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2.6.6Unit 2 — Multicellular Organisms

Practical: Heart Dissection — SQA National 5 Biology Revision Notes & Topical Questions

5 min read 6 parts Lesson 32 of 39

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Part 1 of 6Purpose and Equipment

2.6.6 Practical: Heart Dissection
Purpose and Equipment
Aim
  • Dissection lets you see the form of the heart and relate its structure to its function.
Specimen
  • A pig or sheep heart from a reputable source is placed on a dissection board.
Equipment
  • A scalpel, dissecting scissors, forceps, pins and a mounted needle are used to cut, open and hold the tissue.
Looking for
  • Chambers, valves, walls and the entrances to the major blood vessels can all be seen.

Part 2 of 6External Observations

Front surface
  • The front can be recognised by the coronary arteries that cross between the left and right ventricles.
Coronary arteries
  • These vessels on the outside of the heart supply the heart muscle with oxygenated blood.
Atria
  • The atria appear as small flaps at the top of the heart.
Large vessels
  • Major vessels such as the aorta and pulmonary artery can be identified where they leave the heart.

Part 3 of 6Cutting and Internal Observations

1
Make two vertical cuts through the left and right ventricles and atria, using scissors if they are easier to control.
2
Open out the muscle gently using forceps or a mounted needle and pin back the sides of the ventricles.
3
Compare the thickness of the left and right ventricle walls, which shows the left wall to be thicker.
4
Identify the thin-walled atria, the septum, the valves and the entrances to the major blood vessels.

Part 4 of 6Safety and Ethics

Safety and Ethics
Protection
  • Wear a lab coat, gloves and eye protection to avoid contact with biological material.
Blades
  • Use a sharp clean blade, cut away from your body and keep your fingers away from the cutting edge.
Source
  • Specimens must come from a reputable source and be disposed of correctly after use.
Disinfect
  • Clean equipment and the work surface with disinfectant after the dissection.

Part 5 of 6Linking Structure to Function

Linking Structure to Function
Thicker left wall
  • The left ventricle wall is thicker because it pumps blood at high pressure to the whole body, not just the lungs.
Thin atria
  • The atrial walls are thin because they only need to push blood a short distance into the ventricles.
Septum
  • The septum keeps oxygenated and deoxygenated blood separate, so the blood is not mixed.
Valves
  • Valves between atria and ventricles let the blood flow only in the forward direction.

Part 6 of 6Exam Checklist & Tips

2.6.6 – Key Points for the Exam

  • Dissection Careful cutting of an organism or organ to study its internal structure.
  • Septum The muscular wall dividing the left and right sides of the heart.
  • Specimen The sample of biological material being studied.
  • Coronary artery An artery supplying the heart muscle itself.

Common Mistakes

  • Cutting towards the hand or body, which risks a serious injury.
  • Concluding that the right ventricle is thicker, when the left ventricle wall is the thicker one.
  • Treating this suggested practical as the only way to learn heart structure, rather than one possible approach.
  • Forgetting to wear protective clothing and to dispose of the specimen correctly.

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