7.4 Ventilation And Gas Exchange In Other Organisms Flashcards
What are spiracles?
Small openings along the thorax and abdomen of most insects
What is the function of spiracles?
To allow enter to enter and leave systems through them. However, water is also lost.
What is done to minimise the loss of water in insects through spiracles?
Spiracles have SPIRACLE SPHINCTERS. These sphincters open and close the spiracles, and they are often kept closed as much as possible to minimise water loss.
When are the spiracles of an insect all closed?
When an insect is inactive and oxygen demands are very low.
What do trachea do in an insect?
Transport air into the body and around it. Run into and along the body of an insect.
What are tubes of trachea lined by (in an insect)?
Spirals of CHITIN, which keep the trachea open if they are bent or pressed.
Why is there no gaseous exchange in the trachea of an insect?
Because it is lined with chitin, which is relatively impermeable to gases.
What do the trachea branch to form (in insects)?
Narrower tubules, until they divide into the tracheoles
What is a tracheole (in insects)?
A single, greatly elongated cell with no chitin lining
Is gaseous exchange possible in a tracheole (in insects)? Why / why not?
Yes, because the tracheole have no chitin lining
Where are the tracheoles (in insects)?
Spread throughout the tissues of the insect, running between individual cells
Where does most gaseous exchange take place in an insect?
In the tracheal system
What does tracheal fluid do?
Reduces water loss, limits the penetration of air for diffusion, and carries oxygen
What happens in insects when oxygen demand builds up?
-Lactic acid build-up in the tissues results in water moving out of the tracheoles by osmosis, which exposes more surface area for gaseous exchange.
-Tracheal fluid is absorbed into muscle cells
What are the 2 alternative methods used by larger insects to increase gaseous exchange?
-Mechanical ventilation of the tracheal system
-Collapsible enlarged trachea or air sacs
Describe the mechanical ventilation of the tracheal system done by larger insects.
-Air is actively pumped into the system by muscular pumping movements of the thorax and/or abdomen.
-This changes the volume, and therefore the pressure of the body.
Describe the collapsible enlarged trachea or air sacs of larger insects.
-These act as air reservoirs, used to increase the amount of air moved through the gas exchange system
List the problems mites can cause if they enter an insect through the spiracles.
-Transmit diseases
-Lead to leakage of haemolymph
-Use up O2
-Restrict airflow in the trachea
-Release toxins
What properties of water make it more difficult to use in gas exchange than air?
Water is thicker than air, more dense, and has a much lower oxygen content
What are bony fishes’ organs of gaseous exchange?
Gills.
What are the key features of gills?
Large surface area, good blood supply, thin layers.
Where are gills contained?
In the gill cavity
What are gills protected by?
An operculum (a bony flap)
What is the function of the operculum in fish?
Protect the gills, and maintains a low of water over the gills.
What is the function of gill rakers?
Help gather food and protect the gills
What is the function of a bony gill arch?
Supports the structure of the gills
Describe the gill lamellae.
Have a rich blood supply and large surface area, and are the main site of gaseous exchange in the fish
What are gill plates?
Stacks that hold gill filaments
What are gill filaments?
Parts of the gill that give it the large surface area needed for gaseous exchange.
What has to be done to protect the gill filaments? Why?
Must have a constant flow of water to keep them apart.
Why do fish need to maintain a continuous flow of water over the gills?
To allow efficient gas exchange at all times.
How do bony fish maintain a current of water flowing over their gills at all times?
By opening their mouth and operculum.
Describe what the bony fish does during inspiration.
-Mouth is opened, floor of the buccal cavity is lowered
-Buccal cavity volume increases, pressure drops, and water flows into the cavity
-Opercular valve is shut, and the Opercular cavity containing the gills expands, lowering pressure
-Floor of the buccal cavity moves up, pressure increases, so water moves from the buccal cavity over the gills
Describe what the bony fish does during expiration.
-Mouth is closed, the operculum closes, sides of the opercular cavity move inwards
-So pressure increases, water is forced over the gills and out of the operculum
-Floor of the buccal cavity is steadily moved up, maintaining a flow of water over the gills
State the adaptations of gills to maximise gas exchange.
-Gills have a large surfacce area for diffusion
-Gills have a rich blood supply
-Gills have thin layers
-Tips of adjacent gill filaments overlap
-Water moving over the gills and the blood in the gill filaments flow in different directions
What is the name of the system that bony fish use to breathe?
Countercurrent system.
What is the name of the system that cartiligous fish use to breathe?
Parallel system.
