Normal development of the immune response is due in part to hormones produced by the ________.

Correct Answer: D

Rationale: The correct answer is D: thymus gland. The thymus gland is crucial for the development and maturation of T cells, a type of immune cell. The hormones produced by the thymus gland, such as thymosin, play a key role in the proper functioning of the immune system. Without a functional thymus gland, the immune response would be compromised. Explanation for why other choices are incorrect: A: Adrenal medulla does not play a direct role in immune response development. B: Pancreas primarily produces hormones related to blood sugar regulation, not immune response. C: Thyroid gland produces hormones that regulate metabolism, not directly related to immune response development.

Correct Answer: B

Rationale: Leptin is primarily secreted by adipocytes, which are fat cells. Adipocytes play a crucial role in regulating energy balance and appetite through leptin secretion. Lymphocytes are immune cells, goblet cells secrete mucus, and fibroblasts are connective tissue cells, none of which are involved in leptin secretion.

Correct Answer: C

Rationale: The correct answer is C: hydrocortisones. Eicosanoids are signaling molecules derived from fatty acids, including prostaglandins and leukotrienes, which act as paracrines. Hydrocortisone is a steroid hormone, not an eicosanoid. It functions differently from eicosanoids, which act locally as signaling molecules. Therefore, hydrocortisones do not belong to the eicosanoid category. Choices A, B, and D are incorrect because paracrines, leukotrienes, and prostaglandins are all types of eicosanoids with specific functions in the body.

Correct Answer: D

Rationale: The correct answer is D: steroid. Steroid hormones are lipid-soluble and can pass through cell membranes easily. This property allows them to be taken orally since they are not digested in the stomach and can be absorbed in the intestines. Carbohydrates (A), peptides (B), and proteins (C) are water-soluble and cannot pass through cell membranes easily, making them unsuitable for oral administration.

Correct Answer: C

Rationale: Rationale: 1. Oxytocin is the hormone responsible for stimulating uterine contractions during labor and delivery. 2. Oxytocin also triggers the release of milk during nursing by causing contraction of the cells around the milk-filled alveoli. 3. ADH (A) regulates water balance, glucagon (B) regulates blood sugar levels, and prolactin (D) stimulates milk production but not milk release. Summary: Oxytocin is the correct answer because it specifically stimulates uterine contractions and milk release during nursing, while the other choices are not directly related to these functions.