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Human Reproduction

Human Reproduction. (Chapter 9). Figure 9.1. A step sideways – global population. The Earth is currently experiencing the most population increase in Human history. 2.5 billion in 1955 to 6 billion in 1999 At current rate, will double within 30 years!

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Human Reproduction

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  1. Human Reproduction (Chapter 9)

  2. Figure 9.1 A step sideways – global population The Earth is currently experiencing the most population increase in Human history. 2.5 billion in 1955 to 6 billion in 1999 At current rate, will double within 30 years! Fastest growing nations have growth rates at or above 4% - this will double the countries population every 17 years

  3. Figure 9.2a A step sideways – global population A step sideways – global population

  4. Figure 9.2b A step sideways – global population

  5. Reproduction • How do Humans Reproduce? • Well, by combining egg and sperm of course. • How does this happen? • What Anatomical Structures are Required? • What regulates these structures? • How do hormones play a role?

  6. Male Reproductive System • The male reproductive system must provide: Sperm Production Sperm Maturation Sperm Delivery

  7. Testis--paired gonads within scrotum, sperm and steroids produced here. Epididymis--tightly coiled duct where sperm maturation occurs. Vas Deferens--delivers sperm through abdomen to ejaculatory duct. Urethra--duct through penis where sperm and urine exit

  8. Semen--seminal fluid, contains sperm, fluid and ATP producing nutrients (sugars). Prostate Gland--adds fluid to semen. Seminal Vesicles--contribute nutrients to semen. Bulbourethral gland--contributes mucoid fluid to semen.

  9. Penis • Penis--male organ required for intercourse. Composed of layers of connective tissue and skin surrounding the ducts and erectile tissue. • Erection is produced by the tissue filling with blood. • Ejaculation causes sperm to exit the urethra. The bladder is closed off at this time. • Each ejaculation releases approximately 400 million sperm.

  10. Circumcision • Cuts or otherwise removes some or all of the foreskin (prepuce) from the penis. • Circumcision predates recorded human history, with depictions found in stone-age cave drawings and Ancient Egyptian tombs. The origins of the practice are lost in antiquity. • Theories include that circumcision is a form of ritual sacrifice or offering, a sign of submission to a deity, a rite of passage to adulthood, a mark of defeat or slavery, or an attempt to alter aesthetics or sexuality. • Circumcision of males is a religious requirement of the Islamic and Jewish faiths

  11. Circumcision • The American Medical Association states that medical associations in the US, Australia, and Canada do not recommend routine “non-therapeutic” circumcision, which it defines as the non-religious, non-ritualistic, not medically necessary, elective circumcision of male newborns. • Why? • What about HIV ?

  12. Circumcision • Religion: • Circumcision is fundamental to Judaism. It is an essential component of Jewish practice and is a commandment obligatory under Jewish law for all Jewish males on the eighth day after birth unless health reasons force a delay. • In Islam, the timing of Muslim circumcision varies. • While circumcision may be performed at all ages from newborn period to adulthood, the medical profession has encouraged medical circumcisions in the first week after birth to reduce complications.

  13. Circumcision • Cultural: • Circumcision can be part of an initiation rite in some African, Pacific Islander, and certain isolated Australian aboriginal traditions. • Among the Urhobo people of southern Nigeria it is symbolic of a boy entering into manhood. The ritual expression, Omo te Oshare ("the boy is now man"), constitutes a rite of passage from one age set to another.

  14. Circumcision • HIV: • The most recent data indicate that circumcision is correlated with significantly reduced risks of HIV transfer during heterosexual intercourse. • Between 48% and 53% reduction, although the topic remains the subject of ongoing research and debate in the medical community. • There are also fears that some may mistakenly believe they will be protected against HIV through circumcision and see circumcision as a safe alternative to other forms of protection, such as condoms.

  15. Circumcision • In the USA: • WHY? • WHEN? • WHAT DO YOU THINK?

  16. Back to the male reproductive system.

  17. Sperm production • Sperm are produced in the testis. • Spermatogenesis--production of sperm • Testis contain Seminiferous Tubules--these are tightly coiled tubules where spermatogenesis occurs. • Interstitial cells produce testosterone.

  18. Sperm production is regulated by the hypothalamus. • Sperm production is regulated by the hypothalamus.

  19. Hormonal control of testes • Hypothalamus- secretes gonadotropin-releasing hormone (GnRH). • Stimulates the anterior pituitary to release • Follicle-stimulating hormone (FSH) • Promotes sperm production & release of Inhibin • Luteinizing hormone (LH)*** • ***Sometimes called interstitial cell-stimulating hormone (ICSH). This stimulates the production of testosterone. • All these hormones are involved in negative feedback that maintains the fairly constant production of sperm and testosterone.

  20. Female Reproductive System • The Female Reproductive system must provide: • Eggs • Site for sperm entry • Mechanism for sperm channeling • Place for embryo to grow • Mechanism for embryo to be nourished

  21. Female Reproductive System • Ovaries--produce eggs and steroid hormones. • Oviducts--conduct the egg to the uterus--fertilization occurs here. • Uterus--Womb, where we are developed. • Cervix--Opening to Uterus.

  22. Female Reproductive System • Clitoris--Female analog of the penis. This is also contains erectile and sensory tissue. • Vagina--site of sperm deposition, birth canal, exit for menstrual flow. • Vulva--External folds of skin that protect the vagina.

  23. Female Reproductive Cycles Hormone levels in women cycle on a monthly basis. This drives cycles required for reproduction. • Ovarian Cycle 2)Uterine Cycle

  24. Ovarian Cycle • Hormones drive the Ovarian Cycle. • The Ovarian Cycle drives the Uterine Cycle. • Ovarian Cycle: cycle of events required for oocyte development. • Ovarian Cycle: Follicle Maturation, Ovulation, Corpus Luteum Growth and Degeneration.

  25. Egg Maturation • Primary Oocyte--immature oocytes--200 million in a newborn girl! 400,000 at Puberty, 400 will mature to ovulation. • Secondary Oocyte—mature oocyte—Egg • Primary Follicle--holds oocyte and makes estrogen.

  26. Egg Maturation • Secondary Follicle--maturing follicle holds secondary oocyte and makes estrogen and progesterone. • Vesicular Follicle--follicle that will release the egg. • Ovulation--process of egg release. • Corpus Luteum--gland-like structure that makes mostly progesterone and some estrogen.

  27. Egg production is regulated by the hypothalamus. • Sperm production is regulated by the hypothalamus.

  28. Hormonal Control of Ovaries • Hypothalamus- secretes gonadotropin-releasing hormone (GnRH). • Stimulates the anterior pituitary to release • Follicle-stimulating hormone (FSH) • Luteinizing hormone (LH) • FSH Stimulates the follicle to produce estrogen. • LH Stimulates the corpus leuteum to produce progesterone. • Estrogenand Progesteronemaintain uterus and help regulate the hypothalamus. negative feedback!!!!!!!!

  29. Cycles drive Cycles • Ovarian Cycle: Monthly Follicle changes in the ovary that control the level of sex hormones and also control the uterine cycle. • Uterine Cycle: Monthly changes in the endometrium (lining of the uterus). • Uterine Cycle--Menstruation, Proliferation, Secretion.

  30. Ovarian cycle Days 1-13- FSH secretion Day 14 –OVULATION LH SPIKE Days 15-28 – LH increases corpus luteum forms Progesterone high s Ss

  31. Uterine Cycle s Days 1-5- Menstruation Day 6-13 – Endometrium rebuilds Days 15-28 –Endometrium thickens mucoid glands develop and secrete

  32. Hormone Levels Fluctuate • Low levels of estrogen and progesteronecause the endometrium to disintegrate--this causes menstruation. • The LH Surge promotes ovulation. • High levels of estrogen and progesterone cause the endometrium to thicken in the event of fertilization. • If implantation does not occur, estrogen and progesteronelevels fall--and the cycle starts all over again. • Drops in progesterone dramatically affect mood and hunger. • Fluctuating hormonal levels provide a challenge for many medication programs.

  33. Egg must develop and be released on ovulation day. Egg must be correctly positioned in the oviduct and attract sperm. Vaginal tract must activate sperm. Hormonal levels must be exact. Ensure only one sperm joins with egg. Fertilization

  34. Sperm must undergo capacitation--process of activation by substances in female vaginal tract fluids. Sperm motor from vagina up through cervix, uterus, to the oviduct. Many sperm attempt fertilization, only one succeeds (except for twins). Fertilization

  35. Egg-- Corona Radiata: Cells from follicle that nourished egg in ovary. Zona Pellucida: layer that covers plasma membrane--will form fertilization envelope Plasma Membrane: cell membrane around egg. Egg Nucleus: contains DNA Fertilization

  36. Sperm-- Head: Contains sperm nucleus and acrosome. Acrosome: Contains enzymes. Mid Piece: Contains Mitochondria Tail: Flagella made from Microtubules Fertilization

  37. Pregnancy • If viable sperm contact an egg at the time of ovulation fertilization will occur. • This “typically” occurs on day 14. Remember Day 1 is first day of menstruation. • The fertilized egg will implant on day 6. • The new embryo will begin to produce HCG--Human Corionic Gonadotripin. • Wives tales and morning sickness.

  38. Infertility • Infertility can be attributed to both male and females (about 40% each, 20% together). • Pelvic inflammatory disease, endometriosis, and blocked oviducts are common causes in females. • Low sperm counts and abnormal sperm, diseases (mumps), radiation, chemical mutagens, high testes temperatures and psychoactive drugs are common causes in males. • Endocrine-Disrupting Contaminants: Environmental Estrogens, or Hormone Disruptors are having an increasing affect on our fertility.

  39. Endometriosis • Extremely painful condition--affects 3% of women of reproductive age. • Tissue from “backwards” menstrual flow leaks out of oviduct into abdominal cavity. • Tissue latches onto ovaries, bowel, bladder, wall of vagina and nerves. • Tissue responds to hormones and monthly cycles. • Tissue growth and break down produces scars. • Scars lead to infertility.

  40. Figure 9.12 Outline of in vitro fertilization

  41. Contraception

  42. Abstinence is most effective! Tracking cycles is 98% effective--temps rise with LH surge. No prevention--statistically 30% of sexually active women without any form of prevention will conceive. Birth Control Pills--estrogen and progesterone on a daily basis, this shuts down LH and FSH, no ovulation! How do you think all this extra estrogen will affect the woman? IUD--plastic implant that prevents fertilization and implantation. Preventing Pregnancy

  43. Diaphragm--fits over the cervix and prevents sperm entry. Use with spermicidal for 6 hours. Condoms--best all around defense against both sexually transmitted diseases and unwanted pregnancy. Every responsible sexually active individual* should use these. Contraceptive Implants and Depo-Provera--synthetic progesterone prevents ovulation. Maintain Control! Alcohol impairs judgment. “Everyone” looks better after a couple of beers! Ecstasy--this “love” drug is thought to destroy serotonin and dopamine generating centers of the brain--Parkinson's! Preventing Pregnancy

  44. Figure 9.13 (1) Preventing Pregnancy

  45. Figure 9.13 (2) Preventing Pregnancy

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