**Core Concept**
The corneal endothelium is a single layer of cells lining the posterior surface of the cornea, playing a crucial role in maintaining corneal transparency by regulating fluid and electrolyte balance. Understanding its embryological origin is essential for appreciating its development and potential disorders.

**Why the Correct Answer is Right**
The corneal endothelium is derived from the neural ectoderm, specifically from the lens placode, during embryonic development. As the lens placode invaginates to form the lens vesicle, the surrounding neural ectoderm differentiates into the corneal endothelium. This process occurs around the 6th week of gestation. The neural ectoderm's contribution to the corneal endothelium is essential for its function and structure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the corneal epithelium, not the endothelium, is derived from the surface ectoderm.
**Option B:** This option is incorrect because the iris and ciliary body are derived from the neuroectoderm, but not the corneal endothelium specifically.
**Option C:** This option is incorrect because the sclera and choroid are derived from the mesoderm, which is not the origin of the corneal endothelium.

**Clinical Pearl / High-Yield Fact**
A crucial aspect of corneal endothelium development is its neural ectodermal origin, which highlights the importance of preserving the corneal endothelium's function in maintaining corneal transparency and preventing vision-threatening complications.

**Correct Answer:** C. The corneal endothelium is derived from the neural ectoderm.