PAG 2 Dissection

Question 1

Five safety precautions when carrying out a dissection (5)

Answer 1

Handle all sharp dissection tools with care.

• Wear non-latex gloves to protect against chemicals and harmful microbes.
• Wear safety goggles to protect eyes from splashes or chemicals.
• Wear an apron to protect clothing and skin.
• Dispose of biological waste safely and responsibly

Question 2

Describe the steps for the external examination of a heart (4)

Answer 2

1. Place the heart on a dissecting tray.
2. Use fingers to feel chamber wall thickness (left side thicker than right; ventricles thicker than atria).
3. Identify the four main blood vessels — arteries are thick and rubbery, veins are thinner.
4. Locate the coronary artery and where it connects to the aorta

Question 3

Describe the steps for the internal examination of the left side of the heart (5)

Answer 3

1. Use a scalpel to cut into the left ventricle, following down to the apex.
2. Cut into the wall of the left atrium with scissors.
3. Identify tendinous cords and how they attach to the atrioventricular (AV) valve.
4. Observe AV valve (bicuspid) and semilunar (SL) valve (half-moon shape).
5. Measure the thickness of atria and ventricle walls.

Question 4

Describe the steps for the internal examination of the right side of the heart (3)

Answer 4

• Cut into the right atrium and ventricle.
• Locate the tricuspid AV valve (three flaps) and SL valve.
• Measure the wall thickness and compare to the left side

Question 5

Explain how you would produce a scientific diagram of the heart (3)

Answer 5

1. Draw the external or internal structure clearly.
2. Label all identified features accurately.
3. Add annotations describing the structure and function of each part

Question 6

Describe the steps for preparing and staining a transverse section of a plant stem (6)

Answer 6

1. Use a scalpel to cut a thin cross-section of the stem.
2. Place the section in tap water for 2 minutes.
3. Transfer into stain (e.g. toluidine blue) for 1 minute.
4. Rinse in tap water to remove excess stain.
5. Place on slide with water drop and coverslip.
6. View under low power microscope

Question 7

State the colours seen for each plant tissue when using toluidine blue (5)

Answer 7

Phloem = red.

• Xylem = green/blue-green.
• Sclerenchyma = blue-green or green.
• Collenchyma = red-purple.
• Parenchyma = red-purple

Question 8

Describe the steps for viewing a vascular bundle in high detail under a microscope (4)

Answer 8

1. Position slide to clearly view the bundle.
2. Switch to high power (x10 objective lens).
3. Focus for the clearest view of xylem and phloem arrangement.
4. Draw an annotated diagram of the bundle.

Question 9

Describe the external examination of a kidney

Answer 9

1. Observe the renal capsule covering.
2. Locate the cortex beneath the capsule.
3. Identify the renal hilum (indentation).
4. Locate renal vein, renal artery, and ureter.
5. Draw and label the external structure

Question 10

Describe the internal examination of a kidney (6)

Answer 10

• Slice kidney lengthways to open.
• Observe cortex, which is dense, grainy and lighter than medulla.
• Identify cone-shaped renal pyramids in the medulla.
• Locate renal columns between pyramids.
• Find renal calyces leading from pyramid bases.
• Trace to renal pelvis, which connects to ureter

Question 11

Explain how you would produce a scientific diagram of the kidney (3)

Answer 11

1. Draw the external or internal view accurately.
2. Label all main structures.
3. Add annotations describing appearance and function