1. Reproduction Introduction
sexual determination, differentiation and development
Hormones and male reproduction
Hormones and female reproduction
Hormones of pregnancy, parturition and lactation

2. Parents with diploid somatic cells Offspring with diploid
Female
Male
Meiotic division
of germ cells
Meiotic division
of germ cells
Haploid ovum
Haploid sperm
Fertilization
Diploid zygote
Mitosis
Offspring with diploid
somatic cells
Fig. 16-1, p.707

5. Human Chromosome Karyotype

6. Sexual determination, differentiation and development
Sex determination
Genetic sex
established at the time of conception
governs the development of gonadal sex
two most common chromosomal sex-determining systems:
Mammalian sex determination means testis determination—TDF (SRY)

7. Sex Determination Chromosomal Sex Determination
XO/XX systems
(Grasshoppers)
XX/XY systems
(Some Plants, Insects, Reptiles, all Mammals)
ZZ/ZW systems
(Birds, Moths, Some Amphibians and Fish)

8. Simple molecular pathway for sex determination in the mammalian gonads
Nature Medicine 14, (2008)

9. Evolution of the Y chromosome and SRY

10. Independent origins of sex chromosomes in birds, snakes, and mammals.
Vallender E J , Lahn B T PNAS 2006;103:
©2006 by National Academy of Sciences

11. Temperature-Dependent Sex Determination

14. Fig. 16-6, p.716

16. Sexual determination, differentiation and development
Sexual differentiation
begins with the establishment of chromosomal sex at fertilization, followed by the development of gonadal sex and culminating in the formation of sexual phenotypes
Differentiation of Gonads
differentiation of testis requires TDF
Differentiation of accessory sex organs and external genitalia
mullerian-inhibiting hormone
testosterone

17. Sexual determination, differentiation and development

18. Sexual determination, differentiation and development

19. Sexual determination, differentiation and development
Differentiation of the brain
male vs female
preoptic area
gonadotropins secretion pattern
sexual behavior
induced by testosterone
female patterns are predetermined and male patterns are induced by androgen during critical period

21. Sexual determination, differentiation and development

22. Sexual determination, differentiation and development
Puberty
acquisition of reproductive capability and is manifested by appearance of secondary sexual characteristics
hormones of the brain-pituitary-gonadal axis
appearance of secondary sexual characteristics
rapid body growth
Hormonal control of puberty
Brain is likely the site of activation during puberty
pulsatile GnRH secretion
sensitivity to negative feedback of gonadal steroids
melatonin may control the timing of puberty

23. Sexual determination, differentiation and development

24. Fig. 16-8, p.719

25. Male reproduction Contains seminiferous tubules
3 major types of cells: germ cells, Sertoli cells and Leydig cells
Leydig cells: produce androgens
Sertoli cells: support germ cells development and differentiation

26. Male reproduction Androgen production mainly produced in Leydig cells
cholesterol serves as the substrate
main androgen is testosterone
function of androgens: act in one of 3 forms, DHT, T and E2
sex determination and differentiation
male reproductive organs and secondary sexual characteristics
spermatogenesis
feedback on gonadotropin

27. Table 16-2, p.720

28. Male Reproduction Spermatogenesis
differentiation of spermatogonia to spermatozoa
involves three steps
proliferation of spermatogonia
meiosis of spermatocytes to form spermatids
differentiation of spermatids to form spermatozoa (spermiogenesis): morphological remodeling

29. Fig. 16-9, p.721 Mitotic Proliferation Meiosis Packaging Stages
Spermatogonium
Chromosomes in each cell 2n
(diploid number;
single strands)
One daughter cell remains
at the outer edge of the
seminiferous tubule to
maintain the germ cell line
One daughter cell moves
toward the lumen to produce
Spermatozoa
Spermatogonia 2n
(diploid number;
single strands) 2n
(diploid number;
doubled strands)
Primary
Spermatocytes
First meiotic
division
Secondary
Spermatocytes n
(haploid number;
single strands)
Second meiotic
division
Spermatids n
(haploid number;
doubled strands)
Spermatozoa n
(haploid number;
single strands)
Fig. 16-9, p.721

30. Fig , p.722

31. Gonadotropin-releasing hormone
Hypothalamus
Gonadotropin-releasing hormone + — —
Anterior pituitary
LH-secreting
cells
FSH-secreting
FSH LH
Sertoli
cell
Leydig
Spermatogenesis
Testes +
Inhibin
Testosterone
Fig , p.723

32. Male reproduction Regulation of steroidogenesis
FSH is a major regulator, especially in the initiation of spermatogenesis
increases the size of testis
stimulates the replication of spermatogonia
increases LH-R #, contribute to T production
Testosterone is essential for maintenance of spermatogenesis
Activin: replication of spermatogonia
Inhibin: inhibits differentiation of spermatogonia

33. Male reproduction Regulation of androgen production
LH: major regulator
Increases cholesterol transport into inner mitochondrial membrane
increases enzyme activity (SCC, 3b-HSD)
FSH: enhance LH-R#, protentiates LH effect
Activin: increases basal T but inhibits LH-induced T production, inhibin blocks activin effects

34. Female reproduction
Anatomy of female reproductive system (human)

35. Polar bodies degenerate
Chromosomes in each cell
Stages
Oogonium 2n
(diploid number;
single strands)
Mitotic proliferation
prior to birth 2n
(diploid number;
double strands)
Primary
oocytes
(arrested in first meiotic division) 2n
(diploid number;
doubled strands)
Enlarged primary oocyte
(first meiotic division completed just prior to ovulation) n
diploid number;
doubled strands)
Secondary oocyte
First polar body
Meiosis
(second meiotic division completed after fertilization)
Second polar body
n (haploid number;
single strands) from
ovum plus
sperm for diploid
fertilized ovum with
2n chromosomes
Mature ovum
Polar bodies degenerate
Fig , p.733

36. Female reproduction Ovary produces hormones produces eggs
functional units: ovarian follicles
fallopain tubes
transport of eggs
fertilization occurs here
uterus
site for fetal development

37. Female reproduction
Ovary contains follicles at different stages of development

38. Female reproduction
Functions of ovary
folliculogenesis

39. Female reproduction Ovarian hormonogenesis
Steroids: estradiol and progesterone

40. Female reproduction Estradiol: synthesized mainly by granulosa cells
stimulated by FSH and LH
act on CNS to maintain libido and sexual behavior
feedback regulation of GnRH, LH and FSH (+ve or -ve)
function of female reproductive organs
oocyte maturation
parturition and lactation
metabolic functions
anabolic: weight gain
bone mineral deposition

41. Female reproduction Progesterone synthesized mainly by corpus luteum
stimulated by LH (primed by FSH)
act on CNS to increase sexual receptivity
feedback regulation of GnRH, LH and FSH (-ve)
effects on reproductive tract
pregnancy
metabolic functions
increases basal metabolic rate and thus thermogenic action

42. Female reproduction Others
ovary also produces many nonsteroidal hormones
inhibin and activin
regulate FSH secretion and ovarian function
prostaglandins
PGF2a induces CL regression
PGF2a and PGE2 required for ovulation
insulin-like growth factor
stimulates granulosa cell proliferation; inhibits apoptosis; induces steroidogenesis; induces maturation

43. Female reproduction Reproductive cycle
cyclic change of reproductive activity
seasonal reproductive cycle
related to environmental changes, e.g. photoperiod, temperature, food availability, etc.
estrous cycle (menstrual cycle in primates)
visible sign of ovulation
a behavior strategy to ensure that the female is mated at the time of ovulation

44. Female reproduction human menstrual cycle
cycle of ovarian activity that repeat at approximately one-month interval (menstru=monthly)
menstruation is used to indicate the periodic shedding of endometrium, which become thickened prior to menstruation under stimulation by ovarian steroids
shedding of endometrium is accompanied by bleeding

45. Female reproductive physiology

46. Female reproductive physiology
Ovarian events during menstrual cycle

47. Female reproduction Regulation of ovarian functions Follicular phase:
FSH level is elevated at the beginning of the cycles
FSH stimulates follicular development and production of E2 and inhibin
E2 and inhibin feedback to inhibit FSH and thus FSH level decreases
the follicle that has the highest sensitivity to FSH will be selected and develops into a mature follicle
growth of mature follicle is accompanied by rapid increase in E2
E2 triggers LH surge (positive feedback)

48. Female reproduction
ovulation: rupture of follicular wall and release of oocyte
triggered by LH surge
other hormones: prostaglandin: histamine
Luteal phase
CL formed
progesterone produced by CL
together with E2 feedback to suppress FSH and LH : prevent new follicular development
if pregnancy occurs, hCG stimulates progesterone production and CL function maintained
if no implantation, CL regresses and progesterone level declines (about day 22)

49. Female reproductive physiology
Regulation of uterine events during menstrual cycle
menstrual phase
starts at the first day of bleeding (last 3-5 days)
endometrium degenerates
resulted from decrease in progesterone
proliferative phase
between the cessation of menstruation and ovulation (about 10 days)
endometrium regenerates and thickens
estradiol induces endometrium and myometrium growth, as well as progesterone receptors

50. Female reproduction secretory phase
between ovulation and the onset of next menstruation
occurs when the ovary is at luteal phase
under the action of progesterone and estradiol, endometrium is prepared to accept and nourish an embryo
thick, vascular and “spongy” in appearance
accumulation of glycogen and various enzymes
Progesterone also inhibits myometrium activity

51. Female reproduction Menopause cessation of ovarian activity
during postmenopause years, ovaries are depleted of follicles and stop secreting estradiol
due to failure in the ovary, not pituitary
a weak estrogen (estrone) is produced by adipose tissue from an androgen produced by the adrenal gland
withdrawal of estradiol is responsible for most symptoms of menopause

52. Fig , p.736

53. + — — + + Hypothalamus GnRH Anterior pituitary LH-secreting cells
FSH-secreting
FSH LH + +
Mature follicle
Ovary
Inhibin
Ovulation
High levels
of estrogen
Fig a, p.737

54. + — — + Hypothalamus GnRH Anterior pituitary LH Ovary Corpus luteum
Inhibin
High levels
of estrogen
Fig b, p.737

55. Gonadotropin-releasing hormone—
Hypothalamus
Gonadotropin-releasing hormone
(GnRH) +
Anterior pituitary
LH-secreting
cells
FSH-secreting —
FSH LH + +
Follicular
development
Ovary +
Low levels
of estrogen
Inhibin
Fig c, p.737

56. Fig , p.744

57. Blastocoele Becomes amniotic sac Blastocyst (cross section)
Spermatozoa
Morula
Cleavage
Ovum
(cross section)
Inner cell mass
Destined to
become fetus
Trophoblast
Fertilization
Secondary
oocyte
(ovum)
Accomplishes
implantation
and develops
into fetal
portions of
placenta
Ovulation
Ovary
Implantation
Endometrium
of uterus
Fig , p.746

58. Pregnancy, parturition and lactation
Implantation
fixation of embryo in the wall of uterus
begins with attachment of blastocyte to endometrium and end with the formation of placenta

59. Uterine decidual tissue
Umbilical cord
Amniotic sac
Pool of maternal blood
Placental villus
Intervillus space
Uterine decidual tissue
Maternal arteriole
Maternal venule
Fetal vessels
Chorionic tissue
Chorion
Placenta
Umbilical
vein
Umbilical
artery
Fig , p.748

60. Pregnancy, parturition and lactation
Maternal recognition of early pregnancy
human chorionic gonadotropin rescues corpus luteum

61. Pregnancy, parturition and lactation
Placenta
Transfer nutrients, gases, and waste products between the mother and fetus
barrier between mother and fetus
produces hormones
regulate fetal growth and development
regulate maternal physiology
support pregnancy
parturition

62. Pregnancy, parturition and lactation
Placental hormones
steroids

63. Fig , p.751

64. Pregnancy, parturition and lactation
Progesterone
produced by placenta from cholesterol
maintenance of uterine structure and function
mammary growth and development
feedback on gonadotropin
substrate for cortisol production in fetal adrenal gland
Estrogens
produced by the placenta from precursors derived from adrenal gland
important for parturition and lactation

65. Pregnancy, parturition and lactation
Peptide hormones
hCG
acts at same receptor as LH
stimulates progesterone production
regulate development of fetal adrenal and gonad
hPL
maternal intermediary metabolism
fetal growth
mammary gland differentiation
steroidogenesis

66. Pregnancy, parturition and lactation

67. Pregnancy, parturition and lactation
delivery of baby at term
requires two physiological changes
cervical softening to reduce the resistance to expulsion of baby
coordinated myometrial contraction to increase intrauterine pressure
induced by hormones

69. Pregnancy, parturition and lactation
secretion of milk by mammary glands
mammals are characterized by lactation
lactation provides a primary source of nutrition for new-born
this process includes
milk production
milk let-down

70. Pregnancy, parturition and lactation
Regulation of mammary gland development
stimulated by estrogen, progesterone, PRL, GH and cortisol
Regulation of milk production
PRL: essential for milk production
Cortisol: synergizes with PRL to initiate lactation
Estradiol: increases PRL and cortisol
progesterone: inhibitory
prostaglandins: increase PRL and cortisol
insulin: lipogenesis

71. Pregnancy, parturition and lactation
Milk ejection
accomplished by contraction of the myoepithelial cells surrounding the alveoli
contraction is under the control of oxytocin
oxytocin is released in response to suckling
suckling also induces prolactin release which stimulates more milk production

72. Pregnancy, parturition and lactation