Practical: Lung Dissection (SQA National 5 Biology): Revision Note

Observing structures in the lungs

• Gas exchange system structure can be examined during dissection

Apparatus

• Scalpel: a sharp blade used for precise cutting

• Dissecting scissors: small, sharp scissors used for lower-precision tasks or separating layers of tissue

• Tweezers/forceps: useful for manipulating the specimen during dissection

• Dissecting pins: may be useful for pinning sections of a specimen in place while working

Method

1. Place the specimen on a dissection board with the front (ventral) surface facing upwards

   • If the lungs are attached to the trachea and heart, position them so the trachea is at the top

2. Identify external features, such as the:

   • trachea, which may have visible rings of cartilage

   • bronchi, where the trachea divides into two main branches leading to each lung

   • lobes of each lung; the right lung usually has three, and the left has two

   • pleura, a thin membrane covering the surface of the lungs

3. Feel the texture of the lungs gently

   • They should feel soft and spongy due to the air spaces inside

4. Insert a blunt probe or forceps into the trachea and observe how it divides into the bronchi; follow the bronchi as they branch into smaller tubes

5. Optional demonstration: insert a short piece of tubing into the trachea and gently blow air into the lungs

   • Observe the inflation of the lung tissue, which demonstrates how air fills the alveoli during breathing

6. Make a vertical cut down through one bronchus and into the lung tissue using scissors

7. Gently open the cut surface with forceps or your fingers to examine the spongy texture of the lung and locate the alveoli, which will appear as tiny holes in the tissue

8. Dispose of materials safely and clean all equipment thoroughly after completing the dissection

Safety

• Care should be taken during dissection practical work, including:

  • safety, e.g.:

    • a lab coat, gloves, and eye protection should be worn to avoid contamination with biological material

    • sharp, clean blades should be used for ease and accuracy of cutting

    • scalpel blades should cut away from the body

    • fingers should be kept away from the blade edges

  • responsible use of biological materials

    • Any biological specimen used for dissection should be from a reputable source and should be disposed of in the correct manner