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human reproduction- Presentation

human reproduction class 12 detailed notes

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human reproduction- Presentation

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  1. HUMAN REPRODUCTION

  2. Male Reproductive System • Primary sex organs: A pair of testes suspended in the scrotum • Secondary sex organs: A pair of ducts each differentiated into rete testis, vasa efferentia, epididymis and vas deferens, ejaculatory duct and the associated glands • External genitalia: Penis

  3. Gametogenesis (Spermatogenesis) • The process of formation of male gametes (sperms) in the testes • Spermatogonia (immature male germ cells) undergo mitotic division to increase in number • Spermatogonia differentiate into primary spermatocytes • Primary spermatocytes undergo meiotic division to produce secondary spermatocytes • Secondary spermatocytes undergo meiotic division to produce spermatids • Spermatids are transformed into spermatozoa by the process of spermiogenesis

  4. Hormonal Control of Spermatogenesis • Gonadotropin releasing hormone (GnRH) is secreted by the hypothalamus • GnRH stimulates the anterior pituitary to secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH) • LH acts on Leydig cells in the testes to stimulate the secretion of androgens • FSH acts on Sertoli cells in the testes to support spermatogenesis

  5. Structure of Sperm • Sperm is a microscopic structure composed of a head, neck, middle piece, and tail • The sperm head contains the elongated haploid nucleus, which is covered by an acrosome • The acrosome contains enzymes that help the sperm penetrate the egg.

  6. Female Reproductive System • Primary sex organs: A pair of ovaries • Secondary sex organs: A pair of fallopian tubes, uterus, cervix, and vagina • External genitalia: Mons pubis, labia majora, labia minora, clitoris • Mammary glands: A pair of glands that produce milk.

  7. Gametogenesis (Oogenesis) • The process of formation of female gametes (ova) in the ovaries • Oogonia (gamete mother cells) are formed during embryonic development • Oogonia divide by mitosis to produce primary oocytes • Primary oocytes undergo meiotic division I and arrest in prophase I until puberty • At puberty, a few primary oocytes begin to complete meiotic division I to produce secondary oocytes • Secondary oocytes are ovulated from the ovaries and undergo meiotic division II only if they are fertilized by a sperm

  8. Menstrual Cycle

  9. The menstrual cycle is a series of hormonal changes that occur in the female reproductive system each month

  10. The cycle begins with the menstrual phase, which is the shedding of the endometrium (lining of the uterus)

  11. The follicular phase follows, during which a follicle in the ovary develops and produces estrogen

  12. Estrogen stimulates the proliferation of the endometrium

  13. The ovulatory phase occurs when the follicle ruptures and releases an ovum (egg)

  14. The luteal phase follows, during which the corpus luteum (ruptured follicle) produces progesterone

  15. Progesterone maintains the endometrium in preparation for implantation of a fertilized egg

  16. If the egg is not fertilized, the corpus luteum degenerates and progesterone levels drop

  17. This drop in progesterone triggers menstruation.

  18. Fertilization • Fertilization is the fusion of a sperm with an ovum • Fertilization occurs in the ampullary-isthmic junction of the fallopian tube • After fertilization, the zygote (fertilized egg) travels down the fallopian tube and implants in the endometrium of the uterus

  19. Implantation • Implantation is the process by which the zygote attaches to the endometrium of the uterus • Implantation occurs 5-6 days after fertilization • After implantation, the zygote begins to develop into an embryo.

  20. Embryonic Development • The embryo undergoes cleavage to form a blastocyst. • The blastocyst implants in the endometrium of the uterus. • The inner cell mass of the blastocyst develops into the embryo. • The ectoderm, endoderm, and mesoderm develop from the inner cell mass. • The major organs and external genital organs develop by the end of 12 months.

  21. Parturition and Lactation • Parturition is the process of delivery of a fully developed fetus. • Signals for parturition originate from the fully developed fetus and placenta. • Oxytocin is released from the maternal pituitary to induce uterine contractions. • The mammary glands of the female start producing milk at the end of pregnancy. • The milk produced during the initial few days of lactation is called colostrum.

  22. Polyspermy • Polyspermy is the fertilization of an egg by more than one sperm. • If polyspermy occurs, the resulting cell has too much genetic material to develop normally.

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