Which of the following is the derivative of ultimobranchial body?
**Core Concept**
The ultimobranchial body is a non-epithelial structure derived from the fifth pharyngeal pouch, playing a crucial role in the development of the thyroid gland and parafollicular cells (also known as C-cells). This structure contributes to the formation of the parathyroid glands and the parafollicular cells in the thyroid gland.
**Why the Correct Answer is Right**
The parafollicular cells, also known as C-cells, are responsible for the production of calcitonin, a hormone that helps regulate calcium levels in the blood. These cells are derived from the ultimobranchial body and migrate to the thyroid gland during embryonic development. The parafollicular cells are distinct from the thyroid follicular cells, which produce thyroid hormones.
**Why Each Wrong Option is Incorrect**
**Option A:** The parathyroid glands are indeed derived from the pharyngeal pouches, but they are primarily formed from the third and second pharyngeal pouches, not the ultimobranchial body.
**Option B:** The thyroid gland is formed from the thyroid diverticulum, not the ultimobranchial body.
**Option C:** The parathyroid glands are not derived from the ultimobranchial body.
**Clinical Pearl / High-Yield Fact**
The parafollicular cells (C-cells) are responsible for producing calcitonin, which helps regulate calcium levels in the blood. This hormone is often elevated in medullary thyroid carcinoma, a type of thyroid cancer that originates from the parafollicular cells.
**Correct Answer:** C. Parafollicular cells (C-cells)