Chapter 48 - Trachea

Question 1

1. T/F – The equine trachea is a long flexible tube with a lumen that is maintained by 48-60 complete cartilage rings.

Answer 1

• False, incomplete cartilage rings

Question 2

2. The trachea begins at the ______ of the larynx and ends at the level of the ______.

Answer 2

• cricoid cartilage
• 5th-6th intercostal space

Question 2

3. What are the 2 sections of the trachea?

Answer 2

• Cervical
• Thoracic

Question 2

4. What structure connects the larynx to the proximal trachea?

Answer 2

• Cricotracheal ligament

Question 3

5. What structure marks the transition between the two regions of the trachea?

Answer 3

• Thoracic inlet

Question 4

6. The incomplete hyaline rings are open on the ______ aspect of the trachea, where the ______ spans the gap between the free ends.

Answer 4

• Dorsally
• smooth trachealis muscle

Question 5

7. T/F – Contraction of the smooth trachealis muscle can slightly alter the diameter of the lumen, but it does not change the luminal profile.

Answer 5

• True

Question 6

8. T/F – There is only a limited correlation between the size of the trachea and that of the animal’s body.

Answer 6

• True

Question 7

9. What 4 tissue layers make up the trachea?

Answer 7

• Mucosa
• Submucosa
• Musculo cartilaginous layer
• Adventitia (cervical) or serosa (thoracic)

Question 8

10. What connects neighboring tracheal rings to each other?

Answer 8

• Annular ligaments

Question 9

11. What specialized structures does the tracheal submucosa contain? (3)

Answer 9

• Elastin fibers
• Fat cells
• Seromucous tubular glands

Question 10

12. The lumen of the trachea is lined by respiratory mucosa with _________ epithelium that contains numerous ________ cells and rests on a basement membrane.

Answer 10

• pseudostratified columnar ciliated
• goblet

Question 11

13. The _________ and _________ in the submucosa provide the mucous layer of the trachea.

Answer 11

• secretory cells
• glands

Question 12

14. What are the functions of the mucous layer in the trachea? (3)

Answer 12

• Covers the tracheal epithelium
• Maintains moisture
• Traps foreign particles and pathogens

Question 13

15. The critical barrier against airway infection formed by cilia in the trachea is known as the ________.

Answer 13

• mucociliary escalator

Question 14

16. The esophagus changes its position from dorsal to the left side of the trachea at what level of the neck?

Answer 14

• At the level of the 4th cervical vertebrae

Question 15

17. The carotid sheaths are found dorsolateral to the trachea and contain what structures? (3)

Answer 15

• Common carotid arteries
• Vagosympathetic nerve trunks
• Recurrent laryngeal nerves

Question 16

18. Ventrally, the ______ muscles cover the trachea for the majority of its length, while the most cranial part of the trachea is only associated with the ________ muscle.

Answer 16

• Sternothyrohyoid
• sternohyoid

Question 17

19. What 3 muscles are identified lateral to the trachea near the larynx?

Answer 17

• Sternocephalic
• Omohyoid
• Sternothyroid

Question 18

20. What paired structures can be located lateral to the first tracheal rings? (May or may not be connected by a ventral isthmus).

Answer 18

• Thyroid gland

Question 19

21. What reasons are there that increase the difficulty of performing a tracheotomy more caudally than the cranial 1/3 of the neck?

Answer 19

• Overlying muscle layers require more dissection
• The carotid sheath presumes a more lateral position
• The esophagus moves ventral to the trachea

Question 20

22. What structure closely associated with the trachea may be identified in a very young animal?

Answer 20

• thymus

Question 21

23. How does the horse increase the rigidity of the tracheal wall to withstand the substantial inspiratory pressure drops in the lumen of the trachea?

Answer 21

• Hyperextension of the neck

Question 22

24. T/F – The cross-sectional shape of the trachea also impacts collapsibility, with the ellipsoidal shape found in the more caudal part of the trachea being easier to compress than a circular lumen.

Answer 22

• True

Question 23

25. T/F – The cartilage rings should generally be compressible.

Answer 23

- True

Question 24

26. T/F – Changes in the elasticity of the tracheal rings may indicate pathology, but mineralization and stiffening of the rings is not expected in older horses.

Answer 24

- False, mineralization and stiffening of the cartilage rings are age related changes that are common in older horses