1. Trachea 1 SLIDE 62 Trachea of rat.
Respiratory System
Objectives:
At the end of this practical you should be able to :
1. Describe the structure of the conducting and exchange parts of the respiratory
system and relate this to function.
2. Compare the microscopic structure of the walls of trachea, bronchi and bronchioles.
3. Examine the structure of the alveolar wall. 1
Trachea
SLIDE 62 Trachea of rat.
Use slide 62 to identify the principal features of the trachea.
Make a low power drawing of this slide, decide which is dorsal and ventral.
Use high power to illustrate the inner wall of the trachea.
Low
High
Q 1. What type of cartilage is present?
Q 2. Why is there a need for cartilage?
Q 3. Give two reasons why the cartilage rings are incomplete?
Examine the epithelium lining the trachea.
Epithelial lining at high magnification
Q 4. What type of epithelium is this?
Find the trachealis muscle at the dorsal aspect of the trachea.
Q 5. How would you classify the type of muscle present?
Q 6. What structure lies immediately dorsal to this?
Q 7. Are there any glands in the submucosa? If so, what is their function?

2. Lung SLIDE 63 trachea (cat) Examine slide 63. 2
This is a transverse section of trachea
which has been stained for elastic fibres.
Q 8. Why are these fibres arranged
longitudinally?
Q 9. Why are they so abundant?
Note the presence of lymphocytes in this tissue.
Q10. How are they distributed? 2
Lung
SLIDES 67, 68 and 69 (sections of adult lung)
Examine the sectioned lung in slide 67.
Q 11. What covers its surface?
Q 12. How can you distinguish between a bronchus and a bronchiole?
Use one of the above slides to draw a diagram of a bronchus.
Q 13. Why is cartilage absent from the wall of a bronchiole?

3. SLIDE 70 Lung phagocytes (marsupial mouse).
Again use slides 67,68 or 69 and draw diagrams of (a) a bronchiole.
(b) a respiratory bronchiole. a b
SLIDE 70 Lung phagocytes (marsupial mouse).
This is a section of lung injected to show alveolar phagocytes.
Q 14. What do they look like?
Q 15. What is their function?

4. SLIDE 71 Lung injected to show blood vessels.
Note the blood supply to the lung tissue in slide 71.
The blood vessels have been injected with a red dye.
Note the arrangement of the capillaries supplying the alveoli.
Q 16. What happens to these capillaries during inspiration and expiration?
Q 17. Briefly describe the blood : gas barrier in the alveolus.
SLIDE 72 Lung stained for elastic tissues.
Examine this section which has been stained for elastic tissues.
Note the distribution of these fibres throughout the section especially in relation
to the alveolar ducts and alveoli.
Q 18. Why are there so many elastic fibres in the lung?
Q 19. Why does their distribution differ in different parts of the respiratory tract?