Increased surface area for gas exchange

Extensive blood flow Thin, delicate structure


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Terrestrial vs. aquatic Different challenges to gas exchange

Aquatic animals have less available oxygen

When temperatures change in water, oxygenavailability also fluctuates

Terrestrial animals have to deal withdesiccation of respiratory membranes

Moving water of respiratory membranes takesmore effort Water is denser than air, removes heat from gill

surface and can create osmotic movement


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Body surfaces for gas exchange

Invertebrates with one or a few cell layerscan use diffusion for gas exchange

Some do not even need specializedtransport mechanisms

Some large, complex animal body

surfaces may be permeable to gases Amphibians are the only vertebrates to rely on

their skin for gas exchange under water


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External gills Vary widely in appearance but all have a

large surface area (extensive projections)

May exist in one body area or be scatteredover a large area

Limitations

Unprotected and subject to damage Energy required to wave gills back and forth

Appearance and motion may attract predators


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Internal gills Fish gills are confined and protected within

opercular cavity covered by the operculum

Gill arches main support structure Filaments branch off of gill arches

Lamellae branch off of filaments

Blood vessels run the length of the filaments Oxygen-poor blood travels through afferent vessel

Oxygen-rich blood travels through efferent vessel

Countercurrent exchange arrangement of waterand blood flow maximizes oxygen diffusion intoblood


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2 mechanisms to ventilate gills Buccal pumping hydrostatic pressure

gradient created by lowering jaw to suckwater in and opening operculum to drawwater through Flap of tissue prevents fish from swallowing

water they inhale

Ram ventilation swimming with mouth

open is more efficient Many fish use both methods

Both are flow-through systems watermoves unidirectionally


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Insect tracheae Spiracles on the body surface lead to tracheae

that branch into tracheoles terminating nearevery body cell

Small amount of fluid for gas to diffuse into Muscular movements of body draw air into and

out of tracheae

Open circulatory system of insect not used in

gas exchange Oxygen diffuses directly from air to tracheae to

tracheoles to body cells

Very efficient supports insect flight muscleswith highest metabolic rate known


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A

ir-breathing lungs With few exceptions, all air-breathing

terrestrial vertebrates use lungs

Scorpions and some spiders have book

lungs that resemble gills more

Lungs may be filled using positive or

negative pressure

Lungs can be ventilated using tidal or flow-

through systems


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Most amphibians have lungs that are simplesacs

Low surface area

Ventilate lungs similar to buccal pumping of fish

Boyles law relates gas volume and gas

pressure Decreased volume creates increased pressure

Lowers bottom jaw to create pressure gradientto suck air in

Closes mouth to raise pressure and force air intolungs positive pressure filling

A few species of reptiles also use positivepressure filling


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Mammalian respiratory systems Nose and mouth air is warmed and

humidified

Mucus in the nose cleans the air of dust Pharynx

Larynx vocal cords

Trachea glottis (opening to trachea)protected by epiglottis, rings of cartilage,cilia and mucus trap particles

Lungs


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Trachea branches into 2 bronchi

Bronchioles surrounded by circular

muscle to dilate or constrict passage Alveoli site of gas exchange

One cell thick

Coated with extracellular fluid for gases todissolve

Surfactant prevents alveoli from collapsing


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Pleural sac encases each lung

2 layers

Fluid between layers acts as lubricant andmakes layers adhere to each other

Movements of chest wall will result in lungalso moving

Lungs will be inflated by expansion of thechest wall


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Negative pressure ventilation Reptiles, birds, and mammals

Volume of lung expands, creating negative

pressure, and air drawn into lungs Mammals tidal ventilation

Inhalation intercostals contract to movechest wall up and out, diaphragm contracts

and drops down thoracic cavity enlarges,pressure drops, air sucked in

Exhalation intercostals and diaphragm relax thoracic cavity compressed, pressureincreases, air pushed out


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Tidal volume volume of air normally

breathed in and out at rest (~0.5L)

Lungs can be deflated or inflated further

Lungs never completely deflate

Held open by adherence to chest wall


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Avian lung

Flow-through system

Air sacs expand and shrink not lungs

Air sacs do not participate in gasexchange

Air enters trachea, 2 bronchi

Then parabronchi lungs

Regions of gas exchange

Blood flows crosscurrent with respect tooxygen movement (not as good as fish butbetter than mammals)


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Schmidt-Nielsen Mapped Airflow

in the Avian Respiratory System Determined pattern of air movement using

ostriches

Air flows through trachea, down bronchi, and intoposterior air sacs during inhalation

As bird exhales, air exits posterior air sacs andflows into parabronchi from back to front in the

lungs gas exchange occurs During next inhalation, air at anterior end of lungs

flows into anterior air sac

During second exhalation, air in anterior air sac

exits body


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Control of ventilation in mammals

Respiratory centers in several regions of thebrainstem

Signals travel from brain through Intercostal nerves to intercostal muscles

Phrenic nerves to diaphragm

Stretch receptors send signals to brain that

lungs are inflated this inhibits stimulus tocontract until exhalation

Can be overridden to increase or decrease rate


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Chemoreceptors in aorta, carotid arteries

and brainstem monitor Hydrogen ions (pH)

Partial pressures of oxygen and carbon

dioxide

Increase breathing rate if

Oxygen levels fall

pH drops due to increased acid production

from anaerobic metabolism or carbon dioxidefrom aerobic metabolism


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Carbon dioxide produced as wasteproduct of metabolism

Carried in blood 66% as bicarbonate ions made reversibly by

carbonic anhydrase in red blood cells

25% bound to hemoglobin

7-10% dissolved in solution in plasma and redblood cells


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Small animals have higher metabolic rates

Higher breathing rates to exchangeenough gas

Respiratory centers set at a higher frequency Similar to differences in cardiac output

Small animals have heart and lungs

proportional to body size that must beatfaster/breathe at a higher frequency tosupply higher metabolic rate


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Oxygen transport

Not enough oxygen dissolves into blood to

support metabolic needs

Respiratory pigments increase the amount

of gas carried in solution

May be contained within red blood cells or in

plasma Proteins with one or more metal ions


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Respiratory pigments

Hemoglobin iron Fe2+

4 protein subunits

Each has a heme unit contains iron

Single hemoglobin molecule binds up to 4 oxygen

molecules

Hemocyanin copper Cu2+

All have a high affinity for oxygen

Binding of oxygen is noncovalent and reversible


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Oxygen-hemoglobin dissociation curve

When PO2 is high, more O2 binds to

hemoglobin

When PO2 is low, less O2 binds to

hemoglobin

Sigmoidal curve due to cooperation

shape of hemoglobin changes as oxygenloads and unloads


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Curve can shift in

response tometabolic waste

products

Increasing amountsof CO2, H+ and

temperature make

oxygen load and

unload easier


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Curve can shift

between specieswith different

metabolic rates

Smaller animalsunload hemoglobin

more readily at any

given temperature


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Hemoglobin Evolved over 500 Million

Years Ago Oxygen-carrying molecules appear to have begun

as single-subunit proteins like myoglobin

Gene duplication resulted in hemoglobin and in

subunits of hemoglobin Mutations affect the affinity of hemoglobin for

oxygen

Sickle-cell anemia single amino acid substitutionforms long strands that deform red blood cell underlow oxygen conditions leads to anemia

Relationship between malaria and sickle-cellanemia in Africa


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Malaria caused by

Plasmodiumfalciparum growingand multiplying insidered blood cells

Sickle-cell traitprotects individualfrom developing fullblown malaria

Heterozygoteadvantage nopronounced anemia orsevere malaria


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Extreme conditions

High altitudes hemoglobin with higheraffinity for oxygen, larger hearts and lungs

than predicted for body size, highernumber of red blood cells per volume

Extended diving high numbers of redblood cells, larger blood volumes, large

amounts of myoglobin (spare oxygen forcritical structures lacking myoglobin)


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Impact on public health

Asthma Muscles around bronchioles are hyperexcitable

May have genetic basis Smoking

One of leading global causes of death

Up to 85% of all new cases of lung cancer each

year attributed to smoking In addition to its effects on cancer,

cardiovascular disease, and lung function, long-term smoking is the major cause ofemphysema


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Emphysema

Involves extensivelung damage

Reduces elasticquality of lungsand total surfacearea of alveoli

Reduced bloodoxygen and poorlung function

Several causes

Over 85% ofcases due tosmoking


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Pneumonia Infectious disease

most often caused byviruses, bacteria orother microorganismsthat enter lungs andmultiply

Fluid buildup interfereswith gas exchange

Bacterial form vaccine, antibiotics

Viral form run itscourse

Usually not serious inhealthy people

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Chapt 48 Respiratory Lecture