Biology Class 12 NCERT Solutions: Chapter 3 Human Reproduction Part 2

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Q.3 Draw a labeled diagram of female reproductive system.

Answer:

Image of Female Reproductive System

Image of Female Reproductive System

Q.4 Write two major functions each of testis and ovary.

Answer:

  • Functions of the Testis

  • They produce male gametes called spermatozoa by the process of spermatogenesis.

  • The leydig cells of the seminiferous tubules secrete the male sex hormone called testosterone. Testosterone aids the development of secondary sex characteristics in males.

  • Functions of the ovary

  • They produce female gametes called ova by the process of oogenesis.

  • The growing Graffian follicles secrete the female sex hormone called estrogen. Estrogen aids the development of secondary sex characteristics in females.

Q.5 Describe the structure of a seminiferous tubule.

Answer:

  • The production of sperms in the testes takes place in a highly coiled structure called the seminiferous tubules. These tubules are located in the testicular lobules.

  • Each seminiferous tubule is lined by germinal epithelium. It is lined on its inner side by two types of cells namely spermatogonia and sertoli cells respectively.

  • Spermatogonia are male germ cells which produce primary spermatocytes by meiotic divisions.

  • Primary spermatocytes undergo further meiotic division to form secondary spermatocytes and finally, spermatids.

  • Spermatids later metamorphoses into male gametes called spermatozoa. Sertoli cells are known as nurse cells of the testes as they provide nourishment to the germ cells.

  • There are large polygonal cells known as interstitial cells or leydig cells just adjacent to seminiferous tubules. These cells secrete the male hormone called testosterone.

Image of Seminiferous Tubule

Image of Seminiferous Tubule

Q.6 What is spermatogenesis? Briefly describe the process of spermatogenesis.

Answer:

  • Spermatogenesis is the process of the production of sperms from the immature germ cells in males. It takes place in seminiferous tubules present inside the testes.

  • During spermatogenesis, a diploid spermatogonium (male germ cell) increases its size to form a diploid primary spermatocyte.

  • This diploid primary spermatocyte undergoes first meiotic division (meiosis I), which is a reductional division to form two equal haploid secondary spermatocytes.

  • Each secondary spermatocyte then undergoes second meiotic division (meiosis II) to form two equal haploid spermatids.

  • Hence, a diploid spermatogonium produces four haploid spermatids. These spermatids are transformed into spermatozoa (sperm) by the process called spermiogenesis.

Image of Process of Spermatogenesis

Image of Process of Spermatogenesis

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