Lateral wall of ischiorectal fossa is formed by all EXCEPT:
**Core Concept**
The ischiorectal fossa, also known as the ischioanal fossa, is a fat-filled space in the pelvic region. It is located on either side of the anal canal and plays a crucial role in absorbing shocks and facilitating the passage of stool. The lateral wall of the ischiorectal fossa is formed by several structures that provide support and protection to the surrounding tissues.
**Why the Correct Answer is Right**
The lateral wall of the ischiorectal fossa is primarily formed by the obturator internus muscle and the obturator fascia. The obturator internus muscle is a flat, fan-shaped muscle that originates from the inner surface of the obturator membrane and inserts into the greater trochanter of the femur. The obturator fascia is a layer of connective tissue that covers the obturator internus muscle and helps to separate the ischiorectal fossa from the pelvic cavity.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the levator ani muscle is actually a component of the pelvic diaphragm and forms the medial wall of the ischiorectal fossa, not the lateral wall.
* **Option B:** This option is incorrect because the coccygeus muscle is also a component of the pelvic diaphragm and forms the medial wall of the ischiorectal fossa, not the lateral wall.
* **Option D:** This option is incorrect because the sacrotuberous ligament is a strong ligament that connects the sacrum to the ischial tuberosity and forms part of the posterior wall of the ischiorectal fossa, not the lateral wall.
**Clinical Pearl / High-Yield Fact**
The ischiorectal fossa is an important landmark in pelvic surgery and can be accessed through various approaches, including the transgluteal approach. Knowledge of the anatomy of the ischiorectal fossa is essential for surgeons performing procedures such as hemorrhoidectomy and anal fistulotomy.
**Correct Answer:** A. Levator ani muscle.