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Spermatogenesis and oogenesis

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christenashantaram
christenashantaram

permatogenesis and oogenesis are the processes of formation of male and female gametes. Spermatogenesis leads to the formation of sperms, whereas oogenesis helps in the formation of ova. The fertilization of sperm and ova leads to the formation of a zygote which further develops into an embryo

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MRS.P.CHRISTEN,RNM M.SC-N-OBG ASSISTANT PROFESSOR
 At the beginning of embryonic development, the primordial germ cells lie along the wall of the yolk sac.  In the 4th week, they pass the hindgut to reach the differentiating gonads.  These cells are referred to as oogonia or spermatogonia if they develop into ovaries or testicles, respectively.  Gametes are peculiar in that they have a haploid set of chromosomes. So, they contain only 23 chromosomes with mixed maternal and paternal attributes.  Later in the fertilization of the egg cell by the sperm, a diploid set of chromosomes is formed.  Meiosis is responsible for halving the set of chromosomes.
 Oogenesis is the process of formation of female gamete or ovum through a series of mitotic and meiotic divisions occurring in the female reproductive system.  Oogenesis starts in the fetal period but then pauses.  It is continued during puberty at the age of 12– 15 years.
Oogenesis is the process of formation of female gametes. This process begins inside the fetus before birth. The steps in oogenesis up to the production of primary oocytes occur before birth. Primary oocytes do not divide further. They either become secondary oocytes or degenerate.
Oogenesis occurs in the outermost layers of the ovaries. Oogenesis starts with a germ cell called oogonium and undergoes mitosis to increase in number. The process of oogenesis takes place in the following three stages:  Pre-natal  Antral  Pre-ovulatory
Pre-natal Stage • The primary oocyte grows while being arrested in meiosis-I. • The follicular cells proliferate and form a stratified cuboidal epithelium. Such cells are known as granulosa cells. • These cells secrete glycoproteins to form zona pellucida around the primary oocyte. Antral Stage • The fluid-filled area, present between granulosa cells, combines to form a central fluid-filled space called the antrum. These are known as secondary follicles. • In every month cycle, these secondary follicles develop under the influence of follicle-stimulating hormone and luteinizing hormone. Pre- Ovulatory Stage • This stage is induced by LH surge, and meiosis-I completes here. • Two haploid cells of unequal sizes are formed within the follicle. • One of the daughter cells that receive less cytoplasm forms a polar body. This cell does not participate in ovum formation. • The other daughter cell is known as the secondary oocyte. The two daughter cells undergo meiosis-II. The polar body replicates to form two polar bodies, while the secondary oocyte arrests in the metaphase stage of meiosis-II.
Spermatogenesis and oogenesis
Spermatogenesis and oogenesis
 Spermatogenesis is the process of formation of mature sperm cells through a series of mitotic and meiotic divisions along with metamorphic changes in the immature sperm cell.  In contrast to oogenesis, male germ cells are able not only to develop before birth but also to replicate after birth.
Prenatal maturation of male germ cells • Prenatally, Sertoli cells stop the male germ cells in their maturation process after their immigration into the testicle. As mainly undifferentiated cells, they remain in the testicle whose tubules are not yet canalized. With the onset of puberty, the seminiferous tubules develop and the maturation of the spermatogonia to sperms begins. Postnatal maturation of male germ cells • When puberty begins, the spermatogonia significantly proliferate. Two types of spermatogonia can be recognized: the first type always provides new spermatogonia; the second type begins with maturation. • In the first step, the primary spermatocyte or spermatocyte of the first order develops out of the second type when the spermatogonia enter the prophase of meiosis. They have a diploid set of chromosomes (2n2c). This phase lasts roughly 3 weeks. • Further phases of the first meiotic division follow the long prophase. At the end of it, there are 2 spermatocytes. These are referred to as secondary spermatocytes or spermatocytes of the second order. They undergo the second meiotic division, resulting in 4 haploid spermatids. • With each division, the size of the cells is halved so that the spermatids amount to about a quarter of the size of the spermatocytes.
Spermatogenesis and oogenesis
Spermatogenesis and oogenesis
Basis for comparison Spermatogenesis Oogenesis Definition Spermatogenesis is the process of formation of mature sperm cells through a series of mitotic and meiotic divisions along with metamorphic changes in the immature sperm cell. Oogenesis is the process of formation of female gamete or ovum through a series of mitotic and meiotic divisions occurring in the female reproductive system. Nature of the process It is the male version of gametogenesis which results in the formation of mature male gametes. It is the female version of gametogenesis which results in the formation of mature male gametes.
Basis for comparison Spermatogenesis Oogenesis Stages The process of spermatogenesis is completed through the following three stages; spermatocytogenesis, spermatidogenesis, and spermiogenesis. The overall process of oogenesis is divided into three stages; the follicular phase, the ovulation phase, and the luteal phase. Occurs in The overall process of spermatogenesis occurs in the testes until the sperm moves to the epididymis and gains motility. The overall process of oogenesis occurs in the ovary until the mature ovum moves to the fallopian tube. Continuity of the process Spermatogenesis is a continuous process that begins with puberty and continuous until death. The early stages of oogenesis begin in the fetal stage while the rest continue after puberty till menopause.
Basis for comparison Spermatogenesis Oogenesis Occurrence Spermatogenesis occurs continuously, and all spermatogonia undergo meiosis, producing sperms all the time. Oogenesis occurs for one egg cell at a time, and some cells might require many years to reach maturation. Rate of production Spermatogenesis forms millions of sperms every day. Oogenesis releases one ovum per month. Develops from The male gamete develops from the germinal epithelium of the seminiferous tubules of the testes. The female gamete develops from the germinal epithelium lining the ovary. Starting cell The starting cell during spermatogenesis is the primary spermatocyte. The starting cell during oogenesis is the primary oocyte.
Basis for comparison Spermatogenesis Oogenesis Functional cell produced from division The meiotic division of primary spermatocyte results in four spermatids, each of which develops into a sperm cell. The meiotic division of primary oocyte only forms a single functional secondary oocyte. Cytogenesis Cytogenesis in spermatogenesis forms two equal cells. Cytogenesis in oogenesis forms two unequal cells; larger secondary oocyte and a smaller polar body. Sertoli cells Sertoli cells are found in the testes that provide nourishment to the developing male gamete. Sertoli cells are not found in the ovary, and the nourishment to the female gamete is provided by the yolk present around the ovum.
Basis for comparison Spermatogenesis Oogenesis Growth phase The growth phase during spermatogenesis is shorter than in oogenesis. The growth phase during oogenesis is longer than in spermatogenesis. Resting phase There is no resting phase during the spermatogenesis process. The resting phase occurs during oogenesis from the embryonic stage till puberty. Size of the gametes The male gametes formed after spermatogenesis are smaller in size than the female gametes. The female gametes formed after oogenesis are larger in size than the male gametes.
Basis for comparison Spermatogenesis Oogenesis Motility of the gamete The male gamete formed is motile. The female gamete formed is non-motile. Nuclear condensation Nuclear condensation can be seen in a male gamete. Nuclear condensation doesn’t take place in the ovum. Food preservation The male gamete stores less amount of food within itself. The female gamete stores a lot more food within itself.
Spermatogenesis and oogenesis
Spermatogenesis and oogenesis
https://youtu.be/6fBa8UqEano https://youtu.be/63hFfJOJg9w
 Rogers, K. (2010). The Reproductive System (Human Body (Rosen Educational Publishing)) (Illustrated ed.). Rosen Education Service.  Dutta, D. C., Hiralal, K., & Konar, H. (2018). DC Dutta’s Textbook of Obstetrics: Including Perinatology and Contraception (9th ed.). Jaypee Brothers Medical Pub.  Dutta, C. D. D. D. C. (2021). Textbook of Gynaecology: Including Contraception (5th Revised edition). New Central Book Agency.  The Editors of Encyclopaedia Britannica. (2021). Oogenesis | physiology. Encyclopedia Britannica. https://www.britannica.com/science/oogenesis  GDPR. (2021). BYUS. https://byjus.com/biology/oogenesis/  Lecturio. (2020, October 5). Spermatogenesis and Oogenesis. The Lecturio Online Medical Library. https://www.lecturio.com/magazine/spermatogenesis-and- oogenesis/
Spermatogenesis and oogenesis

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Spermatogenesis and oogenesis

  • 2.  At the beginning of embryonic development, the primordial germ cells lie along the wall of the yolk sac.  In the 4th week, they pass the hindgut to reach the differentiating gonads.  These cells are referred to as oogonia or spermatogonia if they develop into ovaries or testicles, respectively.  Gametes are peculiar in that they have a haploid set of chromosomes. So, they contain only 23 chromosomes with mixed maternal and paternal attributes.  Later in the fertilization of the egg cell by the sperm, a diploid set of chromosomes is formed.  Meiosis is responsible for halving the set of chromosomes.
  • 3.  Oogenesis is the process of formation of female gamete or ovum through a series of mitotic and meiotic divisions occurring in the female reproductive system.  Oogenesis starts in the fetal period but then pauses.  It is continued during puberty at the age of 12– 15 years.
  • 4. Oogenesis is the process of formation of female gametes. This process begins inside the fetus before birth. The steps in oogenesis up to the production of primary oocytes occur before birth. Primary oocytes do not divide further. They either become secondary oocytes or degenerate.
  • 5. Oogenesis occurs in the outermost layers of the ovaries. Oogenesis starts with a germ cell called oogonium and undergoes mitosis to increase in number. The process of oogenesis takes place in the following three stages:  Pre-natal  Antral  Pre-ovulatory
  • 6. Pre-natal Stage • The primary oocyte grows while being arrested in meiosis-I. • The follicular cells proliferate and form a stratified cuboidal epithelium. Such cells are known as granulosa cells. • These cells secrete glycoproteins to form zona pellucida around the primary oocyte. Antral Stage • The fluid-filled area, present between granulosa cells, combines to form a central fluid-filled space called the antrum. These are known as secondary follicles. • In every month cycle, these secondary follicles develop under the influence of follicle-stimulating hormone and luteinizing hormone. Pre- Ovulatory Stage • This stage is induced by LH surge, and meiosis-I completes here. • Two haploid cells of unequal sizes are formed within the follicle. • One of the daughter cells that receive less cytoplasm forms a polar body. This cell does not participate in ovum formation. • The other daughter cell is known as the secondary oocyte. The two daughter cells undergo meiosis-II. The polar body replicates to form two polar bodies, while the secondary oocyte arrests in the metaphase stage of meiosis-II.
  • 9.  Spermatogenesis is the process of formation of mature sperm cells through a series of mitotic and meiotic divisions along with metamorphic changes in the immature sperm cell.  In contrast to oogenesis, male germ cells are able not only to develop before birth but also to replicate after birth.
  • 10. Prenatal maturation of male germ cells • Prenatally, Sertoli cells stop the male germ cells in their maturation process after their immigration into the testicle. As mainly undifferentiated cells, they remain in the testicle whose tubules are not yet canalized. With the onset of puberty, the seminiferous tubules develop and the maturation of the spermatogonia to sperms begins. Postnatal maturation of male germ cells • When puberty begins, the spermatogonia significantly proliferate. Two types of spermatogonia can be recognized: the first type always provides new spermatogonia; the second type begins with maturation. • In the first step, the primary spermatocyte or spermatocyte of the first order develops out of the second type when the spermatogonia enter the prophase of meiosis. They have a diploid set of chromosomes (2n2c). This phase lasts roughly 3 weeks. • Further phases of the first meiotic division follow the long prophase. At the end of it, there are 2 spermatocytes. These are referred to as secondary spermatocytes or spermatocytes of the second order. They undergo the second meiotic division, resulting in 4 haploid spermatids. • With each division, the size of the cells is halved so that the spermatids amount to about a quarter of the size of the spermatocytes.
  • 13. Basis for comparison Spermatogenesis Oogenesis Definition Spermatogenesis is the process of formation of mature sperm cells through a series of mitotic and meiotic divisions along with metamorphic changes in the immature sperm cell. Oogenesis is the process of formation of female gamete or ovum through a series of mitotic and meiotic divisions occurring in the female reproductive system. Nature of the process It is the male version of gametogenesis which results in the formation of mature male gametes. It is the female version of gametogenesis which results in the formation of mature male gametes.
  • 14. Basis for comparison Spermatogenesis Oogenesis Stages The process of spermatogenesis is completed through the following three stages; spermatocytogenesis, spermatidogenesis, and spermiogenesis. The overall process of oogenesis is divided into three stages; the follicular phase, the ovulation phase, and the luteal phase. Occurs in The overall process of spermatogenesis occurs in the testes until the sperm moves to the epididymis and gains motility. The overall process of oogenesis occurs in the ovary until the mature ovum moves to the fallopian tube. Continuity of the process Spermatogenesis is a continuous process that begins with puberty and continuous until death. The early stages of oogenesis begin in the fetal stage while the rest continue after puberty till menopause.
  • 15. Basis for comparison Spermatogenesis Oogenesis Occurrence Spermatogenesis occurs continuously, and all spermatogonia undergo meiosis, producing sperms all the time. Oogenesis occurs for one egg cell at a time, and some cells might require many years to reach maturation. Rate of production Spermatogenesis forms millions of sperms every day. Oogenesis releases one ovum per month. Develops from The male gamete develops from the germinal epithelium of the seminiferous tubules of the testes. The female gamete develops from the germinal epithelium lining the ovary. Starting cell The starting cell during spermatogenesis is the primary spermatocyte. The starting cell during oogenesis is the primary oocyte.
  • 16. Basis for comparison Spermatogenesis Oogenesis Functional cell produced from division The meiotic division of primary spermatocyte results in four spermatids, each of which develops into a sperm cell. The meiotic division of primary oocyte only forms a single functional secondary oocyte. Cytogenesis Cytogenesis in spermatogenesis forms two equal cells. Cytogenesis in oogenesis forms two unequal cells; larger secondary oocyte and a smaller polar body. Sertoli cells Sertoli cells are found in the testes that provide nourishment to the developing male gamete. Sertoli cells are not found in the ovary, and the nourishment to the female gamete is provided by the yolk present around the ovum.
  • 17. Basis for comparison Spermatogenesis Oogenesis Growth phase The growth phase during spermatogenesis is shorter than in oogenesis. The growth phase during oogenesis is longer than in spermatogenesis. Resting phase There is no resting phase during the spermatogenesis process. The resting phase occurs during oogenesis from the embryonic stage till puberty. Size of the gametes The male gametes formed after spermatogenesis are smaller in size than the female gametes. The female gametes formed after oogenesis are larger in size than the male gametes.
  • 18. Basis for comparison Spermatogenesis Oogenesis Motility of the gamete The male gamete formed is motile. The female gamete formed is non-motile. Nuclear condensation Nuclear condensation can be seen in a male gamete. Nuclear condensation doesn’t take place in the ovum. Food preservation The male gamete stores less amount of food within itself. The female gamete stores a lot more food within itself.
  • 22.  Rogers, K. (2010). The Reproductive System (Human Body (Rosen Educational Publishing)) (Illustrated ed.). Rosen Education Service.  Dutta, D. C., Hiralal, K., & Konar, H. (2018). DC Dutta’s Textbook of Obstetrics: Including Perinatology and Contraception (9th ed.). Jaypee Brothers Medical Pub.  Dutta, C. D. D. D. C. (2021). Textbook of Gynaecology: Including Contraception (5th Revised edition). New Central Book Agency.  The Editors of Encyclopaedia Britannica. (2021). Oogenesis | physiology. Encyclopedia Britannica. https://www.britannica.com/science/oogenesis  GDPR. (2021). BYUS. https://byjus.com/biology/oogenesis/  Lecturio. (2020, October 5). Spermatogenesis and Oogenesis. The Lecturio Online Medical Library. https://www.lecturio.com/magazine/spermatogenesis-and- oogenesis/