Gas Exchange Systems Flashcards
– are made up of gas exchange surfaces and the mechanisms that ventilate and perfuse those surfaces
gas exchange systems
cells need to obtain oxygen from the environment to produce an adequate supply of – by cellular respiration
ATP
CO2 is a – product of cellular respiration and it must be removed from the body to prevent toxic effects
end
- is the only means by which respiratory gases are exchanged between an animal’s internal body fluids and the outside medium
diffusion
the total number os gas molecules in a specified volume depends on –
pressure
atmospheric pressure at sea level is
760 mm of mercury
Because dry air is 20.9% O2, the – at sea level is 20.9% of 760 mm Hg or about 159 mm Hg
partial pressure of oxygen
the actual amount of gas in a liquid depends on the partial pressure of that gas in the gas phases in contact with the liquid as well as on the – of that gas in that liquid
solubility
the rate at which a gas such as oxygen diffuses between two locations
Q
D is the – which is a characteristic of the diffusing substance, the medium, and the temperature
diffusion coefficient
all substances diffuse faster at – temperatures and faster in air than in water
higher
cross-sectional area through which the gas is diffusing
A
P1 and P2 are the – of the gas at the two locations
partial pressures
the path length or distance between the two locations
L
(P1 -P2)/L is a
partial pressure gradient
Animals maximize D for respiratory gases by using – rather than – as their gas exchange medium
air rather than water
true or false: the slow diffusion of oxygen molecules in water affects both air-and water- breathing animals
true
oxygen content of air is much – than the oxygen content of an equal amount of water
higher
oxygen diffuses more – in air than in water
rapidly
animals has to do – to mover water or air over its gas exchange surfaces; more energy is required to move the denser water
work
fish need more oxygen when water is warmer but warm water carries – oxygen than cold water
less
– decreases with altitude
oxygen availability
the partial pressure of CO2 in the atmosphere is close to – both and sea level and atop Mount Everest
zero
getting rid of CO2 is not a problem for water breathing animals because CO2 is much more – in water than O2
soluble
– surface area for gas exchange
increase
– partial pressure difference driving diffusion
maximize
– the diffusion path length
minimize
– the diffusion that takes place in an aqueous medium
minimize
highly branched and folded extensions of the body surface that provide a large surface area for gas exchange with water; found in larval amphibians and insects
external gills
very thin tissues in gills and lungs reduce the
diffusion path length
external gills are vulnerable to damages so many animals evolved – for gills
protective body cavities
are internal cavities for respiratory gas exchange with air
lungs
lungs have a large surface area because they are highly – and because they are elastic they can be – with air and deflated
divided; inflated
actively moving the external medium (air or water) over the gas exchange surfaces regularly exposes those surfaces to fresh respiratory medium containing max CO2 and O2 concentrations
ventilation
actively moving the internal medium (blood) over the internal side of the exchange surfaces transports CO2 to those surfaces and O2 away from them
perfusion
insects’ – system have airways throughout their bodies
tracheal
insect respiratory system communicates with the outside environment though gated openings called – in the side of the abdomen
spiracles
spiracles open to allow gas exchange and then close to decrease –
water loss
spiracles open into tubes called tracheae that branch into even finer tubes or tracheoles which end in tiny – that are the actual gas exchange surfaces
air capillaries
in insect’s – are close to an air capillary
highly active tissues
fish gills use - flow to maximize gas exchange
countercurrent
internal gills of fish are supported by – that lie between the mouth cavity and the protective opercular flaps on the sides of the fish just behind the eyes
gill arches
water flows – into the fish’s mouth, over the gils and out from under the opercular flaps
unidirectionally
true or false: fish gills are continuously bathed with fresh water maximizing PO2 on the external gill surfaces
true
on the internal side of the gill membranes, the circulation of blood – the PO2 by sweeping O2 away as rapidly as it diffuses
minimizes
each gill consists of 100s of ribbonlike –
gill filaments
the upper and lower flat surfaces of each gill filament are covered with rows of evenly spaced folds called
lamellae
gas exchange surfaces for fish
lamellae
– blood vessels bring deoxygenated blood to the gills
afferent
– blood vessels take oxygenated blood away from the gills
efferent
blood perfusion of the lamellae is – to the flow of water over the lamellae
countercurrent
some fish (anchovies, tuna, certain sharks) ventilate their gills by – with their mouths open
constantly swimming
most fish ventilate their gills by a
two-pump mechanism
lungs of a bird are - than the lungs of a similar-sized mammal
smaller
bird lungs are – during inhalation and – during exhalation
compressed during inhalation
expand during exhalation
the remaining air in lungs and airways after exhalation
dead space
air flow – through the lungs in birds
unidirectionally
birds have very little – and the fresh incoming air is not mixed with stale air
dead space
birds have – at several locations in their bodies
air sacs
in birds, – receive inhaled air but are not gas exchange surfaces
air sacs
trachea –> bronchi –> parabronchi –> tiny __
air capillaries
the gas exchange surface in birds
air capillaries
a single breath remains in a bird’s gas exchange system for – cycles of inhalation and exhalation
2
in birds, inhalation – the sacs
expands
in birds, exhalation – the sacs
compresses
birds can supply their gas exchange surfaces with a continuous flow of fresh air that has a – close to that of the ambient air
PO2
In birds, even when the PO2 of the ambient air is only slightly above that of the blood O2 can - from air to blood
diffuse
– ventilation produces dead space that limits gas exchange efficiency
tidal
lungs evolved as out pockets of the –
digestive tract
air flows in and exhaled gases flow out by the same route
tidal ventilation
normal amount of air that moves in and out per breath when at rest
tidal volume (TV)
When we breathe in as much as possible, the additional volume is
inspiratory reserve volume (IRV)
additional air that can be forcefully exhaled
expiratory reserve volume (ERV)
the maximum capacity for air exchange in one breather = TV + IRV + ERV
vital capacity
dead space is also called
residual volume (RV)
ERV + RV =
functional residual volume
RV is important because it contributes to the FRC and to the – of oxygen in inhaled air
dilution
trachea’s thin walls are prevented from collapsing by C-shaped bands of – as air pressure changes during the breathing cycle
cartilage
human site of gas exchange
alveoli
because the airways conduct air only to and from the alveoli and do not themselves participate in gas exchange their volume is
dead space
where – meets alveolus very little tissue separates them so the length of diffusion path between air and blood is less than 2 micrometers
capillary
a condition in which inflammation damages and eventually destroys the walls of the alveoli and the 4th leading cause of US deaths
emphysema
emphysema: lungs have fewer but larger alveoli, RV – and lungs lose elasticity
increases
mammalian lungs secrete – and – that do not directly influence gas exchange but rather aid ventilation
mucus and surfactant
lining the airways cilia continually beats sweeping mucus, with its trapped debris, up toward the pharynx where it can be swallowed or spit out
mucus escalator
substance that reduces the surface tension of a liquid
surfactant
gives the surface of a liquid properties of an elastic membrane
surface tension
fatty, detergent-like substance that is critical for reducing the work necessary to inflate lungs
lung surfactant
certain cells in the alveoli release surfactant molecules when they are –
stretched
lungs are ventilated by – in the thoracic cavity
pressure changes
the lungs lie within the – which is bounded by the ribs and the diaphragm
thoracic cavity
each lung is covered by a continuous sheet of tissue called the – that also lines the thoracic cavity adjacent to that lung
pleural membrane
air enters the lungs from the – via the trachea and bronchi and eventually reaches the alveoli
oral cavity or nasal passages
there is no real space between the pleural membranes of the lung and the thoracic cavity but there is a thin –
film of fluid
pleural membranes cannot separate because of the – of the thin film of fluid between them, they pull on the lungs
surface tension
true or false: lungs are a closed cavity
false: they actually have an airway to the atmosphere and can expand
between the ribs are two sets of
intercostal muscle
expand the thoracic cavity by lifting the ribs up and outward
external intercostal muscles
decrease the volume of the thoracic cavity by pulling the ribs down an inward
internal intercostal muscles
inhalation is an – process spurred by contraction of the diaphragm
active
exhalation is generally a – process as the diaphragm relaxes
passive
there is always – pressure in the pleural cavity which is the space between the pleural membranes
negative
during inhalation: diaphragm – thoracic cavity expands, intrapleural pressure becomes more negative, lungs expand, air rushes in
contracts
during exhalation: diaphragm - thoracic cavity contracts, intrapleural pressure becomes less negative, lungs contact, gases are expelled
relaxes
Ventilation and perfusion work together to maximize the – across the gas exchange surface
partial pressure gradients
ventilation deliver – to the environmental side of the exchange surface where it diffuses across and is swept away by the perfusing blood which carries it to the tissue that need it
oxygen
perfusion delivers – to the exchange surface where it diffuse out and is swept away by ventilation
carbon dioxide
red blood cells contain enormous amount of –
hemoglobin molecules
an iron-containing ring structure that can reversible bind a molecule of oxygen
heme group
hemoglobin’s ability to pick up or release oxygen depends on the – in its environment
PO2
as the blood circulates around the body, it releases only about – in four of the O2 molecules it carries
one
hemoglobin keeps 75% of it O2 in reserve to meet the peak demands of –
highly active tissues
CO bind to hemoglobin with a 230-fold higher – than oxygen
affinity
the average PO2 of deoxygenated blood returning to the heart is
40 mm Hg
the PO2 of blood leaving the lungs is about
100 mm Hg
25% of the O2 in arterial blood is released to tissues during – or light exercise
rest
an oxygen reserve of 75% is helm by the hemoglobin and can be released to tissues with a low –
PO2
muscle cells have their own O2 binding molecule
myoglobin
myoglobin consists of just – polypeptide chain associated with an iron-containing ring structure that can bind one O2 molecule
one
myoglobin has a higher – for O2 than hemoglobin does, so it picks up and hold O2 at PO2 values at which hemoglobin is releasing bound O2
affinity
human fetus has a form of hemoglobin consisting of two a-globin and two –
y-globin chains
fetal hemoglobin has a higher affinity for O2 than adult hemoglobin shifting the oxygen binding/dissociation curve to the
left
the influence of pH on the function of hemoglobin
Bohr effect
blood passes through metabolically active tissues picking up acidic metabolites –> blood pH falls –> hemoglobin release – of its O2
more
low PO2 –> increase rate of glycolysis –> producing more – which is an important regulator of hemoglobin function
2,3-Bisphosphoglyceric acid
Like, low pH BPG shifts the O2 binding/dissociation curve of mammalian hemoglobin to the – (lowers hemoglobin’s affinity for O2)
right
when humans go to high altitudes or exercise, their RBC are exposed to lower PO2 and the level of BPG goes up, making it – for hemoglobin to deliver more O2 to tissues
easier
the reason fetal hemoglobin has a left-shifted O2binding/dissociation curve is that its y-globin chains have a – affinity for BPG than the B-globin chains of adult hemoglobin
lower
most CO2 produced by tissues is transported to the lungs in the for of
bicarbonate ions (HCO3-)
When CO2 dissolves in water, some of it slowly reacts with the water molecules to form – some of which then dissociates into a proton (H+) and a bicarbonate ion (HCO3-)
carbonic acid (H2CO3)
In the endothelial cells of the capillaries and in the RBC, the enzyme - speeds up the conversion of CO2 to H2CO3
carbonic anhydrase (only speeds up a reversible react but does not determine direction)
groups of respiratory motor neurons in the – increase their firing rates just before an inhalation begins
medulla
a small amount of CO2 in the bloodstream stimulates a – increase in breathing rate
large
a large drop in arterial O2 has – effect on breathing rates
little
If the brainstem is cut below the pons but above the medulla, breathing –
continues but is irregular
if the spinal cord in the neck is severed, breathing
ceases
for water-breathing animals, – is the primary feedback stimulus for gill ventilation
oxygen
chemoreceptors on the surface of the medulla are sensitive to the – and – of the cerebrospinal fluid
PCO2 and pH
chemoreceptors on large blood vessels leaving the heart are sensitive to the - in blood
oxygen
the real stimulus for breathing is
pH (although me measure PCO2)
carotid and aortic bodies are
chemosensors
