Introduction
Gaseous exchange is a physical process that involves the exchange of gases between the air and the blood in the lungs. Organisms are structurally suited to ensure that the process of the exchange of gases is optimised.
The sheep lung dissection will aid the learner in understanding the different structures and how they assist in breathing.
Task
Dissection
Observe and investigate the structure of the lungs, the diaphragm, associated pulmonary blood vessels and the heart of a sheep.
Lung dissection: https://www.youtube.com/watch?v=uDtZEM3FJnE
Process
1. Lay out the sheep lungs on the dissection board and identify the left and right lungs as well as the position of the heart.
2. Observe the colour and texture of the lung tissue
3. Run your fingers along the inside and outside of the large air passage or windpipe. What do you feel (identify structure)?
4. Follow the trachea as it branches into each lung. What are these two air passages called?
5. Follow these two air passages into the lung tissue and observe what happens as they go deeper into the lungs.
6. If the heart is still attached identify the main vessels entering and leaving the heart.
7. Identify the membrane surrounding the lungs.
8. You will now attempt to inflate the lungs using the straw. Place the straw in the windpipe and press the sides of the windpipe against the straw. Blow into the straw. DO NOT SUCK IN! Observe what happens.
9. Cut along the longitudinal axis of one of the lungs and open the lung up into two halves.
10. Cut a small piece of lung tissue off one of the lungs and place it in a small container of water. Observe what happens.
11. Clean all the apparatus and your workstation. Discard the dissection material. 12. Wash your hands thoroughly and answer the activity questions.
Questions
1. Describe the look, texture (feel), and colour of the lungs. (2)
2. What structures keep the trachea open? (2)
3. Are the lungs hollow bags or spongy tissue? (1)
4. Name the two air passages that branch off the trachea and into each lung. (2)
5. How does the diameter of these air passages compare to the diameter of the trachea? (1)
6. What happens to the piece of the lung when you put it in water? (1)
7. When you inflated the lung what happened after you stopped blowing in? (1)
[10]
Evaluation
MARKING GUIDELINE
1. Large and floppy looking. Spongy and soft feel. Deep / light red in colour (2)
2. C-shaped cartilage rings (2)
3. Spongy tissue (1)
4. The left and right bronchi (1)
5. Slightly narrower in diameter (2)
6. It floats (1)
7. It started deflating (going down) (1)
[10]
Conclusion
The Aim of this Practical is to identify the structure of the lungs and related structure and to observe the inflation of the lung.
Credits
Teacher Page
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Thursday 12:00-12:45
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