**Core Concept**
Adult Leydig cells, also known as interstitial cells of Leydig, are a type of cell found in the testes responsible for producing androgens, particularly testosterone. These cells play a crucial role in male reproductive physiology, particularly in spermatogenesis and the development of secondary sex characteristics.

**Why the Correct Answer is Right**
Leydig cells originate from the mesonephric ridge, a structure that forms during embryonic development. Specifically, they differentiate from the mesenchymal cells that migrate to the genital ridges. This process occurs during the 6th to 9th weeks of gestation. The differentiation is influenced by the expression of specific genes, including the WT1 gene, which is a transcription factor essential for the development of the urogenital system.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Leydig cells do not originate from the adrenal glands, which are responsible for producing other steroid hormones, such as cortisol and aldosterone.

**Option B:** This option is incorrect because Sertoli cells, not Leydig cells, are the somatic cells of the testes that provide support and nutrition to developing sperm cells.

**Option C:** This option is incorrect because peritubular cells, not Leydig cells, are the myoid cells that surround the seminiferous tubules and play a role in sperm transport.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Leydig cells are sensitive to luteinizing hormone (LH) from the pituitary gland, which stimulates them to produce testosterone. Disruptions in this hormonal axis can lead to hypogonadism, a condition characterized by low levels of testosterone.

**Correct Answer: C. Mesonephric ridge.**