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Reproduction

Reproduction. SL and HL – Papers 1 and 2. Introduction to Reproduction. One of the six life functions is to reproduce In humans, the reproductive systems and urinary systems are arranged close to each other Gametes – sex cells Gonads – glands which produce gametes Male – testes

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Reproduction

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  1. Reproduction SL and HL – Papers 1 and 2

  2. Introduction to Reproduction • One of the six life functions is to reproduce • In humans, the reproductive systems and urinary systems are arranged close to each other • Gametes – sex cells • Gonads – glands which produce gametes • Male – testes • Females - ovaries

  3. Male Reproductive System • Urinary tract connected to reproductive tract, through urethra • Parts of system • External • Penis • Scrotum

  4. Male Reproductive System • Internal • Testes • Produce spermatozoa and testosterone • Made up of seminiferous tubules • Tubules end in the epididymis • Inside tubules are sperm cells called spermatogonia • Vas Deferens or sperm duct • Urethra

  5. Male Reproductive System • Three glands • Seminal vesicle – Prostaglandins and fructose • Prostrate gland – Alkaline solution • Cowper’s gland – Mostly mucous • Mixture of mature sperm and seminal fluid is called semen.

  6. Male Reproductive System

  7. Female Reproductive System • Urinary system and reproductive system are separate • Parts of system • External • Labia • Vulva

  8. Female Reproductive System • Internal • Ovaries • Secrete estrogen, initially progesterone and egg cells called oogonia, that mature to ova • Fallopian tubes or oviducts • Ends – fimbriae • Connected to the uterus • Lined by endometrium

  9. Female Reproductive System • Cervix – opening to the uterus • Vagina • Endometrium clears itself every 28 days, called the menstrual cycle.

  10. Female Reproductive System

  11. Secondary Sexual Characteristics • Female Secondary Sexual Characteristics • Usually around age 13, but can be younger • Maturation of the ovaries, and enlargement of the vagina and uterus • Development of breasts • Widening of the pelvis • Deposition of fat under the skin of the buttocks and thighs • Growth of pubic hair and hair under the arm • Monthly ovulation and menstruation • Changes in behaviour associated with sex drive • Male Secondary Sexual Characteristics • Usually around age 15, but can be younger • Development and enlargement of the testes, scrotum, penis, and glands of the reproductive tract • Increased skeletal muscle development • Enlargement of the larynx, deepening of the voice • Growth of pubic hair, underarm hair, and body hair • Continuous production of sperm • Changes in behaviour associated with sex drive

  12. Spermatogenesis and Hormonal Control in Males • The process of producing sperm cells is called Spermatogenesis. • Done by the spermatogonia that line the seminiferous tubules • Sertoli cells nourish the developing sperm • Sperm finish maturation in epididymis

  13. Spermatogenesis • The start germ cells are produced • Contain the full 46 chromosomes (diploid) • Divide using mitosis • Begin to grow to create primary spermatocytes. • Primary Spermatocytesundergo Meiosis I and Meiosis II • Form secondary spermatocytes or spermatids. • Spermatidshave the correct amount of genetic material (haploid). • Spermatidsdifferentiate into spermatozoa, or sperm.

  14. Mature Sperm • Sperm are divided into three main parts – Head, Midpiece and Tail.

  15. Hormonal Control of Spermatogenesis • There are three hormones that control spermatogenesis: • Follicle Stimulating Hormone – FSH • Leuteinizing Hormone – LH • Testosterone • The three hormones are all activated by gonadotropin releasing hormone (GnRH), which is secreted by the hypothalamus.

  16. Spermatogenesis and Hormonal Control in Males

  17. Oogenesis and Hormonal Control in Females • Ovaries contain follicles in varying stages of development • Follicles - where the developing oocytes are found. • Before birth, the follicles develop into oogonia • Diploid cells (2x the normal amount of human chromosomes undergo meiosis • Oogonia grow into primary oocytes, which are surrounded by a primary follicle (called zonapellucida).

  18. Oogenesis and Hormonal Control in Females • The primary oocyte undergoes meiosis, followed by unequal cell division • First division creates a secondary oocyte and a polar body • The follicle, that contains the secondary oocyte, releases it once a month to be fertilized • This is called ovulation.

  19. Oogenesis and Hormonal Control in Females • Secondary oocyte is suspended until it is fertilized. • If the secondary oocyte is fertilized as it travels down the fallopian tube, it will go through the second stage of meiosis. • ovum and a second polar body • The ruptured follicle in the ovary forms a corpus luteum

  20. Secondary Oocyte

  21. Spermatogenesis and Oogenesis

  22. Hormonal Control in Females • In the female there are four hormones at work, during a process called the Menstrual Cycle: • Follicle Stimulating Hormone (FSH) • Luteinizing Hormone (LH) • Progesterone • Estrogen

  23. Menstrual Cycle

  24. Compare Spermatogensis to Oogenesis, looking at the overall process, hormones used, gametes produced and timing of the process

  25. Fertilization • Copulation – the act of coupling of male and female in sexual intercourse • Fertilization – the fusion of male and female gametes (also called conception) • Sperm enters during copulation and fuses with the secondary oocyte, called fertilization, which will go through the last process of oogenesis.

  26. Process of fertilization • Sperm swim up the uterus and into the oviducts. • One or more of the sperms reach the secondary oocyte. • Sperm comes in contact with the zonapellucida. • Head of the sperm contains the acrosome. • Enzymes are released and the head, containing the genetic material can enter into the egg. • This process is called capacitaiton.

  27. Process of fertilization • The head of the sperm, which contains the nucleus, fuses with the oocyte • The cortical granules in the outer cytoplasm of the oocyte will release their contents through exocytosis. This is called a cortical reaction. • Thickens the zonapellucida so that it becomes a fertilization membrane. (cannot be penetrated by other sperm cells)

  28. Process of fertilization • Sperm nucleus enters the oocyte, the completion of Meiosis II is triggered • The male and female haploid nuclei come together to form the diploid nucleus of the zygote.(23 + 23 = 46) • Fertilization is completed.

  29. Fertilization

  30. Early Development and Implantation • Cell goes through several cleavage divisionsand forms the morula • Morulareaches the uterus about four days after fertilization. • Moruladivides unequally, forming a blastocyst. • implants in the endometrium of the uterus about 7 days after fertilization • Cells on the outside of the blastocyst are called the trophoblast which grows villi into the endometrium and absorb nutrients from it. • In about two weeks the placenta develops from the trophoblast cells.

  31. Early Development and Implantation • Trophoblasticcells will secrete human chorionic gonadotrophin (HCG). • This hormone sustains the corousluteum which continue to produce progesterone, maintaining the endometrium.

  32. Early Development and Implantation

  33. Gestation • The period of development in the mother’s body, lasting from conception to birth is called gestation. In humans, it is about 40 weeks. • Embryo – The developing offspring in the first 2 months of gestation • Fetus – development after 2 months

  34. Gestation • The embryo is contained, supported and protected by the amniotic sac and amniotic fluid.

  35. The Placenta • Develops from the trophoblast cells of the blastocyst • Bring maternal and fetal blood supplies together • Exchange is done by active transport and diffusio • Connected by the umbilical cord

  36. The Placenta • Movement across the placenta involves: • Respiratory Gases • Water • Excretory products • Antibodies

  37. The Placenta • Placenta is an endocrine gland • Produces HCG along with the blastocyst • HCG is to maintain the corpus luteum • secrete estrogen and progesterone for the first 16 weeks of pregnancy • corpus luteum breaks down • Placenta secretes estrogen and progesterone.

  38. The Placenta

  39. Birth • About 38 weeks, the fetus is ready for birth • Progesterone declines • Fetuswill send a signal to the extra-amniotic membranes, and prostagladins will be secreted • The hormones will cause the wall of the uterus to contract.

  40. Birth • Posterior pituitary releases oxytocin • More stretching, the more oxytocin will be secreted • Oxytocin stimulates the walls of the uterus to contract in a wave, to push the fetusdown • This process is known as labour • Last stage of birth is the expelling of the placenta or afterbirth.

  41. Hormonal Control of Birth and Gestation

  42. Methods of Detection and IVF • Pregnancy Test • Amniocentesis • In vitro fertilization • Ethical Issues?

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