Which of the following structures form the bulk of each of the testis?

a. Destroy pathogens that enter a break in the skin: While mast cells can contribute to the defense against pathogens by releasing inflammatory mediators, their primary function is not the direct destruction of pathogens.

b. Produce histamine and leukotrienes that initiate inflammation: This is correct. Mast cells are known for their role in releasing histamine and leukotrienes, which are key mediators of the inflammatory response.

c. Cushion bony prominences: This is not a function of mast cells. Cushioning bony prominences is a role more related to adipose tissue.

d. Connect skin to muscles: This is the function of connective tissue, not mast cells.

a. Buffering mechanism of kidneys and sodium bicarbonate: The buffering mechanism and sodium bicarbonate are involved in pH regulation, not directly in sodium and water balance.

b. Aldosterone and renin excretion: Correct. Aldosterone, a hormone produced by the adrenal cortex, and renin, an enzyme secreted by the kidneys, play crucial roles in regulating sodium and water balance.

c. Production of glucocorticoids and reabsorption of glucose: Glucocorticoids are involved in stress responses and metabolism, while glucose reabsorption relates to energy balance, not specifically sodium and water balance.

d. Intestinal absorption and retention of water: While intestinal absorption is important for overall fluid balance, it is not the primary regulatory mechanism for sodium and water balance in the body, which is primarily controlled by renal and endocrine factors.