**Core Concept**
The hypogastric sheath is a fascial condensation that surrounds the internal iliac vessels, playing a crucial role in the pelvic anatomy. It is a fibrous layer that provides structural support to the pelvic organs and helps in the transmission of forces from the pelvic floor to the abdominal wall.

**Why the Correct Answer is Right**
The hypogastric sheath is formed by the condensation of the iliopectineal fascia, which is a layer of connective tissue that surrounds the iliacus and psoas major muscles. This fascial condensation extends from the anterior surface of the sacrum to the lateral border of the rectum, encasing the internal iliac vessels and nerves. The hypogastric sheath serves as a landmark for various surgical procedures, including pelvic surgeries and lymph node dissection. The correct answer will highlight the specific fascial layer involved in the formation of the hypogastric sheath.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because the hypogastric sheath is not formed by the fascia lata, which is a superficial layer of fascia that covers the gluteal region.

**Option B:**
This option is incorrect because the parietal peritoneum is a layer of peritoneum that lines the abdominal cavity and does not contribute to the formation of the hypogastric sheath.

**Option C:**
This option is incorrect because the endopelvic fascia is a layer of connective tissue that surrounds the pelvic organs, but it is not specifically responsible for the formation of the hypogastric sheath.

**Clinical Pearl / High-Yield Fact**
The hypogastric sheath is an important landmark for surgeons performing pelvic surgeries, as it helps to identify the location of the internal iliac vessels and nerves. Knowledge of the hypogastric sheath is crucial for avoiding damage to these critical structures during surgical procedures.

**Correct Answer:** D. Iliopectineal fascia.