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HUMAN REPRODUCTION

EXERCISE SOLUTIONS

For important questions

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Question 1: Fill in the blanks:

(a) Humans reproduce sexually. (asexually/sexually)

(b) Humans are viviparous. (oviparous/viviparous/ovoviviparous)

(c) Fertilization is internal in humans. (external/internal)

(d) Male and female gametes are haploid. (diploid/haploid)

(e) Zygote is diploid. (diploid/haploid)

(f) The process of release of the ovum from a mature follicle is called ovulation.

(g) Ovulation is induced by a hormone called the luteinizing hormone (LH).

(h) The fusion of the male and the female gametes is called fertilization.

(i) Fertilization takes place in the ampulla of oviduct.

(j) The zygote divides to form blastocyst, which is implanted in uterus.

(k) The structure which provides vascular connection between the fetus and uterus

is called placenta.

Question 2: Draw a labeled diagram of male reproductive system.

Male Reproductive Structure 1.png

Question 3: Draw a labeled diagram of male reproductive system.

Female Reproductive Structure 1.png

Question 4: Write two major functions each of testis and ovary.

Ans: Functions of the Testis:

(a) Production of sperms or spermatozoa by the process of spermatogenesis.

(b) Production of male sex hormone, called androgen/testosterone, by Leydig cells.

 

Functions of the ovary:

(a) They produce female gametes called ova by the process of oogenesis.

(b) Production of female sex hormones, estrogen and progesterone. Which are responsible feminine characters.

  

Question 5: Describe the structure of a seminiferous tubule.

Ans: Seminiferous tubules are highly coiled structure located in the testicular lobule help in the production of sperms. 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.

Seminiferous tubules 1.png

Question 6: What is spermatogenesis? Briefly describe the process of spermatogenesis.

Ans: The process of formation of spermatozoa (sperms) from diploid spermatogonia is called spermatogenesis. 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.

 

Question 7: Name the hormones involved in regulation of spermatogenesis.

Ans: Gonadotropin releasing hormones (GnRH) secreted from hypothalamus stimulates anterior pituitary gland and stimulates secretion of two gonadotropins - Follicle-stimulating hormones (FSH) and luteinizing hormones (LH). These hormones are involved in the regulation of the process of spermatogenesis.

FSH acts on Sertoli cells, whereas LH acts on Leydig cells of the testis to produce androgen and stimulates the process of spermatogenesis.

 

Question 8: Define spermiogenesis and spermiation.

Ans: Spermiogenesis: It is the process involving transformation of spermatids into matured spermatozoa or sperms.

Spermiation: It is the process in which sperm heads become embedded in the Sertoli cells and are finally released from seminiferous tubules.

 

Question 9: Draw a labeled diagram of sperm.

Sperm 1.png

Question 10: What are the major components of seminal plasma?

Ans: The major components of the seminal plasma in the male reproductive system are mucus, spermatozoa, and various secretions of accessory glands. The seminal plasma is rich in fructose, calcium, ascorbic acid, and certain enzymes. It provides nourishment and protection to sperms.

 

Question 11: What are the major functions of male accessory ducts and glands?