Chapter 7 Exchange And Transport Flashcards
Explain why single celled organisms do not need specialised exchange surfaces
The metabolic demands of single celled organisms are relatively low
They have a large surface area to volume ratio
Why do multicellular organisms need specialised exchange systems?
-They have a higher metabolic demand
-The diffusion distance is much greater
-They have small surface areas to volume ratios
What are the features of specialised exchange systems?
-Large surface area to volume ratio
-Thin
-Moist
-Good blood supply
-Ventilation to maintain the diffusion gradient
-Permeable
Describe how a large surface area to volume ratio provides an effective exchange surface area?
Provides an area where exchange can happen fast within large organisms
Describe how a thin surface provides an effective exchange surface?
Diffusion distances are much shorter, therefore making the process fast and efficient.
Describe how a good blood supply provides an effective exchange surface?
A good blood supply ensures that substances are constantly delivered to and removed from the exchange surface, this provides a steep concentration gradient for diffusion.
Describe how a moist surface provides an effective exchange surface
Moisture increases surface tension, making it easier and more efficient for gases to diffuse across the surface.
Describe how ventilation provides an effective exchange surface
The ventilation system helps to maintain a concentration gradient for gases and makes the process more efficient.
Identify the key structures of the mammalian gaseous exchange system
Nasal cavity
Trachea
Bronchus
Bronchioles
Alveoli
Describe the structure of the trachea
A wide tube supported by ‘C’ shaped rings of cartilage which stop the trachea from collapsing.
The trachea is lined with Ciliated epithelium, containing goblet cells.
The trachea is also composed of smooth muscles and elastic fibres.
What are the components that make up the trachea?
Cartilage
Goblet cells
Ciliated epithelium
Smooth muscle
Elastic fibres
What is the function of Goblet cells?
Goblet cells line the airways, secreting a mucus onto the lining of the trachea to trap dust and microorganisms.
What is the function of the Ciliated epithelium?
Ciliated epithelium contains cilia which are hair like projections on the end of cells.
The cilia beat and move the mucus, along with dust and microorganisms up and away from the lungs. It is then swallowed and digested in the stomach.
Describe the structure of Bronchi
Bronchi have irregular small rings of cartilage
Composed of smooth muscle, elastic fibres and lined with Ciliated epithelium cells
Describe the structure of Bronchioles
Bronchioles have no cartilage, larger bronchiole walls contain smooth muscle and elastic fibres.
The bronchioles are lined with a thin layer of Ciliated epithelium.
Describe the structure of Alveoli
Alveoli are tiny air sacs, consisting of a layer of thin squamous epithelial cells along with collagen and elastic fibres.
What is the function of Elastic fibres?
Stretch and recoil to aid the process of exhalation.
What is the function of Smooth muscle?
Controls the involuntary contraction and relaxation of muscles.
How does Smooth muscle aid the process of gaseous exchange ?
Contraction of smooth muscle restricts air flow into lungs, while the relaxation of smooth muscles opens up air flow into the lungs.
During exercise, smooth muscle is able to expand.
What is the function of Cartilage?
Providing structural support by holding the airways open during inhalation preventing it from collapsing when air pressure is low.
How do Elastic fibres aid the process of gaseous exchange?
During inhalation, the airways constrict and the elastic fibres stretch, the elastic fibres will then recoil to their original size during exhalation to dilate the airway.
What are the adaptions of alveoli for efficient gas exchange?
-Large surface area
-Thin- one epithelial cell thick so diffusion distances between the alveoli and capillaries is short
-Good blood supply- the capillaries bring a constant flow of carbon dioxide and then carries off oxygen, maintaining a steep concentration gradient.
-Good ventilation- air is moved in and out of the alveoli maintaining a diffusion gradient for oxygen and carbon dioxide between the blood and air in lungs.
How can surface: volume ratio be calculated?
Ratio= surface area / volume
Describe the process of inspiration
External intercostal muscles contract
Internal intercostal muscles relax
Ribcage moves up and out
Diaphragm flattens and contracts
Volume of the thorax increases
Pressure in the thorax is reduced, so air is drawn into the lungs.
Describe the process of expiration
External intercostal muscles relax
Internal intercostal muscles contract
Ribs move down and in
Diaphragm relaxes and domes
Volume of thorax decreases
Pressure of the thorax increases, so air moves out of lungs.
What type of process if expiration?
Passive
What type of process is inspiration?
Active
How can the process of expiration become active?
Exhaling forcibly uses energy,
the internal intercostal muscles contract pulling the ribs down hard and fast
The abdominal muscles contract forcing the diaphragm up to increase pressure in the lungs rapidly, so air is forced out
Why does air flow into the lungs during inspiration?
Oxygen moves into the lungs down a pressure gradient, this is because there is a higher pressure outside the lungs and a lower pressure inside the lungs.
How can the capacity of the lungs be measured?
Peak flow meter
Vitalograph
Spirometer
What does a peak flow test measure?
Rate at which air is expelled from the lungs
What does a Vitalograph test measure?
Measures the volume of air expelled and how fast it is breathed out
What does a Spirometer test measure?
Measures lung volume or investigate breathing patterns
What are the safety precautions of a spirometer test?
-The patient must be healthy and not suffer from lung conditions
-Sterilising mouth pierce between uses to prevent spread of pathogens
-Using medical grade oxygen
-Removing build up of Carbon dioxide by using soda lime
What is Tidal volume?
The volume of air that is exchanged within a single breath
What is the approximate tidal volume of an adult at rest?
500cm^3 or 0.5dm^3
How does tidal volume change during exercise?
Tidal volume increases
What is vital capacity?
The maximum volume of air that can be exchanged in a single breath
On a graph what does the vital capacity include?
Inspiratory reserve volume
Expiratory reserve volume
Tidal volume
What is an approximate vital capacity of an adult at rest?
4.0 - 4.5dm^3
What is the Inspiratory reserve volume?
The maximum volume of air that can be inhaled, over and above normal tidal volume
What is the Expiratory reserve volume?
The extra volume of air that can be exhaled over and above normal tidal volume
What is Residual volume?
Volume of air left in lungs when individuals have exhaled as hard as possible
What is Total lung capacity?
Sum of vital capacity and the residual volume
What is breathing rate?
Number of breaths taken per minute
What is ventilation rate?
Total volume of air inhaled in one minute
How can ventilation rate be calculated?
Tidal volume x breathing rate per minute
How can breathing rate be calculated from a spirometer test?
Peak to peak ( or trough to trough) equals one breath taken
Count the number of breaths taken in one minute
(If span is over 30 seconds then times the number of breaths by two)
The normal tidal volume of a male is 500cm^3. His ventilation rate is 6dm^3 per minute. What is his resting breathing rate?
Ventilation rate = breathing rate x tidal volume
500cm^3 = 0.5dm^3
6/0.5= 12 breaths per minute
During physical exertion the males breathing rate increases to 20 breaths per minute and the ventilation rate to 15dm^3. Calculate the tidal volume.
Ventilation rate = breathing rate x tidal volume
15dm^3= 15000cm^3
15000/20= 750cm^3
Allergens can cause breathing problems when inhaled, as the smooth muscle of the airway contracts.
Suggest the effect that this muscle contraction has on ventilation
Reduces the diameter of the lumen in the airway
Therefore, it becomes difficult to exhale
More air will remain inside the lungs so it becomes more difficult to inhale.
Why do insects require a specialised gaseous exchange system?
They have a tough exoskeleton where little to no gaseous exchange can occur
They do not have a blood pigment which can carry oxygen
What are the different components of the Tracheal system of an insect?
Spiracles
Tracheae
Tracheoles
What are spiracles?
Small holes that line the abdomen of insects which allow for gas exchange.
When do the spiracles open or close?
Spiracles will close when oxygen demands are low in order to reduce water loss
Spiracles will open when the oxygen demand is high or carbon dioxide levels build up
What is the Tracheae?
Two tubes which line either side of the insects body following the spiracles.
The tracheae then branch into smaller tracheoles
What is the structure of Tracheae?
Contain spirals of Chitin that reinforce the tubes
What is the function of Tracheae?
Carries the oxygen into the Tracheoles where gas exchange can occur
What are Tracheoles?
Small and branched tubes that lead to the insects tissues
What is the structure of tracheoles?
Tracheoles have no chitin lining, they are lined with a single layer of cells which are freely permeable
Contain tracheal fluid where oxygen can dissolve
What is the function of tracheoles?
Where gaseous exchange takes place between the air and respiring cells
What is the tracheal fluid?
Fluid found at the end of the Tracheoles in insects to help control the surface area available for gas exchange.
What are the adaptions for effective gas exchange in insects?
-Large number of tracheoles which provide a large surface area
-Walls of tracheoles are thin providing a short diffusion distance
-Concentration gradient is maintained as oxygen is used up and carbon dioxide is produced
-Contraction of abdominal muscles also provides a steep concentration gradient
What mechanisms do larger insects use for effective gas exchange?
Mechanical ventilation
Specialised breathing systems
How do small insects conduct gas exchange at rest?
Air will diffuse along the Tracheae and Tracheoles into tissues
The tracheal fluid reduces the surface area for diffusion to take place when insects are at rest because the demand is less.
How do small insects conduct gas exchange when active?
The muscle cells respire anaerobically producing lactic acid.
The lactic acid lowers the water potential of the cells and so the tracheal fluid will move from the tracheoles into cells via osmosis.
This decreases the volume of tracheal fluid within the tracheoles causing more air to move in.
This increases the surface area in the tracheoles that allows more oxygen to diffuse into cells
How do large insects carry out mechanical ventilation of the tracheal system?
Air is actively pumped into the system by muscular pumping movements of the abdomen. This changes the volume of the body and changes the pressure of the tracheae and tracheoles.
Therefore, forcing air in and out as pressure changes.
How do large insects use their specialised breathing systems?
The insects expand their abdomen, closing the spiracles at the back of their body and opening the spiracles at the front.
Contracting their abdomen, opens the spiracles at the back of their body and closes those at the front.
Driving oxygen in and carbon dioxide out.
Why do large insects require mechanisms of ventilation?
Have higher energy demands
Why do bony fish require specialised gas exchange systems?
-High metabolic demand
-Small surface area to volume ratio
-Scales prevents diffusion
Describe the structure of the Gills
Four layers of gills on both sides of the head, the gills are made up of stacks of gill filaments
Each gill filament is covered in gill lamella which are positioned at right angles to filaments.
How are the gills adapted for gas exchange?
-The gill filaments are covered in gill lamella provide a large surface area
-Short diffusion distance between the capillary network and the gill lamellae providing a constant blood supply
-Maintaining a concentration gradient through the countercurrent flow mechanism
Describe the process that bony fish use to allow the constant flow of water over the gills at any time
The mouth opens, Buccal cavity lowered
This increases volume of the Buccal cavity and decreases its pressure so water moves into the cavity.
During this time, the opercular valve is closed while the opercular cavity expands.
Raising floor of Buccal cavity means the volume of the Buccal cavity decreases while pressure is increased
Water moves from the Buccal cavity over the gills
Mouth closes, the operculum opens and operculum cavity moves inwards
Therefore, water is forced out over the gills
Describe the process of the countercurrent flow mechanism
Water flows over the gills in the opposite direction to the flow of the blood in the capillaries.
This ensures that equilibrium is not reached and a concentration gradient is therefore maintained across the entire Gill lamella.
Describe how a spirometer is used to measure oxygen uptake
An individual will breathe through a tube connected to an oxygen chamber
As the individual breathes the lid of the oxygen chamber will move up and down
The movements are recorded by a pen attached to the lid which draws on a rotating drum
The spirometer could also be connected to a motion sensor to produce electrical signals picked up by a data logger
The soda lime in the tube absorbs the carbon dioxide
Describe why the total volume of gas in the spirometer decreases over time
There is a mixture of oxygen and carbon dioxide in the spirometer
However, the carbon dioxide is absorbed by the soda lime leaving only oxygen in the chamber which gets used up via respiration meaning the total volume decreases.
