Chapter 46 ~ Reproduction

Skill: Annotate diagrams of the male and female reproductive system to show names of structures and their functions.

Male Reproductive System: Structure and Function: Testes~ male gonads (produce sperm and hormones Seminiferous tubules~ sperm formation Leydig cells~ secrete testosterone Epididymis~ sperm develop motility and mature Scrotum~ helps regulate temp. Vas deferens (sperm duct)~ sperm propelled by peristalsis Exocrine glands: Seminal vesicle~ adds fluids and fructose to sperm. Prostate gland~ adds anticoagulant; nutrients, more fluids Bulbourethral glands~ acid neutralizer Penis/urethra~ semen delivery

• Skill: Annotate diagrams of the male and female reproductive system to show names of structures and their functions.

Testosterone A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone. Roles of testosterone Pre-natal development of male genitalia Sperm production Development of secondary sex characteristics

Female Reproductive System: Structure and Function The Human Female Ovaries~ female gonads– make eggs Follicle~ one egg surrounded by one or more layers of follicle cells that nourish and protect egg cell Corpus luteum~ post-ovulation tissue of follicle– secretes hormones (estrogen and progesterone) Oviducts/Fallopian tubes~ where fertilization occurs Uterus/endometrium~ womb/lining Cervix/vagina~ sperm receptacle Be able to annotate

Annotate: The female reproductive system

Female hormones Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones.

Ovulation and the menstrual cycle Really cool 3d ovulation animation video: http://catalog.nucleusinc.com/generateexhibit.php?ID=67312&ExhibitKeywordsRaw=&TL=&A=2

The Menstrual Cycle Estrous cycles/estrus (many mammals) “heat”, endometrium reabsorbed by body. Menstrual cycle: involves menstruation: shedding of endometrium. Menstrual cycle~ (Know the hormones!) FSH causes: follicle growth estrogen secretion Estrogen: Repairs uterine lining after menstruation Stimulates LH secretion (when levels peak) The roles of FSH, LH, estrogen and progesterone in the menstrual cycle are expected.

LH (luteinizing hormone) causes: Ovulation less estrogen More progesterone Follicle to develop into corpus luteum (continues releasing estrogen and progesterone.) Progesterone: maintains uterine lining (endometrium) to prepare for implantation. If no implantation, estrogen and progesterone levels fall, causing menstruation and cycle begins again.

Not in course guide anymore: Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between hormone levels and ovulation, menstruation, and thickening of the endometrium

Menstrual Cycle Menstrual Cycle Animation http://www.pbs.org/wgbh/amex/pill/sfeature/sf_cycle.swf Another http://www.sumanasinc.com/webcontent/animations/content/ovarianuterine.html

In Vitro Fertilization (IVF) Drug injections stop menstrual cycle Large doses of FSH stimulate development of many follicles (rather than one as in normal cycle) Superovulation… HCG is injected to mature the oocytes in the follicles and loosen them so they can be retrieved. Oocytes are retrieved (an invasive procedure) Collect and Prepare the Sperm – the healthiest ones are concentrated during preparation. Inseminate Eggs Incubate fertilized eggs Transfer successful Embryos to the Uterus with a long plastic tube Pregnancy test for implantation http://www.sumanasinc.com/webcontent/animations/content/invitrofertilization.html Discuss the Ethical Issues associated with IVF!

Application: William Harvey’s investigation of sexual reproduction in deer. William Harvey failed to solve the mystery of sexual reproduction because effective microscopes were not available when he was working, so fusion of gametes and subsequent embryo development remained undiscovered. Debunking the ’Soil and Seed’ Theory  William Harvey studied the sexual organs of female deer after mating in an effort to identify the developing embryo He was unable to detect a growing embryo until approximately 6 – 7 weeks after mating had occurred He concluded that Aristotle’s theory was incorrect and that menstrual blood did not contribute to the development of a fetus Harvey was unable to identify the correct mechanism of sexual reproduction and incorrectly asserted that the fetus did not develop from a mixture of male and female ‘seeds’

Topic 11.4: Sexual Reproduction (HL only)

Topic 11.4: Sexual Reproduction (HL only)

Annotate a light micrograph to show the location and function of: interstitial cells (Leydig cells) –produce testosterone germinal epithelium cells constantly divide by mitosis making diploid cells developing spermatozoa –become viable sperm Sertoli cells.– nurse cells (provide nutrients to developing sperm)

Annotate a light micrograph to show the location and function of: interstitial cells (Leydig cells) germinal epithelium cells developing spermatozoa Sertoli cells. Note: Developing sperm move toward the lumen (center) of the seminiferous tubule

Spermatogenesis Constant from puberty until death! Germinal epithelium cells (Primordial germ cells) (2N)~ differentiate into…. Spermatogonia (2N)~ stem cells that give rise to sperm Repeated mitosis into…. Primary spermatocyte (2N) Meiosis I produces… Secondary spermatocytes (1N) Meiosis II produces… Spermatids (1N) not fully developed. Development helped by Sertoli cells Sperm cells (1N) http://highered.mcgraw-hill.com/olc/dl/120112/anim0043.swf 20

The Ovary Annotate to show the location and function of: Germinal epithelium Primary follicles Mature follicle Secondary oocyte

Oogenesis in ovary Germinal epithelium (Primordial germ cells) (2N)– Undergo Mitosis and differentiation to make… More diploid cells (oogonia) which develop into… Primary oocytes (2N) Stopped at prophase I of meiosis I Surrounded by a layer of follicle cells. Primary oocyte + follicle cells = primary follicle All 400,000 primary follicles formed before birth 22

Between birth & puberty; egg cells and follicles grow Every menstrual cycle, a few follicles develop. Here’s how: FSH (follicle stimulating hormone) causes growth of follicles; Primary oocyte completes meiosis I forming two haploid cells: A small polar body (dies) Secondary oocyte – 1N (undergoes prophase II of meiosis then stops.) Follicle ruptures (ovulation) and releases secondary oocyte into oviduct. After fertilization, Meiosis II is completed. This forms 2 cells: Ovum (the egg, already fertilized) 2nd polar body (dies) Note: Polar bodies degenerate

Annotate: a mature egg Note: The Zona pellucida is composed of glycoproteins. With the cortical granules they will be involved in the acrosome reaction at fertilisation

Annotate: a mature sperm Acrosome

Compare Spermatogenesis to Oogenesis Millions produced daily released during ejaculation Begins during puberty Continues until death 4 sperm produced by meiosis One produced every 28 days (approx.) Released on about day 14 of cycle All primary follicles produced as a fetus. Production stops at menopause One egg produced by meiosis (and 2 polar bodies) http://wps.aw.com/bc_martini_eap_4/40/10469/2680298.cw/content/index.html

Fertilization Arrival of sperm at egg Sperm break through layers of follicle cells Acrosome reaction~ acrosome releases hydrolytic enzymes which digest the zona pellucida, allowing the sperm in. Fusion: Egg and sperm plasma membranes fuse and sperm nucleus enters egg. Fast block to polyspermy~ membrane depolarization prevents multiple fertilizations…. Cortical reaction~ enzymes from cortical granules make zona pellucida harden and creates a... Slow block to polyspermy (created by development of fertilization membrane). A zygote has been produced. C:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 38 BDOL IC

Early embryo development Cell division (Mitosis) continues until a blastocyst (hollow ball of cells) is formed. The blastocyst will implant in uterus. Video: http://www.pbs.org/wgbh/nova/miracle/program.html Taking Shape

Pregnancy Gestation~ pregnancy Begins at implantation of blastocyst in endometrium of uterus. 1st trimester:(1st 3 months) Main period of organogenesis fetus (week 8) HCG (human chorionic gonadotropin) hormone– secreted by embryo– maintains progesterone secretion by ovary (during early pregnancy) 30

The placenta and umbilical cord Placenta– organ with embryonic and maternal blood vessels (nutrient, gas & waste diffusion) Placental villi- contain fetal capillaries Intervillus spaces– where maternal blood flows NOTE: The placenta secretes estrogen and progesterone to maintain the endometrium Umbilical cord Umbilical vein carries oxygenated, nutrient-rich blood to baby Umbilical arteries carry wastes and CO2 away from baby http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000101&ptid=17 http://catalog.nucleusinc.com/generateexhibit.php?ID=69893&ExhibitKeywordsRaw=&TL=&A=2

http://www.childrenshospital.org/az/Site636/mainpageS636P0.html

Amniotic Sac and amniotic fluid Supports and protects fetus

Birth End of pregnancy signalled by drop in progesterone Oxytocin is produced, causing Labor~uterine contractions Positive feedback increases oxytocin production and contractions. Note: Estrogen increases oxytocin receptors in uterus

Animal Reproduction comparisons Application: The average 38-week pregnancy in humans can be positioned on a graph showing the correlation between animal size and the development of the young at birth for other mammals. Spectrum ranging from Altricial species: newborns are helpless to Precocial species: newborns are mobile, aware etc. Fertilization in animals can be internal or external.

Nature of science: Assessing risks and benefits associated with scientific research—the risks to human male fertility were not adequately assessed before steroids related to progesterone and estrogen were released into the environment as a result of the use of the female contraceptive pill. (4.8)

End of IB stuff

Ultrasound http://health.howstuffworks.com/adam-200128.htm

Lutenizing Hormone: stimulates secretion of testosterone by testes Outline the origin and the role of the follicle stimulating hormone (FSH), testosterone, and lutenizing hormone (LH) in spermatogenesis. Follicle Stimulating Hormone: stimulates primary spermatocytes to undergo the first division of meiosis. Lutenizing Hormone: stimulates secretion of testosterone by testes Testosterone: stimulates development of secondary spermatocytes into mature sperm. Origin: FSH and LH =Pituitary Testosterone = testes

Odd Reproductive cycles Parthenogenesis unfertilized egg development; haploid, sterile adults (honeybees) Hermaphroditism both male & female reproductive systems; sessile & burrowing organisms (earthworms) Sequential hermaphroditism reversal of gender during lifetime •protogynous (female 1st) •protandrous (male 1st)