Mammalian gas exchange and ventilation Flashcards
Why is it not possible to expel all air from the lungs?
-thorax cannot be completely flattened -trachea/bronchi held open by cartilage
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 nasal cavity adapted for the gas exchange system?
-good blood supply warms air to body temperature -goblet cells secrete muscus to trap dust and bacteria to protect lung tissue, with cilia hairs moving in a swaying motion -moist surfaces reduce evaporation from the exchange surfaces which increase humidity
How is the trachea adapted for the gas exchange system?
-supported by incomplete rings of strong, flexible c-shaped cartilage to allow for movement and prevent the trachea from collapsing -lined with ciliated epithelium and goblet cells
What is the function of goblet cells?
Secrete mucus which traps dust and microogranisms
What is the function of ciliated epithelial cells?
Cilia beat and move mucus away from the lungs, protecting them
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
-diaphragm flattens and contracts -external intercostal muscles contract making the ribs move up and out and internal intercostal muslces relax -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
-diaphragm relaxes and curves upwards -external intercostal muscles relax so ribs move in and internal intercostal muscles contract -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
Outline the steps in forced expiration
-abdominal muscles contract, pushing diaphragm upward quickly making lung pressure less negative -internal intercostal muscles contract pulling ribs down hard and fast
What is inspiration?
the movement of air into the lungs
What is expiration?
the movement of air out of the lungs
Does inspiration require energy?
Yes
Does expiration require energy?
No, it is a passive process
What are the 3 ways lung capacity can be measured?
-peak flow metre -vitalographs -spirometer
label
A- Inspiratory reserve volume
B- Tidal volume
C- exspiratory reserve volume
D- Residual volume
E- Inspiratory capacity
F- functional residual capacity
G- Vital capacity
H- Total lung capacity
what is tidal volume
the volume of air which moves in and out of the lungs with each resting breath
what is vital capacity
the volume of air which can be breathed in when the strongest possible exhale in follwed by the strongest possible inhale
what is inspiratory reserve volume
the maximum volume of air which can be breathed in over and above normal inhilation
what is expiratory reseve volume
the extra amount of air which can be forced out of the lungs over and above the normal tidal volume of air youd breath out
what is residual volume
the volume of air that is left in the lungs after forces exhilation, this cannot be measured directly.
what is total lung capacity
the sum of the vital capacity and residual volume
