**Question:** Waldeyer's ring consists of all of the following except

A. Palatine tonsil
B. Rectangular tonsil
C. Lymph nodes
D. Nasopharyngeal tonsil

**Core Concept:** Waldeyer's ring is a group of lymphoid tissues surrounding the oropharyngeal cavity and nasopharynx. It plays a crucial role in the immune system by providing defense against pathogens entering through the oral and nasal routes.

**Why the Correct Answer is Right:** The correct answer, B. Rectangular tonsil, is not a part of Waldeyer's ring because it is a variant of the palatine tonsil located in the hard palate, not within the oropharyngeal cavity where Waldeyer's ring resides.

**Why Each Wrong Option is Incorrect:**

A. Palatine tonsil: The palatine tonsil is indeed a part of Waldeyer's ring, making it the correct choice and not an option to exclude.

C. Lymph nodes: While lymph nodes are part of the immune system and contribute to Waldeyer's ring, they are not a specific structure within the ring itself, but rather distributed throughout the ring.

D. Nasopharyngeal tonsil: The nasopharyngeal tonsil is a variant of the palatine tonsil found in the nasopharynx, which is part of Waldeyer's ring. Like option A, it is not an option to exclude.

**Clinical Pearl:** The correct identification of Waldeyer's ring components is essential in understanding its function and role in the oral-nasopharyngeal defense. Familiarize yourself with the specific lymphoid structures comprising Waldeyer's ring (palatine tonsil, lingual tonsil, and pharyngeal tonsil) and their locations (oropharynx and nasopharynx) for accurate clinical reasoning when examining patients with oropharyngeal or nasopharyngeal symptoms or diseases.