**Core Concept**
The development of the anal canal is a complex process involving the fusion of ectodermal and endodermal tissues. The anal canal is divided into three parts based on its embryological origin: the upper part is derived from the endoderm, the middle part is a result of the fusion of the ectoderm and endoderm, and the lower part is derived from the ectoderm.

**Why the Correct Answer is Right**
The lower third of the anal canal is derived from the ectoderm, specifically from the cloacal membrane, which is a layer of ectodermal cells that covers the cloaca, a structure that eventually develops into the rectum, anus, and urogenital sinus. During embryological development, the cloacal membrane ruptures, and the ectodermal cells migrate to form the lower part of the anal canal. This process is critical for the formation of the anal sphincters and the anal epithelium.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the upper part of the anal canal is derived from the endoderm, not the ectoderm.
**Option B:** This option is incorrect because the middle part of the anal canal is a result of the fusion of the ectoderm and endoderm, not a separate entity.
**Option D:** This option is incorrect because it is not a valid choice.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the anal canal is a complex structure with distinct embryological origins, which can be important in the context of surgical procedures, such as anal fissures or fistulas.

**Correct Answer:** C.