Gas Exchange Flashcards
How have larger organisms evolved to maintain adequate rates of gaseous exchange?
-developed specialised exchange structures like lungs or gills
-also maintain body temp by changes in body shape/ structure such as large ears to increase surface area for heat loss
Gas exchange system in mammals consists of?
Trachea- supported by incomplete rings of cartilage that prevent it collapsing during pressure changes
Bronchi- repeatedly divides into smaller tubes (Bronchioles)
Alveoli- provides a large surface area where gaseous exchange occurs.
how is the alveoli adapted for gas exchange (6)
- their shape and large number provide a large surface area
- Fluid lining the alveolus allows gases to dissolve and diffuse across
- An extensive network of blood capillaries surrounds each alveolus provides a large surface area for absorbing oxygen and releasing carbon dioxide
- Only two cell layers separate the blood and air (short diffusion pathway)
- a circulatory system maintains a high concentration gradient for gaseous exchange by transporting deoxygenated blood and removing oxygenated blood to and from the lungs
- ventilation mechanism maintains a high concentration gradient for gaseous exchange by providing oxygen concentrated air and removing CO2 concentrated air
describe the steps of gas exchange in lungs
1 - oxygen in the alveolar air space dissolves in the fluid lining the epithelium of the alveolus
2 - oxygen diffuses across the flattened epithelial cells of the alveolus and the endothelial cells of the capillary wall
3 - oxygen combines with the haemoglobin in RBC to form oxyhaemoglobin and CO2 diffuses from the blood in the opposite direction
Inspiration (breathing in)
- diaphragm contracts and moves down and flattens
- external intercostal muscles on ribs contract and move ribs up while internal intercostal muscles relax
- as lungs expand, air is sucked in through mouth and nose
What else can help exhalation?
- elastic recoil of the lung tissue helps to force air out the lungs during expiration
- internal intercostal muscles may also contract, pulling the ribcage downwards and inwards.
expiration (exhalation)
- external intercostal muscles and diaphragm relaxes and the diaphragm moves upwards to its dome shape
- this decreases the volume of the thoracic cavity and the pressure inside the lungs increases above atmospheric pressure and air is forced out of the lungs
What is pulmonary ventilation?
The total volume of air that is moved into the lungs during one minute
How to calculate pulmonary ventilation?
tidal volume x ventilation (breathing) rate
What is the tracheal system in insects?
- a system of pipes that connects the air outside the animal to the tissues of the body that require the oxygen
What is tidal volume?
- the volume of air taken in at each breath
What is breathing rate?
- number of breaths per minute
Trachea System adaptations (insects)
- tracheoles are thin, providing a short diffusion distance and are numerous providing a large surface area
Describe how gaseous exchange occurs into and out of the tracheal system in insects? (extended answer)
- the opening of the trachea to the air is through tiny holes on the insect’s surface called spiracles
- the spiracles have valves that they can close to reduce water loss via evaporation
- each spiracle leads into tubes called tracheae held open by spiral bands of cuticle
- the trachea branches repeatedly to form finer tubes called tracheoles
- oxygen diffuses from the air, through the spiracles along the trachea and tracheoles to the cells
- carbon dioxide leaves the insect’s cells and travels to the atmosphere by the reverse pathway
What word describes how the external and internal intercostal muscles work together
- Antagonistically
- as one of them contracts one of them relaxes
What does the opening of the spiracles depend on?
- Levels of carbon dioxide in the body
What causes the spiracles to widen?
- carbon dioxide levels rise due to respiration and this causes the spiracles to open wider increasing the rate of diffusion of gases in the tracheal system
When do the spiracles close?
- during rest the spiracles close to help reduce water loss by evaporation
How do large/active insects speed up diffusion?
- the muscles contract to compress the trachea forcing air out then the muscles relax and the trachea springs back into shape drawing in fresh air that is rich in oxygen
How are the gills adapted for gaseous exchange?
- the large number of gill filaments provide a large surface area. They possess lamellae increasing the surface area even further
- a short diffusion pathway consisting of two cell layers
- epithelial layer of the gill lamellae
- endothelial layer of the blood capillaries
How does increased activity affect diffusion in insects?
- during increased activity, anaerobic respiration often occurs producing lactic acid in cells lowering the water potential
- some of the water in the ends of the tracheoles moves into the cells by osmosis enabling more air to move in along the tracheoles and into the cells speeding up the diffusion of oxygen to the cells
How does the circulatory system improve/increase the rate of gaseous exchange?
- ensures a continual flow of blood through the respiratory surface to absorb oxygen and remove carbon dioxide thus maintaining a high gradient for gas exchange
How are gills constructed?
4 pairs of gill arches consisting of many gill filaments protected by the operculum
What leaf adaptation increase rate of gaseous exchange?
Leaves are thin which provides a short diffusion pathway
When do plants respire?
During the day and night
How does the ventilation mechanism in the gills improve/increase the rate of gaseous exchange?
- provides a continual flow of water over the gills bringing more oxygen and removing carbon dioxide thus maintaining a high gradient for gas exchange
How is a plant adapted for gaseous exchange?
- numerous mesophyll cells lining the intercellular air spaces providing a large surface area
- respiration and photosynthesis produce CO2 and O2 which maintains the diffusion gradient
- mesophyll cells have moist and thin cell walls/membranes
How does the counter-current system improve/increase the rate of gaseous exchange?
- ensures that blood continually meets water with a higher oxygen concentration so that a high diffusion gradient is kept along the whole length of the lamellae
What is a stomata?
Pores in the epidermis of leaves that gases diffuse in and out of protected by two guard cells
When do plants photosynthesise?
During the day only
Why is there a net uptake of CO2 and loss of oxygen during the day in plants?
The rate of photosynthesis is higher than the rate of respiration in the day.
