Transcript Mader 9e

Chapter 37
Respiratory Systems
Respiratory
Systems
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Gas Exchange Surfaces
Respiration:
The events associated with gas exchange
between the cells and the external environment
Consists of these steps:
- Ventilation = inspiration (air in) & expiration (air out)
- External Respiration = gas exchange between
external environment & the blood within respiration
surfaces. Blood then transports oxygen to the
tissues.
- Internal Respiration = gas exchange between blood
& tissue fluid. Cells exchange gases with tissue
fluid. Blood transports carbon dioxide back to
respiratory surfaces.
Respiratory
Systems
Gas Exchange Surfaces
For diffusion to be effective, gas-exchange
tissues must be:
Moist because gases must be in solution
Thin to allow for rapid diffusion
Relatively large in relation to size of body to
ensure that cells get oxygen in a timely fashion
Relatively small, and flat, animals don’t need a
specialized respiration system:
Planaria - flat, 2-dimensional body allows
surface of animal to be gas-exchange surface
Larger, more 3-dimensional animals need
specialized gas-exchange surfaces such as
gills or lungs.
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Respiratory
Systems
Gas Exchange Surfaces
Effectiveness of diffusion is enhanced by
vascularization:
• Gas-exchange surfaces are usually
associated with capillary beds so that
oxygen and carbon dioxide can be
exchanged efficiently.
Delivery of oxygen to cells is promoted by
respiratory pigments such as hemoglobin that
can pick up the oxygen and carry it.
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Respiratory
Systems
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Gas Exchange in Water Environments
I.
Difficulties obtaining oxygen in water compared to
air:
A. Water contains only a fraction of the oxygen
that would be present in the same volume of air
1. Oxygen has low solubility in water
0.004% in seawater; 21% in air.
B. Diffusion of oxygen in water is thousands of
times slower than in air
C. Water is more dense than air
1. Use more energy to respire than do land
animals.
•Fish use up to 25% of energy output to
respire while terrestrial animals only use
1-2% of their energy output.
Respiratory
Systems
Gas Exchange in Water Environments
II.
Small, simple multicellular animals:
A. Planaria, hydra
1. Gastrovascular cavity helps put cells in
contact with oxygenated water
B. Aquatic worms
1. Use skin that is supplied with blood
vessels
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Animal Shapes and Gas Exchange
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Respiratory
Systems
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Gas Exchange in Aquatic Environments
III. Larger aquatic animals like bony fishes
•Often have gills:
 Outward
extensions of pharynx; said to be
evaginated
 Have finely subdivided surfaces with a huge total
surface area
 Contain a rich supply of blood vessels
(vascularized)
 Ventilation is brought about by combined action of
the mouth drawing water in and gill covers
(operculum) forcing water out of head area
Anatomy of Gills in Bony Fishes
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Respiratory
Systems
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Countercurrent Exchange System
Countercurrent Exchange System in Fish Gills:
•In lamella of gills:
 Blood
flows in the direction opposite to the
movement of water across the gills.
 This maximizes the amount of oxygen picked up
by the blood:
- As the blood gains oxygen, it always encounters
water having an even higher oxygen content.
- No equilibrium is ever reached. 80-90% of
dissolved oxygen is extracted.
If flow of blood was concurrent to water (same
direction) an equilibrium point would occur and
less oxygen would be transferred into blood.
Anatomy of Gills in Bony Fishes
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Respiration in
Terrestrial Environments:
Respiratory
Systems
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Air has much more available oxygen than water
but it is a drying environment. Thus, terrestrial
animals tend to have invaginated respiratory
systems to protect them from too much water
loss.
- Exception is earthworms which breathe
through their skin but must keep body
surface moist by secreting mucus, etc.
- Earthworms also do their best to remain in
damp soil during the daytime.
Land Environments:
Tracheae
Respiratory
Systems
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Insects and other terrestrial arthropods
Respiratory system consists of branched air tubes
called tracheae
Oxygen enters tracheae at spiracles, valvelike
openings on each side of the body.
Tracheae branch & branch until they end in tiny
channels, the tracheoles, that are in direct contact
with body cells.
Very efficient system for delivering oxygen to cells
that does NOT involve any respiratory pigments
or circulatory system.
Tracheae of Insects
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Land Environments:
Lungs of Vertebrates
Respiratory
Systems
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Terrestrial vertebrates have evolved lungs
Vascular outgrowths from lower pharyngeal region
Lungs of amphibians
- Possess a short tracheae which divides into two bronchi that
open into lungs
- Many also breathe to some extent through skin
Reptiles
- Inner lining of lungs is more finely divided in reptiles than in
amphibians
Lungs of birds and mammals are elaborately subdivided
All terrestrial vertebrates, except birds, use a tidal
ventilation system
Air moves in and out by the same route. Thus, fresh
incoming air is mixed with some left-over stale air.
Ventilation in Frogs
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Amphibians use both negative & positive pressure to
ventilate their lungs:
1. Negative pressure: With mouth closed but nostrils
open, the floor of the mouth is lowered. The lower
air pressure will cause air to rush into their mouth
cavity.
2. Positive pressure: With mouth & nostrils shut, floor
of mouth rises & pushes air into the lungs.
Ventilation in
Terrestrial Vertebrates
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Inspiration in mammals (Inhalation)
Create negative pressure in lungs
The rib cage is elevated by intercostal muscles.
The diaphragm contracts and pushes down towards belly
Thoracic pressure decreases to less than atmospheric
pressure
Atmospheric pressure forces air into the lungs
Expiration in mammals (Exhalation)
Create positive pressure in lungs
The rib cage is lowered as intercostal muscles relax
The diaphragm relaxes and rises back up towards chest
Thoracic pressure increases to more than atmospheric
pressure
Forces air out the lungs
Inspiration Versus Expiration
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Respiratory
Systems
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Ventilation in Birds
Birds use a one-way ventilation mechanism in lungs
How does this work?
- Incoming air does not directly enter the lungs,
instead it is carried by trachea to a set of
posterior air sacs.
- Air is then pushed through tiny tubes called
parabronchi which are surrounded by capillaries
- Air ends up in anterior air sacs which expel it from
body.
Thus, fresh & used air never mix in the lungs of birds.
Results in a higher partial pressure of oxygen in the
lungs
Oxygen uptake with each breath is greater than in
other vertebrates
Respiratory System in Birds
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Respiratory
Systems
Human Respiratory System
As air moves through upper respiratory system
(nostrils, nasal cavities, pharynx, larynx,
trachea):
It is filtered to free it of debris (cilia help this
Warmed, and
Humidified
When air reaches lungs
It is at body temperature, and
Its humidity is 100%
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The Human Respiratory Tract
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Respiratory
Systems
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Human Respiratory System
Air passes from pharynx through glottis, an opening in
larynx
Larynx (voice box) contains vocal cords which allow us
to produce sounds
Trachea
Permanently held open by cartilage rings
Facilitates movement of air
When food is swallowed:
The larynx rises, and
The glottis is closed by a flap of tissue called the
epiglottis
Backward movement of soft palate covers the entrance of
nasal passages into the pharynx
The Human Respiratory Tract
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Respiratory
Systems
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Human Respiratory System
Trachea divides and forms two primary bronchi
Bronchi enter the right and left lungs
Bronchi branch until there are a great number of
tiny bronchioles. The walls of bronchioles get
thinner & rings of cartilage are no longer
present.
Each bronchiole terminates in an elongated space
enclosed by a great number of air pockets, or
sacs, called alveoli. Gas exchange occurs
between air in sacs and blood in surrounding
capillaries.
The Human Respiratory Tract
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Respiratory
Systems
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Control of Breathing Rate in Humans
Average person takes a breath about 14 times
per minute when at rest
Respiratory control center, located in pons &
medulla oblongata of the brain, can change the
normal rate according to circumstances.
- When a drop in pH is noted (due to increase in
CO2) the control center increases rate & depth
of breathing.
- Normally, O2 concentration in blood has little
effect on breathing rate. However, if O2 level is
very low detectors in aorta & carotid arteries
send an alarm to resp. control centers in brain.
Respiratory
Systems
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Gas Exchange and Transport
External Respiration
1. Blood flowing into pulmonary capillaries has
higher CO2 concentration than air in the
alveolar air sacs.
CO2 diffuses out of pulmonary capillaries &
into air sacs.
2. Blood coming into pulmonary capillaries has
lower concentration of O2 than alveolar air.
O2 diffuses from alveoli into capillaries.
External and Internal respiration
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Respiratory
Systems
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Transport of Oxygen
Most oxygen that enters the pulmonary capillaries
combines with hemoglobin in red blood cells to
form oxyhemoglobin.
- Each of the 4 polypeptide chains of hemoglobin is
folded around a heme (iron) group.
 Iron forms a loose bond with oxygen.
•At normal partial pressure of O2 in lungs, hemoglobin
is almost saturated with oxygen.
•At partial pressure of O2 in tissues, oxyhemoglobin
gives up much of its oxygen during internal
respiration.
- Acidity & warm temperatures promote this
response in the tissues.
Hemoglobin
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Hemoglobin Saturation
in Relation to Temperature and Acidity
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Respiratory
Systems
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Transport of Carbon Dioxide
Internal Respiration
Carbon dioxide enters blood from the tissues
1. Some carbon dioxide combines with hemoglobin to
form carbaminohemoglobin
2. Most carbon dioxide is transported in the form of
bicarbonate ions (HCO3-)
- CO2 combines with water, forming carbonic acid
(H2CO3) & then dissociates into H+ & HCO3-.
- Carbonic anhydrase, an enzyme, speeds up this
reaction.
- H+ combines with globin part of hemoglobin
(HHb) & HCO3- diffuses into plasma. This plays
vital role in maintaining proper pH of blood.
External and Internal respiration
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Respiratory
Systems
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Transport of Carbon Dioxide
External Respiration
1. As blood enters the pulmonary capillaries,
most of the CO2 is present in plasma as
HCO32. HHb gives up the H+ it has been carrying &
carbonic anhydrase speeds up this reaction:
H+ + HCO3-  H2CO3  H2O + CO2
3. Now free CO2 diffuses out of blood into the
alveoli of lungs.
External and Internal respiration
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Respiratory
Systems
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Respiration and Health
Upper Respiratory Tract Infections
Consists of nose, pharynx & larynx. Infections
can spread from nasal cavities to sinuses, to
middle ears & to larynx
Strep Throat
- Usually starts as viral infection that becomes a
secondary bacterial infection.
- Caused by Streptococcus pyogenes. Can become
generalized upper respiratory infection.
- Symptoms: severe sore throat, high fever, white
patches on dark red throat
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Systems
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Respiration and Health
Sinusitis
- Infection of sinuses, facial cavities that drain into
nasal cavities
- Develops when nasal congestion blocks openings
into the sinuses
Tonsillitis
- Infection of tonsils, masses of lymphatic tissue.
- Tonsils help to remove pathogens from pharynx
Laryngitis
- Infection of larynx accompanied by hoarseness &
possibly an inability to talk.
Respiratory
Systems
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Respiration and Health
Lower Respiratory Tract Infections
Infections of trachea, bronchi, bronchioles &
lungs
Acute bronchitis
- Infection of primary and secondary bronchi
- Usually preceded by a viral upper respiratory
infection that led to secondary bacterial infection
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Systems
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Respiration and Health
Pneumonia
- Viral, bacterial or fungal infection of the lungs in
which bronchi and alveoli fill with pus & fluid
- Most often preceded by influenza, the “flu”.
- Can be localized in specific lobules of lungs;
more lobules the more serious the infection
- AIDS patients often get a rare pneumonia
caused by a fungus called Pneumocystis carinii.
Respiratory
Systems
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Respiration and Health
Pulmonary tuberculosis (TB)
- Caused by tubercle bacillus, a type of bacterium.
- Can test people with a simple skin test to see if
they have been exposed to tuberculosis
- Reaction to bacterium:
1. When the bacteria invade the lung, the cells
build a protective capsule around the bacteria.
This capsule is called a tubercle.
2. With a good immune system the body might kill
the encapsulated bacteria
3. With a weakened immune system, like in AIDS,
the bacteria can be released & hurt the body
Common
Bronchial and Pulmonary Diseases
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Respiratory
Systems
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Disorders
Pulmonary fibrosis
Fibrous connective tissue builds up in the lungs
Due to inhalation of particles such as silica, coal
dust, asbestos & fiberglass.
Lungs can’t inflate properly
Asbestos also associated with cancer
Chronic bronchitis
Airways inflamed and filled with mucus
Coughing causes bronchi to undergo changes,
including loss of cilia & normal cleansing action
Most frequent cause is smoking.
Common
Bronchial and Pulmonary Diseases
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Respiratory
Systems
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Disorders
Emphysema
Alveoli are distended (stretched) and walls are
damaged reducing surface area available for gas
exchange
Often preceded by chronic bronchitis
Elastic recoil of lungs is reduced; thus expiration
is very difficult
Heart works harder to force more blood to lungs
Symptoms: breathlessness & cough, depression
& irritability
Common
Bronchial and Pulmonary Diseases
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Respiratory
Systems
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Disorders
Asthma
Airways are unusually sensitive to specific irritants
- When exposed to the irritants, the smooth
muscles in the bronchioles undergo spasms
- Irritants can be pollen, animal dander, dust,
cigarette smoke, fumes & even cold air
- Not curable but is treatable with inhalers that
can control inflammation of bronchioles &
prevent attack or stop muscle spasms during an
attack
Common
Bronchial and Pulmonary Diseases
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Respiratory
Systems
Disorders
Lung Cancer
Begins with thickening and callusing of the cells
lining the airways
Loss of cilia follows; thus it is impossible to
prevent dust & dirt from settling into lungs
Atypical nuclei appear in callused lining
Creates a tumor of such cells
Final step is when some cells break loose &
penetrate other tissues (metastasis)
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