Physiology Respiratory System Flashcards
What is ventilation in the context of the respiratory system?
Ventilation is the renewal of air or water in contact with the body surface devoted to the uptake of gases.
What are the two main types of respiratory pathways?
The two main types are external respiration and internal respiration.
What is external respiration?
External respiration is the exchange of gases between the lungs and the internal environment.
What is internal respiration?
Internal respiration is cellular respiration for the oxidation of glucose using O2 to obtain energy, producing water and CO2 as waste products.
What is partial pressure (p)?
Partial pressure is the individual pressure exerted by a single gas within a mixture of gases.
How does the amount of O2 available to aquatic organisms compare to that available to terrestrial organisms?
The amount of O2 available to aquatic organisms is about 30 times lower than that available to terrestrial organisms
What law explains the difference in O2 amounts in air and water?
Henry’s Law explains the difference, stating that the concentration of a gas is proportional to its partial pressure.
What factors affect the absorption coefficient of oxygen in water?
Temperature and salinity affect the absorption coefficient; higher temperature and salinity lower the dissolution capability of O2 in water.
How is the exchange of O2 and CO2 with the external environment achieved?
The exchange is achieved by simple diffusion following the 1st Fick’s law.
What does the 1st Fick’s law state about solutes?
Solutes move down a concentration gradient, and this process doesn’t require energy as it is passive.
What is the equation for the rate of diffusion (Q) according to Fick’s law?
What do the variables in the diffusion rate equation represent?
How do small organisms with simple organization achieve respiratory exchange?
They have a short distance (Δx) between cells and the external medium, allowing for efficient gas exchange.
How have large animals solved the problem of distance in gas exchange?
- they evolved a circulatory system
- expanded the exchange surfaces (A)
- increased the partial pressure gradient of O2 (ΔpO2)
- enhanced O2 solubility with molecules like hemoglobin
What are the five main gas exchange mechanisms in the animal kingdom?
- Simple diffusion
- tidal exchange
- cocurrent exchange
- countercurrent exchange
- crosscurrent exchange.
Describe the simple diffusion mechanism of gas exchange.
The external fluid does not circulate while the internal fluid is renewed. The gradient in pO2 is determined by O2 consumption by cells or the presence of a respiratory pigment.
In which organisms is simple diffusion present?
It is present in unicellular organisms, diblastic animals (e.g., sponges, cnidarians), and some triblastic animals with integumentary respiration (e.g., flatworms, amphibians).
Describe the tidal exchange mechanism of gas exchange.
Both the external fluid (usually air) and the internal fluid are renewed, with pO2 gradient favored by ventilation and the binding of O2 with hemoglobin. This system is present in mammalian lungs.
How does air move in tidal exchange?
Air enters alveoli during inhalation, exchanges gas with the respiratory surface, and exits with exhalation. There is a mixing of new and old air in the alveoli.
Describe the cocurrent exchange mechanism of gas exchange.
The external fluid (usually water) and the internal fluid move in the same direction, with the gradient in pO2 being maximal at the beginning of the exchange. This system is typical of the gills of many invertebrates.
Why is cocurrent exchange not very efficient?
As O2 concentration in blood increases and O2 concentration in water decreases, the diffusion slows down until it stops completely, making it insufficient for fast-moving or large animals.
Describe the countercurrent exchange mechanism of gas exchange.
The external fluid and the internal fluid flow in opposite directions, maintaining a low but constant pO2 gradient for continuous O2 exchange. This system is found in the gills of teleost fish and the placenta of non-primate mammals.
Why is countercurrent exchange efficient?
The constant gradient allows for continuous O2 diffusion, making it efficient throughout the length of the respiratory surface.
Describe the crosscurrent exchange mechanism of gas exchange.
The external fluid and the internal fluid circulate in the same direction, but the afferent vessel temporarily contacts the interface. This is typical of bird lungs and allows high oxygen extraction efficiency.
How does the crosscurrent exchange mechanism work in bird lungs?
Capillaries from a main vessel contact the exchange surface perpendicularly, allowing sequential uptake of O2 along the capillaries. The final oxygen level in blood is higher than the exhaled air’s oxygen level.
What is a key advantage of air-breathing animals regarding oxygen supply?
Air-breathing animals can use an unlimited oxygen supply which is much greater than the amount available to animals using oxygen dissolved in water.
Why is ventilation less energy-intensive for air-breathing animals?
- Air is less dense than water, meaning it takes less effort to move it into and out of the lungs or other respiratory organs.
- Therefore, air-breathing animals expend less energy in ventilating their respiratory systems compared to water-breathing animals
- which must overcome the higher density of water to obtain oxygen
How does gas diffusion in air compare to water?
Gas diffusion is faster in air than in water, allowing quicker diffusion inside alveoli and into the blood.
What is a major disadvantage of air-breathing animals related to dehydration?
Air-breathing animals face the risk of dehydration because air is a dry fluid, leading to potential water loss through the respiratory surface.
Why is it necessary for the respiratory surface of air-breathing animals to have a water layer?
Oxygen must be hydrated to pass through the respiratory surface, so a thin water layer is necessary for the initial solubilization of O2.
What challenge do air-breathing animals face regarding the water layer on the respiratory surface?
Maintaining the water layer is difficult due to the high possibility of water evaporation.
Why don’t water-breathing animals risk dehydration?
Their respiratory surfaces are surrounded by water, preventing dehydration.
How is the respiratory surface in water-breathing animals adapted for gas exchange?
The respiratory surface is already in contact with water, making oxygen passage easier since it’s already hydrated.
What is a significant disadvantage for water-breathing animals regarding oxygen availability?
The amount of O2 in water is smaller because the solubility of oxygen in water is quite low.
How does the density of water affect ventilation in water-breathing animals?
Moving water from the external environment to the exchange surface is difficult and requires greater energy consumption.
What is integumentary breathing?
Integumentary breathing is the use of the entire body surface for the exchange of O2 and CO2.
Which animals primarily use integumentary respiration?
Many small aquatic invertebrates and some large ones like sea spiders use integumentary respiration.
How do amphibians utilize integumentary respiration?
Amphibians exchange up to 20% of O2 and up to 90% of CO2 through their skin.
How do annelids like Arenicola marina manage respiration?
They extract O2 from water entering their burrow and renew the water by moving in and out of the tube, using a cross-current mechanism for high efficiency.
What percentage of oxygen extracted by annelids is devoted to metabolism?
50-60% of the extracted oxygen is devoted to metabolism.
What are the main components of fish gills?
Fish gills consist of 4 gill arches, primary lamellae, and secondary lamellae.
What is the function of primary lamellae in fish gills?
Primary lamellae increase the surface area for gas exchange.
How does countercurrent exchange in fish gills work?
Blood in the secondary lamellae flows in the opposite direction to water, allowing efficient oxygen uptake.
How does the Root effect facilitate oxygen diffusion into the swim bladder?
High H+ ion production in the gas gland lowers pH, decreasing hemoglobin’s oxygen affinity and enabling oxygen release and diffusion into the swim bladder.
How is ventilation controlled in terms of muscle activity?
Respiratory muscles, particularly the diaphragm controlled by the phrenic nerve, initiate inspiration through contraction and relaxation for expiration.
