1.

(a) Differentiate between spermatogenesis and Oogenesis on the basis of (i) Time of initiation of the process (ii) Site of completion of the process (iii) Nature of meiotic division undergone by gamete. mother cells (b) Name the hormones and state their role involved in controlling spermatogenesis in humans.

Answer»
SupermatogenesisOogeniesis
(i) Time of initiation of the processit starts in males at the age of puberty.it starts in females during embryonic development stage before their birth.
(ii) Site of completion of the processit is the formation of mature sperms and occurs in the testes.it is the formation of mature female gametes in the ovaries.


                  		it involves developmental changes and differentiation of spermatogania into primary spermatocytes, which divide to form two secondary spermatocytes.it involves the developments of oogania into primary oocytes,



 		Each secondary spermatocyte divides to form two spermatids. which divide to form one secondary oocyte and one polar body.Each secondary oocyte divides to form one ootid and one polar body.




 		It is completed in the testes and the mature sperms are released from the testes.It is completed in the female reproductive tract or in water because oocytes are released from the ovaries.


(iii) Nature of meiotic division undergone by gamete mother cells.

 		It involves equal cytoplasmic divisions.It involves unequal cytoplasmic divisions.

(b) Spermatogenesis is initiated due to increase in gonadotropin-releasing hormone (GnRH) by hypothalamus. This hormone stimulates anterior pituitary to secrete two gonadotropins: luteinizing hormone (LH) and follicle stimulating hormone (FSH). LH acts on the Leydig’s cells of the testes and stimulates them to synthesize and secrete androgens (testosterone) which in turn stimulate spermatogenesis. FSH acts on Sertoli cells of seminiferous tubules of the testes and stimulate them to secrete an androgen binding protein (ABP) and inhibin. ABP binds to testosterone, keeping its concentration high, thus stimulating the final steps of spermatogenesis in the seminiferous tubules. Once the degree of spermatogenesis required for male reproductive functions has been achieved, Sertoli cells release inhibin, a protein hormone named for its role in inhibiting FSH secretion by the anterior pituitary.


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