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“Indifferent” ducts of embryo Y chromosome present Y chromosome absent penis testis ovary uterus vagina MaleFemale.

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Presentation on theme: "“Indifferent” ducts of embryo Y chromosome present Y chromosome absent penis testis ovary uterus vagina MaleFemale."— Presentation transcript:

1 “Indifferent” ducts of embryo Y chromosome present Y chromosome absent penis testis ovary uterus vagina MaleFemale

2 Determining gender Sex chromosomes determine gonadal sex (testis-determining factor) Phenotypic sex is depends on development of external genitalia

3 Undifferentiated genitalia At 7 weeks Differentiation of genitalia depends on whether testosterone is present

4 Intersex individuals experience opposite hormones during early development or are insensitive to normal hormones. Some examples: Androgen insensitivity Lack of enzyme for testosterone production Congenital adrenal hyperplasia (enzyme missing to produce cortisol, aldosterone. Steroids converted to androgens instead.)

5 Male reproductive anatomy

6 During fetal development, testes move from abdomen into scrotum Inguinal area is a common spot for hernias (intestine pokes through abdominal wall) The scrotum provides a cool area optimal for spermatogenesis

7 Epididymis Ductus deferens Seminiferous tubules The cells of Leydig in testes secrete testosterone (T) T secreted at puberty produces 2 o sex characteristics, maintains tracts & spermatogenesis Sperm production

8 Spermatogenesis: spermatogonia (2N) spermatozoa (N) Epididymis Ductus deferens Seminiferous tubules Sperm production

9 Lumen of seminifeous tubule Sertoli cell Spermatids Secondaryspermatocyte Primaryspermatocyte Spermatogonium Mitosis Meiosis Sertoli cell

10 Controlling sperm production Unlike females, males produce sperm from puberty onward Spermatogenesis controlled by LH and FSH

11 LH & FSH in males LH acts on Leydig cells for T prod’n FSH acts on Sertoli cells for sperm prod’n (inhibin provides negative feedback)


13 Causes of infertility Sperm production and viability influenced by: – Smoking, marijuana use – Alcohol abuse – Anabolic steroids, overly intense exercise, stress – Tight underwear, pants – Environmental pollutants (pesticides, lead, paint, radiation, heavy metals)

14 Spermatids become motile and are stored in epididymis and ductus deferens Sperm storage

15 Making something to swim in Seminal vesicles supply fructose, prostaglandins for muscle contraction, & fibrinogen Prostate gland secretes alkaline fluid and clotting enzymes Bulbourethral glands add mucus for lubrication Prostate gland Testis Ductus deferens Bulbourethral gland Urinary bladder Seminal vesicle

16 Signals for erection and ejaculation Arousal Pudenal nerves carry signals from penis to lower spinal cord & brain – Spinal reflex and brain send PNS signals to penile arterioles – Arousal causes muscle contractions that incr. physical stimulation – positive feedback Ejaculation Dramatic shift to SNS – contractions move semen to urethra and out



19 Female reproductive anatomy Ovaries produce estrogen, progesterone, and are site of oogenesis Estrogen: maintenance of the female tracts, 2 o sex characteristics, ova maturation and release

20 Oogenesis overview Oogonia divide mitotically Meiosis I produces a primary oocyte (diploid), surrounded by follicle cells These oocytes develop into secondary oocytes on a cyclical basis

21 Ovarian cycle Follicular phase - first half of cycle when follicles mature and are ovulated Luteal phase - second half of cycle when uterus is prepared for implantation

22 Primary follicle oocyte Follicle cells Looking within the ovary…follicular phase FSH and LH levels are increasing

23 Follicle cells secrete estrogen Dividing follicular cells Thecal cells Primary oocyte Looking within the ovary…follicular phase

24 antrum Antrum collects fluid with estrogen Estrogen inhibits FSH and LH, so FSH Looking within the ovary…follicular phase


26 Thecal cells Granulosa cells Antrum primary oocyte Late follicular phase High estrogen levels promote LH secretion w/ positive feedback loop


28 Late follicular phase Mature follicle Antrum Oocyte finishes meiosis I it now is a 2 o oocyte

29 Follicle remains secondary oocyte Egg is flushed out Pop! Ovulation!

30 corpus luteum Luteal phase Corpus luteum secretes progesterone and estrogen

31 Estrogen and progesterone Estrogen initiates preparation of endo- and myometrium, ‘prime’ uterus for progesterone (follicular phase) Progesterone endometrium vascularization, glycogen, decrease contractions (luteal phase) Progesterone inhibits LH and FSH – (this is how birth control pills work)

32 BCP links to breast cancer In 2002, estrogen was labeled a carcinogen Some studies show increased risk of breast, cervical, liver cancer in those taking BCP, some studies don’t. Ovarian, endometrium cancer risk reduced with BCP Modern BCP have less estrogen than earlier pills Risk drops once BCP are no longer taken

33 Changes in endometrium If the corpus luteum degenerates, progesterone drops and menstruation occurs Degenerating corpus luteum

34 What causes menstrual cramps? Prostaglandins are released to break down endometrium via uterine contractions, vasc. Prostaglandins: local messengers throughout body w many, many functions (Table 18-3) – intensifies feelings of pain (aspirin inhibits prost.) – incr. cortisol, inflammation


36 But if there are sperm around… Fertilization normally occurs within a day of ovulation Contractions of the myometrium help some sperm reach the oviduct acrosome in action

37 Embryo Trophoblast Implants the embryo Blastocyst Cleavage Fertilization Ovulation Implantation Embryo forms before reaching the uterus

38 Settling into the uterus… Blastocyst secretes chorionic gonadotropin Endometrium has glycogen, and becomes more vascularized from progesterone 40% of blastocysts never implant

39 Settling into the uterus… Trophoblast enzymes digest proteins of the endometrium. This carves a hole for implantation. Endometrium Trophoblast Embryo Endometrium

40 Placenta development Placenta = chorion from embryo and uterine lining from mother. These tissues interlock like ‘fingers’ Projections of chorion have capillaries to form placental villi. They extend into the mother’s blood.

41 Placenta development Gasses, wastes, nutrients diffuse bw capillaries of mother and fetus Drugs, pollutants, chemicals also diffuse mother’s blood Placentalvillus Amniotic sac Chorion

42 Figure 20.27 Page 791 Human chorionic gonadotropin (hCG) Estrogen Progesterone FertilizationDelivery

43 Getting ready for birth.... Relaxin from placenta softens the cervix and pelvis Uterus has mild contractions. Baby’s head is down in pelvis High levels of estrogen make the uterus more sensitive to oxytocin. Progesterone levels drop

44 Positive feedback with oxytocin Stretching the cervix causes more oxytocin to be released Oxytocin induces stronger contractions

45 Lactation

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