In the pancreas, which are the cells that secrete insulin, decrease the blood levels of glucose.

Correct Answer: C

Rationale: The correct answer is C: beta cells. Beta cells in the pancreas secrete insulin, which helps decrease blood glucose levels by facilitating the uptake of glucose into cells for energy production. Delta cells (choice A) secrete somatostatin, which inhibits insulin and glucagon secretion. Alpha cells (choice B) secrete glucagon, which increases blood glucose levels. Choice D is a duplicate of choice C. Therefore, the correct answer is C as beta cells play a crucial role in regulating blood glucose levels through insulin secretion.

Correct Answer: B

Rationale: The correct answer is B because exocrine glands secrete their products through ducts out onto the skin or into body cavities, unlike endocrine glands that release hormones directly into the bloodstream. This distinction is crucial as exocrine glands do not release hormones into the blood (A), do not necessarily affect many body organs (C), and are not limited to the reproductive organs (D). The unique characteristic of exocrine glands secreting through ducts sets them apart from endocrine glands.

Correct Answer: D

Rationale: The correct answer is D: target cells. Target cells are specific cells that have receptors for a particular hormone, allowing them to respond to the hormone's signal. These cells are the intended recipients of the hormone's message and carry out the appropriate physiological response. Receptor cells (A) are more general and can refer to any cell with receptors, not necessarily for hormones. Sensor cells (B) detect stimuli but may not necessarily respond to hormones. Secretory cells (C) release hormones rather than respond to them.

Correct Answer: C

Rationale: The correct answer is C: Anterior pituitary. Releasing and inhibiting hormones from the hypothalamus act on the anterior pituitary to regulate the secretion of pituitary hormones. This interaction is known as the hypothalamic-pituitary axis. The hormones released by the hypothalamus travel through the hypophyseal portal system to the anterior pituitary, where they stimulate or inhibit the release of specific pituitary hormones. Choices A, B, and D are incorrect because the primary target of hypothalamic releasing and inhibiting hormones is the anterior pituitary, not the liver & adipose tissue, gonads, or bone marrow.

Correct Answer: B

Rationale: The correct answer is B: Hashimoto's thyroiditis. This autoimmune condition is a common cause of primary hypothyroidism as it leads to inflammation and destruction of the thyroid gland, resulting in reduced production of thyroid hormones. Graves' disease (A) is actually a cause of hyperthyroidism, not hypothyroidism. Toxic multinodular goiter (C) is also associated with hyperthyroidism. TSH-secreting pituitary adenoma (D) causes secondary, not primary, hypothyroidism.