QuestionSBA
QuestionChoice
The annotated space is the ischioanal fossa. Alcock’s canal or the pudendal canal is an anatomical structure formed by the obturator fascia lining the lateral wall of the ischioanal fossa. Within it lies the pudendal artery, vein and nerve.
10014233
a
Internal pudendal artery, nerve and vein
QuestionChoice
This forms part of the lateral wall of the fossa but is not within the space.
10014235
c
Ischial tuberosity
QuestionChoice
This does not lie within the ischioanal fossa.
10014234
b
Sigmoid colon
QuestionChoice
This forms the floor of the ischioanal fossa but is not within the space.
10014237
e
Deep transverse perineal fascia
QuestionChoice
This does not lie within the ischioanal fossa.
10014236
d
Sciatic nerve
Concept
Chapter
#### Summary

The ischioanal fossa is a paired fat filled triangular space located lateral to the anal canal.

#### Anatomy
This region is bounded by the ischial tuberosities and the anal canal. The apex of this triangular space is directed towards the pubic symphysis in an anteromedial direction. The base is continuous posteriorly allowing the two ischioanal fossae to communicate. The two fossae are continuous with each other anteriorly and posteriorly to the anal canal.

* **Lateral wall** - formed by the ischium, obturator internus muscle and the sacrotuberous ligament.
* **Medial wall** - levator ani muscle

The pudenal canal is a fascial tunnel in the lateral wall of each fossa. The internal pudenal vessels and the pudenal nerve run in this canal and give rise to the inferior rectal vessels and nerve.

Fat also fills the ischioanal fossa which extends forwards between the lower surface of the pelvic diaphragm and the upper surface of the perineal membrane.

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#### Clinical points

- The ischioanal fossa is susceptible to the formation of abscesses which can cause fistulation between the anus and the skin. This is particularly seen in Crohn's disease.

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Ischioanal fossa.gif
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Ischioanal fossa
Topic
237
Pelvic Anatomy
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Picture
1978
8 - Ischioanal fossa.png
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Topic
237
Pelvic Anatomy
Which of the following structures lies within the annotated space?

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a