Exchange surfaces Flashcards
3.1.1
Define diffusion:
The net movement of particles from a region where they are a higher concentration to a region where they are at a lower concentration
Features of perfect gas exchange
- Large surface area: The larger the area across which a substance can diffuse the more sustance can cross in a given time
- Thin: The shorter the distance for a substance to diffuse the less time it takes
- Diffusion gradient: Concentration of the substance must be higher on one side than the other for diffusion
- Protected from drying out: In terrestrial animals water vapor diffuses out of the cells. If to much is lost the plasma membrane will lose its structure and cells die
Exchange in lungs
- Large surface area - millions of alveoli
- Thin: alveoli has a thin walled membrane (parenchymal cells )
- Concentration gradient - high co2 in the blood and low o2 in the alveoli
- protection from dying out: mucus prevents contact with air
Exchange in plant leaves
- Large surface area: highly branched shapes with leaves providing high SA:V ratio
- Thin: Short distance for CO2 to diffuse through few cells thick
- Concentration gradient - produces a diffusion gradient in the opposite direction
- Protection from drying out - waxy skin - prevents extra water loss by transpiration stomata can close
Ec
Exchange in amoeba
- Large surface area: yes compared volume
- Thin: width of its cell surface membrane
- Concentration gradient: Enough difference to maintain supply
- Protection from drying out: Lives in water
How is the alveolus adapted to fulfil its role?
- One cell thick so short diffusion distance and therefore less time
- High concentration gradient difference as the alveolus has a high o2 and has a very low o2 - so large concentration difference
- Lungs - Large surface area so millions of alveoli
- Blood cell is constant
- Surfactant reduces surface tension of fluid in the lungs and helps make the alveoli more stable. This keeps them from collapsing when an individual exhales
What is the role of marcophages in the lungs?
- Patrol alveolas surfaces
- Scavenge for any harmful material; eg bacteria
- Engluf anything they find
- Some substances cant be digested
Cartilage
Distribution: Trachea and bronchi
Function: supports, holds them open and prevents collapse
Smooth muscle
Distribution: walls of trachea, bronchi and bronchioles
Function: involuntary muscle that contracts to narrow the lumen
Elastic fibres
Distrubtion:Walls of all airways and alveoli
Function: recoil of elastic tissue widens airways (after contractions) and forces air out of the alveoli ( after alveoli)
Goblet cells
Distribution: throught ciliated epithellum
Function: Secrete sticky mucus to trap particles and prevent drying out
Ciliated epithelium
Distribution: lines the trachea,brochus and brochioles
Function: cilia move in synchronised pattern to waft mucus up the air way to the back of the throat
Ventiliation
The movement of gases in and out of the lungs
Breathing
The physical changes that occur in the ribcage and diaphragm to cause ventiliation
Inspiration - Breathing in
- Contraction of the external intercostal muscles causes the ribcage to move upwards and outwards increasing the volume in the throax
- Concentration of muscle in the diaphragm pulls the diaphragm downwards and lower - increasing the volume in the throax
- Pressure in the throax falls with the increase in volume caused by the rib and diaphram movements.Air flows in down a pressure gradient
Expiration - Breathing out
Relaxed breathing out - Elastic fibres in the spaces between alveoli are strenched when breathing in. When the diaphragm and intercoastal muscles relax, the elastic fibres recoil causing the pressure in the throax to rise. Air flows out of the lungs
Forced breathing out: contraction of the internal intercostal muscles causes the ribcage to move downwards and inwards. This decreases the volume of the throax and increase the pressure of air inside so that it now flows out of the lungs. Diaphragm muscle relaxes. Contraction of the abnominal wall raises pressure in the abdomen and raises the diaphragm
Define tidal volume
The volume of air moved in and out of the lungs with each breath when you are at rest - 0.5dm3
Define vital capacity
The largest possible volume or air that can moved into and out of the lungs in one breath - 5dm3
Define inspiratory reserve volume
how much more air can be breathed in over and above tidal volume
Define expiratory volume
how much more air can be breathed in over and above tidal volume
THEREFORE VITAL CAPACITY = TIDAL VOLUME + INSPIRATORY RESERVE VOLUME + EXPIRATORY RESERVE VOLUME
Define residual volume
the volume of air that always remains in the lungs, even after the biggest possible exhalation. It is approximately 1.5 dm3
Define dead space
the air in the bronchioles, bronchi and trachea. There is no gas exchange between this air and the blood
What precautions should be taken when measuring a persons vital capacity to ensure equipment is used accurately and safely?
- Wear a nose clip to prevent breathing in and out through their nose
- Use a clean / disposable mouthpiece
- Ensure that spirometer contains fresh / enough air
- Ensure that the person is in good health i.e. take asthma into consideration
- Ensure that equipment is used correctly – give an example
Define breathing rate
number of breaths per minute
Define ventialtion rate
Total volume of air breathed in and out in one minute
ventilation rate = breathing rate + tidal volume
example
Breathing rate = number of breaths per minute
Ventilation rate = total volume of air breathed in or out in one minute
SO….
You take 12 breaths per minute (breathing rate)
Your mean tidal volume is 0.5dm3 (amount of air breathed in or out each breath)
Ventilation rate = number of breaths per minute x amount of air breathed in or out each breath
Ventilation rate = breathing rate x tidal volume
Ventilation rate = 12 x 0.5dm3
Ventilation rate = 6dm3 per minute
Oxygen consumption
- Chamber must be filled with oxygen not air
- Soda lime must be in the container
- Each time you breathe back out the carbon dioxide in your expired air is absorbed by the soda lime
- So the total volume of air going back into the container is less
- Therefore traces drawn by the pen go down and down
- If we measure how much they go down over a period of time this tells us the volume of oxygen you have used
Gas exchange in bony fish
They are often large active organisms who must exchange oxygen with the water – what challenges does this create?
SA:V ratio is small. Metabolic activity is high. Multicellular. Water is 100x more viscous and has a much lower oxygen content. Moving water in and out of the body would not be an economical use of energy.
Adaptions of bony fish
Large SA = increased area for diffusion
Rich blood supply = maintains a concentration gradient
Thin layers = short diffusion gradient
The tips of adjacent gill filaments overlap = increases resistance to flow of water over the gills. Movement of water SLOWS allow more TIME for diffusion to take place
The water moving over the gills and the blood in the gill filaments flow in opposite directions = maintains a steeper concentration gradient
Buccal - opercular pump
- The mouth is opened and the floor of the buccal cavity is lowered
- The VOLUME in the buccal cavity INCREASES
- The PRESSURE in the buccal cavity DECREASES
- Therefore water moves in to the buccal cavity
- The mouth closes and the floor of the buccal cavity is raised INCREASING the PRESSURE and pushing water over the gills
- As water is pushed from the buccal cavity, the operculum moves outwards
- The PRESSURE in the opercular cavity DECREASES, helping water to flow through the gills
Gas exchange insects :
Many insects are very active = high oxygen requirements. They are mainly terrestrial (desiccation risk) . Tough exoskeleton through which no gaseous exchange can take place. No O2 carrying blood pigments.
Adaptions for Gas exchange in insects:
- Small openings along thorax and abdomen = SPIRACLES
- Air enters and leaves the insects body via the spiracles
- WATER is also lost. To increase efficiency of gas exchange but minimise water loss SPIRACLE SPHINCTERS can open or close the spiracles.
Adaptions for Gas exchange in insects:
- Leading away from the spiracles are the TRACHEAE (up to 1mm in diameter). Lined by spirals of CHITIN.
- Tracheae branch forming narrower tubes until they divide into TRACHEOLES (approx. 0.7μm in diameter). No chitin. This is where gases are exchanged.
- TRACHEAL FLUID limits the penetration of air. During activity LACTIC ACID builds up in the insects tissues and water moves out of tracheoles increasing the area for exchange.
Further Adaptions for Gas exchange in insects:
- Some large active insects have very high energy demands. Therefore they need extra oxygen.
To supply this extra O2 they have adaptations such as: - Mechanical ventilation of the tracheal system – muscular pumping movements of the thorax and/or abdomen change the VOLUME of the body and therefore the PRESSURE. The pressure changes force air in and out of the body.
- Collapsible air sacs – these act as air reservoirs increasing the volume of air moving through the exchange system. They are usually deflated and inflated by the movements of the abdomen / thorax
