dissections Flashcards

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1
Q

what must you wear during a lung dissection

A

a lab coat

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2
Q

describe dissecting tools

A

scalpels, dissecting scissors

they should all be clean, sharp and free from rust

blunt tools do not cut well and could be dangerous

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3
Q

when you lay your lungs down onto the cutting board what should u see first

A

the trachea and the two bronchi going into the lungs

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4
Q

how do we see the lungs inflate

A

attach a peice of rubber tubing into the trachea and punp air into the lungs using a foot or bicycle pump

the lungs will deflate by themselves because of the elastin in the walls of the alveoli

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5
Q

why should we never blow down the tube to inflate the lungs

A

you could end up sucking up stale air from inside the lungs into your mouth

pop the lungs in a clear plastic bag before you start to stop bacteria inside the lungs from being released into the room

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6
Q

when do we start to examine the different tissue types in the lungs

A

when the lungs have inflated

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7
Q

describe how we open up the trachea

A

cut the cartliage lengthways, down the gap in the c-shaped rings.

use dissecting scissors or a scalpel to make the cut.

if using a scalpel cut downwards and dont apply too much pressure to the blade

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8
Q

why does the tissue feel spongy when u cut off a piece of the lung

A

the tissue will feel spongy because of the air trapped in all the alveoli

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9
Q

describe where the gills are located on the fish head

A

the gills are located on either side of the fish head.

they’re protected on each side by a bony flap called an operculum and supported by gill arches

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10
Q

how do we dissect the gills

A

to remove the gills, push back the operculum and use scissors to carefully remove the gills.

cut each gill arch through the bone at the top and the bottom

if you look closely you will see the gill filaments

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11
Q

what types of insects are best for dissecting

A

big insects like grasshoppers are cockroaches are usually best for dissecting because they are easier to handle

for dissection, u need to use an insect thats been humanely killed fairly recently

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12
Q

describe how to perform a dissection on an insect

A

place insect on dissecting board and put dissecting pins through its legs to hold it in place

to examine the tracheae, cut and remove a piece of exoskeleton from along the length of the insects abdomen

use a syringe to fill the abdomen with saline solution. you should be able to see a network of tracheae

they look silvery because they are filled with air

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13
Q

how can we examine the trachea

A

under an optical microscope using a temporary mount slide

again, the trachea will appear silver or grey.

you should also be able to see rings of chitin in the walls of the tracheae- these are there for support

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14
Q

ethical issues involved in dissecting animals

A

its morally wrong to kill animals just for dissections, as its unnecessary killing

however many dissections involve animals that have already been killed for their meat

animals used for dissections are not always raised in a humane way

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15
Q

describe gas exchange in plants

A

When the guard cells are turgid (full of water) the stoma remains open allowing air to enter the leaf

The air spaces within the spongy mesophyll layer allows carbon dioxide to rapidly diffuse into cells

The carbon dioxide is quickly used up in photosynthesis by cells containing chloroplasts - maintaining the concentration gradient

No active ventilation is required as the thinness of the plant tissues and the presence of stomata helps to create a short diffusion pathway

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16
Q

how to prepare a slide with a liquid specimen

A

Add a few drops of the sample to the slide using a pipette

Cover the liquid/smear with a coverslip and gently press down to remove air bubbles

Wear gloves to ensure there is no cross-contamination of foreign cells

17
Q

Preparing a slide using a solid specimen:

A

Use scissors to cut a small sample of the tissue

Peel away or cut a very thin layer of cells from the tissue sample to be placed on the slide (using a scalpel or forceps)

Some tissue samples need be treated with chemicals to kill/make the tissue rigid

Gently place a coverslip on top and press down to remove any air bubbles

A stain may be required to make the structures visible depending on the type of tissue being examined

Take care when using sharp objects and wear gloves to prevent the stain from dying your skin

18
Q

why do we always start with the lowest objective lens when using an optical microscope

A

It is easier to find what you are looking for in the field of view

This helps to prevent damage to the lens or coverslip incase the stage has been raised too high

19
Q

how do we prevent the dehydration of tissue

A

Adding a drop of water to the specimen (beneath the coverslip) can prevent the cells from being damaged by dehydration

20
Q

how do we get rid of unclear or blurry images

A

Switch to the lower power objective lens and try using the coarse focus to get a clearer image

Consider whether the specimen sample is thin enough for light to pass through to see the structures clearly

There could be cross-contamination with foreign cells or bodies

21
Q

how do we use an eyepiece graticule on an optical microscope

A

As a graticule has no fixed units it must be calibrated for the objective lens that is in use.

This is done by using a scale engraved on a microscope slide (a stage micrometer)

By using the two scales together the number of micrometers each graticule unit is worth can be worked out

After this is known the graticule can be used as a ruler in the field of view

22
Q

describe the mamalian gas exchange system under the optical microscope

A

The alveoli are of different sizes and shapes
This is because they are no longer inflated as they would be in a living lung

The nuclei are shown as dark dots

Blood vessels can found in between the alveoli

Sometimes white blood cells are present in tissue samples

23
Q

what do we expect to see when viewing fish under the optical microscope

A

The gill arch resembles a backbone for the gills

The different filaments are shown with many of the lamellae visible