Module 3: Exchange and Transport Flashcards
How do single-called and small organisms use diffusion?
They use diffusion to exchange materials across their cell surface membranes
Definition of diffusion
Movement of molecules from a region of high to low concentration
Why is the exchange surface in small organisms adequate to exchange materials by diffusion?
Because they have a large surface area to volume ratio
What does diffusion distance depend on?
Thickness of the cell surface membrane
Why is diffusion insufficient to supply requirements to large multicellular organisms
Because larger organisms have a lower SA:Volume ratio
What does large SA:volume ratio mean?
It means that the organism has a lower amount of surface in contact with the external environment in relation to its volume
Why do larger organisms have a greater demand for materials?
Larger organisms produce greater amounts of toxic waste and heat
(Due to large number of cells undergoing metabolism)
Waste needs removing quickly
(Heat must be dissipated to prevent the denaturing of enzymes)
Exchange surfaces in large multicellular organisms
Intestine - for absorption of digested nutrients
Alveoli - in lungs for gas exchange
Example of a transport system in a large multicellular organism
Circulatory system
How would an exchange surface increase efficiency??
Use of active transport
Bulk transport
Facilitated diffusion
Advantages of having a large surface area
Provides more space for molecules to pass through
How is surface area increased
Folds in walls and membranes
What is the purpose of a thin barrier?
Reduces diffusion distance
What is the purpose of having a fresh supply of molecules on one side?
Maintain concentration gradient
In the nose, when air is breathed in it is:
Warmed
Moistened
Filtered
What other structures must air pass through?
Trachea
Bronchi
Bronchioles
Ends up in air sacs/alveoli
Why will a large multicellular organism need the most highly developed transport system?
- has many cell layers
* larger organisms so there is a larger diffusiosn distanc
Position of the lungs
Situated in the thorax
Surrounded by the ribcage
Each lung is covered by pleural membrane
Pleural membrane
Secretes a lubricating fluid
Allows lungs to inflate/deflate without rubbing up against the inner walls of the ribcage
Appearance of the muscular diaphragm
Normally domed
Muscular contraction flattens it
Alveoli in the mammalian lung
Covered in a thin film of moisture
Gases dissolve in the alveoli before diffusing through the alveolar wall
What does the blood flow do
Brings CO2 rich blood
Removed oxygenated blood
Trachea - smooth muscle
Contracts and relax to allow diameter of airways to be controlled
What happens to the airways when the smooth muscle relaxes??
During exercise the muscles relax which makes the airways wider
This reduces resistance to air flow and ventilation
What happens to the airways when the smooth muscles contracts??
The smooth muscles contracts which narrows the airways when challenged with foreign material to protect airways and alveoli
Trachea - elastic fibres
Stretch to allow expansion during inhalation and recoil during exhalation
Prevents over expansion
Trachea - c-shaped rings and cartilage
Provide structural support
Prevent collapse of airway during inhalation
Allows flexibility during movement without narrowing of airways
Allows oesophagus to expand during swallowing
What is the inside surface of the trachea named??
The epithelial lining
What does the epithelial lining consist of?
Goblet mucus cells
Ciliated epithelium
Loose tissue
Function of the goblet mucus cells
Secrete mucus
Traps particles
Reduce risk of infection and inflammation
Ciliated epithelium
Cilia beat in a synchronised pattern
Wafts mucus (with particles) towards the throat
Mucus is then swallowed
Prevents infection
Loose tissue
Inside surface of cartilage
- glandular tissue
- connective tissue
- elastic fibres
- smooth muscles and blood vessels
Bronchi
Two narrower branches arising from the trachea
What is the protective function of the bronchi?
Allows material entering the airways by accident to be directed into the right side, keeping the left functional
Difference between the left and right bronchi
The right bronchi is more vertical and wider than the left
Cartilage in bronchi
Cartilage in the bronchi is similar to the cartilage in the trachea
The cartilage provides mechanical strength and prevents collapse
Cartilage is less regular
Bronchioles
Branches arising from the bronchi
Much narrower than the bronchi
Contain cartilage in the larger bronchioles
What are the bronchioles made from?
Mainly smooth muscle and elastic fibres
What is the significant difference between terminal bronchioles and bronchioles
Terminal bronchioles have clusters of alveoli at their ends, where gas exchange takes place
Cilia are not present in terminal bronchioles
Capillaries in the lungs
Close contact with alveolar wall
1 cell thick (short diffusion distance)
Narrow - allows close contact with capillary wall
Large surface area
How is diffusion gradient maintained?
Diffusion gradient is maintained by rhythmic ventilation
Description of simple squamous epithelium
Single layer of flattened cells
Disc shaped central nuclei
Sparse cytoplasm
Function of the simple squamous epithelium
Allows passage of materials by diffusion and filtration in sites where protection is not important
Location of the simple squamous epithelium
Air sacs of the lungs
Lining of the heart
Blood vessels
Lymphatic vessels
Features of a bronchiole-
Alveolus wall
Thin - single cell thick
Squamous epithelium
Reduces diffusion distance
Features of a bronchiole-
Bronchiole wall
Ciliated epithelium - cilia move mucus upwards
Goblet cells - secrete mucus
Features of a bronchiole -
Blood capillary
Close to alveoli
Thin - single cell thick
Squamous epithelium
Reduces diffusion distance
Features of a bronchiole -
Pulmonary vein
Carries oxygenated blood to heart
Sometimes contraction of the smooth muscle leads to difficulty in breathing
What can be used to alleviate symptoms??
Bronchodilators
Function of elastic fibres in the lung
In the lungs elastic fibres aid recoil of lung tissue during exhalation
Phagocytic cells
Where are they found??
What is their purpose??
Mostly in alveoli
Defence
Mechanism of breathing
Movement of he ribcage and diaphragm ventilate the lungs
Inspiration (inhalation)
Brings fresh supplies of O2 to maintain the O3 concentration gradient
Expiration
Removes waste air CO2 to maintain the CO2 gradient
Breathing in
Chest expands
Ribs move up and out
Diaphragm flattens and contracts
Breathing out
Chest contracts
Ribs move in and down
Diaphragm relaxes
Inspiration (active process)
External intercostal muscles contract
Pulling the ribcage upwards and outwards
Diaphragm contracts - pulling it from a domed to flattened shape
Combined effect of inspiration
Volume of lungs and thorax increase
Pressure is reduced
Air enters, goes down the pressure gradient
Expiration (active process)
External intercostal muscles relax, ribcage falls under its own weight
Diaphragm relaxes and gut pressure pushes it back into its domed shape
Elastic recoil of lung tissue
Combined effect of expiration
Volume of thorax and lungs decrease
Pressure is increased
Air is forced out
Expiration (forced)
Internal intercostal muscles contract, pulling the ribcage down and in
Abdominal muscles contracts pushing the diaphragm upwards
Combined effect of forced expiration
Volume of thorax and lungs decrease
Pressure is increased
Air is forced out
Examples of activities where forced expiration may be used
Exercise
Singing
Playing an instrument
Spirometer traces
When inspiring the trace will dip down
When expiring the trace will climb up
Tidal volume
Amount of air moving in/out of the lungs breathing at rest
Inspiration reserve volume
How much extra air you can breathe during forced inspiration
Exploratory reserve volume
How much extra air you can breathe out during forced expiration
Residual volume
Volume remaining in lungs even after maximum expiration
Vital capacity
Largest possible volume change in the lungs
How is CO2 removed from a spirometer
Soda lime absorbs co2
Why does the gas volume of a spirometer decrease?
When breathing, we are using up oxygen from the tank
Meanwhile carbon dioxide is absorbed by the soda lime when we breathe out
Role of the cartilage
Keep trachea and bronchi open
Prevent collapse under low pressure
C-shaped to allow expansion of oesophagus
Role of the goblet cells
Secrete mucus
Mucus trap pathogens, reduces risk of lung infections
Role of ciliated epithelial cells
Function of moving particles over epithelial surface
Move trapped particles up to throat
Role of the smooth muscle
Allows lumen to constrict by contracting
Role of elastic tissue
When breathing in, the fibres stretch to allow alveoli and airways to expand
When breathing out, they recoil helping to reduce the volume of alveoli and expel air from lungs
Prevent the alveoli from bursting
Role of blood vessels
Deliver co2 to alveoli for exhaling, remove o2 from alveoli and deliver to tissues
Maintain concentration gradient for diffusion
Short diffusion distance
Role of squamous epithelial cells
In alveoli allow oxygen from the air to enter the blood in the capillaries of the lung
Provide thin surface for gaseous exchange
What are air sacs in the lungs??
Alveoli
Why are there many air sacs in the lungs??
Many alveoli are needed as they have a large surface area
There is a gaseous exchange between the air sacs and surrounding capillary blood vessels
What is the type of epithelium in the walls of the air sacs
Squamous epithelium
Role of elastic fibres in air sacs during ventilation
Return air sacs to original shape or size
Prevent bursting
Why does refreshing the air in the air sacs help to maintain a steep diffusion gradient
Refreshing the air in the air sacs increases the concentration of oxygen
Higher concentration of O2 than in the blood
Volume of CO2 decreases so concentration of co2 is lower than in the blood
Describe how the appearance of lungs of a person with emphysema would differ from the lung tissue of a person with no medical disorder
Less alveoli sacs because they would have burst
One symptom that would help a doctor diagnose emphysema
Shortness of breath
Two different ways fish can ventilate
Passively
Actively
Passive ventilation in fish
Fish swims forward with mouth open
Fish points mouth upstream
Active ventilation in fish
Mouth opens and operculum closes
Buccal floor lowers - buccal cavity volume increases ( as the volume increases, pressure decreases, water flows in )
Mouth closes
Buccal floor raises so the pressure increases
Operculum opens so the water is pushed out through the gills
Which type of fish ventilate actively
Bony fish
Ventilation in cartilaginous fish
Rely on continual movement to ventilate gills
Process of ventilation in cartilaginous fish
Gas exchange occurs in the gills
Gills supported by a gill bar
Gill bars are made of bone or cartilage
Each gill has 2 rows of filaments
Each filament are covered with folds called lamellae which is where the gas exchange occurs
What is the space between the gill bars called??
Gill slits
Where does gas exchange occur in the gills
In the lamellae
What is the distance between the water and blood cells in the lamellae
5 um
What prevents lamellae from collapsing
Water
What is the distance between 2 lamellae
50 um
What maximises diffusion in gills??
Extensive network of blood capillaries
What essential characteristics of an efficient exchange surface do gills have??
Large SA
Rich blood supply (maintain conc gradient)
Thin layers reduce distance for diffusion
Tips of gill filaments overlap
Countercurrent exchange system
What is counter current exchange??
Water moving over the gills moves in an opposite direction to blood flow
Maintains steep concentration gradient across the gill
Why can fish not survive out of water??
When out of the water
Gill bars cannot float (no water present)
Collapses and fish suffocates
Why will sharks drown if they stop moving??
Because the steady flow of oxygen will stop passing over the gills
Why do insects have a separate tracheal system??
They are active and require a good supply of oxygen
Supplies air to all of the respiring tissues directly
Role of tracheal fluid in insects tracheal system
Tracheal fluid is drawn into the insects body when the tissue is very active in order to increase the surface area of the tracheal wall exposed to air
Which organisms rely on the diffusion of gases across their outer membrane??
Simple organisms
Eg amoeba, jellyfish
Adaptions of simple organisms using diffusion of gases across their membranes as ventilation
Membranes are moist and permeable to gases
Diffusion distance is short
Oxygen need is low
Gas exchange in flatworms
Exchange gases exclusively through diffusion through their body surface
All cells in the flatworm are localised relatively near to the exterior as gases diffuse cell by cell
Gas exchange in earthworms
Earth worms have a series of thin-walled blood vessels known as capillaries
Gas exchange occurs at capillaries located throughout the body as well as those in the respiratory surface
Adaptations of earthworms to allow efficient gas exchange
Cells on surface for gas exchange
Live in moist conditions to prevent water loss
Slimy covering to reduce evaporation
What type of circulatory system do insects have??
Open circulatory system
What are the pores in which air enters an insects tracheal system??
Spiracle
How does air travel through the tracheal system of an insect??
Air enters system through spiracles
Air transported into the body via tracheae (series of tubes)
Divide into smaller and smaller tubes called tracheoles
Ends of tracheoles are open and filled with tracheal fluid
When tissues are active tracheal fluid is withdrawn into body fluid
Increases SA of tracheoles wall exposed to air
Parallel system
Blood in the gills and water flowing over the gills travel in the same direction
Gives initial steep o2 concentration gradient between blood and water
Diffusion occurs until oxygen conc of blood and water reach equilibrium
Double pump system
Elaborate system of passing water over gills while fish stays stationary
spiracles
Opening on the body
Lets air diffuse in and out
valves
Used for opening/closing spiracles
tracheae
Series of large tubes held open by rings of cartilage through which air passes
Tracheoles
Smaller branched tubes that air passes through
Ending in the muscle of an insect
Air sacs
Pumping air in and out of the tracheal system in very active insects
What effect do body movements or contractions have on an insect’s gas exchange
Speed up the rate of diffusion of gases from tracheoles into body cells
Explain using the term surface area to volume ratio why large, active organisms need a specialised surface for gas exchange
Large organisms cannot rely on diffusion for gaseous exchange because the surface area to volume ratio is very small
Larger organisms also has a higher demand for o2
Outline how diaphragm and intercostal muscles cause inspiration
External intercostal muscles contract
Pulls ribcage upwards and outwards
Diaphragm contracts which pulls it from domed shape to flattened shape
Volume of both lungs and thorax increase
Pressure is reduced and air enters
2 ways in which a spirometer trace recorded while a person took strenuous exercise would differ from a trace of a person at rest
Larger tidal volume due to heavier breathing
Breaths would be more frequent
Why can a spirometer not measure the total volume of the lungs??
Always a small amount of air in the lungs that does not leave the lungs
Residual volume
How do cells lining the bronchus protect the alveoli from damage
Goblet mucus cells secrete mucus which traps particles
Ciliated epithelium cell’s have cilia which beat in a synchronised pattern to waft the mucus away from the throat
