3.1.1 Exchange Surfaces COMPLETE Flashcards
DEFINITION- Diffusion
Net movement of particles from a higher to a lower concentration, passive process
Factors affecting diffusion
- SA
- Temperature
- Conc. gradient
- Length of diffusion path
- Pressure
- Permeability
The problems with larger organism
When something gets bigger its SA:V is reduced as volume increases more than SA
Large surface area
A larger surface area for a substance to diffuse across means more of it can cross in a given time
Short Diffusion Path
Shorter distance for a substance to diffuse across so it’ll take less time
Diffusion gradient
Concentration must be higher one side than the other for diffusion down a gradient to take place
Protection for drying out
Water vapour will diffuse out of the cell, too much water loss will cause the membrane to change shape or die
Exchange In Mammalian Lungs
SA: Lots of alveoli
Thin: Each alveolus is one epithelial cell thick
Conc. gradient: Constant ventilation replaces the air to maintain it
Drying out: Kept moist by water diffusing out of other cells
Exchange in Plant Leaves
SA: Lots of leaves, also lots of spongey mesophyll cells
Thin: Gases diffuse directly into the cells
Conc. gradient: Wind replaces the air around leaf
Drying out: Guard cells swell up and close the stomata
How is the Alveolus Adapted
- Elastic fibres in the walls allow them to recoil and stretch
- One cell thick
- Thin layer of surfactant fluid keeps them moist and reduces tension
- NOT SA
Role of the Macrophages
Patrol alveolar surfaces and scavenge for any harmful material. If they find any they will engulf them, some however can’t be digested
Distribution and function of the cartilage
Found in the trachea and bronchi
Supports and holds them open preventing collapse
Distribution and function of smooth muscle
Found in the walls of the trachea, bronchi and bronchioles
Involuntary muscle that narrows the lumen
Distribution and function of the elastic fibres
Found in the walls of all the airways and alveoli
Recoil of the elastic tissue will widen the air way and force air out the alveoli
Distribution and function of Goblet cells
Found throughout the ciliated epithelium
Secrete a sticky mucus that traps particles and prevent drying out
Distribution and function of the ciliated epithelium
Found in the trachea, bronchi and bronchioles
Cilia move in a synchronised pattern to waft mucus up the airway to the back of the throat.
Respiratory System
Organs and tissues that carry out ventilation and gas exchange
Respiration
The reaction that utilises ATP to release energy from glucose, occurs in every living cell.
Inspiration
Breathing in
- External intercostal muscles contract moving ribcage up and out
- Diaphragm flattens as muscle contracts
- Thoracic cavity volume increases
- Pressure lower than outside body
- Air flows down the pressure gradient
Exhalation
Breathing out
- External intercostal muscles relax
- Elastin fibres between alveoli recoil
- Volume decreases, pressure increases so air moves out
- More air is forced out when internal intercostal muscles move ribcage down and in
- Abdominal muscles contract so diaphragm releases upwards
Breathing
Physical changes that occur in the ribcage and diaphragm to cause ventilation
Forced breathing uses the internal intercostal muscles
Ventilation
Movement of gases into and out of the lungs
Tidal Volume
Volume of air moved in and out of the lungs with each breath at rest.
Vital Capacity
The largest possible volume of air that can be moved into and out of the lungs in one breath.
Effected by age, size, exercise
Inspiratory Reserve volume
How much more air can be breathed in over and above the tidal volume
Expiratory Reserve Volume
How much more air can be breathed out over and above the tidal volume
Residual Volume
Volume of air that always remains in the lungs even after the biggest possible exhalation
Dead Space
Parts where no gaseous exchange takes place i.e. in the trachea.
Still vital parts as without them no ventilation could happen
Spirometer
A tool used to measure breathing rate and vital capacity. Soda lime is used to absorb and CO2 released. Precautions include using a clean disposable mouth piece, a nose clip, supply of fresh air to breath in.
Lines draw up indicate the person breathing out
Breathing Rate
Number of breaths per minute
Count the number of peaks within a set period of time, then work that out for one minute.
Ventilation Rate
Total volume of air breathed in or out in one minute.
Breathing rate x Mean Tidal Volume
Calculating Oxygen Consumption
Chamber must be filled with pure oxygen, soda lime must also be added to absorb the CO2
Tidal volume of air going back into the container will be decreasing so the pen line has a gradient.
Therefore by calculating the gradient we can work out the volume of O2 being used.
Gas Exchange in Bony Fish
Often are large active organisms this means they have a low SA:V but a high metabolic rate they’re also multicellular. Water has a low O2 content so moving water in and out would waste energy.
Adaptions of gills in bony fish
Large SA or diffusion
Rich blood supply to maintain gradient
Thin layers to shorten diffusion path
Tips of adjacent gills overlap increases resistance to the flow of water so more time for diffusion
Water moving over gills and blood move in opposite direction as a countercurrent
Buccal- Opercular Pump
Ensures water constantly flows over gills.
The mouth opens and the floor of the buccal cavity is lowered so volume increases and pressure decreases. Water moves in then the mouth closes to increase the pressure again.
Water is pushed from the buccal cavity to the operculum outwards and the pressure there decreases helping water flow over the gills
Tracheal system
A system of air filled tubes in insects
Problems with gas exchange in insects
They’re very active so lots of O2 needed, high risk of desiccation, no blood carrying O2, exoskeleton makes gas exchange difficult
Gas exchange in insects
Air enters through small openings in the thorax and abdomen called spiracles, water is also lost. To reduce this spiracle spinsters can open or close them.
The trachea leads away from the spiracles, these are lined with chitin. These brach to form tracheoles this is where gas is exchanged.
Tracheal Fluid
Found at the end of tracheoles, limits the penetration of air as lactic acid builds up and water moves out by osmosis
Spiracle
An external opening or pore that allows air in and out of the trachea
Mechanical Ventilation in insects
Muscular pumping movement of the thorax and abdomen change the volume and therefore pressure forcing air in and out of the insect.
Collapsible Air Sacs in insects
These act as reservoirs increasing the volume of air moving through the exchange system, they’re usually deflated and inflated by the movement of the abdomen and thorax.
