Exchange- Dissecting Gas Exchange Systems

Question 1

What safety precautions should be taken when dissecting lungs, fish gills or the gaseous exchange system in insects?

Answer 1

• Wear lab coat or apron

- Dissecting tools should be clean, sharp and free from rust

Question 2

How should lungs be laid out ready for dissection?

Answer 2

On a cutting board, able to see the trachea and 2 bronchi

Question 3

How can you see the lungs inflate?

Answer 3

Attach a piece of rubber tubing to the trachea and pump air into lungs

Question 4

How is the trachea supported?

Answer 4

By C-shaped rings of cartilage

Question 5

How should you cut the trachea to open it up?

Answer 5

Lengthways, down the gap in the C-shaped rings using dissecting scissors or a scalpel (if using a scalpel cut downwards and don’t apply too much pressure)

Question 6

What do you do after cutting the trachea?

Answer 6

Continue cutting down the bronchi- should be able to see bronchioles branching off

Question 7

After cutting down the bronchi, what do you do next?

Answer 7

Cut off a piece of the lung- tissue will feel spongy because of air trapped in alveoli

Question 8

Why should you wash your hands and disinfect work surfaces after dissecting the lungs?

Answer 8

The lungs could still contain bacteria that cause food poisoning

Question 9

How do you remove the gills when dissecting a fish?

Answer 9

Push back the operculum and use scissors to carefully remove the gills, cut each gill arch through the bone at the top and bottom

Question 10

What should you be able to see in fish gills if you look closely?

Answer 10

Gill filaments

Question 11

What must you do to examine the trachea of an insect?

Answer 11

Carefully cut and remove a piece of exoskeleton from along the length of the insect’s abdomen

Question 12

What must you do after removing the exoskeleton of an insect?

Answer 12

Use a syringe to fill to abdomen with saline solution and you should be able to see a network of very thin silvery-grey tubes (tracheae) and they are this colour because they’re filled with air

Question 13

What should you be able to see when viewing the insect under an optical microscope?

Answer 13

Rings of chitin in the walls of tracheae for support

Question 14

What are the ethical issues in dissecting animals?

Answer 14

• Some argue it is morally wrong to kill animals for dissections- unnecessary killing
• Animals used for dissections are not always raised in a humane way