Exchange and transport Flashcards
Why is diffusion alone enough to suffice single-celled organisms?
Metabolic activity of a single-celled organism low —-> oxygen demands and CO2 production of cell = relatively low.
The surface area to volume (SA: V) ratio of the organism is large
Why do more complex organisms need an exchange system?
Oxygen demands of the muscle cells = high produce lots of CO2.
Distance between the cells where the oxygen is needed and the supply of oxygen is too far for effective diffusion to take place.
Bigger the organism = smaller the SA: V ratio.
Calculations for surface area and volume?
4^r2
4/3^r3
What are the features of specialised exchange surfaces?
Increased surface area —> root hair cells/ villi in small intenstines
Thin layers —> short diffusion distance
Good blood supply—> substances constantly delivered/removed.
~~> Maintains steep conc gradient for diffusion
Ventilation to maintain diffusion gradient
Why are human gaseous exchange systems important?
Minimise amount of water lost
Have small SA:V ratio
High metabolic rate —> maintain external conditions
Need lots of oxygen for cellular respiration
Produce CO2 = removed
Key features of nasal cavity:
Large surface area with a good blood supply = warms the air to body temperature.
Hairy lining = secretes mucus =
**trap dust/bacteria ~~~~> protect delicate lung tissue from irritation + infection
Moist surfaces = increase the humidity of air; reduce evaporation from exchange surfaces.
Key feature of trachea:
Main airway
Wide tube supported by incomplete rings of flexible cartilage
Incomplete —> food can move down oesophagus
Lined with ciliated epithelium –> goblet cells inbetween
Role of goblet cells
Secrete mucus on lining of trachea.
Trap dust/microorganism
Cilia beat + move mucus away from lungs
Goes to throat = swallowed
+ digested
Role of bronchus?
trachea divides:
left bronchus = left lung,
right bronchus = right lung.
~~ Similar structure to trachea
same supporting rings of cartilage > smaller.
Role of bronchioles?
Diameter < 1mm
No cartilage
Walls = smooth muscle
When smooth muscles contract –> bronchioles constrict
When relaxed = bronchioles dilate.
Changes amount of air reaching lung.
Role of alveoli?
Tiny air sacs
Main site of gas exchange
Layer of thin, flattened epithelial cells, + collagen + elastic fibres
Allow alveoli to stretch as air drawn in.
Resting size = squeeze air out
~~~> known as elastic recoil
What are the main adaptations of alveoli for effective gas exchange?
Large surface area
Thin layers –> only single epithelial cell thick —> short diffusion distance
Good blood supply —> 280 milly capillaries
~~~> maintains steep conc gradient of O2 + CO2
Good ventilation —> steep diffusion gradient as air moves in/out alveoli
What is lung surfactant?
Makes it possible for alveoli to remain inflated.
How does air move in/out of the lungs?
Result of pressure changes in thorax via ventilation (breathing movements)
What are the internal and external intercostal muscles?
Internal = muscles towards inside.
External = muscles towards outside.
Key feature of Thorax?
Lined by pleural membranes
Space between (pleural cavity) filled with thin layer of lubricating fluid so membrane easily slide over each other.
What is inspiration?
Inhalation
Energy-using process
Diaphragm contracts = flattened = lowering
External intercostal muscles contract = ribs move up/down
Volume increases
Pressure decreases
What is expiration?
Exhalation
Passive process
Diaphragm relaxes
External intercostal muscles relax = ribs move down and inwards
Volume decreases
Pressure increases
So air moves out
How can you measure capacity of the lungs?
Peak flow meter –> measures rate at which air is expelled from lungs.
Vitalographs –> sophisticated peak flow.
Spirometer –> investigate breathing patterns.
Describe tidal volume
Volume of air that moves in/out of lungs with each resting breath.
Describe Vital capacity
Volume breathed in –> deepest possible intake of breath after the strongest possible exhalation.
Describe inspiratory reserve volume
Maximum volume breathed in above normal inhalation
Describe expiratory reserve volume
Extra air forced out of lungs above normal tidal volume of air breathed out.
Describe residual volume
Volume of air left in lungs after exhaling as hard a possible.
Not measured directly
Describe total lung capacity
Sum of vital capacity and residual volume
Equation for breathing rate
ventilation rate (total number of air inhaled in 1 minute) = tidal volume x breathing rate (per minute)
Why is soda lime used in spirometer?
Absorbs any CO2 exhaled.
