M3- Chapter 7 - Exchange surfaces and breathing Flashcards
Why can microscopic animals exchange gases through diffusion
They have a low metabolic activity and a low demand for oxygen. Even then, their walls are thing enough that gases can travel through quick enough.
They have a large SA:V ratio
Why can’t larger animals exchange gases through just diffusion
They have more cells, tissues and organs that all need more energy, hence a higher demand for oxygen. This is because they have a higher metabolic activity. The bigger the organism, the smaller their SA:V ratio, hence diffusion can’t handle the pressures of such demands.
What are the 4 things that make an effective exchange surface?
- Increased SA
- Thin layers
- Good blood supply
- Ventilation to maintain concentration gradient
How does good blood supply help create an effective exchange surface?
Having a steeper concentration gradient created faster diffusion. Having constant good blood supply allows that there is always a good concentration gradient.
How does ventilation to maintain a concentration help create an effective exchange surface?
It makes the process more efficient overall.
What are the main features of the nasal cavity
- Large SA: V ratio
- Good blood supply (warms the air to body temperature)
- Hairy lining (mucus)
- Moist surfaces (increasing humidity of the incoming air)
Main features of trachea
- It carries the air from the nose down to the chest
- It has incomplete ‘C’ shaped, cartilage rings that provide support and flexibility
- It’s lined with ciliated epithelium cells and goblet cells that secrete mucus. Also has cilia
Bronchus features
The trachea then splits into 2 to form 2 bronchi. They have c-shaped cartilage.
Bronchioles
Don’t have cartilage
They have smooth muscle.
When the smooth muscle in bronchioles relax what does that do to the air flow
Bronchioles open up
When the smooth muscle in bronchioles constrict what does that do to the air flow
Bronchioles close up
What is inside bronchioles
A layer of flattened epithelium and goblet cells.
Also smooth muscle
Alveoli
They are like tiny air sacks, each with a diamete of 200–300 ym.
Each alveoulus contains:
thin flattened epithelial cells
collagen and elastic fibres.
What is elastic recoil
Elastic tissues allow alveoli to stretch as air is drawn in .
When they return to their resting size, they squeeze the air out.
How have alveoli adapted?
Large SA:V ratio Thin layers (less distance to travel) Good blood supply Good ventilation The inner surface of alveoli is covered in a thin layer of water, salts and a lung surfacant. The surfacant allows the alveoli to remain inflated.
What is ventilation
The movement of air
What is the main rule about gases to remember
They move from an area of high pressure to low pressure.
What is inside the pleural cavity
A thin layer of lubricating fluid so the different membranes can slide over each other as you breathe,
Inspiration
The diaphragm and external intercoastal muscles contract.
Ribs move up and out
Increasing the interpulmonary volume
Decreasing the pressure
The interpulmonary pressure is now lower than atmospheric pressure, so air moves in.
Expiration
The diaphragm and external intercoastal muscles relax.
Ribs move inside
Decreasing the interpulmonary volume
Increasing the pressure
The interpulmonary pressure is now higher than atmospheric pressure, so air moves out.
What are the 3 ways to measure lungs etc.
- Peak flow meter
- Vitalographs
- Spirometer
Peak flow meter
measures the rate at which air can be expelled from the lungs
Vitalographs
A more sophisticated version of a peak flow meter. The instrument produces a graph of how quickly and how much amount of air is breathed out. The volume of air is called the forced expiratory volume in 1 second.
Spirometer
Investigates breathing patterns
Different aspects of the lung volume.
Tidal volume
Volume of air that moves into and out of lungs
Vital capacity
Volume of air that can be let out after the maximum inhalation.
Inspiratory Reserve volume
The max volume of air you can breathe in over and above the inhalation.
Expiratory Reserve Volume
The extra amount of air you can force out of your lungs over and above the normal tidal volume of air.
Residual volume
Volume of air in your lungs left when you have exhaled as hard as possible.
Total lung capacity
sum of the vital capacity and the residual capacity
Breathing rate
number of breaths per minute
Ventilation rate
Tidal volume x breathing rate
Explain the basics of insects’ gaseous exchange system
They have a high oxygen demand
But, because they have their exoskeleton on the outside, they can’t allow gases and liquid to diffuse in or out of them.
They also don’t usually have a blood pigment that carried the oxygen for them.
How can insects’ exchange gases?
They have small opening called spiracle along the thorax and their abdomen.
They also have spiracle sphincters to control the spiracles.
The spiracles lead to trachea, which lead to tracheoles.
Trachae
They are tubes lined with spirals of chitin (to keep it open). Chitin is relatively impermeable to gases, so gaseous exchange doesn’t happen.
Tracheole
They don’t have chitin, so permeable to any gaseous exchange.
They run next to the cells to allow gas exchange.
A large number of these, gives a large surface area.
Trachea Fluid
This limits the penetration of air for diffusion.
The oxygen dissolves in moisture along the walls of tracheoles.
However, when the oxygen demands build up, lactic acid also builds up inside the tissues. This means that the water moves out of the trachea through osmosis, allows gases to move.
What about bigger insects
Then need even more oxygen.
So:
when the muscles move, they pump the thorax and the abdomen, changing the volume and pressure in the trachea and tracheoles forcing the air in or out.
And:
There are air sacks which act as reservoirs. They increase the amount of air moved. They are inflated and deflated by the movement of tte thorax and the abdomen.
Gaseous exchange in bony fishes
they have such a SA: V ratio that doesn’t allows diffusion to happen. So, instead they have gills.
In these gills they have gill filament, which have gill lamellae on them. The lamella consists of a network of blood vessels. It comes deoxygenated and then gains oxygen from the water and then returns oxygenated,
What about bigger insects
They rely on pure movement to allow the water to move through them. This is called Ram Ventilation.
What happens when the buccal cavity is open
It increases the volume at the mouth, decreasing the pressure. Hence the operculum closes.
What happens when the buccal cavity is closed
The pressure builds up and then the operculum opens.
How are fishes made for gas exchanges
- Large surface
- Rich blood supply
- Thin layers for diffusion
- Tips of adjacent filaments overlap, to increase resistance, giving more time for oxygen to move through the water.
- Water and blood are countercurrent flows in opposite direction. This ensures a steep concentration gradient is maintains in comparison to if the system is parallel.
It removes 80% of oxygen rather than 50%.
Explain how the alveoli creates a surface for efficient gaseous exchange
Walls are 1 cell thick.
Constant blood supply - maintains the blood supply.
A large number of alveoli provides a large surface area: volume ratio.
Alveoli are quite small so it provides a large surface area: volume ratio.
Lung surfacant prevents it from collapsing.
Elastic recoil helps to expel the air (from elastic fibres)
Explain how the different cells and tissues enable the effective exchange of gases.
Thin squamous epithelium cells, so that there is a shorter diffusion distance.
Lung surfacant prevents the alveoli from collapsing.
Ciliated epithelium and goblet cells trap dirt and bacteria.
Cartilage or smooth muscle keeps the airways open and changes the size of the airways.
Elastic fibres for elastic recoil and ventilation.
Explain how a spirometer works
The person would have to breathe out through their mouth normally, at rest. Then, the lid of the spirometer would go down when the person breathes in, and then back up when they breathe out. This creates a wave on a trace. They should measure the height of the waves created, and measure at least 3 waves, then calculate the mean of those.
How can you measure the volume of oxygen in a spirometer?
Measure the decrease in the trace, such as from the height of the first peak to the height of the last peak.
How does having a good ventilation allow a fast gaseous exchange
It increases the pressure of in the air sack, so that it is greater than the oxygen concentration in the blood. So it constantly moves into the blood down the concentration gradient that has been set up, because there had been a high concentration of oxygen in the alveoli.
