**Core Concept**
Kiesselbach's plexus, also known as the nasal septal artery, is a vascular network located in the anterior part of the nasal septum. This plexus is formed by the anastomosis of several branches from nearby arteries, providing a rich blood supply to the nasal mucosa.

**Why the Correct Answer is Right**
Kiesselbach's plexus is primarily formed by the anastomosis of the following branches:
- **Anterior ethmoidal artery**: A branch of the ophthalmic artery, which is itself a branch of the internal carotid artery.
- **Septal branch of the superior labial artery**: A branch of the facial artery, which is a terminal branch of the external carotid artery.
- **Sphenopalatine artery**: A branch of the maxillary artery, which is also a terminal branch of the external carotid artery.
- **Turbinate branch of the sphenopalatine artery**: Another branch of the sphenopalatine artery.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not directly involved in the formation of Kiesselbach's plexus. The **posterior ethmoidal artery** primarily supplies the posterior ethmoidal cells and the sphenoid sinus.
* **Option B:** Not involved in the formation of Kiesselbach's plexus. The **middle meningeal artery** primarily supplies the dura mater and the calvaria.
* **Option C:** Not involved in the formation of Kiesselbach's plexus. The **greater palatine artery** primarily supplies the hard palate.
* **Option D:** Not involved in the formation of Kiesselbach's plexus. The **lesser palatine artery** primarily supplies the soft palate.

**Clinical Pearl / High-Yield Fact**
Kiesselbach's plexus is a common site for nasal bleeding (epistaxis) due to its rich blood supply and superficial location. It is often referred to as the "Little Boy's nose" due to its tendency to bleed in children.

**Correct Answer:** D. The lesser palatine artery.