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Hello everyone,

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Dr. Sidney Levy here, continuing our discussion

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of the anatomy of the hypopharynx.

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I'd like to conclude by demonstrating the posterior

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hypopharyngeal wall, which is the third subsite after

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the piriform sinuses and the postcricoid region.

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So firstly, let's draw some boundaries.

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On this pre-contrast non-fat-suppressed T1-weighted

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imaging, let's start off with the sagittal projection.

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So the superior margin of the posterior hypopharyngeal

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wall is the junction of the posterior hypopharyngeal

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wall and the posterior oropharyngeal wall.

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Now, there actually isn't a specific structure at this

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level, but we use the hyoid as a discriminating landmark.

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So the hyoid's actually situated here, and

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it happens to also be at a similar level to the inferior

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margin of the laryngeal surface of the epiglottis here.

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So this can be considered our superior

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margin of the posterior hypopharyngeal

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wall, above which we have the oropharynx.

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From there, we need to look at the inferior margin as well.

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And the inferior margin is as for the rest of the

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hypopharynx, the inferior border of the cricoid cartilage.

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So we've defined our superior and inferior boundaries.

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So nsext thing is, let's draw it.

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Posterior hypopharyngeal wall extends

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down between those two boundaries.

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And then we need to think about its anterior relations.

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So, anterior to the posterior hypopharyngeal wall, beyond

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the laryngeal inlet, we have the postcricoid space.

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So the postcricoid space is a thin section of soft tissue.

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So let's just draw it as a line here.

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And I will also just quickly point out that

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this tissue here is abnormally thickened.

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So there is actually a postcricoid

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space lesion in this patient.

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Which we will discuss in a subsequent vignette, but for

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the moment, I just want to concentrate on the anatomy.

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The lumen of the hypopharynx is collapsed at

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this level, so whether it be in the sagittal

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projection or the axial projection, you can't see

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the distinction between the postcricoid space and

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the posterior hypopharyngeal wall in this patient.

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It is appearing as a single structure, but I will just

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for the purposes of explanation draw this red area to

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signify the postcricoid space and then behind it,

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this yellow area to signify the posterior hypopharyngeal

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wall because there is a collapsed lumen between them.

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The other boundaries to keep in mind for

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the posterior hypopharyngeal wall are

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better appreciated on the axial projection.

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We have the piriform sinuses laterally.

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So this is the posterior hypopharyngeal

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wall at a higher level.

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And then we have the piriform sinuses on each side.

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The soft tissues which lie deep to the posterior

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hypopharyngeal wall include the middle layer of the

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deep cervical fascia and the retropharyngeal space.

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And then beyond that, the prevertebral fascia.

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So in summary, the posterior hypopharyngeal wall extends

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from the level of the hyoid to the inferior border

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of the cricoid cartilage and has as its anatomical

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relations the posterior oropharyngeal wall superiorly,

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the cervical esophagus inferiorly, the postcricoid

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space anteriorly, and the piriform sinuses laterally.