Hassall’s corpuscle is present in:
**Core Concept**
Hassall's corpuscle is a structure composed of whorls of squamous epithelial cells that are found in the thymus. It plays a crucial role in the maturation and selection of T-lymphocytes. Hassall's corpuscles contain a protein called involucrin, which is a marker of epithelial cell differentiation.
**Why the Correct Answer is Right**
Hassall's corpuscles are formed during the embryonic development of the thymus. They are composed of concentric whorls of epithelial cells that are derived from the third pharyngeal pouch. The involucrin protein is produced by these epithelial cells and is involved in the formation of the corpuscles. The presence of Hassall's corpuscles is a characteristic feature of the thymus and is essential for its function in T-lymphocyte development.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Hassall's corpuscles are not found in the lymph nodes. Lymph nodes contain lymphoid follicles and a medulla, but they do not have the characteristic whorls of epithelial cells seen in Hassall's corpuscles.
**Option B:** This option is incorrect because Hassall's corpuscles are not found in the spleen. The spleen contains red and white pulp, but it does not have the same type of epithelial cell whorls as Hassall's corpuscles.
**Option D:** This option is incorrect because Hassall's corpuscles are not found in the tonsils. Tonsils contain lymphoid tissue and a surface epithelium, but they do not have the characteristic whorls of epithelial cells seen in Hassall's corpuscles.
**Clinical Pearl / High-Yield Fact**
Hassall's corpuscles are a key histological feature of the thymus and are essential for its function in T-lymphocyte development. They can be used as a marker for the presence of thymic tissue in histopathological samples.
**Correct Answer: C. Thymus. Hassall's corpuscles are characteristic structures found in the thymus.**