Module 3 - Exchange Surfaces Flashcards
Why is diffusion across the outer membranes too slow in multi-cellular organisms?
- Some organisms are deep within the body (a big distance)
- Large animals have a slower SA:V ratio (as it is difficult to exchange substances)
- They have a higher metabolic rate than single-celled organisms (they use up oxygen and glucose faster)
How does SA:V and the size of organism correlate?
- The larger the organism, the smaller the SA:V ratio.
- takes longer for substances to reach the cells.
- it is impossible to absorb enough oxygen through the surface area to meet the needs of the body
How are gas exchange surfaces adapted to be efficient?
- Increased SA:V: gas exchange takes place quicker.
- Thin layers: short diffusion distances
- Good blood supply: steeper the concentration gradient, the faster diffusion takes place.
- Ventilation - maintains diffusion gradient and makes the process more efficient
how does gas exchange system occur in mammals?
- consists of lungs which air is carried in and out.
- lungs: inflatable sacs in the chest cavity.
- air passes through the nose along the trachea, bronchi and bronchioles.
- It then reaches the alveoli (gas exchange takes place)
- lungs are protected by the ribcage.
- Ribcage are held by intercostal muscles.
- action of these muscles and the diaphragm help with ventilation
What are alveoli?
Surfaces where gas exchange takes place
What is the diaphragm?
A layer of muscular tissue beneath the lungs
What is ventilation?
Breathing movements
What does it mean mammals have a large metabolic rate?
If mammals have a large SA:V ratio, it means they have lots of energy and can supply to the cells
what features does the nasal cavity have?
- a large surface area with a good bloody supply: this warms the air to body temperature.
- Hair lining: this secretes mucus to trap dust and bacteria protecting lung tissue from irritation and infection.
- Moist surfaces: increases humidity of the incoming air, reduces evaporation from exchange surfaces.
what is the Nasal cavity?
- after air enters the nasal cavity
- air enters the lung which is similar to temperature and humidity to the air
What do the trachea, bronchi and bronchioles do?
- They are tubes which lead down into the alveoli, delivering oxygen and removing carbon dioxide
What are goblet cells?
(lining in the airways) - secretes mucus. This traps microorganism and dust particles which stops air reaching the alveoli.
What is cilia?
- They are hair liked structures on the surface of epithelial cells lining the airways.
- They beat the mucus secreted by the goblet cells.
- Upwards away from the alveoli towards the throat
prevents lung infection
What are elastic fibres?
- In the walls of the trachea, bronchi, bronchioles and alveoli help the process of breathing out
- they stretch and then recoil to push air out when exhaling.
What are smooth muscles?
- In the walls of trachea, bronchi and bronchioles
- they contract and relax depending on the level of activity.
How do smooth muscles act during exercise?
- They relax, making the tubes wider.
- less resistance to air flow and air can move in and out of the lungs more easily
What are cartilages?
- In the walls of the trachea and bronchi
- Its strong but flexible
stops the trachea and bronchi collapsing when you breath in - so the pressure drops
how is the trachea adapted?
- Large C shaped pieces of cartilage
- smooth muscles
elastic fibres - goblet cells
ciliated epithelium
howis the Bronchi adapted?
- smaller piece of cartilage
- smooth muscles
elastic fibres - goblet cells
ciliated epithelium
how are Larger bronchioles adapted?
- no cartilage
- smooth muscles
elastic fibres - goblet cells
ciliated epithelium
how are the Smaller bronchioles adapted?
- no cartilage
- smooth muscles
elastic fibres - no goblet cells
ciliated epithelium
how are the Smallest bronchiole adapted?
- no cartilage
- no smooth muscles
elastic fibres - no goblet cells
- no cilia
how is the alveoli adapted?
- no cartilage
- no smooth muscles
elastic fibres - no goblet cells
- no cilia
Why do smoker often develop long term coughs?
- Cigarette smoke stops the cilia beating
- it cannot waft mucus or trap microorganisms
- this then causes infection and irritation
Why does the amount of cartilage reduces as we move from the trachea to the bronchi to the bronchioles?
The airway tubes become smaller in diameter and do not need the same amount of support to hold them open.
Why do cilia and goblet cells disappear deeper down in the airways?
They produce mucus in the airways to trap microorganisms so it should not be needed further down the airways.
- Cilia would take up too much space in the lumen of very small bronchioles, obstruct air flows.
Why is the cartilage c shaped around the trachea?
- They are strong and flexible
- stops the trachea from collapsing
- rings are incomplete
- allows food to move easily down the oesphagus behind the trachea
how is the Alveoli adapted?
- gas exchange takes place
- diameter around 200-300 um
- consists of thin layers, flattened epithelial cells along with some collagen and elastic fibres
- elastic recoil of the lungs
How the alveoli are adapted for efficient gas exchange?
- Good ventilation - helps maintain steep diffusion gradient.
- good blood supply - maintains a steep concentration gradient for both carbon dioxide and oxygen.
- Thin layers - short diffusion distances
- Large surface area - needed for the amount of oxygen to be diffused into the body
Gills
- fish have 4 gills on each side of their head
- they have a large SA, good blood supply & thin surface area for gas exchange
- found within the gill cavity covered by a flap called the operculum
- helps maintain one way flow of water over the gills
- this brings water in with fresh oxygen, carries water away that has picked up carbon dioxide.
Structure of gills
- each gill made up of 2 rows of gill filaments
- attached to a bony gill arch
- each filament is thin, surface is folded into lamellae (gill plates)
- provides a big surface area
What is a counter- current system?
blood flows through the gill plates in one direction and water flows in the opposite direction.
- means water with a relatively high oxygen concentration gradient always flows next to blood with a lower concentration of oxygen.
- a steep concentration gradient is maintained between water and blood.
Water flows over the gills
- fish use their mouth and operculum flap to maintain a flow of water over their gills.
- tips of the adjacent gill filaments overlap.
Increases the resistance to the flow of water and slows down water movement
Ventilation in bony fish (1)
- fish opens its mouth
- lowers the floor of the buccal cavity
- increases volume of buccal cavity
- pressure inside the buccal cavity to fall
- water is then drawn into the buccal cavity due to the pressure gradient
Ventilation in bony fish (2)
- Fish closes its mouth
- floor of the buccal cavity raises
- volume of inside the buccal cavity falls
- pressure inside the buccal cavity increases
- water is forced over the gill filaments - where gas exchange occurs
How is the structure of a fish gill adapted?
- Gills have a large SA - diffusion
- Rich blood supply - maintain steep concentration gradient
- Tips of adjacent gills overlap- shows water flow
- thin layers - short diffusion pathway
Dissecting fish gills
- Place your chosen fish in a dissection tray or on a cutting tray.
- Push back the operculum and use scissors to carefully remove the gills. Cut each gill arch through the bone at the top and bottom.
- You should be able to see the gill filaments
- then draw the gills
Gas exchange and ventilation in insects
- they have high demands for oxygen
- have a hard exoskeleton - prevents gas exchange occuring across the body
- they have a open circulatory system
- no blood or blood vessels
- oxygen is delivered directly to the cells
- CO2 removed directly from the cells
How does this occur in insects?
- Insects have spiracles: small openings where air enters and leaves the insects.
- tubes lead to TRACHAE: carrying air into the body
- tubes have CHITIN around them - which provide flexible support (keeping the tubes open)
- smaller tubes (TRACHEOLES) - it is a single elongated with no chitin
- walls are permeable and very thin
How are insects adapted for gas exchange?
- Tracheoles: site for gas exchange. (large SA)
- Single layer of cells - short diffusion pathway
- steep concentration gradient
- good ventilation
Limits to the diffusion of oxygen
- end if the tracheole is the tracheal fluid - limits air getting to the end of the tracheoles
- can be overcome when the insects is very active
- insect activity increases, cell respiration increases, some anareobic respiration occurs producing lactic acid in cells
Active ventilation in insects
- tracheal system are expanded and have flexible walls.
- Repetitive expansion and contraction of these sacs ventilate the tracheal system
- movement of wings alter the volume if the thorax.
- when the thorax increases in volume, the pressure inside drops and air is pushed into the tracheal system from outside
- locusts can alter volume of their abdomen by specialized breathing movements.
- They coordinate and closing valves in the spiracles
- as the abdomen reduces in volume, the spiracles at the rear end of the body open and air can leave the tracheal system.
How can this reduces the volume of fluid in the tracheoles?
- contains the tracheal fluids: flooding the tracheoles and limits air penetration.
- Increase in lactic acid
- water potential decreases.
- tracheal fluid enters muscle cells
- moves out by osmosis
CO^2 produced in muscle cells -> tracheoles and out of spiracles
why are there sphincter around the spiracles of an insect?
- This so air can enter and leave the cells when it needs to depending on their activity. They need to conserve water
How does inspiration work?
- external intercostal and diaphragm muslces contract
- ribcage moves upwards and outwards, diaphragm flatterns
- increases volume of thorax,
lung pressure decreases - causes air to flow into the lungs
Inspiration
It is an active process - requires energy
How does expiration work?
- external intercostal and diaphragm muscles relax
- ribcage moves downwards and inwards, diaphragm becomes curved
- thorax volume decreases
- air pressure increases
- air is forced out of the lung
Expiration
passive process - does not require energy
Spirometer
Is a piece of equipment that can be used to investigate breathing.
How does a spirometer work? (1)
- The person breathes in and out of their mouth via the mouthpiece
- air is trapped between the enclosed chambers between the float and water
- when breathing in, the volume of air in the chamber decreases and float drops
How does the spirometer work (2)
- when breathing out, the volume of air inside the chamber increases and the float rises.
- the float is attached to a pen which writes on the paper on the revolving drum, recording the breathing movements.
- when soda lime is used, the carbon dioxide breathed out into the mouthpiece is absorbed and it does not reach the chamber.
Tidal volume
the volume of air in each breath (about 0.4dm^3)
Vital capacity
the maximum volume of air that can breathed in and out in one breath
Breathing rate
How many breaths are taken per unit time
Oxygen uptake
the rate at which the person uses up oxygen
