**Core Concept**
Meckel's diverticulum is a congenital anomaly of the small intestine, resulting from the incomplete closure of the vitelline duct. This vestigial structure can lead to complications such as gastrointestinal bleeding, intestinal obstruction, and diverticulitis.

**Why the Correct Answer is Right**
Meckel's diverticulum typically presents with pain, gastrointestinal bleeding, or obstruction in the right lower quadrant of the abdomen. The presence of ectopic gastric or pancreatic tissue within the diverticulum can lead to acid production, causing ulceration and subsequent bleeding. The diverticulum is usually located 60 cm from the ileocecal junction and can be identified on imaging studies.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because Meckel's diverticulum is indeed a true diverticulum, containing all layers of the intestinal wall.
**Option B:** This statement is incorrect because the vitelline duct typically obliterates by the 6th week of gestation, but remnants can persist and form a Meckel's diverticulum.
**Option C:** This statement is incorrect because Meckel's diverticulum is not a result of a congenital defect in the muscularis propria, but rather the incomplete closure of the vitelline duct.

**Clinical Pearl / High-Yield Fact**
Meckel's diverticulum is the most common congenital anomaly of the small intestine and can be a source of significant morbidity if left untreated. A 50% reduction in the risk of complications can be achieved with surgical resection.

**Correct Answer:** A.