3:1:1 Exchange Surfaces Flashcards
Why do single celled organisms not need specialised exchange surfaces
- High SA:V allows for exchange of substances through diffusion
- Large surface area allows for maximum absorption of substances
- Small volume allows for short diffusion distance to organelles
Why do larger organisms need specialised exchange surfaces
- SA:V is lower so there is less surface area for absorption and higher volume meaning a larger diffusion distance
What is the formula for surface area to volume ratio
Ratio = surface area/volume
What is basal metabolic rate
- BMR is the metabolic rate of an organism at rest, which is significantly lower than when an organism is actively moving
- It can be measured by O2 consumption, CO2 production, or heat production
- BMR increases with body mass
What are the features of effective exchange surfaces
- Large surface area
- Short diffusion distance
- Good blood supply
- Ventilation mechanism
How are root hair cells adapted to be specialised exchange surfaces
- Root hair which increases surface area
- Increases rate of water uptake
How are alveoli adapted to be specialised exchange surfaces
- Walls of alveoli are one cell thick and flattened for short diffusion distance for quick and efficient gas exchange
- Large number of alveoli to increase the surface area for gas exchange
- Extensive capillary network surrounding alveoli, with one cell thick capillary walls to shorted diffusion distance
- Constant flow of blood through capillaries to maintain the concentration gradient
How are fish gills adapted to be specialised exchange surfaces
- Large capillary network to directly extract oxygen from water
- Extensive capillary system covers the gills so that blood flows in an opposite direction to the flow of water (counter current system)
- Counter current system maintains concentration gradient, and ensures oxygen is absorbed along the whole surface of the filament
How are mammalian lungs adapted to be an efficient ventilation mechanism
- Maintain a concentration gradient by ensuring there is a higher concentration of oxygen in the alveoli than the blood
- Ventilation movements allow the air in the alveoli to exchange
Where does gas exchange take place in humans
It takes place in the thorax, a collection of organs and tissues in the chest cavity
What are the different tissues in the mammalian gas exchange system
- Cartilage
- Ciliated epithelium
- Goblet cells
- Squamous epithelium
- Smooth muscle
- Elastic fibres
- Capillaries
Why is cartilage involved in the mammalian gas exchange system
- Strong and flexible tissue
- Supports the trachea in ring shapes to allow it to stay open and flexible
Why is ciliated epithelium involved in the mammalian gas exchange system
- Cells have cilia projections
- Along the trachea and bronchi to sweep mucus, dust and bacteria away from the lungs
Why are goblet cells included in the mammalian gas exchange system
- Scattered in the ciliated epithelium cells
- Secrete mucus which traps bacteria and prevents it from reaching the lungs
Why is squamous epithelium tissue included in the mammalian gas exchange system
- Flat cells that form a thin and permeable layer
- Present as the alveoli walls to allow short diffusion distance
Why is smooth muscle tissue involved in the mammalian gas exchange system
- Found in the walls of the bronchi and bronchioles
- Regulates air flow into and out of the lungs by dilating and constricting
Why are elastic fibres included in the mammalian gas exchange system
- Present in all lung tissues
- Enable the lungs (alveoli) to expand and recoil
- Allows expiration to be a passive process
Why are capillaries included in the mammalian gas exchange system
- Large network of capillaries surrounding each alveolus
- Allows O2 to diffuse into the blood and CO2 to diffuse out
- Capillaries are around 3-4um, so only one RBC can move through at once to allow gas exchange to happen
What are the different components of the gas exchange system
- Trachea
- Bronchi
- Bronchioles
- Alveoli
What tissues are included in the trachea and why
- C shaped rings (shaped to avoid friction with the Oesophagus) of cartilage to support it and to ensure it remains open whilst also being flexible
- Lined with climaxed epithelium cells so bacteria can get swept away from the lungs
- Goblet cells in the ciliated epithelium cells which secrete mucus to capture the bacteria
- Trachea walls have smooth muscle and elastic fibres
What tissues are included in the bronchi structure and why
- Same structure as trachea, but cartilage forms full rings or irregular blocks
What tissues are included in the bronchioles and why
- Narrow self supporting tubes (no cartilage)
- Lined with ciliated epithelium tissue, without the goblet cells
- Large bronchioles have elastic fibres and smooth muscle to adjust the airway size
- Small bronchioles near the alveoli have no smooth muscle but do have elastic fibres
Label a diagram of the human gas exchange system
What is ventilation
The mass flow of gases in the lungs which works with the continuous flow of blood in the capillaries to help ensure that there is always a higher concentration of oxygen in the alveoli than in the blood
What is the order of the passage of air
- Nose/mouth
- Trachea
- Bronchi
- Bronchioles
- Alveoli
What happens during inhalation
- External intercostal muscles contract, internal intercostal muscles relax
- Ribcage moves up and out
- Diaphragm contracts and flattens
- Volume in the chest increases and pressure in the lungs decreases
- Air moves down the pressure gradient into the lungs
What happens during exhalation
- External intercostal muscles relax, and internal intercostal muscles contract
- Ribs move down and back
- Abdominal muscles contract to push organs up against the diaphragm to increase internal pressure
- Diaphragm relaxes and becomes dome shaped
- Volume of chest decreases, and pressure of lungs increases
- Elastic fibres in alveoli recoil and force air out
What are the ways breathing can be measured
- Vital capacity: maximum volume of air that can be taken in or out in one breath
- Tidal volume: volume of air breathed in or out at rest (normal breathing)
- Breathing rate: number of breaths (in and out) taken in one minute
- Oxygen uptake: volume of oxygen used up in a given time
What is a spirometer
Apparatus for breathing measurements
How does a spirometer work
- The person breaths in and out through the device
- CO2 is absorbed from the exhaled air by soda lime, to stop the volume of CO2 increasing in the rebreathed air
- A trace or graph is drawn from the person breathing through the device
- The trace can be used to measure vital capacity, tidal volume and breathing rate
- Oxygen uptake is calculated by the change of volume of air in the spirometer (as CO2 is removed from the breath the air available in the spirometer decreases)
Label a diagram of data from a spirometer
How to calculate breathing rate from a spirometer
- One breath (up and down)
- Count how many breaths in a time (e.g. one minute)
- Give appropriate values
What are the components of the insect tracheal system
- Spiracles
- Tracheae
- Muscle fibres
What is a spiracle and why is it involved in the tracheal system of an insect
Openings with valves in the waxy, impermeable exoskeleton of an insect, to allow air to enter the insect and flow into the tracheal system
What are the tracheae and why is it involved in the tracheal system of insects
Tubes with rigid rings of chitin within the insect that lead to the tracheoles
What are the muscle fibres and why are they involved in the tracheal system of insects
Tracheoles run into muscle fibres, which are the site of gas exchange
Label a insect tracheal system diagram
Describe the ventilation mechanism in insects
- Abdominal muscles create a pumping movement for ventilation
- Air is brought into the spiracles and the system
- Tracheal fluid is drawn into respiring muscles so gas can diffuse across the tracheoles quicker
What are the components of the gas exchange system in fish
- Gills
- Gill arches
- Filaments
- Lamellae
- Capillaries
How are fish adapted to extract oxygen from water
- Series of gills on either side of the head
- Each gill arch has two stacks of filaments
- Each filament has rows of lamellae
- Lamellae cover a vast network of capillaries which ensure the blood flow is in the opposite direction to the flow of water (counter current system)
- Counter current system ensures the concentration gradient is maintained along the length of the capillary
Describe the ventilation system in fish
- Water is constantly pushed over the gill surface
- Fish open their mouth and the buccal cavity floor lowers, increasing buccal cavity volume, and decreasing cavity pressure
- Water flows into the buccal cavity down the pressure gradient
- Water flows from the high pressure buccal cavity to the low pressure gill cavity
- Water pressure builds up in gill cavity and operculum (tissue covering gills) opens allowing water to exit the fish
- Operculum is pulled shut as the buccal cavity lowers starting the cycle
Describe the process of a fish gill dissection
- Lab coat, gloves and eye protection should be worn to avoid contamination
- Use tools to cut and expose the specimen
- Use pins to expose the desired section
- Key structures are the gill arches and filaments, and the gill can be placed in water in order to view the movement of water
