1. Topic 6.6 IB Biology 2 Van Roekel
Reproduction
Topic 6.6
IB Biology 2
Van Roekel

2. BILL
What are the main purposes of the reproductive systems in the body (be appropriate)
Produce sperm cells in male, egg cells in females
Allow for fertilization (joining of an egg cell and sperm cell) and gestation (pregnancy and giving birth)
ensure that offspring have genetic variety by combining half of the genetic material from one parent with half the genetic variety from another.

3. Statements
6.6.1 Draw and label diagrams of the adult male and female reproductive systems.
6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinizing hormone), estrogen and progesterone.
6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and thickening of the endometrium.
6.6.4 List three roles of testosterone in males.
6.6.5 Outline the process of in vitro fertilization (IVF).
6.6.6 Discuss the ethical issues associated with IVF.

4. Key Points About Reproduction
Reproduction depends entirely on the union of a male gamete/sperm and female gamete/egg (fertilization) to produce a zygote.
Half of genetic material is derived from each contributing parent…leading to genetic diversity.
Hormones play many significant roles in development of sexual dimorphism and regulation of sexual physiology.

5. 6.6.1 Draw and label diagrams of the adult male and female reproductive systems. pg.185

6. Female pg. 186

7. Points about the Menstrual Cycle
6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinizing hormone), estrogen and progesterone.
Points about the Menstrual Cycle
Prepares the ovaries for ovulation and the uterus for implantaion
Lasts approximately 28 days…time between the females release of the egg from the ovaries (known as ovulation).
Egg must be released to the endometrium (the inner lining of the uterus.)
The endometrium is highly vascularized which allows implantation if egg is fertilized
If egg is not fertilized, endometrium breaksdown, which leads to menstrual bleeding
Menstruation is a sign that pregnancy has not occurred.

8. Bill
What hormones are responsible for regulating the menstrual cycle and what does each do?
Gonatrophic Releasing Hormone – stimulates release of FSH and LH
Follicle Stimulating Hormone – develops the oocyte and follicles, while preparing for ovulation
Luetinizing Hormone – spikes and causes the ovulation of oocyte
Estrogen – causes vascularization of endometrium
Progresterone – maintains vascularization of endometrium

9. Hormones of Menstrual Cycle
Hypothalamus is the control center for the menstrual cycle.
Gonadotrophin Releasing Hormone (GnRH) causes pituitary gland to secrete follicle stimulating hormone (FSH) and Leutinizing Hormone (LH) to be released into the blood stream.
Both hormones target ovaries.

10. Anterior Pituitary Hormones:
Follicle Stimulating hormone (FSH)
Stimulates the development of a primary follicles, which surround the oocyte (egg) providing protection and nutrients.
Develops the oocyte in the follicle and Produces follicular fluids.
Increases the number of follicular cells which in turn produce estrogen, which causes vascularization of endometrium.

12. Anterior Pituitary Hormones:
Luteinizing Hormone (LH):
high LH is associated with a resumption of meiosis in the oocyte. Meiosis has been arrested in Prophase I since the embryonic stage. Only at the point of fertilization does meiosis complete.
surges in mid cycle (12 days) to bring about ovulation, or release of oocyte (surrounded by follicles) from ovary.
Some follicle cells remain in the ovaries and develop into the corpus luteum. These cells also release progesterone, which maintains the thickened vascularized endometrium

14. Hormonal Control of Menstrual Cycle
As long as Progesterone is produced, it prevents break down of endometrium and implantation can still occur
High levels of Estrogen and Progesterone are negative feedback signals w/ hypothalamus, as it will not produce GnRH, which in turn will not allow FSH and LH to affect ovaries
Assuming no pregnancy, corpus luteum breaks down, progesterone and estrogen levels decline, endometrium breaks down causing menstruation
Drop in estrogen and progesterone levels signals the hypothalamus to release GnRH and another menstrual cycle begins

16. Hormone levels during menstruation

17. Hormone levels during menstruation

18. Corpeus Luteum
The corpus luteum is essential for establishing and maintaining pregnancy in females. The corpus luteum secretes progesterone, which is a steroid hormone responsible for the vascularization of the endometrium (its development) and maintenance, respectively.
When egg is not fertilized
If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays (after approximately 14 days in humans).
The uterine lining breaks down without progesterone and is expelled through the vagina (in humans and some great apes, which go through a menstrual cycle).
When egg is fertilized
If the egg is fertilized and implantation occurs, blastocyst secretes the hormone human chorionic gonadotropin (hCG, or a similar hormone in other species).
Human chorionic gonadotropin signals the corpus luteum to continue progesterone secretion, thereby maintaining the thick lining (endometrium) of the uterus and providing an area rich in blood vessels in which the zygote(s) can develop. From this point on, the corpus luteum is called the corpus luteum graviditatis.

20. 6.6.4 List three roles of testosterone in males
1. Week 7 of embryonic development, testosterone initiates the development of male genitalia.
2. Around mid teens, testosterone initiates the development of secondary sexual characteristics
increase in muscle mass
increase in the length of the long bones (height)
increase in the length of the vocal cords (voice deepens)
spermatogenesis
growth of the penis and testis
3. Post puberty testosterone maintains the production of sperm cells and the male sex drive.

21. Fertilization
Typically occurs in fallopian tubes hours after ovulation
Resulting zygote travels to the endometrium of the uterus, while already beginning to divide by mitosis
Embryo implants into vascular tissue of endometrium and pregnancy begins

22. Problems with Fertilization
Low sperm counts
Males w/ impotence (failure to achieve/maintain an erection)
Females who cannot ovulate normally
Females with blocked fallopian tubes
Reproductive technologies are able to help overcome these situations

23. In-vitro Fetrilization (IVF)
Woman injected with FSH for about 10 days, causing production of many follicles, and allows for several eggs to be harvested
Man donates his sperm into an external container
Fertilization occurs in separate culture dishes and observations reveal which ova are fertilized and appear normal and healthy
2-3 healthy embryos inserted into woman’s uterus for implantation

24. Ethical Issues Pro IVF Anti IVF Enables couples to have children
Embryos not healthy can be eliminated to increase chance of implantation
Genetic screening is possible to eliminate chance of passing on some genetic diseases
IVF tech can advance and lead to further benefits of reproduction
Embryos not implanted are frozen or destroyed
Legal issues concerning frozen embryos when couples split
Genetic screening could lead to society choosing desirable traits
Bypasses natures way of decreasing genetic frequency of reproductive/genetic problems
Multiple births and problems associated with multiple births are more likely with IVF than natural conception

25. GATTACA https://www.youtube.com/watch?v=ZppWok6SX88

26. 11.4 Reproduction

27. Assessment Statements
Annotate a light micrograph of testes to show the location of interstitial cells (leydig cells), germinal epithelium cells, developing spermatozoa, and Sertoli cells
Outline the process involved in spermatogenesis within the testes, including mitosis, cell growth, meiosis, and cell differentiation
State the role of LH, FSH, and testosterone in spermatogenesis
Annotate a diagram of the ovary to show the location and function of germinal epithelium, primary follicles, mature follicle, and secondary oocyte
Outline the processes involved in oogenesis within the ovary, including mitosis, cell growth, two divisions of meiosis, unequal division of cytoplasm, and degeneration of polar bodies
Draw and label the structure of a mature sperm and egg
Outline the role of the epididymis, seminal vesicle, and prostate gland in the production of semen
Compare the process of spermatogenesis and oogenesis, including the number of gametes and the timing of the formation and release of gametes
Describe the process of fertilization, including acrosome reaction, penetration of the egg membrane by a sperm, and the cortical reaction
Outline the role of HCG in early pregnancy
Outline early embryo development up to the implantation of the blastocyst
Explain how the structure and functions of the placenta, including its hormonal role in secretion of estrogen and progesterone, maintain pregnancy
State that the fetus is supported and protected by the amniotic sac and amniotic fluid
State that materials are exchanged between the maternal and fetal blood in the placenta
Outline the process of birth and its hormonal control, including the changes in progesterone and oxytocin levels and positive feedback.

28. Spermatogenesis and the Testes
Spermatogenesis: the production of sperm cells, which occurs within the testes
Testes located outside the body to provide cooler temps for spermatogenesis
Occurs within seminiferous tubules
Spermatogonia: diploid germinal epithelial cells that will undergo mitosis (to produce more spermatogonia) or they will undergo meiosis (to produce 4 haploid spermatozoa, aka sperm cells)

29. Testes Leydig Cells: Produce testosterone and other hormones
Germinal Epithlium Cells: spermatogonia
Spermatozoa: sperm cells
Sertoli Cells: provide nutrients to spermatozoa during sperm differentiation

31. Spermatogenesis
Spermatogonia cells contain 23 pairs of chromosome (46 total) – undergo normal parts of cell cycle (G1, S, G2)
Meiosis occurs after DNA replication to cut number of chromosomes in half (23 total chromosomes), making spermatozoa (1 spermatogonia  4 spermatozoa)
Spematozoa must differentiate into fully functioning sperm cell (spermatozoon) inside seminiferous tubule, attached to sertoli cells for nutrients
Flagellum for motility
Acrosome contains enzyme necessary for fertilization
As sperm cells develop, they move closer to lumen of seminiferous tubule
Once development is completed, they detach from sertoli cells and carried to epididymis where it is stored

32. Hormones and Spermatogenesis
Leutinizing Hormone (LH) stimulates Leydig Cells to produce testosterone
Follicle Stimulating Hormone (FSH) and testosterone stimulate meiotic divisions of spermatogonia into spermtozoa
Sperm cell production starts at puberty and continues throughout life, producing millions of sperm cells a day

33. Bill- How are sperm cells formed?
LH and FSH stimulate production of testosterone and meiotic division of spermatogonia cells forming spermatozoa
Spematozoa must differentiate into fully functioning sperm cell
Flagellum for motility
Acrosome contains enzyme necessary for fertilzation
As sperm cells develop, they move closer to lumen of seminiferous tubule
Once development is completed, they detach from sertoli cells and carried to epididymis where it is stored

35. Mature Sperm Cell Flagella provides motility for swimming
Mitochondria provides ATP for energy for swimming
Head contains haploid nucleus with half number of chromosomes
Acrosome contains hydrolytic enzymes to help with fertilization process
Small size allows them to swim great distances

37. Production of Semen
Semen: Fluid that is ejaculated during intercourse, contains sperm cells and fluids that assist in reproduction
Epididymis: Stores sperm cells allowing them to gain motility
Vas Deferens: sperm moves from epididymis to urethra through vas deferens
Seminal Vesicles: Add large volume of fluid (70%) that contains high concentration of fructose, needed to provide energy to sperm cells to swim to ovum
Prostate Gland: Adds more fluid (30%) that contains alkaline and helps sperm cells survive environment in female vagina
Urethra: excretory tube, site of ejaculation

38. Oogenesis and the Ovary
Oogenesis: the production of ovum (egg cells) through meiosis
Produces four haploid cells, however, only one becomes an egg cell
3 are too small to produce zygote upon fertilization and become polar bodies (containers for divided chromosomes after meiosis)
1 is very large and becomes egg cell

39. Oogenesis before birth
During fetal development, oogonia cells (diploid) undergo mitosis, increasing number of cells in ovary
Oogonia cells grow into larger cells called primary oocytes (diploid), which will undergo initial steps of meiosis (through prophase 1, then pauses)
Follicle cells undergo mitosis and a single layer surrounds primary oocytes, forming primary follicle
Females born with half a million primary follicles

40. Oogenesis and Menstrual Cycle
Each menstrual cycle, primary follicle finishes meiosis I and forms 1 secondary oocyte and polar bodies
Follicle cells begin dividing and forming 2 rings with a fluid filled cavity around secondary oocyte
Secondary Oocyte begins Meiosis II, but again is paused during prophase forming Graafian Follicle
Secondary Oocyte and its inner follicle ring are released during ovulation and only completes Meiosis if fertilized by sperm cell
* Be able to relate these steps to what happens in menstrual cycle and hormones that are used.

42. Mature Ovum Largest cell in body by volume
Unequal distribution of cytoplasm ensured on cell has all nutrients, cytoplasm, and organelles necessary for a new life.
Haploid nucleus/nucleolus
Nutrients are referred to as yolk
Follicle cells, protect and nourish egg
Cortical granules ensure only one sperm cell can fertilize egg
Zona pellucida (layer of glycoproteins) becomes impermeable to other sperm cells upon fertilization

45. Spermatogenesis vs. Oogensis
Pg. 312

46. Fertilization

47. Fertilization
The union of haploid male and female gametes to form a diploid zygote
Typically occurs in the Fallopian Tube
Takes many sperm cells to accomplish fertilization, however only one can fuse its membrane with the egg cell to create a zygote

48. Fertilization
Many sperm cells are needed to penetrate the follicle cell layer.
Several Sperm cells gain access to zona pellucida and release hydrolytic enzymes, enabling the cells to penetrate the zone and reach plasma membrane
One sperm cell reaches the plasma membrane of secondary oocyte
Plasma membranes fuse together and initiates the cortical reaction

49. Fertilization – Cortical Reaction
Cortical granules fuse with cell membrane and release enzymes, making the zona pellucida impermeable to other sperm cells
Takes place immediately after first sperm cell fuses with egg cell and ensures only one sperm cell fertilizes egg
Egg now completes meiosis II as haploid nucleus from sperm cell enters the egg
Resulting in a diploid zygote

51. Pregnancy
Fertilization triggers mitotic division in zygote, which takes roughly 5 days to reach uterus
Embryo consists of about 100 cells by time implantation occurs (7 days after fertilization), which appear as a ball of cells, called a blastocyst
Blastocysts consist of:
Trophoblast – surrounding layers of cells that will help form fetal portion of placenta
Inner Cell Mass – interior cells located towards one end of blastocyst that will become body of embryo
Fluid filled cavity

53. Pregnancy - HCG
Human Chorionic Gonadotrophin (HCG): hormone secreted by embryo that signals to corpus luteum, causing it to maintain secretions of estrogen and progesterone
Maintains endometrium, which will form placenta after implantation

54. Pregnancy – Placenta
Forms from trophoblast layer of blastocyst, and the endometrium of mother
Two fetal blood vessels within umbilical cord carry fetal blood to placenta and exchanges materials with mother, which are brought back using a separate fetal blood vessel
Embryo passes CO2, urea, water, and hormones to mother
Mother passes O2, nutrients, water, hormones, vitamins/minerals, alcohol/drugs (if taken), and viruses (if infected)
At no point does blood mix, only materials are exchanged

56. Pregnancy - Placenta
Placenta will also act as an endocrine organ during pregnancy, secreting estrogen and progesterone
Functions to maintain vascularized endometrium and provide rich blood supply to embryo

57. Pregnancy – Amniotic Fluid
Amniotic sac surround embryo as it continues to grow and develop
Amniotic Fluid inside sac functions to:
Cushion embryo from blunt force applied to mother’s abdomen
Provide environment for movement allowing exercise, muscular and skeletal development
Thermal stability (mainly water, so has excellent temperature stability)
General support so that the embryo does not experience any excess pressure

58. Hormonal Events @ Birth
Physiological events preparing for birth are called parturition
Progesterone levels decrease, and the hormone oxytocin is secreted from posterior pituitary gland
Initial low levels of oxytocin are associated with first contractions of uterus
Each uterine contraction signals to posterior lobe of pituitary to produce more oxytocin
Higher levels of oxytocin cause more intense and frequent contractions
This is a positive feedback mechanism and will continue and only stops when birth occurs and uterus no longer has something to contract on.

59. Major Events @ Childbirth
Major Hormone Change (discussed above)
Dilation/Opening of Cervix to 10 cm
Baby positioned head first, face down
Shoulders typically widest part to pass through birth canal
Afterbirth is name of expelled placenta
Lactation (breast milk production) begins soon after birth.