Module 3 - Exchange Surfaces and Breathing

Why do organisms need exchange and how surface area to volume ratio affects exchange?

need to exchange materials like oxygen + glucose which they need to survive + to remove waste product so it doesnt build up
high SA:V - have large surface area relative to their volume so diffusion of substances is fast - generally smaller organisms (so exchange can take place over the surface) as living cells need to take in oxygen/nutrients + remove metabolic waste + diffusion rate is too slow if SA:V ratio is too small + have a short diffusion pathway so diffusion fast enough to supply all needs so don’t need a specialised exchange surface as they have small so demand for, O2 as diffusion alone is adequate to meet their needs
low SA:V - have small surface area relative to their volume so diffusion of substances is slower - generally larger organisms (need specialised surface for exchange)

How to calculate the surface area to volume ratio?

calculate the surface area of shape and the volume then convert the ratio til volume is 1

Why do multicellular organisms require specialised surfaces?

cells are not in direct contact with external environment + surface area too small to supply their needs
diffusion distance between cells and their environment are large meaning diffusion is too slow to enable sufficient supply to innermost cell
larger organisms have higher metabolic rates so they need more oxygen and glucose + need to remove CO2 faster - uses energy from food + requires oxygen to release energy in aerobic respiration - cells of active organism need good supplies of oxygen to supply energy for movement - increased in animals such as mammals that keep themselves warm
small organisms have large surface area and volumes so surface area large enough to supply all their cells with sufficient oxygen as size increases volume rises more quickly but can be increased by changing shape eg flatworm has very thin,flat body but limits size can reach
to solve this problem multicellular organisms have evolved specialised exchange surfaces

Why are transport systems needed?

large multicellular organisms need a transport system as they have a low surface area to volume ratio,diffusion too slow to supply enough nutrients like oxygen and prevent waste like CO2 from building up as distance is too great and larger organisms are more active
human body has small surface area to volume ratio, but the lungs provide a large surface area to volume ratio - body SA:Vol is not big enough to meet body’s needs but lung SA:Vol is big enough to meet body’s needs in terms of transferring oxygen into the blood and carbon dioxide out of the blood 

What are the key features of specialised exchange surfaces?

specalised structures that allow materials to be transferred between cells and an organisms surrounding environment
large surface area - provides a larger area for molecules to pass through meaning more substances can be exchanged often achieved by folding walls and membranes involved
thin walls - minimises diffusion distance + barrier must be permeable
extensive blood supply and/or ventilation - brings fresh molecule supplies to keep the concentration high maintains steep concentration gradients so diffusion occurs faster
surrounded by selectively permeable plasma membranes - controls what substances are exchanged

What is the gas exchange system?

consists of lungs and air passages - allows oxygen to enter the blood and carbon dioxide to leave the blood through gas exchange surfaces called alveoli - lungs (pair of inflatable sacs) located inside the chest in thoracic cavity protected by the ribcage where ribs held together by intercostal muscles where actions of these muscles helps to produce breathing movements (ventilation)
inside the body as air not dense enough to support and protect these delicate structures + body woul lose water and dry out

What is the pathway of air?

1.air first enters the trachea via the nose
2.air travels into the two bronchi with one bronchus going to each lung
3.air travels into smaller airways called bronchioles
4.air travels into clusters of air-filled sacs called alveoli at the end of the bronchioles where gaseous exchange occurs

What are ciliated epithelium?

contains goblet cells which produce and secrete mucus that traps pathogens and microbes + cilia on ciliated epithelial cells which waft mucus upward to the mouth so it can be swallowed - which lines the airways

What is trachea and the adaptations?

large/main tube that carries air from the throat down to the lungs
adaptations
rings of cartilage keeps the airway open - is C-shaped allowing flexiblity + space for food essential in the trachea to keep the trachea open and prevent collapse during inspiration as volume of the chest cavity increases so there is lower/negative pressure in the thorax
smooth muscle can contract or relax to constrict or dilate the airway and change airflow
elastic tissue contains elastic fibres with elastin that allows stretching and recoiling
lined with ciliated epithelial cells and goblet cells

What is bronchi and the adaptations?

two main branches narrower than trachea extending from the trachea that carry air into each lung
adaptations
reinforced with cartilage (form of connective tissue) to keep airway open
smooth muscle (involuntary) can contract or relax to constrict or dilate the airway and change airflow
elastic tissue contains elastic fibres (protein fibres) with elastin that allows stretching and recoiling
lined with ciliated epithelial cells and goblet cells

What are bronchioles and the adaptations?

smaller airways branching from the bronchi that carry air to the alveoli
adaptations
no cartilage can change shape
smooth muscle can contract or relax to constrict or dilate the airway and change airflow
elastic tissue contains elastic fibres with elastin that allows stretching and recoiling
simple squamous epithelium (only larger bronchioles have ciliated epithelium)
hard to exhale if bronchioles become reduced in diameter as reduced diameter means increased resistance to air flow as exhalation is passive there is no muscular force behind exhalationbut with bronchioles that are reduced in diameter additional force is needed to exhale

What is alveoli?

tiny air sacs clustered at ends of bronchioles - surrounded by network of capillaries so gases van be exchanged between the air in the alveoli and the blood - carry out gas exchange by - 1.oxygen diffuses from the alveoli into pulmonary capillaries where it binds to haemoglobin in rbc 2.carbon dioxide dissociates from haemglobin and diffuses from the blood into the alveoli

What are the adaptations of the alveoli for gas exchange?

wall consists of 1 layer of squamous epithelial cells (2 cells thick) - allows rapid diffusion
large surface area (due to how many there are) as many alveoli - increases rate of gas exchange as more area for diffusion
partially permeable - means only certain gases can move across the wall of oxygen and carbon dioxide as are small and non-polar
surrounded by dense network of capillaries - bring blood close to air for gas exchange so shorter diffusion distance so that the concentration gradient is steep, so that there is a high rate of gaseous exchange and can carry oxygen away from alveoli also as combines with Hb keep concentration low
ventilation of air due to intercostal muscles - maintains steep diffusion gradient refreshing air in alveoli as supplies oxygen
elastic fibres - allows stretching during inspiration and recoiling to help push air out during expiration
collagen fibres/elastic tissue - contain strong collagen that prevents alveoli from bursting and limits overstretching by streching + recoiling
moist inner surface - allows gases to dissolve and lung surfactant helps alveoli remain inflated
surfactant (from epithelial cells) - reduces surface tension in the alveoli preventing them from collapsing

What are pulmonary blood vessels and its adaptations?

blood vessels involved in circulation of lungs - including pulmonary artery which delivers deoxygenated blood from heart to pulmonary capillaries - pulmonary vein which delivers oxygenated blood from capillaries to heart - pulmonary capillaries which are the site of gas exchange between blood and alveoli
adaptations
thin walls (one endothelial cell thick) - maintains short diffusion distance
red blood cells pressed against capillary walls - reduces diffusion distance which slows flow
large surface area - increases diffusion speed
movement of blood - maintains steep diffusion gradient
slow blood movement - allows more time for diffusion

What is ventilation?

constant movement of air into and and out of the lungs which allows air to enter and leave the lungs providing the body with oxygen and removing carbon dioxide
replaces used air with fresh air bringing in more oxygen and removing carbon dioxide
ensures concentration of oxygen in air of alveolus remains higher than in the blood + concentration of carbon dioxide in alveoli remains lower than that in the blood
concentration gradient necessary for diffusion to be maintained
air we breath in is rich in oxygen + air we breath out is rich in carbon dioxide
refreshing of air in the lungs so there is a higher oxygen concentration than in the blood

What are the muscles involved in ventilation?

ribcage made up of bones called ribs that enclose the thorax (cavity where lungs are located) - three sets of muscles act on the ribcage - 1.diaphragm - layer of muscle beneath the lungs that moves ribcage up and out when it contracts 2.external intercostal muscles - found between the ribs and pull the ribcage up and out when they contract 3.internal intercostal muscles - found between the ribs but pull the ribcage down and in when they contract
where the intercostal muscles have opposite effects on the ribcage as external expand ribcage during inspiration while internal shrink it during expiration

How does partial pressure affect ventillation?

ventilation maintains a steep diffusion gradient as it increases the partial pressure of oxygen in the air sac so concentration of oxygen in the air sac is higher than that in the blood + decreases the partial pressure/concentration of carbon dioxide in air sac so concentration of CO2 in the air sac is lower than that in the blood

What is inspiration?

breathing in and is an active process requiring energy for muscle contractions
1.external intercostal muscles contract while the internal intercostal muscles relax moving the ribcage up and out
2.volume of the thoracic cavity increases
3.diaphragm contracts and flattens further increasing the volume of the thoracic cavity
4.lung pressure decreases below atmospheric pressure
5.air flows into the lungs down the pressure gradient

What is expiration?

breathing out and at rest is a passive process so it does not require energy however can be forced by contracting internal intercostal muscles
1.external intercostal muscles relax moving the ribcage down and in and internal intercostal muscles can contract
2.volume of the thoracic cavity decreases
3.diaphragm relaxes and unflattens further decreasing the volume of the thoracic cavity
4.lung pressure increases above atmospheric pressure
5.air is forced out of the lungs down pressure gradient
elastic fibres in alveoli also shrink and recoil back to original shape when thoracic cavity volume decreases which increase the pulmonary pressure and helps to push air out of the lungs
just after expiration the lungs are less inflated so have a smaller volume, the diaphragm is arched/not flat as it is relaxed + the rib cage is/ribs are in the lowered position/not raised
considered passive as it does not use muscle contraction as the rib cage falls due to gravity + the lungs recoil because they contain elastic tissue

What some example of instruments that provide data on lung function?

peak flow meter - measures the maximum speed of expiration through a mouthpiece by tracking the movement of an indicator
vitalograph - records a graph showing the volume and rate of forced expiration through a mouthpiece
spirometer - calculates different lung volumes using a chamber containing a known volume of gas connected to a mouthpiece and recorder

What can the graph from spirometer traces be used to calculate?

1.breathing rate - number of breaths taken per minute measured by counting number of peaks in a minute
2.tidal volume - volume of air breathed in or out in average breath during rest measured from the height of each peak at rest/inhaled and exhaled in each breath during regular breathing
3.vital capacity - maximum volume of air that can be exhaled from the lungs after taking the deepest possible breath measured from maximum peak height then force as much air out
4.inspiratory reserve volume - maximum volume of air that can be inhaled above normal inhalation
5.expiratory reserve volume - maximum volume of air that can be exhaled above normal exhalation
6.residual volume - volume of air that remains in the lungs after largest possible exhalation (can’t be measured) - you cannot expel all air from your lungs as the thorax cannot be completely compressed as the trachea and bronchi are held open by cartilage + the bronchioles and alveoli are held open by elastic fibres
7.total lung capacity - vital capacity added to the residual volume

How can a mammalian chest model be used?

to demonstrate tidal volume you would do small and steady up and down movements of the rubber sheet
to demonstrate vital capacity you would pull down on the rubber sheet as far as possible and then pushed up as far as possible
the balloons expand when the sheet is pulled down because the volume inside the jar increases and the pressure inside the jar and thus the balloons decreases to below pressure in atmosphere so air moves into the balloons down the pressure gradient

How do you measure tidal volume?

to measure tidal volume the participant must not breathe through their nose the subject must breathe normally and the amplitude of the waves from the trace are used we would measure at least three waves and calculate mean

How to calculate oxygen consumption?

is volume of oxygen used per minute - if had spirometer trace could measure oxygen consumption which is the slope where measure change in volume of gas in spirometer over period of time and divide value by time taken
to measure oxygen uptake using a spirometer measure the volume of oxygen used by the decrease in volume of the chamber measure time taken to use this oxygen + divide volume by time taken

How to calculate ventilation rate?

is the volume of oxygen inhaled per minute - calculated by measuring tidal volume (dm3) then measure breathing rate (min-1) then times the two values (dm3min-1)

Why do insects need gas exchange?

have high oxygen demands as very active so tracheal fluid can be withdrawn into body to increase surface area of tracheole exposed to air meaning more oxygen can be absorbed when active but tough external skeleton prevents direct gas exchange
need efficient system for: - to deliver oxygen to cells which allows aerobic respiration to occur to release energy for cellular processes - to remove carbon dioxide from cells as build up as wate product of respiration reduces pH which denatures enzymes
gas exchange systems adapted to balance two conflicting needs by maximising gas exchange efficiency + minimising water loss
exoskeleton covered with waterproof cuticle which further prevents water loss

What are the three main things involved in insect gas exchange system?

have open respiratory system where body fluid acts as both blood and tissue fluid comprised of tubular structures that transport air - gaseous exchange occurs between air in tracheole and tracheal fluid
1.tracheae - air-filled tubes branching throughout the body
2.tracheoles - fine branches of tracheae that deliver gases to cells + ends open and filled with trachiel fluid
3.spiracles - external openings of tracheal system on the exoskeleton along the abdomen and thorax

What are the adaptations of trachea?

reinforced with spirals of chitin - which prevents collapsing
multiple tracheae - this increases the surface area insect tracheal system provides a large surface area as there are many branched tubes (tracheae and tracheoles)

What are the adaptations of tracheoles?

penetrate direclty into tissues - reduces gas diffusion distance
thin walls - reduces gas diffusion distance
highly branched - maximises the surface area
not reinforced with chitin - allows gas exchange to occur
fluid at ends - tracheal fluid allows oxygen to dissolve to aid diffusion and reduce water loss

What are the adaptations of spiracles?

open and close - allows them to control gas exchange with the atmosphere and minimise water loss

How does gas exchange occur in insects?

1. air enters the tracheal system through open spiracles

2. air moves into larger tracheae and diffuses into smaller tracheoles

3. tracheoles branch throughout the body transporting air directly to cells

4. oxygen dissolves in water in tracheal fluid and diffuses down its concentration gradient from tracheoles into body cells

5. carbon dioxide diffuses down its concentration gradient out of body cells into the tracheoles

6. air is then carried back to spiracles via trachea and released from the body

these are the steps

How is the concentration gradients between the tissues and air in the tracheal system maintained?

cells using up oxygen for respiration - keeps oxygen concentration low in cells
cells producing carbon dioxide in respiration - keeps carbon dioxide concentration high in cells
continuous ventilation - fresh air is supplied to the tracheal system via spiracles

What accumulates in insects?

latic acid which can affect rate of gas exchange: - reduces the water potential in tracheal fluid at end of tracheoles - water leaves the tracheoles via osmosis - a higher surface area is exposed for gas exchange

How do insects and animals respiratory systems compare?

insect tracheae differ from animal trachea as mammals have just one trachea and insects have multiple tracheae
mammal tracheas have a much larger diameter than insect tracheae
in mammals the trachea has cartilage to support it whereas insect tracheae are supported by chitin,
mammals have C-shaped ‘rings’ of supporting tissue (cartilage), whereas  insects have spiral supporting tissue (chitin)
mammal tracheas are longer + branch into bronchi whereas insect tracheae branch into tracheoles,mammal trachea has smooth muscle/goblet cells/ciliated epithelium + insect tracheae do not

What are some challenges of respiratory systems in bony fish?

have high oxygen needs which exceed simple diffusion therfore have evolved specialised respiratory system to meet challenges of extracting oxygen from water
challenges include: - water is dense and more viscous than air resulting in slower difusion of oxygen - water has less oxygen concentration than air - bony fish are very active so have high oxygen demands
this means organisms develop gills in habitats where oxygen is in short supply as otherwise rate of diffusion is too slow to meet their needs if they have a small surface area to volume ratio + high metabolic rate

What is the structure of gas exchange systems in bony fish?

gills allow bony fish to efficiently take up oxygen from water and to release carbon dioxide to water
structure of gills: - most have 5 gills covered by an operculum flap - each gill has 2 rows of gill filaments (primary lamellae) attached to bony arch - filaments are very thin and their surface is folded into many secondart lamellae (provides very large surface area) which are surrounded by extensive blood vessels/capillaries which carries deoxygenated blood for exchange

What are the adaptations of the gills for efficient gas exchange?

lamellae provide a large surface area as there are many lameliae increased surface area increases oxygen absorption usefulwhere oxygen concentration is low
lamellae membranes are thin to minimise diffusion distance
gills have a rich blood supply to maintain steep diffusion gradients
countercurrent flow of blood and water creates even steeper concentration gradients
overlapping filament tips increase resistance slowing water flow over gills and allowing more time for gas exchange

What is the countercurrent exchange principle?

gills of bony fish allow countercurrent flow of blood and water which is much more effcient than parallel flow
in system: - blood and water flow over lamellae in opposite directions - means oxygen-rich blood meets water that is at its most oxygen rich when it first moves across the gills maximising diffusion of oxygen into the blood - oxygen-poor blood returning from body tissues meets oxygen-reduced water that has had most of its oxygen removed still allowing diffusion of oxygen into the blood - maintains a steep concentration gradient across the enttire gill - able to absorb maximum amount of oxygen from the water

What is parallel flow?

flow of blood and water moves in same direction - countercurrent exchange systems enable more effcient gas transfer than parallel flow as parallel flow reduces concentration gradient so less oxygen can be absorbed

How does a fish get ventilation through its mouth?

buccal cavity is the mouth and throat area of fish - fish ventilate gills by opening and closing their mouths changing volume of buccal cavity: - when a fish opens its mouth as floor moves downwards it increases the volume of the buccal cavity - decreases the pressure which pulls water into the buccal cavity - water flows over the gills - water flows out through the operculum which moves outwards which reduces pressure in opercular cavity helping water to flow through gills
this drives unidirectional water flow for ventilation providing freshly oxygenated water and removing carbon dioxide - mouth closes + floor raised pushing water through thr gills

How do you use a spirometer?

measures the movement of air in and out of the lungs - consists of chamber of air floating on tank of water - during inspiration air is drawn from chamber so lid moves down + during expiration air returns to the chamber raising the lid and these movements can be recorded on a data logger where assumes volume of CO2 absorbed by soda lime or a hydroxide equals volume of oxygen absorbed by blood so measuring gradient of decreases means can calculate rate of oxygen uptake
carbon dioxide-rich air exhaled passed through soda lime which absorbs the carbon dioxide so only oxygen consumption measured
volume of air in a spirometer drops over time as oxygen is used in respiration + carbon dioxide is released in respiration then absorbed by soda lime

What are some precautions of measuring vital capacity with a spirometer?

subject should be healthy - soda lime should be fresh + working - no air leaks as would give inaccurate results - water chambers must not be overfilled - must use a nose clip to ensure all air breathed comes from chamber (to prevent  escape of air or entry of air, through nose) and as if they didn’t use the nose clip it would make the results invalid
using medical grade oxygen, disinfecting the mouthpiece for each volunteer, that there is sufficient oxygen in chamber that the water level is not too high as water must not enter tubes + ensuring that the valves are working correctly

How else can instects get ventilation?

larger insects can also ventilate their tracheal system by movements of the body
can be achieved by: flexible walls which can repetively expand - wing movement alters the volume of the thorax
mechanism is an increase in the volume of body cavity reduces pressure so air enters tracheal system + decrease in volume raises pressure to push air out again

How do you calculate oxygen uptake from a spirometer trace?

draw a line from initial oxygen volume (A) down to horizontal axis and another line from final oxygen volume (B) + measure length of time between points - measure difference in volume between points A and B and divide by time taken for the decrease

What can cause higher oxygen uptake?

will result from higher demand for oxygen such as during exercise when muscles are respiring more
increased oxygen uptake will result from:increased breathing rate and deeper breaths

What does smooth muscle and elastic tissue in respiratory system?

smooth muscle contracts which constricts the airway making lumen of airway narrower - restricts flow of air to alveoli - not a voluntary acts + may occur due to allergic reaction or overreact to certain substances which is cause of asthma - once contracted cannot reverse effects on its own - smooth muscle elongated again by elastic fibres which deform when muscle contracts - as muscles relax elastic fibres recoil to original size and shape - acts to dilate the airway

How can the airways be effective?

be large enough to allow sufficient air to flow without obstruction
be supported to prevent collapse when the air pressure inside is low during inspiration
be flexible in order to allow movement

Why is a good blood supply needed?

blood supply helps maintain a steep concentration gradient so gases continue to diffuse where blood system transports carbon dioxide from tissues to lungs which ensures carbon dioxide concentration in blood than in air of alveoli therfore it diffuses into alveoli - blood also transports oxygen away from lungs which ensures concentration of oxygen in blood kept lower than in alveoli so oxygen diffuses into blood

What is involved in dissection?

to dissect a fish gaseous exchange system in maximum detail remove the operculum of fish to observe the gills eg by observing the structures under water placing,a rod/pencil into buccal cavity to display lamellae
for dissecting an insect you would cut open the exoskeleton to view the tracheoles + stain the tracheoles with methylene blue