Transcript Reproductive Physiology

Reproductive
Physiology
What will we discuss in this chapter?
(Outline)
I. Sexual differentiation and formation of genitalia
II. Male reproductive system: function and regulation
III. Female reproductive system: function and regulation
IV. Pregnancy and parturition
V. Mechanism of milk secretion
VI. Sex Physiology
I. Sexual differentiation and formation of genitalia
1. Sexual Differentiation
• Sexual differentiation is determined at three levels: chromosomes,
gonads, and phenotype.
• Males have XY and females have XX chromosomes.
• Female characteristics develop spontaneously in the absence of the Y
chromosome.
• Y chromosome contains the gene－sex-determining region (SRY)－that is
necessary for the development of male characteristics.
• Gonads are composed of three cell types in both males and females:
supporting cells (Sertoli or granulosa cells); stomal cells (Leydig or theca
cells); and germ cells (spermatogonia or oocytes).
• Fetal testes secrete two hormones－antimullerian hormone and
testosterone－that are essential for development of the male gonads and
internal genitalia; in their absence female gonads and internal genitalia
develop.
• Dihydrotestosterone is responsible for development of male external
genitalia.
Human chromosomes
Chromosomes may decide sex
2. Formation of internal genitalia
3. Formation of external genitalia
Origin of mammalian life
Puberty
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
years).
In the male, FSH stimulates sperm and Sertoli cell
development while LH stimulates Leydig cell proliferation
and testosterone secretion.
In the female, FSH stimulates follicle development and,
along with LH, the synthesis of estradiol.
Testosterone and estradiol stimulate the development of
secondary sex characteristics and a growth spurt in the
male and female, respectively.
II.
Male reproductive system:
function 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.
Spermatogonia
Spermatozoa
Sertoli Cell
Basement
Membrane
Leydig Cell
The testes are composed of maturing sperm (spermatogonia, spermatozoa), Sertoli
cells, and Leydig cells that interact to ensure a continuous production of sperm.
Histology of testes
Histology of testes
Testicle tissue under the microscope
Structure of sperm
Male formation
Male main sexual gland —Testis
Anatomy of male genitalia
Anatomy of male external genitalia
Endocrine regulation of male reproduction
sperm
III. Female reproductive system:
function 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 genitalia
Anatomy of female genitalia
Female internal genitalia
Female main sexual gland —Ovary
Structure of uterine wall
Cavity
Synthesis of testosterone,
progesterone and estradiol
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
late follicular phase and ovulation
Various sexual hormones changes in late
luteal phase
Mechanism of menstrual cycle induced by
the changes in various sexual hormone *
Endometrium
IV. Pregnancy and parturition
1. 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
ovary
Theca Cells
Cholesterol
Granulosa Cells
Cholesterol
Pregnenolone
Pregnenolone
---
17-Hydroxypregnenolone
Dehydroepiandrosterone
Androstenedione
Androstenedione
Testosterone
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
combine with sperm to be zygote
The process of zygote Formation
Ovulation and fecundation
Growth of fetus (10 weeks)
Structure of placenta
Synthesis of the major form of
estrogen—estriol during pregnancy
Fetal Adrenal
Placenta
From the
maternal blood
DHEA-Sulfate
Cholesterol
Pregnenolone
Fetal Liver
Estriol
16-OH-DHEA-Sulfaye
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.
2. Parturition
Parturition
Parturition
Expulsion of the placenta after
Parturition
Endocrine mechanism of Parturition
V. Mechanism of milk secretion
1. 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
3. Mechanism of milk secretion
VI. Sex Physiology
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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 ?