Dissecting Gas Exchange Flashcards
Why must you do the lung dissection with a lab coat?
It will get messy
Why shoud your dissecting tool (e.g scapels, dissecting scissors) be all clean , sharp and free from rust?
Blunt tools don’t cut well
Can be dangerous
What should you be able to see when first laying the lung on the cutting board?
See the trachea and two bronchi going into the lungs
How to practically see the lungs inflate?
- Attach a piece of rubber tubing to the trachea and pump air into the lungs using foot/bicycle pump
- Lungs will deflate by themselves because of the elastin in the walls of alveoli
Why should you not blow down the tube to inflate the lungs?
You could end up sucking stale air from the lungs into the mouth
Pop the lungs into a clear plastic bag before you start
this stops the bacteria inside the lungs from being released into the room
Seeing different tissue types in the lungs
What is the trachea supported by?
C-rings of the cartilage
Diagram of a cross-section of trachea
How do you practically open up the trachea?
- Since cartilage is tough, open the trachea by cutting it lengthways down the gap in the C-shaped rings
- Use dissecting scissors/scalpel to make the cut
- Continue cutting down one of the bronchi
- Able to see the bronchioles branching off
- Cut off a piece of lung - tissue feel spongy because of air trapped in alveoli
Why should you be careful to cut the cartilage in trachea?
- You need to wear goggles to protect your eyes
- If use scalpel cut downwards ( not towards you) and don’t apply too much pressure to the blade
What are the safety problems from lungs from butcher?
- It is safe
- But may contain bacteria cause food poisoning
- Wash your hands after dissection and disinfect work surfaces
What is the safety procedures for dissecting fish?
- Wear apron or lab coat
Where should you place your fish?
In dissection tray or cutting board
Practical instructions to dissect fish gills in bony fish
- Gills located on either side of fish’s head. They are protected by bony flap called operculum and supported by gill arches
- To remove gills , push back operculum and use scissors to carefully remove gills
- Cut each gills arch through the bone at the top and bottom
- You can see the gill filaments
What type of insects do you need to use?
- Big insects like grasshopper or cockroaches
- Easier to handle
- Need to use one that is humanely killed fairly recently
Instructions to dissecting insect:
- Fix insect onto dissecting board using dissecting pins to hold legs in place
- Examine trachea , need to carefully cut and remove piece of exoskeleton (hard outer shell) from along the length of insect’s abdomen
- Use syringe to fill abdomen with saline solution - seeing network of thin , silvery-grey tubes , these are trachea
- Examine the trachea under an optical microscope using a temporary mount slide
Why in insect they still look silver?
Filled with air
What will you be able to see observing trachea under optical microscope?
Trachea appear silver-grey
Rings of chitin in the walls of trachea - support (like rings of cartilage in trachea)
Why should you be careful like live insects e.g grasshoppers to be handled carefully?
- They can cause allergic reactions in some people
1st ethical issue
Some people think it is morally wrong to kill animals for dissection as it is unnecessary killing
Contradicting point:….
- Many dissections that are carried out in schools involve animals that have already been killed for their meat
- E.G Sheet lung dissection
- Some people disagree with killing animals altogether
2nd ethical issue
Concerns using animals for dissections are not raised in a humane way
- Subject to overcrowding , extremes of temperature or lack of food
- May not be killed in a humane way either*
- Animals raised in school for dissection:
- Make sure they are looked after properly and killed humanely to minimise any suffering or distress
Explain why she shouldn’t inflate the lungs by blowing into them
She could end up sucking the stale air from the inside of lungs into her mouth
Give one another safety precaution the student should take while inflating the lungs
Put the lungs in a plastic bag while inflates them
Prevents the bacteria released into the air
Once the lungs are inflated , the student stops pumping air into them. Describe and explain what the student would expect to see next
Lungs deflate by themselves because of the elastin in the walls of alveoli
Describe how the student would cut the trachea?
Lengthways , down the gaps in the C-shaped rings of the cartilage
How can you make sure your dissecting tools are safe to use?
Check they are sharp and free from rust
clean
A student is examining grasshopper trachea under the microscooe
Grasshopper was killed in some time ago and kept in a liquid preservative
Trachea do not appear silver under the microscope
Instead they are dark grey
Suggest why this is the case
Liquid preservative has entered the grasshopper trachea
no longer filled with air
e.g appear silver in colour if they are filled with air
The student cuts off a piece of lung tissue and drops in a beaker of water
The lung tissue floats in water
Explain why it floats
Alveoli still contains some air
Give on safety precaution the student should take when carrying out this lung dissection
Make sure dissecting tools clean, sharp, free from rust
Carry out dissection on cutting board
Wash hands/disinfect work surfaces after carrying out dissection
