M3C7 - Exchange surfaces Flashcards
(31 cards)
What are spiracles?
Small openings on the surface of the exoskeleton that allow gases to diffuse into the body of the insect.
Describe gas exchange in insects
-Passive process
-Delivers O2 directly to cells.
What are tracheae and describe their structure?
Network of tubes leading from spiracles, extend down into the insects body.
Reinforced with spirals of chitin prevents collapse when insects move.
What are tracheoles and describe their structure in relation to their function:
Fine tubes that extend from tracheae, each is a single cell extended to form a hollow tube.
Not supported by chitin.
Short diffusion distance for O2 and C02.
Huge number provides large SA for gas exchange - rapid rate of aerobic respiration in insects.
What is the purpose of tracheal fluid in the ends of tracheoles?
During intense activity, cells around tracheoles undergo anaerobic respiration - producing lactic acid which lowers water potential in cells.
-Water in tracheal fluid moves into cells, draws air into tracheoles.
How do insects reduce water loss through spiracles?
Each spiracle is surrounded by a muscular sphincter, so they can close their spiracles when oxygen requirement is low.
How are insects evolved to increase the rate of gas exchange?
-Some can contract muscles in thorax, causing pressure changes in tracheaea and tracheoles, pushing air in and out.
-In some insects trachaea contain expanded sections called air sacs - changes in vol of abdomen and thorax squeeze the air sacs, causing air to move to tracheoles.
-Insects can also use O2 in sacs when spiracles are closed.
What is the flap of tissue on either side of a bony fish called?
Operculum
Where are the gills located in bony fish?
In the opercular cavity (behind the operculum)
Describe the basic movement of water through the bony fish
-Oxygen-rich water enters the fish through the mouth.
-Water passes over gills.
-In gills, O2 diffuses from water to blood, CO2 passes from blood to water.
-Water passes out through opercular opening.
Describe the structure of the gills in bony fish
-Consist of several bony gill arches.
-Extending from each gill arch are many gill filaments.
-Gill filaments are covered by gill lamellae (where gas exchange takes place).
How are gill lamellae adapted for gas exchange?
-Large SA
-Short diffusion distance between walls of lamellae and blood.
-Extensive network of capillaries.
adaptation
Describe the counter-current exchange system in bony fish:
-Blood with low O2 conc passes into capillaries of lamellae.
-As blood passes through lamellae, oxygen diffuses from water to blood.
-O2 rich blood passes out of lamellae and leaves gills.
>Flow of blood is in opposite direction to flow of water. (counter-current)
-So steep concentration gradient for O2 is always maintained.
How do bony fish maintain constant water flow?
-Water flows into buccal cavity (mouth space).
-Floor of buccal cavity drops down - increases vol available for water.
-Fish shuts operculum and increases vol of opercular cavity (contains gills).
-Due to increased vol - pressure in opercular cavity falls.
-At same time, floor of buccal cavity lifts up.
-Increases pressure of water causing it to flow over gills.
-Fish closes mouth and opens operculum.
-Opercular cavity squeezes inwards, increasing pressure of water and forcing it out of operculum.
What are the adaptations of the trachea in mammals?
1)Contain cartilage, prevents collapse during inhalation. Cartilage forms a C-shape to allow food to pass down oesophagus.
2)Walls of trachea are lined with ciliated epithelial and goblet cells. Cilia moves mucus containing trapped pathogens to stomach.
Describe the structure of the bronchi
Like the trachea, contains cartilage, ciliated epithelial and goblet cells.
Describe the structure of bronchioles
-Larger bronchioles supported by cartilage.
-Also contain smooth muscle - allows more air into lungs by widening bronchioles when relaxed.
Describe the structure of the alveoli
-Covered with an extensive network of capillaries.
-Contain thin layer of moisture on inside of wall which gases dissolve into.
How are alveoli adapted for gas exchange?
1)Hundreds of millions in the lungs, provide a huge SA for diffusion.
2)Wall of alveolus and wall of capillary are only 1 cell thick = short diffusion distance.
3)Extensive network means that once O2 diffuses into blood, its quickly carried away = steep concentration gradient. & steep conc gradient for Co2 as more is always brought by blood.
What is the diaphragm?
Muscle that separates thorax (chest cavity) from abdomen.
What happens during inhalation?
(active process)
-External intercostal muscles contract - pulls ribcage upwards and outwards.
-Diaphragm contracts causing it to flatten.
-This increases the volume of the thorax and the lungs (decreases pressure).
-Air is drawn in due to pressure in lungs being lower than atmospheric.
-Air drawn into alveoli and elastic muscles between them stretch.
What happens during exhalation?
(passive process)
-External intercostal muscles relax and return to original shape.
-Diaphragm relaxes, returning to domed shape.
-Reduces vol of thorax and lungs.
-Air pressure in lungs is greater than atmospheric so air is forced out.
-Elastic fibres between alveoli recoil, pushing air out.
What is breathing rate?
Number of complete breaths per minute
What represents one breath on a spirometer trace?
Distance between 2 peaks or 2 troughs
