Exchange Between Organisms And Their Environment Flashcards
The external environments is different from the internal environment found within an organism and within its cells. In order to survive organisms transfer
Materials between the two environments; this transfer takes place at exchange surfaces and always involve crossing cell plasma membranes
What role does tissue fluid play in organisms for exchange?
Tissue fluid is the environment around the cells of multicellular organisms. The majority of cells are too far from exchange surfaces for diffusion alone to supply or remove their tissue fluid with the various materials needed to keep its composition relatively constant. Therefore, once absorbed materials are rapidly distributed to the tissue fluid and the waste products returned to exchange surface for removal- this involves a mass transport system
What’s the importance of the mass transport system?
Maintains the diffusion gradient that brings materials to and from the cell-surface membranes
What are some examples of things that need be interchanged between an organism and its environment?
- respiratory gases e.g. oxygen and carbon dioxide
- nutrients (glucose, fatty acids, amino acids, vitamins, minerals
- excretory (urea and carbon dioxide)
- heat (most organisms need to stay roughly at the same temperature)
Except for heat substances that need to be interchanged between an organism and it’s environment can occur in 2 ways:
1- passively (no metabolic energy is required) by diffusion and osmosis
2- actively (metabolic energy is required) by active transport
Define diffusion
The movement of molecules or ions from a region were they are highly concentrated to one where their concentration is lower until equilibrium is reach
Define osmosis
The passage of water from a region of high water potential to a region where its water potential is lower through a partially (selectively) permeable membrane
Exchange takes place at the surface of an organism, but the materials absorbed are used by cells that mostly make up its volume. What is needed for the exchange to be effective?
Exchange surface of the organism must be large compared to its volume
Small organisms have a surface area that is large enough, compared with their volume to allow efficient exchange across their body surface. However, as organisms become larger
Their volume increases at a faster rate than their surface area. Because of this, simple diffusion of substances across the outer surface can only meet the needs of relatively inactive organisms. Even if the outer surface could supply enough of a substance, it would still take too long for it to reach the middle of the organism if diffusion alone was the method of transport
Organisms have evolved one or more of the following features:
- a flattened shape so that no cell is ever far from the surface e.g. flatworm or a leaf
- specialised exchange surfaces with large areas to increase the surface area e.g. lungs in a mammal or gills in a fish
How do you calculate surface area of a cube?
1- area of cross section X number of faces
2- e.g. 4X4 = 16
16X6= 96cm
How do you calculate the volume?
BXWXH
Larger cells have a smaller surface area for exchange across plasma membrane so
Diffusion across plasma membrane is insufficient to meet metabolic needs
Describe the effect of SA:V ratio on the rate of diffusion
As SA:V ratio decreases the rate of diffusion also decreases
Explain the importance of SA:V ratio to living organisms
- Larger animals have a smaller SA:V ratio
- Are unable to obtain enough nutrients and oxygen by diffusion across outer surface
- Require specialised exchange surfaces (to increase SA)
- Require a transport system to transport nutrients / oxygen larger distances to cells deep within body
All cells and organisms must exchange substances with their environment and so, many organisms have specialised
exchange surfaces adapted to make it easier for substances to cross from one side of the surface to another
Some organisms can exchange nutrients and gases across their outer surface if:
- Large SA:V ratio
- Short diffusion distance
- Less metabolically active
Single-celled organisms like Amoeba do not require specialised exchange surfaces Why?
- Large SA:V ratio
- Exchange gases (e.g. oxygen / carbon dioxide) by simple diffusion across plasma membrane
- Short diffusion distance to centre of organism
- No transport system required
Some multicellular organisms
e.g. tapeworm also do not require specialised exchange surfaces Why?
- Some multicellular organisms are very thin and flat
- Large SA:V ratio
- Short distance for diffusion of gases e.g. oxygen
- Not very metabolically active
- Also do not require a transport system
More complex multicellular organisms do require specialised exchange surfaces Why?
- Small SA:V ratio
- Outer surface is too small to allow sufficient gas exchange to meet metabolic needs of the large volume of organism
- So require a specialised exchange surface
Complex multicellular organisms may also need a transport system Why?
- In larger organisms some cells are deep within the body
- Increases the diffusion distance for gases
- More metabolically active
- Must supply cells with oxygen and glucose more rapidly for aerobic respiration
- Diffusion is therefore too slow to meet metabolic needs so also require a transport system
Factors that determine the need for a transport system:
- SA:V ratio
- Size (determines diffusion distance)
- Metabolic rate
Some multicellular organisms do not require a transport system if:
- Large SA:V ratio (easy enough to exchange enough substances to a small volume of animal but large outer surface for gas exchange across cell-surface membrane)
- Short diffusion distance
- Low level of activity
More complex multicellular organisms do require a transport system if:
- Smaller SA:V ratio
- Larger diffusion distance
- More metabolically active
- Must supply cells with oxygen and glucose more rapidly for aerobic respiration
What are the features of exchange surfaces?
•Large surface area often achieved by folding
•Thin so short diffusion distance
•Steep concentration gradient
•Maintained by a fresh supply of substances on one side (to maintain high concentration)
•Rapid removal of substance on the other side (to maintain low concentration)
- selectively permeable to allow selected materials to cross
What are some examples of exchange surfaces?
-Alveoli in lungs: gas exchange (oxygen in / carbon dioxide out) •Gills in fish •Villi in small intestine •Hepatocytes in liver •Mesophyll tissue in leaf •Root hair cells
Villi in small intestine increase
surface area for absorption of the products of digestion- microvilli further increase surface area of epithelial cells in small intestine and of hepatocytes in liver
What are the functions of the liver?
- Removes excess glucose from blood to store as glycogen
- Releases glucose back into blood when blood glucose levels are low
- Removes excess amino acids from blood
How is a plant root adapted
for the uptake of water and
mineral ions?
Root hairs increase surface area for:
•Uptake of water by osmosis
•Uptake of mineral ions by active transport
Single-celled organisms are small and therefore have a large SA:Vol ratio. Oxygen is absorbed by diffusion across their body surface which is covered only by
A cell-surface membrane (in the same way,carbon dioxide from respiration diffuses out across their body surface- where a living cell is surrounded by a cell wall, this is no additional barrier to the diffusion of gases)
If a cell has the shape of a sphere, and is 10 micrometers in diameter, work out the SA: Vol ratio
1- surface area of a sphere= 4X pi X r squared
2- surface area of the cell = 4 X 3.14 X (5X5) = 314 micrometers squared
3- volume of a sphere= 4/3 X pi X r cubed
4- volume of the cell = 4/3 X 3.14 X (5X5X5)= 523.33 micrometers cubed
5- SA: V ratio = 3.14/ 523.33= 0.6:1
Name some factors that affect the rate of diffusion of substances into cells:
- surface area/ thickness of cell-surface membrane
- permeability of cell-surface membrane to particular substance
- concentration gradient of substance inside/outside of cell
- temperature
What is Fick’s Law?
Rate of diffusion =
area of diffusion surface X difference in conc
———————————————————
Thickness of surface over which diffusion takes place
Insects and some other terrestrial invertebrates exchange gases with their surroundings via a system of air filled tubes called tracheae- the insect breathing system is therefore known as the
Tracheal system
Describe and explain the tracheal system
- insects have evolved an internal network of tubes called tracheae
- the trachea are supported by strengthened rings to prevent them from collapsing
- the trachea divide into smaller dead-end tubes called tracheoles
- the tracheoles extend throughout all the body tissues of the insect
- in this way, atmospheric air with the oxygen it contains is brought directly to the respiring tissues as there is a short diffusion pathway from a tracheole to any body cell
Respiratory gases move in and out of the tracheal system in 3 ways:
1- along a diffusion gradient
2- mass transport
3- the ends of tracheoles are filled with water
Explain how respiratory gases move in and out of the tracheal system along a diffusion gradient
When cells are respiring, oxygen is used up and so its concentration towards the end of the tracheoles falls. This creates a diffusion gradient that causes gaseous oxygen to diffuse from the atmosphere along the trachea and tracheoles to the cells. Carbon dioxide is produced by cells during respiration; this creates a diffusion gradient in the opposite direction. This causes gaseous carbon dioxide to diffuse along the tracheoles and trachea from the cells to the atmosphere
What is a benefit of respiratory gases moving in and out of the tracheal system along a diffusion gradient?
Diffusion in air much faster than in water, respiratory gases are exchanged quickly by this method
Explain how respiratory gases move in and out of the tracheal system by mass transport?
The contraction of muscles in insects can squeeze the trachea enabling mass movements of air in and out. This further speeds up the exchange of respiratory gases
Explain how respiratory gases move in and out of the tracheal system from the ends of tracheoles being filled with water
- During periods of major activity, the muscle cells around the tracheoles respire and carry out anaerobic respiration, producing lactate which is soluble and lowers the water potential of the muscle cells. Water therefore moves into the cells from the tracheoles by osmosis
- the water in the ends of the tracheoles decreases in volume and in doing so draws air further into them
- this means the final diffusion pathway is in a gas rather than a liquid phase and therefore diffusion is more rapid = increases the rate at which air is moved into the tracheoles but leads to greater water evaporation
Gases enter and leave the trachea through tiny pores called
Spiracles
Where are spiracles located?
On the body surface
The spiracles may be opened or closed by
A valve
When the spiracles are open
Water vapour can evaporate from insect; so most of the time, insects keep their spiracles closed to prevent this water loss. But periodically they do open the spiracles to allow gas exchange
Explain how the tracheal system limits the size of insects?
- because it relies on diffusion to bring oxygen to the respiring tissues
- if insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply their needs
Explain why there is a conflict in terrestrial insects between gas exchange and conserving water?
Gas exchange requires a thin, permeable surface with a large area and conserving water requires thick, waterproof surfaces with a small area
Why are fish body surfaces not adequate to supply and remove their respiratory gases?
Fish have a waterproof (and therefore gas-tight) outer covering; being relatively large they have a small SA:vol ratio= like humans and insects they have evolved a specialised internal gas exchange- the gills
Describe the structure of the gills
- The gills are located within the body of the fish, behind the head
- they are made up of stacked gill filaments
- perpendicular to the gill filaments are gill lamellae which increase the surface area of the gills
- water is taken in through their mouth and forced over the gills out through an opening on each side of the body
- the flow of water over the gill lamellae and the flow of blood within them are in opposite directions = counter-current flow
Explain the countercurrent exchange principle
- the essential feature of the countercurrent exchange system is that blood and water flow over the gill lamellae in opposite directions meaning that:
- blood that is already well loaded with oxygen meets water that has its maximum concentration of oxygen therefore diffusion of oxygen from water to the blood takes place
- blood with little oxygen in it meets water which has had most, but not all of its oxygen removed. Again, diffusion of oxygen from the water to the blood takes place
What is the result of the countercurrent exchange system?
A diffusion gradient for oxygen is maintained across the ENTIRE WIDTH of the gill lamellae. In this way, about 80% of the oxygen available in the water is absorbed into the blood of the fish
What would be the result if fish didn’t have a countercurrent exchange system?
If the flow of water and blood was in the same direction (parallel flow) the diffusion gradient would only be maintained across part of the length of the gill lamellae and only about 50% of the available oxygen would be absorbed
How are gills adapted for gaseous exchange?
- gill filaments and lamellae increase the surface area increasing rate of exchange of gases
- lamella have lots of blood capillaries and thin epithelium increasing rate of diffusion- thin layer of cells= short diffusion pathway
Water flow over fish gills is one-way whereas the flow of air in and out of the lungs is two-way. Suggest why one-way flow is an advantage
Less energy is required because the flow does not have to be reversed (important as water is dense and difficult to move)
If an organism has a large volume is it easier or harder to lose heat from its body?
If an organism has a large volume e.g. hippo, its surface area is relatively small making it harder to lose heat from its body
If an organism is small (has a small volume) is it easier or harder to lose heat from its body?
If an organism is small e.g. mouse its relative surface area is large, so heat is lost more easily meaning smaller organisms need a relatively high metabolic rate in order to generate enough heat to stay warm
Will animals with a compact shape lose or conserve more heat?
Animals with a compact shape have a small surface area relative to their volume, minimising heat loss from their surface- animals with a less compact shape (those that are a bit gangly or have sticky outy bits) have a larger surface area relative to their volume, increasing heat loss from their surface
Organisms have behavioural and physiological adaptions to aid exchange (not all organisms have a body size or shape to suit their climate, some have other adaptive instead) give some examples
1- animals with a high SA: volume ratio tend to lose more water as it evaporates from their surface. Some small desert mammals have kidney structure adaptions so that they produce less urine to compensate
2- to support their high metabolic rates, small malls living in cold regions need to eat large amounts of high energy goods such as seeds and nuts
3- smaller mammals may have thick layers of fur or hibernate when the weather gets very cold
4- larger organisms living in hot regions e.g. elephants and hippos find it hard to keep cool as their heat loss is relatively slow. Elephants have developed large flat ears to increase their surface area, allowing them to lose more heat
- hippos spend much of their day in the water- behavioural adaption to help them lose heat
When it comes to gas exchange, plants show one major difference from animals:
Some plant cells (plant cells with chloroplasts) photosynthesis
During photosynthesis plant cells take in carbon dioxide and release oxygen; at times the gases produced in photosynthesis can be used
In respiration and vice versa- reducing gas exchange with the external air
Volumes and types of gases that are being exchanged by a leaf change depending on
The balance between rates of photosynthesis and respiration
The diffusion gradients in and out of the leaf are maintained by
mitochondria carrying out respiration and chloroplasts carrying out photosynthesis
When photosynthesis is taking place, although some carbon dioxide comes from respiration of cells, most of it is obtained from
The external air
some oxygen from photosynthesis is used for respiration but most of it
Diffuses out of the cell
When photosynthesis is not occurring e.g. in the dark, what happens to oxygen?
Oxygen diffuses into the leaf because it is constantly being used by cells during respiration; in the same way, carbon dioxide produced from respiration diffuses out
In what ways is plant is gas exchange in plants similar to insects?
- no living cell is far from the external air and therefore, a source of oxygen and carbon dioxide
- diffusion takes place in the gas phase (air) which makes it more rapid than if it were in water
There is no specific transport system for gases in plants
Which simply diffuse in and out the leaves
Dicotyledonous plants exchange gases at
The surface of the mesophyll cells in the leaf. Gases move in and out through special pores in the epidermis called stomata (occur mainly on underside of leaf) which can open to allow exchange of gases and close if the plant is losing too much water
What controls the opening and closing of stomata?
Guard cells
How are leaves adapted for rapid diffusion?
1- many stomata (small pores), so no cell is far from a stomata and therefore the diffusion pathway is short
2- numerous interconnecting air spaces that occur throughout the mesophyll so that gases can readily come into contact with mesophyll cells
3- Large surface area of mesophyll cells for rapid diffusion
State some differences between gaseous exchange in a plant leaf in a terrestrial insect
- insects may create mass air flow whereas plants never do
- insects have a smaller SA: vol ratio than plants
- insects have special structures (trachea) along which gases can diffuse, whereas plants do not
- insects do not interchange gases between respiration and photosynthesis whereas plants do
Explain the advantage of a plant being able to control the opening and closing of stomata
Helps to control water loss by evaporation/ transpiration
The features that make a good gas-exchange system are the same features that increase water loss so in order to survive terrestrial organisms must limit their water loss without
Compromising the efficiency of their gas-exchange systems
What adaptions have insects evolved to limit water loss?
- small SA: vol ratio to minimise the area over which water is lost
- waterproof coverings over their body surfaces: a rigid outer skeleton of chitin that is covered with a waterproof cuticle
- spiracles: if losing too much water they close their spiracles using their muscles
- tiny hairs around spiracles to reduce evaporation
An insect’s adaptions to minimise water loss means that insects cannot use their body surface to diffuse respiratory gases in the way a single-celled organism does. Instead they have
An internal network of tubes called tracheae that carry air containing oxygen directly to the tissues
Why can’t plants have a small SA: vol ratio like insects do to minimise water loss?
Plants photosynthesis which requires a large SA for the capture of light
How do terrestrial plants limit water loss?
- waterproof waxy cuticle over parts of the leaves
- stomata: stomata are usually kept open in the dah to allow gaseous exchange. Water enters the guard cells, making them turgid which opens the stomata pore. If the plant starts to become dehydrated, the guard cells lose water and become flaccid which closes the pore
Some plants are specially adapted for life in warm, dry or windy habitats where water loss is a more significant problem- what are these plants called?
Xerophytes
Xerophytes have evolved a range of adaptions to limit water loss through evapotranspiration - give some examples:
- thick waxy cuticles on leaves and stems to reduce evaporation
- rolling up of leaves: protects the lower epidermis from the outside helps trap a region of still air within the rolled leaf. This region becomes saturated with water vapour and so has a very high water potential. There is no water potential gradient between the inside and outside of the leaf and therefore no water loss e.g. Marram grass
- layer of ‘hairs’ on epidermis traps still,moist air next to the leaf surface. The water potential gradient between the inside and the outside of the leaves is reduced and therefore less water is lost through evaporation e.g. species of heather plant
- reduced number of stomata = fewer pores for water to escape
- reduced SA:volume ratio of the leaves e.g. pine needles as opposed to broad flat leaves considerably reduces rate of water loss (reduced evaporation)- this reduction in SA is balanced against the need for a sufficient area for photosynthesis to meet the requirements of the plant
Insects and plants face the same problems when it comes to living on land- what is the main problem they share?
Efficient gas exchange requires a thin, permeable surface with a large area. On land these features can lead to a considerable loss of water by evaporation
State one modification to reduce water loss that is shared by plants and insects
- Waterproof covering to the body
- Ability to close the openings of the gas exchange system (stomata and spiracles)
Plants such as marram grass roll up their leaves with the lower epidermis on the inside to reduce water loss. Why would rolling the epidermis the other way not be effective n reducing water loss?
Almost all stomata are on the lower epidermis. This would be exposed to air currents that would reduce the water potential immediately outside the leaf. The water potential gradient would be increased and a lot of water vapour would be lost
In humans where does gaseous exchange take place?
Epithelium of the alveoli in the lungs
The volume of oxygen that has to be absorbed and the volume of carbon dioxide that must be removed in mammals are large because:
- relatively large organisms with a larger volume of living cells
- they maintain a high body temperature which is related to them having metabolic and respiratory rates
As a result, mammals have evolved specialised surfaces called lungs to ensure efficient has exchange between the air and their blood
The lungs are the site of gas exchange in mammals. Why are they located inside the body?
- air is not dense enough to support and protect these delicate structures
- the body as a whole would otherwise be a great deal of water and dry out
The lungs are supported and protected by a bony box called
The ribcage
The ribs can be moved by
The muscles between them
The lungs are ventilated by
A tidal stream of air, thereby ensuring that the air within them is constantly replenished
What are the main parts of the human gas-exchange system?
- lungs
- trachea
- bronchi
- bronchioles
- trachea
Describe the structure and function of the lungs
Pair of lobed structures made up of a series of highly branched tubules called bronchioles, which end in tiny air sacs called alveoli
Describe the structure and function of the trachea
Flexible airway supported by rings of cartilage that prevent the trachea collapsing as the air pressure inside falls when breathing in. The tracheal walls are made up of muscle lined with ciliated epithelium and goblet cells
Describe the structure and function of the bronchi
Two divisions of the trachea, each leading to one lung. They are similar in structure to the trachea and, like the trachea, they also produce mucus to trap dirt particles and have cilia that move the dirt-laden mucus towards the throat. The larger bronchi are supported by cartilage but the amount of cartilage is reduced as the bronchi get smaller
Describe the structure and function of the bronchioles
Series of branching subdivisions of the bronchi. Their walls are made of muscle lined with epithelial cells. This muscle allows them to constrict so that they can control the flow of air in and out of the alveoli
Describe the structure and function of the alveoli
Minute air-sacs with a diameter between 100-300 micrometers, at the end of the bronchioles. Between the alveoli there are some elastic and collagen fibres and the alveoli are lined with epithelium. The elastic fibres allow the alveoli to stretch as they fill with air when breathing in. They then spring back during breathing out in order to expel the carbon dioxide rich-air. The alveoli membrane is the gas exchange surface.
List in the correct sequence all the structures that air passes through on its journey to the alveoli and the capillary
Oxygen in air moves through the nose, the trachea, the bronchi and bronchioles into the alveoli down a pressure gradient. Once in the alveoli, the oxygen diffuses across alveolar epithelium, then the capillary endothelium down a diffusion gradient ending up in the capillary itself
Explain how the cells lining the trachea protect the alveoli from damage
ciliated epithelium and goblet cells- goblet cells produce mucus that ‘traps’ particles of dirt and bacteria in the air breathed in. The cilia on these cells moves the debris up the trachea and into the stomach. The dirt/bacteria could possibly cause damage to the alveoli
The ribcage, intercostal muscles and diaphragm all work together to
Move air in and out
What is the process of ventilation (breathing)?
To maintain diffusion of gases across the alveolar epithelium, air is constantly moved in and out the lungs= ventilation
What is inhalation?
When the air pressure of the atmosphere is grater than the air pressure inside the lungs air is forced into the lungs
What is exhalation?
When the air pressure inside the lungs is greater than that of the atmosphere, air is forced out the lungs
The pressure changes within the lungs are brought about by the movement of what muscles?
- the diaphragm (sheet of muscle that separates the the thorax from the abdomen)
- the intercostal muscles which lie between the ribs. There are 2 types of intercostal muscles:
- internal intercostal muscles= whose contraction leads to exhalation
- external intercostal muscles= whose contraction leads to inhalation
Describe the process of inhalation
- the external intercostal muscles and diaphragm contract while the internal intercostal muscles relax
- causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thoracic cavity (space where lungs are)
- as the volume of the thoracic cavity increases the lung pressure decreases (to below atmospheric pressure)
- as air moves down a pressure gradient, the air flows down the trachea into the lungs
- inhalation is an active process so requires energy
Describe the process of exhalation
1- the external intercostal muscles and diaphragm relax
2- the ribcage moves downwards and inwards and the diaphragm becomes curved again
3- the volume of the thoracic cavity decreases causing the air pressure to increase (above atmospheric pressure)
4- air is forced down the pressure gradient and out of the lungs
5- normal exhalation is a passive process so doesn’t require energy
Describe how forced exhalation works e.g blowing out candles
The external intercostal muscles relax and the internal intercostal muscles contract, pulling the ribcage further down and inwards- during this time, the movement of the two sets of intercostal muscles is said to be antagonistic
How do you work out pulmonary ventilation rate? (Total volume of air that is moved into the lungs in 1 minute)
Pulmonary ventilation= tidal volume X breathing rate
Check camera roll for units
To maintain a diffusion gradient there has to be movement of both the environmental medium (e.g. air)
And the internal medium (e.g. blood)
Each alveolus is made from a single layer of
Thin, flat cells called the alveolar epithelium
Describe the process of gaseous exchange via the alveoli
1- there’s a huge number of alveoli in the lungs which means there’s a big surface area for exchanging oxygen and carbon dioxide
2- the alveolar are surrounded by a network of capillaries
3- oxygen diffuses out of the alveoli across the alveolar epithelium and the capillary endothelium (type of epithelium that forms the capillary wall) and into the haemoglobin in the blood
4- Carbon dioxide diffuses into the alveoli from the blood and is exhaled out
Diffusion of gases between the alveoli and the blood will be very rapid because:
- red blood cells (erythrocytes) are slowed as they pass through pulmonary capillaries allowing more time for diffusion
- the distance between the alveolar air and the erythrocytes is reduced as the erythrocytes are flattened against the capillary walls
- alveoli have only a single layer of epithelial cells and the blood capillaries have only a single layer of endothelium cells therefore short diffusion pathway
- alveoli and pulmonary capillaries have a very large total surface area
- breathing movements constantly ventilate the lungs and the action of the heart constantly, circulates blood around the alveoli. Together, these ensure that a steep concentration gradient of gases to be exchanged is maintained
How are the alveoli alone adapted to gas exchange?
- thin surface exchange- alveolar epithelium single layer of epithelial cells = short diffusion pathway which speeds up diffusion
- large surface area= the large number of alveoli means there’s a large surface area for gas exchange
- each alveolus is covered by a dense network of pulmonary blood capillaries= steep concentration gradient of oxygen and carbon dioxide between alveoli and capillaries which increases rate of diffusion- this is constantly maintained by the flow of blood and ventilation (blood capillaries have only a single layer of endothelial cells)
What is tidal volume?
Volume of air in each breath- usually between 0.4dm^3 and 0.5dm^3 for adults
What is ventilation rate?
Number of breaths per minute- for a healthy person it’s about 15 breaths
What is forced expiratory volume?
Maximum volume of air that can be breathed out in 1 second
What is forced vital capacity?
Maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in
You can figure out tidal volume, ventilation rate and other measures of breathing from a graph produced from a
Spirometer
What are the different lung diseases we need to know about?
- pulmonary tuberculosis (TB)
- fibrosis
- asthma
- emphysema
What is TB and what are its effects?
- when someone becomes infected with TB, immune system cells build a wall around the bacteria in the lungs forming small, hard lumps known as tubercles
- infected tissue within the tubercles dies and gaseous exchange surface is damaged so tidal volume is decreased
- tuberculosis also causes fibrosis which further reduces the tidal volume
- a reduced tidal volume means less air can be inhaled with each breath. In order to take in enough oxygen, patients have to breathe faster I.e. ventilation rate is increased
- common symptoms include a persistent cough, coughing up blood and mucus, chest pains and shortness of breath and fatigue
What is fibrosis and what are its effects?
- fibrosis is the formation of scar tissue in the lungs; this can be the result of an infection of exposure to substances like asbestos or dust
- scar tissue is thicker and less elastic than normal lung tissue = lungs less able to expand so can’t hold as much air as normal = tidal volume decreased and so is forced vital capacity (FVC)
- there’s a reduction in the rate of gaseous exchange- diffusion is slower across a thicker scarred membrane
- symptoms of fibrosis in our shortness of breath, a dry cough, chest pain, fatigue and the weakness
- fibrosis sufferers have a fast ventilation rate than normal (to get sufficient air into their lungs to oxygenate their blood)
What is asthma and what are its effects?
- asthma is a respiratory condition where the airways become inflamed and irritated- the causes vary from case to case but it’s usually because of an allergic reaction to substances such as pollen and dust
- during an asthma attack, the smooth muscle lining the bronchioles contracts and a large amount of mucus is produced = constriction of the airways making it difficult for the sufferer to breathe properly. Air flow in and out of the lungs is severely reduced,so less oxygen enters the alveoli and moves into the blood. Reduced air flow means that forced expiratory volume is severely reduced I.e. less air can be breathed out in 1 second
- symptoms include wheezing, a tight chest and shortness of breath. During an attack, the symptoms come on very suddenly- they can be relived by drugs (often in inhalers) which cause the muscle in the bronchioles to relax, opening up the airways
