**Core Concept**
The lymphatic drainage of the penis is a complex process involving the convergence of lymphatic vessels from different regions into larger collecting vessels. The glans penis, being a highly vascularized and innervated structure, has a unique lymphatic drainage pattern.

**Why the Correct Answer is Right**
The lymph from the glans penis primarily drains into the deep inguinal lymph nodes, which are located in the femoral canal. This is because the glans penis is innervated by the pudendal nerve and receives a rich blood supply from the dorsal arteries of the penis. The lymphatic vessels from the glans penis converge to form the superficial inguinal lymphatic trunk, which then drains into the deep inguinal lymph nodes. This pathway is facilitated by the presence of lymphatic valves that prevent backflow and ensure efficient drainage of lymphatic fluid.

**Why Each Wrong Option is Incorrect**
**Option A:** The superficial inguinal lymph nodes are primarily responsible for draining the lower limb, not the glans penis.
**Option B:** The axillary lymph nodes are involved in the drainage of the upper limb and breast tissue, not the glans penis.
**Option C:** The inguinal lymph nodes are indeed involved in the drainage of the lower limb, but the glans penis specifically drains into the deep inguinal lymph nodes.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the lymphatic drainage of the penis is a complex process, and the deep inguinal lymph nodes play a critical role in the drainage of the glans penis. This knowledge is crucial for understanding the spread of infections and malignancies in this region.

**Correct Answer: D. Deep inguinal lymph nodes.**