PAG 2: Dissection

Question 1

Why are dissections important? (1)

Answer 1

To understand the internal biological function of an organism

Question 2

What steps should be followed for an external heart examination? (4)

Answer 2

1. Try to identify the four main blood vessels
2. Observe that arteries are thick and rubbery
3. Observe that veins are thinner
4. Identify the right and left atria

Question 3

What steps should be followed for an internal heart examination? (6)

Answer 3

1. Cut along the lines to open the heart
2. Measure and record the thickness of the ventricle walls
3. Note any differences in the ventricular walls
4. Cut open the atria and examine inside, noting whether atrial walls are thicker or thinner than ventricular walls
5. Identify the atrioventricular (AV) valves and semi-lunar valves
6. Draw a sketch to show the location of the valves

Question 4

What are the rules for a scientific drawing? (6)

Answer 4

Only use continuous lines and do not use sketching

Add labels using horizontal ruled lines with no arrowheads, ensuring label lines do not cross over

State the magnification of the drawing

Draw all parts to the same scale

Do not use shading or hatching

Use at least 50% of the available space and maintain correct proportions

Question 5

What precautions should a student take when performing a dissection? (5)

Answer 5

Wear a disposable apron or a lab coat

Cover any cuts with a waterproof dressing

When using a scalpel, cut away from yourself and use forceps to hold tissue while cutting

Wear disposable gloves

Cut on a hard surface

Question 6

What precautions should a student take when clearing away a dissection? (4)

Answer 6

Disinfect hands after handling specimens

Disinfect instruments and surfaces

Carry sharp instruments by pointing them down

Dispose of gloves, paper towels, and organs in a separate bag or bin

Question 7

What are the ethical issues involved in dissecting animals? (3)

Answer 7

It is morally wrong to kill animals just for dissection, so use animals that have already been killed for meat

Animals raised for dissection may suffer from overcrowding or lack of food

If animals are being raised for dissection, they should be properly cared for and humanely killed

Question 8

A student used her hand to hold the specimen during a dissection. Suggest an improvement to her method. (1)

Answer 8

Use pins to hold the specimen in place