Reproductive Reproductive PhysiologyPhysiology

I. Sexual differentiation and I. Sexual differentiation and formation of genitalia

II. II. Male reproductive system: function and regulation

III. III. Female reproductive system: function and regulation

IV. IV. Pregnancy and parturition

V. V. Mechanism of milk secretion

VI. Sex Physiology

What will we discuss in this chapter?What will we discuss in this chapter?(Outline)(Outline)

I. Sexual differentiation and formation of genitaliaI. Sexual differentiation and formation of genitalia

1. Sexual Differentiation• Sexual differentiation is determined at three levels: chromosomes, Sexual differentiation is determined at three levels: chromosomes,

gonads, and phenotype.gonads, and phenotype.•Males have XY and females have XX chromosomes.Males have XY and females have XX chromosomes.• Female characteristics develop spontaneously in the absence of the Y Female characteristics develop spontaneously in the absence of the Y

chromosome.chromosome.• Y chromosome contains the geneY chromosome contains the gene －－ sex-determining region (SRY)sex-determining region (SRY) －－ that that

is necessary for the development of male characteristics.is necessary for the development of male characteristics.•Gonads are composed of three cell types in both males and females: Gonads are composed of three cell types in both males and females:

supporting cells (Sertoli or granulosa cells); stomal cells (Leydig or theca supporting cells (Sertoli or granulosa cells); stomal cells (Leydig or theca cells); and germ cells (spermatogonia or oocytes).cells); and germ cells (spermatogonia or oocytes).

• Fetal testes secrete two hormonesFetal testes secrete two hormones －－ antimullerian hormone and antimullerian hormone and testosteronetestosterone －－ that are essential for development of the male gonads that are essential for development of the male gonads and internal genitalia; in their absence female gonads and internal and internal genitalia; in their absence female gonads and internal genitalia develop.genitalia develop.

•Dihydrotestosterone is responsible for development of male external Dihydrotestosterone is responsible for development of male external genitalia. genitalia.

Human chromosomesHuman chromosomes

Chromosomes may decide sexChromosomes may decide sex

2. Formation of internal genitalia2. Formation of internal genitalia

3. Formation of external genitalia3. Formation of external genitalia

Origin of mammalian lifeOrigin of mammalian life

Puberty Puberty Onset of puberty is marked by pulsatile secretion of GnRH, Onset of puberty is marked by pulsatile secretion of GnRH,

FSH, and LH (female, age of 6-8 years and male, age of 9-10 FSH, and LH (female, age of 6-8 years and male, age of 9-10 years).years).

In the male, FSH stimulates sperm and Sertoli cell In the male, FSH stimulates sperm and Sertoli cell development while LH stimulates Leydig cell proliferation development while LH stimulates Leydig cell proliferation and testosterone secretion.and testosterone secretion.

In the female, FSH stimulates follicle development and, In the female, FSH stimulates follicle development and, along with LH, the synthesis of estradiol.along with LH, the synthesis of estradiol.

Testosterone and estradiol stimulate the development of Testosterone and estradiol stimulate the development of secondary sex characteristics and a growth spurt in the secondary sex characteristics and a growth spurt in the male and female, respectively. male and female, respectively.

II.II. Male reproductive system: Male reproductive system: function and regulationfunction and regulation

Testes are composed of seminiferous tubules that produce sperm and Leydig cells, which produce testosterone.

Spermatogenesis results from conversion of spermatogonia to mature sperm through mitosis, meiosis, and differentiation.

Sertoli cells of the seminiferous tubules support sperm development as well as surround and isolate developing sperm from the blood supply.

Leydig cells, under the influence of LH, secrete testosterone.FSH and testosterone acting through Sertoli cells enable

spermatogenesis.Blood levels of testosterone and inhibin feed back to regulate

pituitary release of FSH and LH.

Maturing sperm come from the testes.Maturing sperm come from the testes.

Basement Basement MembraneMembrane

Leydig CellLeydig Cell

SpermatozoaSpermatozoa

SpermatogoniaSpermatogonia

Sertoli CellSertoli Cell

The testes are composed of maturing sperm (spermatogonia, spermatozoa), Sertoli The testes are composed of maturing sperm (spermatogonia, spermatozoa), Sertoli cells, and Leydig cells that interact to ensure a continuous production of sperm.cells, and Leydig cells that interact to ensure a continuous production of sperm.

Histology of testes Histology of testes

Histology of testesHistology of testes

Testicle tissue under the microscopeTesticle tissue under the microscope

Structure of sperm Structure of sperm

Male formationMale formation

Male main sexual gland —TestisMale main sexual gland —Testis

Anatomy of male genitaliaAnatomy of male genitalia

Anatomy of male external genitaliaAnatomy of male external genitalia

Endocrine regulation of male reproduction

sperm

III. Female reproductive system: III. Female reproductive system: function and regulationfunction and regulation

Ovary has three regions: cortex composed of follicles; medulla composed of stromal and hormone-producing cells; and hilum, the point of entry of blood vessels and nerves.

Follicles are composed of three cell types: oocytes, granulosa, thecal.Initial development of oocytes beings in fetal life, but maturation is

delayed until puberty when single oocytes mature and are released monthly for the next 4 decades.

Progesterone and estradiol are main steroid hormones produced by the ovaries –estradiol from granulosa cells and progesterone from many cell types.

Estradiol is released prior to ovulation, progesterone after ovulation; both prepare the uterus for egg implantation.

FSH stimulates monthly development of follicles, LH stimulates monthly ovulation, and both stimulate synthesis and secretion of progesterone and estradiol.

Corpus luteum, the postovulation follicle, secretes estradiol and progesterone to sustain the egg and uterus if fertilization and implantation occur.

Anatomy of female genitaliaAnatomy of female genitalia

Anatomy of female genitaliaAnatomy of female genitalia

Female internal genitaliaFemale internal genitalia

Female main sexual gland —OvaryFemale main sexual gland —Ovary

Structure of uterine wall

Cavity

Synthesis of testosterone, Synthesis of testosterone, progesterone and estradiol progesterone and estradiol

Endocrine regulation of sexual hormone Endocrine regulation of sexual hormone

Various sexual hormones changes in early to mid-follicular phase

Various sexual hormones changes in early to mid-luteal phase黄体期

Various sexual hormones changes in Various sexual hormones changes in late follicular phase and ovulationlate follicular phase and ovulation

Various sexual hormones changes in late luteal phase

Mechanism of menstrual cycle induced by the changes in various sexual hormone *

EndometriumEndometrium

IV.IV. Pregnancy and parturitionPregnancy and parturition1. Pregnancy1. Pregnancy

Fertilization of the oocyte occurs within 24 hours of ovulation in the distal end of the oviduct.

Fertilized egg completes second meiosis and divides repeatedly to form multicelled blastocyst.

Blastocyst implants in uterine wall within 5 days of ovulation.After implantation, blastocyst secretes human chorionic gonadotropin

(hCG, within 9 days of ovulation), which signals the corpus luteum to continue secreting progesterone and estradiol and is basis of the pregnancy test.

Progesterone is produced from cholesterol by the placenta and estriol through the interaction of the placenta and fetal adrenal cortex and liver.

Progesterone and estriol support development of the fetus as well as maternal breast development.

The mechanism by which parturition is initiated is unclear but involves an interplay between progesterone, prostaglandins, and oxytocin that increase the frequency of uterine contraction.

Effect of the theca and granulose cells of the Effect of the theca and granulose cells of the ovaryovary

Granulosa CellsTheca Cells

Cholesterol Cholesterol

Pregnenolone Pregnenolone

17-Hydroxypregnenolone

Dehydroepiandrosterone

Androstenedione

Testosterone

Androstenedione

Testosterone

Estradiol

- - - -

Androstenedione&

Testosterone

Estradiol

The theca and granulose cells of the ovary interact to ensure adequate production of androgens (androstenedione, testosterone) and estradiol.

Precondition of pregnancy is ovum must combine with sperm

Precondition of pregnancy is ovum must Precondition of pregnancy is ovum must combine with sperm to be zygotecombine with sperm to be zygote

The process of zygote FormationThe process of zygote Formation

Ovulation and fecundation

Growth of fetus (10 weeks)

Structure of placenta Structure of placenta

Synthesis of the major form of Synthesis of the major form of estrogen—estriol during pregnancyestrogen—estriol during pregnancy

Ensuring an adequate production of estriol during pregnancy requires exchange of substances between the maternal blood, the placenta, the fetal adrenal gland, and the fetal liver.

Placenta

Cholesterol

Pregnenolone

Estriol

Fetal Adrenal

DHEA-Sulfate

Fetal Liver

16-OH-DHEA-Sulfaye

From the maternal blood

2. Parturition 2. Parturition

Parturition

ParturitionParturition

Expulsion of the placenta after Parturition

Endocrine mechanism of ParturitionEndocrine mechanism of Parturition

V. Mechanism of milk secretionV. Mechanism of milk secretion 1.1. Anatomy of breast Anatomy of breast

Progesterone and estrogen stimulate the development and growth of the mother’s breasts. Estrogen also stimulates prolactin secretion by the anterior pituitary, which participates in breast development. At parturition, the breasts are ready for milk production and release induced by increased prolactin and oxytocin levels brought on by suckling.

2. Histology of breast 2. Histology of breast

3. Mechanism of milk secretion3. Mechanism of milk secretion

VI. Sex PhysiologyVI. Sex Physiology Viripotent representation

Changes in physique during puberty (青春期 ) Genital (生殖器的 ) development Secondary sexual characters appearance Sex maturation regulation Sexual abnormality during puberty

Sexual excitation and sexual behavior Male Female

Sexual behavior regulation Nervous regulation Hormonal regulation Sexual dysfunction

Consideration after class

1. Please describe testicular sperm formation and its

endocrine function.

2. Please describe ovarian ovum formation and its endocrine

function.

3. What is mechanisms of menstrual cycle ?

4. Please describe pregnant maintenance and hormonal

regulation.

5. What is phenotype of sex maturation ?