Question

The hormone released by X marked in the given figure helps to restore Y. Identify X and Y.

X	Y
A. Thyroxine	Too much calcium in blood
B. PTH	Lowered level of calcium in blood
C. Thymosin	Decreased level of blood sugar
D. Adrenaline	Excessive loss of Sodium in extracellular fluid

Answer 1

Hint: As the label X releases a hormone, it must be a gland. So we need to identify the gland by looking at its location. We can identify Y from the functions of X.

Complete Step by Step Answer:
According to the question, the indicated structure must be a gland as it releases a hormone, and the lack of duct in the figure suggests that it is an endocrine gland.
Now that we know the nature of the gland, let us pay attention to its location. They seem to be present in the neck region and the two lobes, which are almost butterfly-shaped, are most likely the thyroid glands. Our gland X is small in size (almost pea-sized), four in number, and two behind each thyroid gland lobes. This indicates that the X marked in the figure are parathyroid glands.
Parathyroid glands release a hormone called parathyroid hormone (PTH), also known as parathormone or parathyrin. It is a peptide hormone that plays a major role in the maintenance of blood calcium levels in our body by stimulating the osteoblasts and activation of Vitamin D.
Calcitonin helps in inhibiting the activity of osteoblasts. And hence too much calcium in the blood is restored by this hormone produced by the thyroid gland.
Insulin, secreted by the pancreas, helps in restoring decreased levels of blood sugar.
Aldosterone is secreted by the adrenal gland and restores the excessive loss of sodium in extracellular fluid.

So, the correct answer is option B.

Note: Students are most likely to confuse parathyroid glands as parts of the thyroid gland due to their small size and location. The cells of a parathyroid gland are packed relatively more densely than those in the thyroid glands. They are much smaller in size and four in number instead of two.