Anatomy of the external and middle ear

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Anatomy of the external and middle ear

USMLE® Step 1 questions

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Anatomy of the External and Middle Ear

Figure 1. A. Anterior view of coronal section of the subdivisions of the ear. B. Lateral view of the auricle (external ear). 
Figure 2. A. Anterior view of coronal section highlighting features of external ear. B. Otoscopic view of right tympanic membrane.
Figure 3. A. Coronal section of the middle ear. B. Sagittal section showing pharyngotympanic tube opening in nasopharynx. C. Lateral view of the medial wall of the middle ear showing the tympanic plexus.
Unlabelled Diagrams


USMLE® Step 1 style questions USMLE

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A 39-year-old man is diagnosed with Bell palsy and has paralysis of the stapedius muscle. Which of the following is true regarding the stapedius muscle in the middle ear?  


The ear is made up of three parts: the external, middle, and inner ear. Together, these structures help process air vibrations as sound, and this helps us enjoy our favourite music, as well as alert us of potential threats. Now, while the inner ear also plays a role in balance, the main role of the external and middle ear is to transfer and amplify sound to the inner ear with the help of the three smallest bones in the body: the auditory ossicles.

Let’s start with the external ear, which is by far the most common anatomical spot to hang earrings from. The external ear is actually a complex structure made of the auricle, also called the pinna; and the external acoustic meatus.

Now, let’s take a closer look at the auricle, which is the part of the external ear that surrounds the opening of the external acoustic meatus, and funnels soundwaves towards the external acoustic meatus. It is made of irregularly shaped cartilage covered with skin. The elevated outer rim of the auricle is the helix. The smaller elevated rim parallel to the helix is called the antihelix. The depression in the middle of the auricle is called the concha. Right next to the concha, there’s the opening of the external acoustic meatus. Inferior to the concha, there’s the lobule of the auricle. And finally, anterior to the opening, there’s an elevation called the tragus.


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