Chapter 8 Adaptaions For Gas Echange Flashcards
Define gas exchange
The diffusion of gases down a concentration gradient across a respiratory surface, between an organism and its environment
What are the essential characteristics of a respiratory surface?
Large surface area Thin Permeable to respiratory gases Moist Maintain a concentration gradient
What is the parallel flow mechanism in cartilaginous fish?
Blood and water flow in the same direction at the gill lamellae, maintaining a concentration gradient for oxygen to diffuse into the blood only up to the point where its concentration in the blood and water is equal.
Why is the ventilation system in cartilaginous fish less efficient than bony fish?
They do not have a special mechanism to force water over the gills, and so many must keep swimming for ventilation to happen.
Parallel flow reaches equilibrium, so the bloods oxygen concentration is limited to 50% of its possible maximum value.
What is the operculum?
The covering over the gills of a bony fish.
How does the ventilation mechanism operate in bony fish?
The mouth opens, operculum closes, floor of mouth is lowered, volume inside mouth increases, pressure decreases, water flows in as the pressure outside is higher than inside mouth. The mouth closes, operculum opens and the floor of the moth is raised. The volume inside the mouth decreases and pressure increases. Water flows out over the gills because pressure inside is higher than outside the mouth. Water flows out of the operculum cavity.
What are the characteristics of gills in bony fish?
Bony fish have 4 gills, each supported by a gill arch made of bone. Along each gill arch are many thin projections called gill filaments. On the gill filaments are the gill lamellae, the gas exchange surface. They are held apart by water flowing between them and they provide a large surface area for gas exchange. Out of water they collapse, much less area is exposed, efficiency of gas exchange decreases and the fish dies.
What is counter current flow?
Blood and water flow in opposite directions at the gill lamellae, maintaining the concentration gradient for oxygen diffusion, along their entire length.
What percentage of oxygen is extracted from the available oxygen in bony fish?
80%
Why is counter current flow more efficient than parallel flow?
Water contains less oxygen than air and so a more efficient system is needed to extract as much oxygen as possible.
Oxygen diffuses across the entire length of the gill lamellae in counter current flow.
Counter current flow does not reach equilibrium.
What is the structure of the human breathing system?
Pleural membranes cover each lung, the membranes fluid prevent friction between the lungs and chest cavity as the lungs move. The intercostal muscles control the movement of ribs. The trachea is a flexible airway, bringing air to the lungs. Two bronchi branch off the trachea into bronchioles. At the end of the bronchioles are air sacs called alveoli.
How does the ventilation system of inhalation (inspiration work)?
The intercostal muscles contract, the ribs are pulled up and outwards. At the same time, the diaphragm muscles contract. Both actions increase thorax volume reducing pressure in the lungs. Atmospheric pressure is higher than the pressure in the lungs, so air is forced into the lungs.
How does the ventilation system of exhalation (expiration)?
The intercostal muscles relax. The ribs move downwards and inwards. At the same time, the diaphragm relaxes. Both actions decrease thorax volume, increasing pressure in the lungs. Air pressure in the lungs is greater than atmospheric pressure, forcing air out of the lungs.
What is the function of surfactant?
A moist secretion containing phospholipids and proteins creating a low surface tension preventing the alveoli from collapsing during expiration/exhalation. It also provides a medium for gases to dissolve in before they diffuse in or out.
How are the alveoli a good gas exchange surface?
Large sugar face area
Moist with surfactant
Alveoli walls are one cell thick=short diffusion pathway
Capillary network maintains diffusion gradient
