Unit 3 - Mammalian gas exchange and ventilation Flashcards
Why are specialised exchange surfaces are needed by some organisms?
-they have a low SA:V so exchange surfaces increase that
-maximise efficiency of diffusion
-ensure the demand for oxygen and glucose is met
What are the 4 features of efficient exchange surfaces?
-Increased surface area
-Thin layers
-Good blood supply
-Ventilation to maintain a diffusion gradient
Why does an increased surface area make an exchange surface efficient?
Provides the area needed for exchange overcomes limitations of low SA:V ratio
Why do thin layers make an exchange surface efficient?
the distances that substances have to diffuse across is short making it fast and efficient
Why does a good supply make an exchange surface efficient?
the greater the difference in concentration the greater the rate of diffusion. A good supply means substances are constantly being delivered and removed, maintaining the steep concentration gradient
Why does ventilation make an exchange surface efficient?
For gases ventilation helps to maintain concentration gradients
How is the trachea adapted for the gas exchange system?
-supported by incomplete rings of strong, flexible cartilage to allow for movement and prevent the trachea from collapsing
-lined with ciliated epithelium and goblet cells
How are the bronchi adapted for the gas exchange system?
-supported by small rings of cartilage
How are bronchioles adapted for the gas exchange system?
-contain no cartilage
-contain smooth muscle
-smooth muscle contracts when bronchioles constrict and relaxes when they dilate
How are the alveoli adapted for the gas exchange system?
-very thin walls
-contain elastic fibres which allow alveoli to stretch as air is drawn n and when they return to size help squeeze air out
-good capillary blood supply
-coated in surfactant
What is breathing?
The movement of air in and out of the lungs
What is gas exchange?
the delivery of oxygen from the lungs to the bloodstream and the elimination of carbon dioxide from the blood stream
Outline the steps in inspiration/inhalation
-diaphragm flattens and contracts
-external intercostal muscles contract making the ribs move up and out
-this increases the volume of the thorax so reduces pressure
-pressure is more negative than the atmosphere air
-air is drawn into the lungs to equalise the pressures inside and outside the chest
Outline the steps in normal expiration/exhalation
-diaphragm relaxes and curves upwards
-external intercostal muscles relax so ribs move in
-decreases volume of the thorax
-pressure in the lungs is less negative than atmospheric air
-air moves out of the lungs until pressure inside and out is equal
What is inspiration/inhalation?
the movement of air into the lungs
