External Auditory Canal Flashcards

Explore the external auditory canal's bony and cartilaginous walls, skin, glands, innervation, blood supply, and clinical anatomy.

Card 1 of 30Question

What is the external auditory canal?

A passage extending from the external acoustic opening to the tympanic membrane, conducting sound toward the middle ear.

In This Section

1. What is the external auditory canal?

A passage extending from the external acoustic opening to the tympanic membrane, conducting sound toward the middle ear.

2. What is another anatomical name for the external auditory canal?

The external acoustic meatus.

3. What is the approximate length of the adult external auditory canal?

Approximately 2.5 cm, although its dimensions vary between individuals.

4. What are the two structural portions of the external auditory canal?

The lateral cartilaginous portion and medial bony portion.

5. What proportion of the external auditory canal is cartilaginous?

Approximately the lateral one-third.

6. What proportion of the external auditory canal is bony?

Approximately the medial two-thirds.

7. Which bone forms the bony portion of the external auditory canal?

The temporal bone, primarily its tympanic part, with contributions from the squamous and mastoid parts.

8. What type of cartilage supports the lateral external auditory canal?

Elastic cartilage continuous with the auricular cartilage.

9. Which membrane forms the medial boundary of the external auditory canal?

The tympanic membrane.

10. What is the general shape of the adult external auditory canal?

An irregular, slightly S-shaped passage with bends in its cartilaginous and bony portions.

11. In which direction is the auricle pulled to straighten the adult external auditory canal during otoscopy?

Superiorly and posteriorly.

12. Why is the auricle generally pulled downward and backward during otoscopy in young children?

Their external auditory canal is shorter, more horizontal, and less developed than in adults.

13. How does the skin of the cartilaginous canal differ from that of the bony canal?

The cartilaginous canal has thicker skin with hair follicles and glands, while the bony canal has thin skin closely adherent to periosteum.

14. Which glands produce the waxy secretions found in the external auditory canal?

Ceruminous glands, which are modified apocrine sweat glands.

15. Where are ceruminous glands primarily located?

In the skin of the cartilaginous portion of the external auditory canal.

16. What is cerumen?

Earwax formed from ceruminous and sebaceous secretions mixed with desquamated epithelial cells.

17. How does the external auditory canal normally remove accumulated epithelial debris?

Through outward migration of the squamous epithelium toward the external opening.

18. What are the fissures of Santorini?

Small clefts in the cartilaginous external auditory canal that may provide pathways for infection to spread into adjacent tissues.

19. Which trigeminal nerve branch supplies much of the anterior and superior external auditory canal?

The auriculotemporal nerve, a branch of the mandibular division of the trigeminal nerve (cranial nerve V3).

20. Which cranial nerve supplies much of the posterior and inferior external auditory canal?

The auricular branch of the vagus nerve (cranial nerve X).

21. Why can stimulation of the external auditory canal trigger coughing?

Stimulation of the auricular branch of the vagus nerve can produce the ear-cough reflex, also called Arnold's reflex.

22. Which arteries supply the external auditory canal?

Branches of the superficial temporal, maxillary, and posterior auricular arteries.

23. Which branch of the maxillary artery supplies the deep external auditory canal and outer tympanic membrane?

The deep auricular artery.

24. Which lymph nodes receive lymphatic drainage from the external auditory canal?

Primarily the superficial parotid, mastoid, and upper deep cervical lymph nodes.

25. Which joint lies immediately anterior to the external auditory canal?

The temporomandibular joint.

26. What is the isthmus of the external auditory canal?

A relatively narrow segment of the bony canal near its medial end.

27. Why is inflammation of the bony external auditory canal particularly painful?

Its thin skin is tightly adherent to periosteum, leaving little space for inflammatory swelling.

28. What is external auditory canal exostosis?

A benign bony outgrowth of the canal, often associated with repeated exposure to cold water.

29. What is congenital aural atresia?

A developmental absence or closure of the external auditory canal, often associated with external and middle ear abnormalities.

30. What type of hearing loss can result from obstruction of the external auditory canal?

Conductive hearing loss due to impaired transmission of sound waves to the tympanic membrane.