B7 - Exchange Surfaces And Breathing Flashcards
Features of an exchange surface
Increased surface area, thin layers, good blood supply, ventilation to maintain diffusion gradient.
Increased surface area
provides the area needed for exchange and overcomes the limitations of the SA: V ratio of larger organisms. Examples include root hair cells in plants and the vili in the small intestine of mammals.
Thin layers
these mean the distances that substances have to diffuse are short, making the process fast and efficient. Examples include the alveoli in the lungs (see next topic) and the villi of the small intestine
Good blood supply
the steeper the concentration gradient, the faster diffusion takes place. Having a good blood supply ensures substances are constantly delivered ot and removed from the exchange surface. This maintains a steep concentration gradient for diffusion. For example the alveoli of the lungs, hte gills of a fish and the villi of the small intestine.
How ventilation affects exchange surfaces
for gases, a ventilation system also helps maintain concentration gradients and makes the process more efficient, for example the alveoli and the gills of a fish where ventilation means a flow of water carrying dissolved gases.
Tough exoskeleton
No gaseous exchange takes place
Provides protection
Spiracles
Air enters and leaves, water is also lost
Can be opened or closed by sphincters
Most spiracles stay closed, bit when oxygen demand is high they open
Tracheoles
Trachea narrow to form Tracheoles which are 0.6 to 0.8 wide each
No chitin
Where gaseous exchange between air and respiring cells takes place.
Tracheae (in insects)
Largest tubes of the insect respiratory system (up to 1mm in diameter)
Tubes lined with chitin
Tracheal fluid
Limits the penetration of air for diffusion
Can be withdrawn to increase surface area at times of high oxygen demand
Trachea (in humans)
Wide tube supported by rings of cartilage that help it stay strong and flexible and also keep it’s shape. Incomplete rings so food can move easily down the oesophagus.
Lined with ciliated epithelial cells that waft mucus up towards the throat. Also have goblet cells which secrete mucus and trap pathogens.
Alveoli
Tiny air sacs that area 200-300 micrometers across
They are thin flattened epithelial cells
Contains collagen and elastic fibres
Where gas exchange takes place
They have a large surface area, thin layers, good blood supply and good ventilation.
Bronchioles
The bronchi divide to form many small bronchioles.
The smaller bronchioles (1mm or less) have no cartilage.
The walls of the bronchioles contain smooth muscle
They can contract and relax to change the amount of air reaching the lungs.
Bronchus
The trachea divides to form the left bronchus and the right bronchus.
They are similar to the structure of the trachea (with supporting rings of cartilage) but are smaller.
Nasal cavity
The nasal cavity has a large surface area with good blood supply to warm the air to body temperature.
A hairy lining, which secretes mucus to trap dust and bacteria protection the lungs from irritation and infection.
Moist surfaces, which increase the humidity of the incoming air, reducing evaporation from the exchange surfaces.
Tidal volume
Tidal volume is the volume of air that moves in and out of the lungs with each resting breath. It is around 500cm cubed in most adults at rest, which uses about 15% of the vital capacity of the lungs
Vital capacity
Vital capacity is the volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath.
Inspiration reserve volume
Inspiration reserve volume is the maximum volume of air you can breathe in over and above a normal inhalation.
Expiratory reserve volume
Expiratory reserve volume is the extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.
Residual volume
Residual volume is the volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly.
Total lung capacity
Total lung capacity is the sum of the vital capacity and the residual volume
2 types of epithelial tissue found in lungs and airways
Ciliated and pavement
Pavement epithelial cells
Provide a short distance for gas to diffuse over
Ciliated epithelial cells
Propels mucus along airways
Surfactant
Cells secrete surfactant to reduce the surface tension of the moisture in the alveoli. To maintain the surface area of the alveoli.
Gill lamellae
Where all the gaseous exchange happens in a gill
Gill filaments
The parts of the gill that hold the gill lamellae and where the blood flows
Countercurrent flow
Where the most oxygenated blood meets the most oxygenated water and the least oxygenated blood meets the least oxygenated water. This maintains a concentration gradient all along the gill meaning that a much higher level of oxygen saturation of the blood is achieved.
Why do large organisms need a specialised surface area (surface area to volume ratio question)
Larger animals have a smaller SA:V ration meaning than smaller ones.
They are also more active and therefore the rate of diffusion cannot meet their metabolic rate.
How ram ventilators get water to the gills
They ram water past the gills by swimming constantly. Used by sharks and rays.
How bony fish get water flow over the gills
They lower their buccal cavity by opening their mouth enabling water to flow into it. The mouth then closes causing the buccal cavity floor to raise, thus increasing pressure. The water is forced over the gill filaments by the difference in pressure between the mouth cavity and opercular cavity. The operculum acts as a valve and pump and lets water out and pumps it in.
Function of elastic tissue
Recoils to aid in ventilation
Goblet cells
Secretes mucus up to trap pathogens
Smooth muscle function
To contract and constrict airways
How do gases move through an insect when its at rest
The concentration gradient in tracheae causes air to flow into tracheoles via diffusion
