The correct option is Leydig cells.
Explanation
The testis serves a dual function as a primary sex organ (producing gametes) and an endocrine gland. Its histological structure comprises seminiferous tubules, where spermatogenesis occurs, and interstitial spaces (stromal tissue) located between these tubules.
Analysis of Cell Types:
- Leydig cells (Correct): Also known as interstitial cells, these are located in the intertubular spaces (outside the seminiferous tubules). Regulated by Luteinizing Hormone (LH) from the pituitary gland, Leydig cells synthesize and secrete testicular hormones called androgens, the most important of which is testosterone.
- Sertoli cells (Incorrect): Found inside the seminiferous tubules, these are often called "nurse cells." Their primary function is to provide nutrition and structural support to developing germ cells. While they secrete Androgen Binding Protein (ABP) and Inhibin, they do not synthesize androgens.
- Germ cells (Incorrect): These are the spermatogonia within the seminiferous tubules that undergo differentiation and meiosis to produce spermatozoa. They are not responsible for hormone secretion.
- Interstitial macrophages (Incorrect): These are immune cells present in the interstitial tissue involved in local defense mechanisms, not endocrine function.
Key Takeaway: Leydig cells are the endocrine source of androgens (testosterone) in the testis, whereas Sertoli cells facilitate the nourishment and maturation of sperm.