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
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
Label a diagram of the human gas exchange system
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
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
Label a insect tracheal system diagram
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
