1. REPRODUCTIVE SYSTEM MALE AND FEMALE

2. Human Life Cycle Adult has 46 chromosomes 23 pairs = diploid
meiosis occurs in gonads -- leads to gametes -- each is haploid, has 23 chromosomes --each is unique because of certain steps in meiosis that create genetic variation -- meiosis is not mitosis
ZYGOTE = FERTILIZED EGG

3. Each pair is called a homologous chromosome
KARYOTYPE
Each pair is called a homologous chromosome
22 autosomes and one pair of sex chromosomes
XX = female; XY = male
Each pair has 2 alleles of each gene
Alleles are variant forms of a gene XY
Both alleles may be active or one may be silenced by “genomic imprinting” which refers to epigenetic changes (DNA methylation or modification of histones)

4. BARR BODIES
In females, one of the two X chromosomes is inactive.
This produces a visible Barr Body.
An easy way to visually determine the sex of a cell.

5. Sex Determination
A gene of the Y chromosome codes for sex-determining factor, which leads to the development of testes before day 50 Rare XX males: scientists discovered they had a region of Y chromosome inserted into X chromosome SRY for sex-determining Region of Y
Develop w/in 50 days

6. Klinefelter Syndrome
47 instead of 46 chromosomes
XXY
Due to nondisjunction
Failure of XY to separate in the father
Person is male, infertile
Lower than normal testosterone

7. Fetus gets only one chromosome, the X, from the mother
Turner’s Syndrome
Fetus gets only one chromosome, the X, from the mother
Nondisjunction results in O from father
Infertile
Lower than normal estrogen
Turner’s Syndrome XO

8. TESTICULAR FEMINIZATION SYNDROME
Normally functioning testes (inside body cavity); testosterone is normal, but is not under negative feedback control, and so a lot of it is produced and turns into estrogen
Cells lack testosterone receptor
Female genitalia develop
Vagina ends blindly
Uterus and fallopian tubes do not develop

9. Endocrine Regulation
Hypothalamus secretes GnRH
GnRH stimulates anterior pituitary to release LH + FSH (gonadotropins) “tropin” means “stimulating effect”
gonads are stimulated with release of LH when puberty begins. This stimulates the formation of sex hormones.
person becomes sexually mature, not necessarily emotionally mature.

10. OVERVIEW OF HORMONAL CONTROL

11. Female Reproductive Organs

12. Oogenesis
At 4-5 months of gestation, ovaries contain 6-7 million oogonia (egg-forming cells)
Most die
Others begin meiosis and become primary oocytes toward end of gestation
Oogenesis is arrested at prophase I of meiosis
Follicle = hollow ball of cells containing oocyte
400 will ovulate during lifespan

13. Oogenesis
In response to FSH stimulation, follicles get larger, becoming secondary follicles
Graafian follicle = the follicle that forms an antrum (fluid filled sac) and is ovulated
The primary oocyte completes meiosis I and is called secondary oocyte
Meiosis II begins, but is arrested at metaphase II

14. Zona pellucida is a barrier to sperm penetration
Oogenesis
After the secondary oocyte forms, layers of cells form around it (zona pellucida and corona radiata)
Zona pellucida is a barrier to sperm penetration
Corpus luteum forms
(yellow body)
Secretes estrogen and progesterone
Negative feedback to hypothalamus and pituitary shuts off further ovulation
Birth control pill is like the corpus luteum

15. Oogenesis
By the 10th – 14th day of cycle, ovulation occurs
If it is not fertilized, it degenerates in 1-2 days
If it is fertilized, it completes the second meiotic division
Fertilized egg is called the zygote

16. Menstrual Cycle
Approximately 28 days
Day 1 = first day of blood flow
Menstruation = shedding of endometrium, which becomes thickened due to estrogen and progesterone

17. Menstrual Cycle Changes occur in cycle
Follicular phase – day 1-13 – primary follicle grows (stimulated by FSH), ovary secretes estrogen; estrogen reaches a peak at day 13 – 14, which stimulates the pituitary to secrete LH (LH surge), which causes ovulation
Luteal phase – corpus luteum makes progesterone and estrogen

18. Changes occur in endometrium
Menstrual Cycle
Changes occur in endometrium
Proliferative phase – day 1-13 – increasing estrogen from ovary stimulate proliferation of endometrium
Secretory phase – combined action of estrogen and progesterone thickens the endometrium
Menstrual phase – absence of fertilization causes hormones to fall. Endometrium is not maintained.

19. Menstrual cycle

20. Additional information
Rhythm method of birth control – rise in temperature from LH (not reliable)
Ovulation test kit – based on the LH surge; LH is found in urine
Fertility pills – combinations of LH and FSH cause ovulation; may result in multiple eggs released
Women living together – pheromones released from nasal cavity may trigger hypothalamus to release hormones simultaneously

21. Additional information
Amenorrhea – lack of menstruation; possible causes: few energy stores (adipocytes). Adipocytes release leptin which stimulates GnRH. Stress also shuts off GnRH
Menopause – ovaries stop working; 50 is an average age, but differs among women

22. Over 300 million sperm enter the female at ejaculation.
Fertilization
Over 300 million sperm enter the female at ejaculation.
Only about 100 of these live to enter the fallopian tube.
Fertilization occurs in fallopian tube (aka oviduct or uterine tube)

23. pH, Ca2+ and cAMP in sperm increases higher pH activates the flagellum
Capacitation of sperm
In order to fertilize the ovum, a sperm must become capacitated. This takes at least 7 hours after ejaculation.
pH, Ca2+ and cAMP in sperm increases
higher pH activates the flagellum
Capacitated sperm are guided to the oocyte by chemotaxis and thermotaxis

24. Sperm Sperm Oocyte Sperm
(b) Sperm surround the oocyte, attacking its defensive barriers.
Oocyte
Sperm

25. Sperm must degrade zona pelucida (acrosome reaction)
Only nucleus enters egg
Zygote mitochondria are from the mother
Cytoplasmic RNA establish polarity

26. Ca2+ has several effects:
Acrosome reaction
When the sperm enters the oocyte, Ca2+ is released from endoplasmic reticulum.
A Ca2+ wave travels through the oocyte to the opposite side from the entry of the sperm
Ca2+ has several effects:
Prevents other sperm from entering the oocyte (polyspermy)
Activates oocyte to finish meiosis to become a haploid ovum

27. Journey of fertilized egg
Identical twins?
4-5 days
6-7 days

28. Human Chorionic Gonadotropin
During implantation, blastocyst releases hCG
hCG keeps the corpus luteum alive to continue releasing estrogen and progesterone.
Keeps the endometrium thick and vascular to house the blastocyst; prevents menstruation
Secretion of hCG declines by 10th week as placenta takes over hCG production to maintain the pregnancy.
hCG antibody is used in early pregnancy test kits.

29. Implantation
Trophoblast cells form the chorion
Trophoblast will help form placenta, and secretes hCG
DAY 6
DAY 9-10
DAY 6 – blastocyst attaches to uterine wall; trophoblast produces enzymes that penetrate wall
DAYS 9-10 – blastocyst is completely buried in endometrium; inner cell mass becomes disc

30. Inner cell mass begins to differentiate
1-2 weeks
16 DAYS
Inner cell mass begins to differentiate
Ectoderm – epidermis and neural tissue
Mesoderm – connective tissue and muscle
Endoderm – epithelium of lungs and gut

31. Gastrulation: germ layers form
Weeks 2-8
Yolk sac
Forms at
Week 2
23-13

32. Bird – yolk feeds bird; allantois is for waste
A Comparison of Human with Bird Sacs
HUMAN
BIRD
Bird – yolk feeds bird; allantois is for waste
Human – yolk and allantois become umbilical cord

33. Cytotrophoblast forms projections called chorionic villi
1-2 weeks
16 DAYS
Formation of placenta:
Cytotrophoblast forms projections called chorionic villi
Chorionic villi produce the chorion frondosum (next slide)

34. Chorion frondosum = contributes to the placenta

35. Decidual Reaction
Decidual reaction = formation of decidua basalis from endometrium
Decidua basalis
contributes to the placenta;
Joins with chorion frondosum to form placenta

36. Circulation of blood in the placenta
Umbilical arteries – send deoxygenated blood from fetus to placenta
Oxygenated blood returns to fetus through umbilical vein
Maternal blood is also delivered to/from placenta.
Maternal and fetal blood do not mix, but are separated by only two cell layers.
Molecules diffuse across tissues of the placenta for exchange.

37. Circulation of blood in the placenta
Umbilical arteries – send deoxygenated blood from fetus to placenta
Oxygenated blood returns to fetus through umbilical vein
Maternal blood is also delivered to/from placenta.
Maternal and fetal blood do not mix, but are separated by only two cell layers.
Molecules diffuse across tissues of the placenta for exchange.

38. Amniocentesis
Samples from the amniotic fluid can help diagnose genetic abnormalities such as Down syndrome.
Samples are taken at week 16

39. Chorionic Villi Sampling can be done at 10 – 12 weeks and provides a larger number of fetal cells

40. Pregnancy
Averages 38 weeks from fertilization
Takes 2 weeks for blastocyst to form
Weeks 3 to 8: embryonic period
Weeks 9 to birth: fetal period

41. release from pituitary
LABOR
Labor is initiated by rising levels of corticotropin-releasing hormone (CRH) from fetus and placenta
CRH triggers ACTH
release from pituitary
ACTH triggers cortisol and DHEAS release from adrenal cortex
Cortisol increases the secretion of more cortisol (pos. fdbk)

42. Production of surfactant.
LABOR
Cortisol causes
Fetal lung maturation
Production of surfactant.

43. Stretching triggers release of oxytocin
LABOR
Stretching triggers release of oxytocin
Cortisol and DHEAS trigger reactions that lead to:
increased sensitivity of uterus to oxytocin,
prostaglandins,
trigger gap junction formation.

44. Male Reproductive System

45. Vasectomy

46. Changes in Blood Flow Cause Erection
Cross section through relaxed penis
(a) Normally, smooth muscles encircling the arterioles leading into the penis are contracted, limiting blood flow.

47. Changes in Blood Flow Cause Erection
Cross section through erect penis
Sexual stimulation triggers the release of NO from parasympathetic axons into the corpora cavernosua and penile arteries and smooth muscle. NO activates guanylate cyclase, which converts GTP to cGMP, which closes Ca2+ channels. The lowered Ca2+ causes the relaxation of smooth muscles and vessel dilation, leading to erection.
(b) During sexual excitement, these muscles relax, and blood flows into spaces within the penis. The swelling penis squeezes off the veins leaving the penis, thereby increasing the pressure produced by fluids within the penis and causing it to become elongated and firm.

48. Nitric Oxide and Erection

49. Semen = Sperm + Secretions
Secretions from epididymis aid sperm maturation
Seminal vesicle secretes fructose and prostaglandins
Prostate-gland secretions buffer pH in the acidic vagina
Bulbourethral gland secretes mucus

50. The Structures Involved in Spermatogenesis
Section of the testis
Seminiferous tubules
Epididymis
Vas deferens
Cross section of a seminiferous tubule
Sertoli cells: Nourish the developing sperm
Spermatogonia
Leydig cells
Lie between the seminiferous tubules
Secrete testosterone
(a) A section of the testis, showing the location of the seminiferous tubules, epididymis, and vas deferens.
(b) Cross section of a seminiferous tubule. The walls of the seminiferous tubules are lined with Sertoli cells and spermatogonia. As spermatogonia undergo meiosis, the daughter cells move inward, embedded in infoldings of the Sertoli cells. There they differentiate into sperm (spermatazoa), drawing on the Sertoli cells for nourishment. Mature sperm are freed into the central cavity of the tubules for transport to the penis. Testosterone is produced by the interstitial cells in the spaces between tubules.