Gas Exchange Flashcards
What is gas exchange?
Gas exchange is the inhalation of O2 into the body, used to produce ATP in cells, and the exhalation of CO2, a by-product of these reactions.
What is the primary function of the respiratory system?
Efficient way to bring oxygen in and remove waste products.
How is respiration related to environment? Provide an example.
Similar to other functions throughout an animal’s body, the way an animal breathes is largely dependent upon the environment in which it lives.
O2 in aquatic environment:
* Lower diffusion rate & solubility
* Less available O2 in a given volume of fluid
We can conclude that animals need to use more energy to run an
O2 ’pump’ or need an more efficient O2 ‘pump’ in water.
What is Fick’s first law?
Fick’s first law a solute will move from a region of high concentration to a region of low
concentration across a concentration gradient.
What is Fick’s second law?
Fick’s second law the amount of substance diffuses across a surface is proportional to the
area of that surface and inversely proportional to the distance across which it diffuse.
Name and describe the two components of external respiration
Ventilation - active
movement of respiratory
medium
* Perfusion: gas uptake
What is internal respiration?
Use of O2 to make energy
What is important about perfusion and ventilation in gas exchange?
for gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible. Ventilatory structures and perfusion structures have thus evolved to maximize said compatibility.
How does scaling affect external respiration? Why?
Determines ventilation mechanism. Respiratory systems get more complex as animals get larger, since increase in size correlates with larger diffusion distances and a drop in SA:V ratio.
How does ventilation occur for small scaled animals?
For small multicellular organisms, diffusion across the outer membrane is sufficient to meet their oxygen needsThis is what is known as direct diffusion. The cells are close enough to the surface of the body and are kept moist for quick diffusion. Their flatness also increase the available SA. Large SA:V.
What is ventilation like for large scaled animals?
- SA:V small, X and A
must improve
oxygen uptake - Need specialized
structures, such as
gills or lungs
What are examples of structures that increase SA?
gills and lungs
How do gills work? Why is this possible?
Dissolved oxygen diffuses across the gills from water and directly into the bloodstream or coelomic fluid. O2 concentration in water is higher than in the gills.
What groups are gills found in?
Gills are found in mollusks, annelids, and crustaceans.
How do gills increase SA?
- Gill arch (larger blood vessels)
- Gill filaments (smaller blood vessels)
- Gill lamellae (capillaries)
What is unidirectional flow? What animals use it?
Unidirectional flow: medium enters at one point and exits via another; fish, insects (spiracular), birds
What kind of blood flow is in fish gills?
blood flows in opposite direction of blood: countercurrent exchange/flow
Why is countercurrent exchange more efficient in gills than same direction?
diffusion would be restricted to a smaller distance; countercurrent is therefore more efficient.
What is spiracular breathing?
Tracheal system open to air via spiracles which lead into
trachea internally to contact hemolymph
What is the most efficient form of breathing in active animals?
Tracheal system open to air via spiracles which lead into
trachea internally to contact hemolymph
What do spiracles do?
- Control air flow into trachea
- Control water loss
- Keeps dust out
How do insects increase rate of gas exchange?
- Tips of tracheoles are filled with fluid
- In active tissues, fluid is replaced by air (via osmosis to tissues)
How do birds breathe?
Two complete cycles of inhalation and exhalation for each breath of air
Explain the movement of air in each breath in birds.
First inhalation: air moves to posterior air sacs
First exhalation: air moves to parabronchi from posterior air sacs
Second inhalation: air moves to anterior air sace
Second exhalation: air exits through trachea
What kind of exchange happens in birds? What is it?
Cross-current exchange: capillaries are perpendicular to parabronchi
How efficient is cross-current exchange?
more efficient than concurrent but less so than crosscurrent
How do mammals breathe?
Tidal flow: medium enters and exits a chamber
What purposes does inhalation serve?
inhalation serves several purposes in addition to bringing oxygen into the respiratory system: warming, humidifying, removal of particles.
What are differences between breathing in mammals and birds?
- alveoli vs. air sacs
- tidal flow vs. unidirectional flow
What is Dalton’s law?
Total pressure is the sum of all the partial pressures of a gaseous mixture
What is Boyle’s law?
- gases move from areas of high pressure to areas of low
pressure - The pressure of a gas is inversely proportional to the
volume of its container
What is Henry’s Law?
the concentration of gas in a liquid is directly proportional to the solubility and
partial pressure of that gas
* In other words, the partial pressure of oxygen or carbon dioxide is directly
proportional to the concentration of these gases in blood
How does pulmonary ventilation occur?
Chest expands, increasing volume and decreasing pressure in order to draw air in.
What are the 3 types of pressure that affect pulmonary ventilation?
- Atmospheric
* 760 mm Hg at sea level - Intra-alveolar
* Also known as intrapulmonary pressure, this is the pressure of the air within the
alveoli, which changes during the different phases of breathing - Intrapleural
* the pressure of the air within the pleural cavity, between the visceral and parietal
pleurae
How are intrapleural and intraalveolar pressure connected?
intrapleural always lower than, or negative to, the intra-alveolar pressure (and therefore
also to atmospheric pressure)
What does intrapleural pressure do?
ensures that lungs stay closely connected to thoracic wall and follow its
movements during a breath cycle
How are atmospheric and intra alveolar pressure connected?
alveolar decreases, is less than atmospheric, allowing air to enter
What is the major cause for pressure changes in respiration in mammals?
Contraction and relaxation of the diaphragm and intercostals muscles (found between the ribs) cause most of the pressure changes
Are the lungs passive or active during breathing?
The lungs are passive during breathing. The movement is dependent upon muscle fibers in the diaphragm and thorax.
What is ventilation?
active movement of respiratory medium
What is perfusion?
the flow of blood in the pulmonary capillaries which ensures gas delivery
within the body
What about the alveoli allows perfusion to be so effective in mammals?
The large surface area, combined with the thin-walled nature of the alveolar cells, allows
gases to easily diffuse across the cells. Increased A, decreased X.
What is the difference in regulation of ventilation and perfusion?
Ventilation is regulated by the diameter of the
airways, whereas perfusion is regulated by the
diameter of the blood vessels.
Size is independent of complexity of some organ systems, like the respiratory system, of an organism. T or F?
F
Based on the figure above and our discussion in class, which frustum from the two above, if turned upside down, will empty first and why?
The smaller frustum since it contains less sand.
