7 - Exchange Surfaces And Breathing 🫁 Flashcards
What do organisms need to exchange?
water, minerals, oxygen, fats, proteins, glucose
How do Amoeba obtain substances required to survive?
diffusion across membrane
How do multicellular organisms ensure sufficient materials to survive?
transport systems
What are the 2 main reasons why diffusion alone is enough to supply the needs of single-celled organisms?
- large SA:V ratio
- metabolic activity is low, so resource demands are low too
Specialised Exchange Surface
List the 4
increased SA, good blood supply, thin layers, ventilation to maintain diffusion gradient
Specialised Exchange Surface
How does increased SA help exchange?
provides the area for exchange and overcomes limitations of SA:V
Specialised Exchange Surface
How do thin layers help?
decreases diffusion pathway
Specialised Exchange Surface
How does good blood supply help?
The steeper the conc gradient, the faster diffusion takes place. So having a good blood supply keeps substances constantly moving
Specialised Exchange Surface
How does ventilation to maintain diffusion gradient help?
maintains gradient and makes the process more efficient
What is the formula for percentage yield?
actual yield / theoretical yield X100
What is the formula for surface area of a cuboid?
2(bh+bl+hl)
What is the formula for volume of a cuboid?
hbl
When can organisms use simple diffusion to exchange gases?
When the diffusion pathway is less than 1mm
What is Fick’s Law?
SA x conc gradient / thickness of membrane
What else affects diffusion that isn’t in Fick’s Law?
moisture
What is a peak flow meter?
A simple device that measures the rate at which air can be expelled from the lungs
What are vitalographs?
More sophisticated versions of peak flow meters
How does a vitalograph work?
Patient being tested breathes out as quickly as possible through a mouthpiece, and the instrument reproduces a graph of the amount of air they breath out and how fast
What is a spirometer?
A device that detects changes in ventilation and presents the data on a digital display
Why is a nose clip used in spirometry?
To stop the patient from exchanging air not in the tank
- this would make the experiment invalid
What is the purpose of a soda lime canister in spirometry?
To absorb the CO2 so it isn’t breathed in
In inspiration, what happens to the graph line in spirometry?
- air chamber decreases in volume
- graph line goes down
In expiration, what happens to the graph line in spirometry?
- air chamber increases in volume
- graph line goes up
What is vital capacity?
The maximum volume of air that can be breathed in and out in 1 breath
What is tidal volume?
The volume of air breathed in and out at rest (normal breathing)
What is the breathing rate?
The number of breaths take in 1 minute
What is oxygen uptake?
The volume of oxygen used up by someone in a given time
How do you calculate pulmonary ventilation?
Tidal volume (dm3) X ventilation rate (min-1)
What is the residual volume?
The volume of air that is left in your lungs when you have exhaled as hard as possible
- this can not be measured directly
What is inspiration reserve volume?
The maximum volume of air you can great in over and above a normal inhalation
What is expiratory reserve volume?
The extra amount of aid you can force out of your lungs over and give the normal tidal volume
How do you calculate total lung capacity?
Vital capacity + residual volume
What are some control variables when testing lung capacity using a spirometer?
- height
- gender
- medical history
- location eg. higher altitudes
- lifestyle eg. smoker/obese
- oftenest of exercise
Why do insects have high oxygen requirements?
They are active, so have a high metabolic demand
Why do insects have exoskeletons with a waxy coating?
Acts as a support structure and protection as it is made from chitin
Why can’t gas exchange happen across the exoskeleton in insects?
It is impermeable to gases
What is the system in insects used to deliver oxygen directly to tissues?
Tracheal system
Gas exchange in insects
What are spiracles?
An opening in the exoskeleton of insects to allow air to enter and flow into the tracheae
Gas exchange in insects
What is also lost through spiracles and how is this adapted?
Water - spiracles can be opened or closed by sphincters
Gas exchange in insects
What do spiracles have around them and how does this help?
Have hairs around them to prevent and trap water vapour
Gas exchange in insects
What are trachea?
Largest airways in the system (diameter up to 1mm) leading from spiracles to tracheoles
Gas exchange in insects
What are trachea tubes lined with?
Spirals of chitin, which keep them open if they are bent or pressed
Gas exchange in insects
What are tracheoles?
Single, elongated cells with no chitin lining so they are freely permeable to gases
Gas exchange in insects
How do tracheoles allow most gas exchange to take place?
As they are very small in size (0.6-0.8um) so can run between cells
Gas exchange in insects
In most insects, air moves along the tracheae and tracheoles by…
diffusion alone
Gas exchange in insects
How do insects increase their SA:V to ensure diffusion?
By having many small tracheoles
Gas exchange in insects
What is at the end of tracheoles?
Tracheal fluid, which limits the penetration of air for diffusion
Gas exchange in insects
What happens to tracheal fluid when oxygen demands build up (eg. when the insect is flying)?
A lactic acid builds up in the tissues, resulting in water moving out of the tracheoles by osmosis, exposing more SA for gas exchange
Gas exchange in insects
How do collapsible enlarged tracheae of air sacs help increase level of gas exchange?
Act as air reservoirs, increasing amount of air moved through the gas exchange system
Gas exchange in insects
How does mechanical ventilation of the tracheal system help increase gas exchange?
Air is actively pumped into the system by muscular pumping movements of the thorax/abdomen
These movements change the volume of the body, changing pressure, drawing air in or forcing it out
Gas exchange in insects
At rest, what happens to tracheal fluid?
Seeps into tracheoles, decreasing SA as fluid is in the way
Why do fish need an exchange system to cope with breathing in water?
- water is 1000x denser than air
- 100x more viscous
- lower oxygen content
Gas exchange in bony fish
What is the operculum?
A moveable gill cover that is reinforced with rays of bones and encloses the fill within an operculum cavity
Gas exchange in bony fish
What is the gill arch?
Resembles a backbone for the gills
Gas exchange in bony fish
What is attached to each gill arch?
Two stacks of filaments (stack is a plate)
Gas exchange in bony fish
What is on the surface of each filament?
Many lamellae perpendicular to filaments, consisting on single layer of flattened cells
Gas exchange in bony fish
Why are gills good for gas exchange in fish?
- large SA
- good blood supply
- thin layers = short diffusion pathway
Gas exchange in bony fish
What do fish need to ensure to allow efficient gas exchange at all times?
To maintain a continuous flow of water over the gills, even when they’re not moving
Gas exchange in bony fish
How do fish keep water flowing over gills when they are swimming?
By simply opening their mouth and operculum
Gas exchange in bony fish
What is the counter-current system?
The capillary system within the lamellae ensures that the blood flow is in the opposite direction to water flow
Gas exchange in bony fish
Why do fish have counter-current mechanisms?
To maintain a conc gradient for maximum diffusion
Gas exchange in bony fish
How is a counter-current system achieved?
The water with the lowest oxygen concentration is found adjacent to the most deoxygenated blood
Gas exchange in bony fish
Why don’t fish use parallel exchange systems?
Fails to provide a persistent oxygen concentration gradient, so equilibrium is reached and no further gas is exchanged
Gas exchange in bony fish
How is ventilation achieved then?
Volume changes in the buccal cavity and opercular cavity creates pressures that are responsible for providing an almost continuous flow of water
Gas exchange in bony fish
How does the tips of gill filaments overlapping help gas exchange?
Increases resistance to the flow of water over the gill surfaces, and slows down the movement of water so there is more time for gas exchange
Gas exchange in bony fish
How does inspiration happen in a fish?
- muscle contraction lowers the floor of the pharynx
- volume of buccal cavity increases
- this decreases pressure
- water enters the mouth as pressure outside fish is higher than inside mouth
- operculum bulges outwards
- this lowers pressure
- opercular valves are closed
- pressure decreases in cavities
- causing water to flow into opercular cavity
Gas exchange in bony fish
How does expiration happen in fish?
- buccal cavity contracts
- floor of pharynx is raised, closing mouth
- pressure increases, forcing water through gill slits
- water moves across gills = pressure rises
- also opercular cavities contract
- pressure increases
- causing opercular calved to open and water to be expelled
Gas exchange in bony fish
What is ram ventilation?
Fish swim with their mouths partly open to force water to flow over gill vents continuously
Eg. Mackerel, sharks
Mammalian gas exchange
What is ventilation?
A term used to describe air moving in and out of the lungs due to pressure changes in the thorax
Mammalian gas exchange
Define the thorax
The chest cavity
Mammalian gas exchange
What does the rib cage provide?
A semi-rigid case within which pressure can be lowered
Mammalian gas exchange
What is the diaphragm?
A broad, domed sheet of muscle, forming the floor of the thorax
Mammalian gas exchange
Where are the intercostal muscles found?
Between the ribs
Mammalian gas exchange
What lines the thorax?
Pleural membranes, which surround the lungs
Mammalian gas exchange
The spaces between pleural membranes, the pleural cavity, is filled with what?
A thin layer of lubricating fluid so the membranes can easily slide over each other during breathing
Mammalian gas exchange
What happens when the pressure in the chest is less than the atmospheric pressure?
Inspiration (active)
Mammalian gas exchange
What causes expiration (passive)?
When the pressure in the chest is greater than the atmospheric pressure
Mammalian gas exchange
What is the process of inspiration?
- diaphragm contracts
- diaphragm flattens & lowers
- external intercostal muscles contract
- internal intercostal muscles relax
- causing ribs to up and out
- volume of thoracic cavity increases
- so pressure in thorax is reduced
- drawing air in, increasing lung volume
Mammalian gas exchange
What is the process of expiration?
- diaphragm muscles relax
- diaphragm moves up and domed
- volume of thoracic cavity decreases
- external intercostal muscles relax
- internal intercostal muscles contract (forced expiration)
- ribs move down and inwards
- elastic fibres in alveoli recoil
- pressure inside thorax is greater than outside, so air moves out
Mammalian gas exchange
What happens in forced exhalation?
- intercostal muscles contract
- this pulls ribs down fast and hard
- abdominal muscles contract, forcing diaphragm up to increase pressure in lungs rapidly
Mammalian gas exchange
Why do athletes train at altitudes?
To increase EPO = the hormone producing red blood cells
What happens to smooth muscle and the bronchioles in an asthma attack?
- cells lining bronchioles release histamines
- stimulates goblet cells to make more muscle
- smooth muscle in bronchiole walls contracts
- causes bronchi to constrict
- can’t breathe
Mammalian gas exchange
What is the structure of the lungs?
Right lung has 3 lobes and left lung has 2 lobes (due to heart)
Mammalian gas exchange
Order of structures in gas exchange
Nasal cavity
Pharynx (cavity at back of throat)
Larynx
Trachea
Bronchi
Bronchioles
Alveoli
Mammalian gas exchange
What features does the nasal cavity have?
- large SA with a good blood supply
- goblet cells and hairy lining
- moist surfaces
Mammalian gas exchange
What does the nasal cavity do?
- blood supply warms the air
- mucus traps particulates
- humidifies air to protect more delicate structures in lungs
Mammalian gas exchange
What does the trachea do?
A wide tube that carries clean, warm, moist air from the nose down into the chest
Mammalian gas exchange
What stops the trachea from collapsing?
Has incomplete rings of cartilage and smooth muscle that divides into the 2 primary bronchi at mid-thorax
Mammalian gas exchange
Why is the cartilage in the trachea C-shaped?
So that food can easily pass down the oesophagus, which is behind the trachea
Mammalian gas exchange
Why is the trachea lined with ciliated epithelium?
As a source of goblet cells, to secrete mucus onto the lining of the trachea, to trap microorganism and be wafted by cilia to throat to be swallowed
Mammalian gas exchange
What is the effects of cigarettes on cilia?
Stops them beating
Mammalian gas exchange
What adaptations do bronchi have?
- cartilage and smooth muscle
- lined with ciliated epithelium cells and goblet cells
Mammalian gas exchange
What does each bronchus divide into?
Secondary, then tertiary bronchi then bronchioles
Mammalian gas exchange
What don’t bronchioles have?
No cartilage rings
Mammalian gas exchange
What does smooth muscle in bronchiole walls do?
Smooth muscle contracts, causing bronchioles to constrict
Smooth muscle relaxes, causing bronchioles to dilaye
Mammalian gas exchange
What are bronchioles lined with?
A thin layer of squamous epithelium for a short diffusion pathway
Mammalian gas exchange
The smallest bronchioles don’t have smooth muscle. What do they have instead?
Elastic fibres
Mammalian gas exchange
What occurs at the alveoli?
Exchange of O2 and CO2 by diffusion
Mammalian gas exchange
What does each alveolus consist of?
A layer of thin squamous epithelium, collagen, elastic fibres
Mammalian gas exchange
How do elastic fibres in alveoli help their function?
Allows alveoli to stretch as air is drawn in, and recoil when air is exhaled
Mammalian gas exchange
How big are alveoli?
200-300um
Mammalian gas exchange
Why are there so many alveoli?
To create a large SA:V for diffusion
Mammalian gas exchange
Why are alveoli made of squamous epithelium?
To provide a thin layer = short diffusion pathway
Mammalian gas exchange
Why do alveoli have good blood supply from many capillaries?
To maintain a conc gradient for diffusion
Mammalian gas exchange
What makes alveoli moist?
A lung surfactant, allowing the lungs to remain inflated and for oxygen to dissolve in the water before diffusion
Mammalian gas exchange
Alveoli
What are type 1 pneumocytes?
- Line alveoli
- are squamous
- can’t replicate
- 95% are type 1
Mammalian gas exchange
Alveoli
What are type 2 pneumocytes?
- 5% of cells
- secrete surfactant which reduces surface tension and helps gases dissolve
