Identify the growth factor that is released by cancer cells to create a capillary network that aids the cancer growth.

Correct Answer: C

Rationale: The correct answer is C, tumor angiogenesis factor. Cancer cells release this growth factor to promote the formation of new blood vessels (angiogenesis) around the tumor, providing a supply of nutrients and oxygen to support their growth. This process is essential for cancer progression. A: Macrophage colony-stimulating factor is involved in the production and differentiation of macrophages, not in angiogenesis. B: Platelet-derived growth factor promotes cell growth and division, but it is not specifically responsible for angiogenesis in the context of cancer. D: Epidermal growth factor is a signaling molecule that promotes cell proliferation and differentiation but is not the primary factor released by cancer cells to induce angiogenesis.

Correct Answer: D

Rationale: The correct answer is D: Parathyroid hormone. Parathyroid hormone plays a crucial role in regulating calcium homeostasis by increasing calcium levels in the blood through various mechanisms. It promotes calcium release from bones, enhances calcium absorption in the intestines, and reduces calcium excretion from the kidneys. Insulin (Choice A) primarily regulates blood sugar levels, not calcium. Erythropoietin (Choice B) stimulates red blood cell production and does not directly affect calcium homeostasis. Aldosterone (Choice C) regulates sodium and potassium balance but not calcium levels. Thus, Parathyroid hormone is the correct choice for controlling calcium homeostasis.

Correct Answer: C

Rationale: The correct answer is C: luminal acid. Gastrin secretion is primarily stimulated by the presence of luminal peptides and vagal discharge. Luminal acid inhibits gastrin secretion through negative feedback mechanisms. Phenylalanine does not directly stimulate gastrin secretion. In summary, luminal acid is the correct answer because it acts as an inhibitory factor for gastrin secretion, whereas the other choices are known stimulatory factors.

Correct Answer: D

Rationale: The correct answer is D. Folate absorption is not Na+ dependent because it is absorbed in the small intestine through a carrier-mediated process independent of sodium. Thiamin, riboflavin, and niacin require sodium-dependent transport mechanisms for absorption in the small intestine. Thiamin is absorbed through thiamin transporters that are Na+ dependent. Riboflavin is absorbed by sodium-dependent multivitamin transporters. Niacin absorption also involves sodium-dependent transporters. Therefore, folate is the only option that is not Na+ dependent for absorption.

Correct Answer: C

Rationale: Rationale for Choice C: Plasma norepinephrine levels are generally unchanged after adrenalectomy in the adrenal medulla because norepinephrine is mainly produced by postganglionic sympathetic nerve endings rather than the adrenal medulla. Adrenalectomy removes the adrenal gland, which primarily secretes epinephrine, not norepinephrine. Therefore, plasma norepinephrine levels would not be significantly affected by adrenalectomy. Summary of other choices: A: Incorrect. Epinephrine is formed from norepinephrine, not tyrosine, through methylation and hydroxylation. B: Incorrect. The majority of cells in the adrenal medulla are epinephrine-secreting cells, not just 10%. D: Incorrect. The half-life of catecholamines in the circulation is very short, around 2 minutes, not 10 minutes.