(a)
Functions :
Sertoli cells - secrete factors which help in the process of spermiogenesis/provide nutrition to germ cells.
Spermatogonia - divide to produce spermatids/sperms.
Leydig cells - synthesis or secretion of androgens/ testosterone.
(b) Pituitary hormones - LH (luteinizing hormone) - acts on Leydig cells and stimulates synthesis and secretion of androgens.
FSH/follicle stimulating hormone - acts on Sertoli cells and stimulates secretion of some factor that help in spermatogenesis.
Sex hormone - (Androgen/testosterone) stimulate process of spermatogenesis.