Gas exchange Flashcards
What is the tissue fluid?
The environment around the cells of multicellular organisms
How have organisms evolved to improve exchange?
A flattened shape (leaf) or specialised exchange areas (lungs/gills)
What are the features of specialised exchange surfaces?
Large SA relative to the volume of the organism, very thin to decrease diffusion distance, selectively permeable, movement of environmental medium (air) to maintain diffusion gradient and transport system (blood) to move internal medium
What are the tracheae or insects?
Internal network of tubes
How does the tracheae prevent from collapsing?
Strengthened rings
What does the tracheae divide into?
Tracheoles
Where do the tracheoles extend to?
All the body tissue of the insects
How do respiratory gases move in and out of the tracheal system?
Along a diffusion gradient, mass transport and the ends of tracheoles are filled with water
How does the contraction of respiratory muscles aid mass transport?
Squeezes the trachea enabling mass movements of air
How does anaerobic respiration affect the muscle cells?
Produces lactate which lowers the water potential of the cells, so water moves into the cells from tracheoles by osmosis.
Why does the tracheoles being filled with water benefit the insect?
When the water level drops due to anaerobic activity, more air is drawn into the insect, the air diffuses quicker than the liquid
How does gas enter the insects?
Spiracles on the body surface
How are spiracles opened?
A valve
What are the limitations of insect gas exchange?
Small insects for short diffusion pathway
Why do fish require require a specialised gas exchange surface?
They are too large for SA:V and waterproof skin
Where are the gills located?
Within the body of the fish behind the head
How are gill filaments structured?
Stacked up in a pile
Where are the gill lamellae?
At right angles to the gill filaments to increase the surface area of the gills
How does water travel through the fish?
It moves in through the mouth and is forced over the gills before leaving through opening at either side of the fish
What is the countercurrent flow?
Flow of water over the gill lamellae and the flow of blood within them are in opposite directions
How is the countercurrent exchange system beneficial?
Blood well-loaded with oxygen meets water with the maximum amount of oxygen, therefore diffusion into the blood can still occur
How much of the oxygen in the water is transferred to the blood?
80%
How is gas exchange in plants similar to that of insects?
No living cells are far from external air and diffusion takes place in the gas phase
How are leaves adapted for efficient gas exchange?
Many stomata (short diffusion pathway)
Numerous interconnected air spaces
Large SA of mesophyll cells (rapid diffusion)
What are stomata?
Minute pores
Where are the stomata mainly found?
Mostly, but not exclusively, on the underside
How does a stoma open and close?
Has a pair of guard cells that swell to close and control gas exchange
What is a dicotyledonous plant?
A plant that has seeds made of two parts
How have insect evolved to reduce the water loss?
Small SA:V, waterproof covering and spiracles
What is the waterproof covering in insects?
Rigid outer skeleton of chitin that is covered with a waterproof cuticle
What are plants with restricted water supply called?
Xerophytes
How are leaves modified for limiting water loss?
A thick cuticle, rolling up of leaves, hairy leaves, stomata in pits or grooves and reduced SA:V
How much water loss occurs through the waxy cuticle?
10%
What grass rolls its leaves?
Marram grass
What is the benefit of plant leaves rolling?
Traps air and becomes saturated with water vapour to give a high water potential and stop diffusion
How do hairy leaves benefit the plant?
Traps moisture to decrease potential gradient
What plant type has hairy leaves?
One type of heather plant
What plant has stomata in pit or grooves?
Pine trees
Why are the volumes of CO2 and O2 that have to be exchanged in mammals large?
Relatively large organisms with a large volume of living cells and they maintain a high body temperature which is related to them having high metabolic and respiratory rates
What are the lungs?
A pair of lobed structures made up of a series of tubules, called bronchioles, which end in tiny air sacs called alveoli
What supports the trachea?
Rings of cartilage, that prevent it collapsing when the air pressure falls inside the lungs when breathing in
What are the tracheal walls made up of?
Muscle tissue, lines with ciliated epithelium and goblet cells
What does the mucus and cilia in the bronchi do?
Mucus traps dirt and cilia moves the dirt-laden mucus towards the throat
How does the support of bronchi differ from trachea?
The cartilage is reduced ass the bronchi gets smaller
What are the bronchioles walls made of?
Muscle lined with epithelium cells
How does the muscle benefit the bronchioles?
They can constrict to control the flow of air into and out of the alveoli
What is the diameter of alveoli
100-300 micrometers
What exists between the alveoli?
Collagen and elastic fibres
What are the alveoli lined with?
Epithelium
What do the elastic fibres between alveoli do?
Allow the alveoli to stretch as they fill with air when breathing in, they then spring back to breathe out and force CO2 out
What is ventilation?
Constant moving of air in and out of the lungs
What causes inspiration?
When the atmospheric pressure of air is greater than that in the lungs
What causes expiration?
When the atmospheric pressure is lower than that of the lungs
What is the diaphragm?
A sheet of a muscle that separates the thorax and abdomen
What contractions cause inspiration?
External intercostal muscles and diaphragm
What contractions cause expiration?
Internal intercostal muscles
Is inspiration active or passive?
Active
How does expiration differ?
During normal quiet breathing the elastic tissue is the main cause, however under strenuous conditions such as exercise do the various muscles play a major part
What is the calculation for pulmonary ventilation rate?
Tidal volume x breathing rate
How are the lungs adapted to enable efficient transfer of materials?
Thin, partially permeable membrane and have a large SA
How are we adapted to maintain a diffusion gradient?
Capillary network (rich blood supply) and ventilation
How many alveoli are there in each human lung?
About 300 million
What is the total SA of all the alveoli in each human lung?
70m2
How thick are the epithelial cells lining the alveoli?
0.05- 0.3 micrometers
What is the lumen diameter of the surrounding cappilaries?
7-10 micrometers
How thick are capillaries?
0.04-0.2 micrometers
How is diffusion into capillaries rapid?
RBC are slowed, allowing more time
Distance reduced as RBC are flattened against capillary walls
Thin walls
Very large total SA
Steep concentration gradient
What are the risk factors of lung disease?
Smoking, air pollution, genetic makeup, infections and occupation
How is an insect’s tracheal system adapted for efficient gas exchange?
Tracheoles have thin walls so short
diffusion distance to cells
Highly branched/large number of
tracheoles so short diffusion distance to
cells and large surface area
Tracheae provide tubes full of air so fast
diffusion
Fluid in the end of the tracheoles that
moves out into tissues, during exercise
so faster diffusion through the air to the
gas exchange surface and larger surface area
Body can be moved (by muscles) to move
air so maintains diffusion/concentration
gradient for oxygen/carbon dioxide;
