USMLE Step 1 Review 04 11 Anatomy Anus 1

USMLE Step 1 Review 04 11 Anatomy Anus 1

 

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Let’s continue our USMLE Review with Anatomy from the Gold Standard USMLE Step 1 Audio Review program.

Play USMLE Audio MP3 04 11 Anatomy Anus 1 Below

 

Begin 04 11 Anatomy Anus 1 Transcription

What is the name for the base of the troughs?

  • These are called anal valves which are not to be confused with the superior, middle, and inferior rectal valves we’ve just covered.

Now in each of these valves at the base of these vertical troughs there is a small pocket of space and what is this called?

  • The anal sinuses.

What lies beneath the anal sinuses opening into them?

  • The anal glands.

The anal glands are generally located in what layer?

  • The submucosa.

Sometimes these glands become infected and this results in what?

  • Anal abscesses.

If these get bad enough they may lead to the formation of?

  • Fistulas.

Alright, the mucosa that is raised up into longitudinal folds extending in fingerlike projections that are raised up from the anus towards the rectum are called?

  • Anal columns.

What’s the other name for them?

  • Columns of Morgagni.

What underlies the anal columns or Columns of Morgagni, where the mucosa is raised up into longitudinal folds?

  • Loops of arteries and veins running down to the anal valves which are between the anal columns at the base.

Branches of what artery and what vein are looped or coiled under the anal columns?

  • Branches of the superior rectal artery and superior rectal vein.

Where do the transverse anastomoses between these arteries and veins in adjacent anal columns run?

  • They run between the bases of the anal columns at the anal valves.

What is the name for the submucous venous anastomosis at the base of the anal valves?

  • This is the internal rectal venous plexus. Now the branches of the superior rectal vein in three of these six to ten anal columns, two on the left and one on the right, are liable to becoming distended together with the plexus that is behind the anal valves.

When this happens, what do we call it?

  • Internal hemorrhoids or piles.

Because internal hemorrhoids or piles occur in the region of the anal columns, what is the name then, for the zone from the top of the anal columns which is within the rectum, down to anal verge which is the outlet of the anus?

  • This entire zone is termed the surgical anal canal whereas the anus proper or anatomical anal canal extends only from the dentate line down to the anal verge that is, from the base of the anal valves.

Now what artery and vein supply the anal canal below the pectinate line?

  • The inferior rectal artery and inferior rectal vein.

The anastomoses between these in the anatomical anal canal is called?

  • The inferior rectal venous plexus.

This inferior rectal venous plexus which is in the submucosa, when it becomes distended and bulges into the lumen, is called?

  • External hemorrhoids.

Question: Are internal hemorrhoids generally painful?

  • No.

And why not?

  • The mucosa above the pectinate or dentate line is innervated by autonomic nerves and is normally insensitive to touch sensation or pain sensation.

What normally sensitive or painful technique can be used with the internal hemorrhoids that would probably not be advisable for the external hemorrhoids?

  • This is injecting the internal hemorrhoids with corrosive or irritating substances to cause thrombosis and fibrosis.

The epithelial lining over the anatomical anal canal, however, is extremely sensitive to touch and to pain and is supplied by what class of nerve?

  • By somatic nerves.

And what branch of what nerve supplies the epithelium in the anatomical anal canal?

  • The inferior rectal branch of the pudendal nerve. This is why fissures, tears, and external hemorrhoids in the anatomical anal canal are so painful.

****END OF TRANSCRIPTION****

 

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