Step 1: Identifying the diagram.
The given diagram represents a transverse section of a seminiferous tubule of the testis. Various stages of spermatogenesis can be seen arranged from the periphery towards the lumen. Step 2: Identification of structure A.
Structure A points to a large supporting cell extending from the basement membrane towards the lumen. Such cells are characteristic of Sertoli cells, also called nurse cells. Step 3: Function of Sertoli cells.
Sertoli cells provide nourishment and structural support to developing spermatogenic cells. They also help in regulation of spermatogenesis by forming the blood–testis barrier and secreting factors required for sperm maturation. Step 4: Analysis of options. (A) Sertoli cell; secretion of testosterone: Incorrect, testosterone is secreted by Leydig cells. (B) Sertoli cell; nutrition of maturing sperms: Correct statement. (C) Follicular cell; secretion of thyroxine: Refers to thyroid gland, unrelated here. (D) Leydig cell; secretion of testosterone: Leydig cells lie outside seminiferous tubules, not inside as shown. Step 5: Conclusion.
Structure A is a Sertoli cell, and its function is to provide nutrition to maturing sperms.
