exchange surfaces and breathing Flashcards
What are the three main factors that affect the need for an exchange system
- size
- surface area to volume ratio
- Level of activity
How does size affect the need for an exchange system
- In small organisms or the cytoplasm is close the environment in which they live
- diffusion supplies enough oxygen and nutrients to keep the cells alive and active
- multicellular organisms may have several layers of cells
- here any oxygen or nutrients diffusing in from outside have a longer diffusion pathway
- Diffusion is too slow to enable a sufficient supply to the innermost cells
What types of organisms don’t need an exchange system
unicellular organisms like amoeba
How do you work out SA:V
SA=4piR(2)
Volume=4/3piR(2)
What is the surface area to volume ratio in small organisms
- have a large surface area to volume ratio
- Surface area is large enough to supply all the cells with sufficient oxygen
What is a surface area to volume ratio like with larger organisms
- Small surface area to volume ratio
- volume increases but SA doesn’t
How do some large organisms not need an exchange system (shape)
things like the flatworm have a large SA:V of skin so can take in O2
How does the level of activity of an organism affects the need for an exchange system
- some organisms are more active than others
- more metabolic activity takes place
- need good supplies of nutrients and oxygen to supply energy for movement
- This is further increased in animals such as mammals that keep themselves warm
How is a large surface area part of a good exchange surface
provides more space for molecules to pass through
What features make a good ES
- large SA
- Short diffusion distance
- good blood supply
How is a thin barrier a feature of a good exchange surface
reduces diffusion distance
Why is a good supply of blood a feature of a good exchange surface
Maintains a steep conc gradient
What is the need for exchange
Take in O2 and glucose and get ride of waste products (CO2)
What features in organisms make good ES
Intestines: microvilli Lungs Gills Insect tracheal system Leaves Root hair cells
How does the mammalian exchange system work
- Lungs are a pair of inflatable sacks lying in chest cavity
- Air passes into the lungs through the nose and along the trachea bronchi and bronchioles
- finally it reaches tiny airfield sacs called alveoli (surfaces with the exchange of gases takes place)
What is ventilation
-The refreshing of air in the lungs so there is a higher oxygen concentration in the blood and the lower carbon dioxide concentration
How does gaseous exchange in the lungs work
- gases pass by diffusion through the thin walls of the alveoli
- oxygen passes from air in the alveoli to blood in the capillaries
- carbon dioxide passes from blood to the air in the alveoli
- Lungs must maintain a steep concentration gradient in each direction in order to ensure that diffusion can continue
What are the features of the Trachea
- Pipe is supported by a layer of cartilage that holds the trachea open and prevents it from collapsing
- rings are incomplete to allow it to bend when food is entering down the oesophagus behind
- Trachea lined with ciliated epithelium cells and goblet cells that prevent dust and bacteria from Entering
- Glandular tissue is the loose tissue also produces mucus
What are the certain requirements the airways need to work
- large enough to allow sufficient air to flow without obstruction
- supported to prevent collapse when the air pressure inside is low during inspiration
- Flexible in order to allow movement
What are the key features of the Bronci
- similar structure to trachea but narrower
- also supported by rings of cartilage
- Extensions of the Trachea that split into left/right lung
- Cartilage rings hold the pipe open
What is the purpose of goblet and epithelial cells in the airways
- Goblet cells secrete mucous to trap pathogens
- Cilia waft mucous to the back of the throat where pathogens swallowed and neutralized in the stomach
What are the key features of the bronchioles
- the bronchus split into smaller bronchioles
- Not much cartilage and held open by smooth muscle
- when muscles contract the bronchioles contract this is dependent on air flow
Where does gas exchange occur
respiratory bronchioles and aveoli
What does smooth muscle cause
The airway to constrict
How do asthma attacks occur
- bronchioles smooth tissue can be responsible for asthma attacks
- smooth muscle constricts (when smoke enters e.g)
- bronchioles lumen becomes narrower
- difficult to get air to the gas exchange surfaces
- inhalers act to relax the smooth muscle
What do elastic fibers do
reinflate the airways and aveoli if smooth muscle is constricted
- allows recoil
- in all connective tissue
- prevent bursting in aveoli allow them to recoil and return to original shape
What are the key features of the alveoli
- air sack
- wall is one cell thick for short diffusion pathway
- network of capillaries wrap around it in cross sections maintaining steep conc
- small size - large SA:v
- compromised of squamous epthelium cells - short diffusion distance
- large amounts provide large SA
- elastic so recoil helps ventilation
- cell secrete surfacant to mantain SA
Why must exchange surfaces be moist
gases must be in solution to cross membrane
why do the lungs make sure the aveoli stay moist
-produce a surfacant to prevent collapse of aveoli by decreasing surface tension
What happens to your lungs when you smoke and what are the consequences of a repetitive cough
- Tar
- cigarette smoke destroys ciliated epithelium
- Mucus in airways builds up and can’t be removed
- more pathogens become trapped in mucus
- cough is an attempt to increase airflow/remove microbes by removibg mucus
- Frequent cough damages airway/aveoli/elastic fibres
- formation of scar tissue
- Airway/bronchi/bronchioles thicken - lunen narrowes
- Flow of air restricted
- damage to alveoli reduces SA:V For gaseous exchange
How does inspiration work
1) diaphragm contracts to move down and become flatter
2) external intercostal muscles contract to raise the ribs
3) volume of chest cavity is increased
4) pressure in chest cavity drops below the atmospheric pressure
5) Air is moved into the lungs
How does expiritation work
1) diaphragm relaxes
2) external intercostal muscles relax
3) diaphragm moves up
3) volume of chest cavity is decreased
4) pressure in the lungs increases and rises above the pressure in surrounding atmosphere
5) Air is moved out of the lungs down the pressure gradient
What does a spirometer do
measures gas exchange
-the movement of air in and out of the lungs as a person breathes
what happens to the lid during inspiration/expiration
up-expiration (air returns to the chamber)
down-inspiration
How does a spirometer work
- as person breathes the tank moves down - holding air
- when breathes back in the tank will inflate
- pen moves down when they inhale and up when they exhale
- produces a trace
- produces a diagram called the spirometer trace which flips the trace upside down
What does the soda lime do
-soda lime absorbs CO2 as it is toxic and allows us to measure O2 consumption
Precautions that must be take when using a soda lime
- fresh O2 otherwise person could suffer from hypoxia
- subject healthy and in particular free of asthma
- soda lime fresh and functioning
- mouthpiece sterilised
- water chamber not overfilled as otherwise it could get out and into the tubes
What is tidal volume
Volume of air that is moved in and out of the lungs at rest
A typical tidal volume is - 0.5 dm(3)
What is residual volume
Cannot be measured using a spirometer trace
- total amount of air still in the lungs after forced expiration
- typical residual volume is 1.5 dm(3)
What is vital capacity
total volume in the lungs between maximum exhale and maximum inhale
-typical vital capacity is 2.5-5.0 dm(3)
What factors affect tidal volume
different when sitting/walking
What factors affect vital capacity
fitness/exercise/age/size/gender/height
What is total lung capacity
whole - from max inhale to bottom
How do you measure oxygen uptake using a spirometer
The chamber is filled with 100% O2 at the beginning and as we breathe in and out the soda lime is absorbing C02
- volume of O2 decreases
- CO2 = O2 we’re breathing in O2 but not replacing it with CO2
- Can measure the gradient of decrease in volume of O2 in the spirometer to measure the O2 uptake
How do you calculate O2 uptake on a spirometer trace
- pick two points on the trace A + B
- Find out what the decrease in volume is from these two points
- Measure the change in time
- Divide the change in volume by the change in time
How is mean tidal volume calculated
counting the height of peaks between a certain amount of time
-divide by amount of peaks
What factors can affect O2 uptake
breathing rate
deeper breaths
What are the different features on a fish
buccal cavity - mouth
gill arch- blood vessels
operculum -covers gills
Girl arch consisting of primary and secondary llamale
What do the gill arch and llamle do
girl arch - makes sure CO2 goes to gills and out /O2 goes to the fish
llamelle provides a large SA
How does water go through a fish
In through the buccal cavity and out of slits in the fishes side
Why do fish need a more advanced exchange surface
As there is less O2 in water than in the air so they need to extract as much O2 from the water as possible
-counter current flow
How does counter current flow work
- water flows in one way system across the gill plates so blood is always flowing one way
- Blood starts with little 02 and as it moves across the gills it absorbs 02 from the water flowing past it as it leaves
- Blood exits gill having extracted most of 02 available
What is counter current flow
blood flows in the opposite direction to the flow of water
Why is counter current flow important
- maintains a conc gradient along the llamele
- if went in the same way blood and water will reach an equilibrium and contain the same amount of O2 so no exchange would be able to take place
How do fish ventilate
- movement
- open and close mouth so water moves in through the buccal cavity and out of the gill pate
What kind of system do insects use
- open circulatory system
- air filled tracheal system which supplies O2 directly to respiring tissues
How does the tracheal system work
- air enters body through a pore called a spiracle
- air is transported through body through a series of tubes called trachea
- these divide into smaller tubes called tracheoles
- -ends of the tracheal fluid is open and contains a fluid called tracheal fluid
- Gas exchange occurs between air in the tracheole and tracheal fluid
How does the trachea control O2 uptake
modifying SA of ES
Low demand - tracheal fluid leaks into the tracheole so total SA is less - lose less water
High demand - withdraw tracheal fluid - more SA - more O2
How do insects ventilate
- expand and contracts body segments
- flex abdomen/movement of flight muscles
- locusts can open/close different combinations of spiracoles
What are diseases associated with breathing
chronic bronchitis
asthma
Why is their always residual volume
lungs cannot be completely flattened
trachea/bronchi held open by cartilage
bronchioles/alveoli held open by elastic fibres
Why do large plants need an ES
small SA:V
diffusion to slow to supply requirements
transport system needed for water and minerals
need SA for gaseous exchange system to meet demand
How do different cells/tissues allow gaseous exchange in mammals
- thin squamous epithelium/thin endothelium of capillary provides short diffusion distance
- surfactant from epithelial cells reduces surface tension
- erythrocytes transport blood to and from alveoli
- diaphragm maintains concentration gradient
- ciliated/ goblet cells removes dust
- cartilage holds airways open
- smooth muscle constricts
- elastic fibres allow recoil
Explain why the curve for fetal oxyhaemoglobin is to the left of the curve for adult
oxyhaemoglobin
- fetal haemoglobin has a higher affinity for oxygen then adult haemoglobin
- fetal haemoglobin takes up O2 at low partial pressure
- placenta has low partial pressure of O2
- at low partial pressure of O2 in placenta adult oxyhaemoglobin will dissociate
What does smooth muscle constricting cause
- constricts bronchi
- lumen decreases in diameter
- resistance to airflow
- harder to exhale
- less air can be inhaled
- harder to ventilate
How do you breathe into a spirometer
breathe in as deeply as possible and breathe out as deeply as possible
