Physiology of ReproductionII

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Physiology of Reproduction(II)

• Teng Yincheng M.D.,
  Ph.D., Professor
• 
  Department Of Obstetrics
  Gynecology
• 
  Renji Hospital Affiliated to SJTU
  School of Medicine
• 
  

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Pregnancy is defined as the course of embryo and
fetal growth and development in uterine It
begain at the fertilization and end the delivery
of the fetal and its attachment

• Pregnancy occurs when a mature liberated ovum
• is fertilized by a mature capacitated
  spermatozoon

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The Sperm

• The spermatozoa leave the testis carrying 23
  chromosomes but not yet capable of fertilization.
• Their maturation is completed through their
  journey in the 6 meters of the epididymis and
  when mixed with the seminal plasma from the
  epididymis, seminal vesicle and prostate gland.

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The Sperm

• After semen is ejaculated, the sperms reach the
  cervix by their own motility within seconds
  leaving behind the seminal plasma in the vagina

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The Sperm

• At time of ovulation, the cervical mucous is in
  the most favourable condition for sperm
  penetration and capacitation as
• It becomes more copious, less viscous and its
  macromolecules arrange in parallel chains
  providing channels for sperms passage.
• Its contents from glucose and chloride are
  increased.

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The Sperm

• The sperms ascent through the uterine cavity and
  Fallopian tubes to reach the site of
  fertilization in the ampulla by
• Its own motility, and by
• Uterine and tubal peristalsis which is aggravated
  by the prostaglandins in the seminal plasma.

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The Sperm

• The sperms reach the tube within 30-40 minutes
• But they are capable of fertilization after 2-6
  hours.
• This period is needed for sperm capacitation.

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Capacitation of sperms

• Is the process after which the sperm becomes able
  to penetrate the zona pellucida,that surrounding
  the ovum and fertilize it.
• The cervical and tubal secretions are mainly
  responsible for this capacitation.

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Capacitation of sperms

• Capacitation is believed to be due to
• Increase in the DNA concentration in the nucleus,
• Increase permeability of the coat of sperm head
  to allow more release of hyaluronidase.

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The ovum

• The ovum leaves the ovary after rupture of the
  Graafian follicle, carrying
  23 chromosomes
  and surrounded by the
  zona pellucida and corona radiata.

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The ovum

• The ovum is picked up by the fimbrial end of the
  Fallopian tubes and moved towards the ampulla by
  the
• Ciliary movement of the cells and
• Rhythmic peristalsis of the tube.

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Fertilization

• Millions of sperms ejaculated in the vagina, but
  only hundreds of thousands reach the outer
  portion of the tubes.
• Only few succeed to penetrate the zona pellucida,
  and only one spermatozoon enters the ovum
  transversing the perivitelline space.

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Fertilization

• After penetration of the ovum by a sperm, the
  zona pellucida resists penetration by another
  sperms due to alteration of its electrical
  potential.
• The pronucleus of both ovum and sperm unite
  together to form the zygote (46 chromosomes).

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Zygote
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Sex Determination

• The mature ovum carries 22 autosomes and one X
  chromosome, while the mature sperm carries 22
  autosomes and either an X or Y chromosome.
• If the fertilizing sperm is carrying X
  chromosome the baby will be a female (46 XX), if
  it is carrying Y chromosome the baby will be a
  male (46 XY).

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Cleavage and blastocyst formation

• On its way to the uterine cavity, the fertilized
  ovum (zygote) divides into 2,4,8 then 16 cells
  (blastomeres).

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Cleavage and blastocyst formation

• This cleavage starts within 24 hours of
  fertilization and occurs nearly every 12 hours
  repeatedly
• The resultant 16 cells mass is called morula
  which reaches the uterine cavity after about 4
  days from fertilization.

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Cleavage and blastocyst formation

• A cavity appears within the morula converting it
  into a cystic structure called blastocyst.
• The cells become arranged into an
• Inner mass (embryoblast) which will form all the
  tissues of the embryo, and an
• Outer layer called trophoblast which invade the
  uterine wall.

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Cleavage and blastocyst formation

• The blastocyst remains free in the uterine cavity
  for 3-4 days, during which it is nourished by the
  secretion of the endometrium (uterine milk).

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Implantation (nidation)
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The necessary conditions of imbed
The stage of egg imbed

• Disapearing of
• the pellucid zone
• Syntrophoblast
• formed from the blast
• Synchronizing development of blast
• and the endometriun
• P Secretory enough

Apposition Adhesion Penetration
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The decidua

• It is the thickened vascular endometrium of the
  pregnant uterus.
• The glands become enlarged, tortuous and filled
  with secretion.
• The stromal cells become large with small nuclei
  and clear cytoplasm, these are called decidual
  cells.

• The decidua, like secretory endometrium, consists
  of three layers
• The superficial compact layer,
• The intermediate spongy layer,
• The thin basal layer.

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The decidua

• After implantation the decidua becomes
  differentiated into
• Decidua basalis under the site of implantation.
• Decidua capsularis covering the ovum.
• Decidua parietalis or vera lining the rest of
  the uterine cavity.

• The trophoblast of the blastocyst invades the
  decidua to be implanted in
• -The posterior surface of the upper uterine
  segment in about 2/3 of cases,
• -The anterior surface of the upper uterine
  segment in about 1/3 of cases.

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The decidua
As the conceptus enlarges and fills the uterine
cavity the decidua capsularis fuses with the
decidua parietalis This occurs nearly at the end
of 12 weeks
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The decidua

• The decidua has the following functions
• 1.It is the site of implantation.
• 2.It resists more invasion of the trophoblast.
• 3.It nourishes the early implanted ovum by its
  glycogen and lipid contents.
• 4.It shares in the formation of the placenta.

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Chorion

• After implantation, the trophoblast
  differentiates into 2 layers
• a. An outer one called syncytium
  (syncytiotrophoblast) which is multinucleated
  cells without cell boundaries,
• b. An inner one called Langhans layer
  (Cytotrophoblast) with simple cytoplasm.
• A third layer of mesoderm appears inner to the
  cytotrophoblast.

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Chorion

• The trophoblast and the lining mesoderm together
  form the chorion.
• Mesodermal tissue ( connecting stalk) connects
  the inner cell mass to the chorion and will form
  the umbilical cord later on.

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Chorion

• Spaces (lacunae) appear in the syncytium,
  increase in size and fuse together to form the
  " chorio-decidual
  space" or " intervillus
  space".
• Erosion of the decidual blood vessels by the
  trophoblast allows blood to circulate in this
  space.

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Chorion

• The outer syncytium and inner Langhans cells
  form buds surrounding the developing ovum called
  primary villi.
• When the mesoderm invades the center of the
  primary villi they are called secondary villi.
• When blood vessels (branches from the umbilical
  vessels) develop inside the mesodermal core, they
  are called tertiary villi.

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Primary villous
Secondary villous
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Transverse section of tertiary villous
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Chorion

• At first, the chorionic villi surround the
  developing ovum.
• After the 12th week, the villi opposite the
  decidua capsularis atrophy leaving the chorion
  laeve which forms the outer layer of the foetal
  membrane and is attached to the margin of the
  placenta.

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• The villi opposite the decidua basalis grow and
  branch to form the chorion frondosum and together
  with the decidua basalis will form the placenta.
• Some of these villi attach to the decidua basalis
  ( the basal plate) called the "anchoring villi",
  other hang freely in the intervillus spaces
  called "absorbing villi"

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Amnion

• After implantation, 2
  cavities appear in the
  inner cell mass
  the amniotic cavity and yolk sac and in
  between these 2 cavities the mesoderm develops.

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Development of embryo and fetus
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8 weeks
3 weeks
4 weeks
6 weeks
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Attachment of the fetal
1.Placenta 2.Fetal membranes 3.Umbilical cord
4.Amniotic fluid
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1.Placenta
Its an exchange organ between maternal and fetal
Amniotic membrane chorion frondosum Basal
decidua
Round Weight450-650g Diameter16-20cm
Thickness1-3cm thick in center and thin
in margin
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The functions of placenta

• Gas exchange
• Suply of nutrition
• Depletion of fetal product of metabolisn
• Defense function
• Hormone synthesis
• Human chorionic gonadotropin(HCG)
• Human placental lactogen(HPL)
• Pregnancy specific ?-glycoprotein(PS ?1G)
• Human chorionic thyrotropin(HCT)
• Estrogen, P, Oxytocinase, heat stable alkaline
• phosphatase(HSAP)

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2.Fetal membrane Chorion
Amnion 3.Umbilical cord Length30-70cm
average50cm Consist of 2 artery and 1 vein
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4.Amniotic fluid
Source early from serum dialysis
late from fetal urine Absorse by fetal
membrane, fetal
swallowing(500ml/day) Amniotic exchange between
maternal and fetal
400ml/h Status of amniotic fluid pH7.20
Density1.007-1.025 Contained water(98-99)
inorganic substance
organic substance(1-2)
Volume of amniotic fluid 8 weeks5-10ml 10
weeks30ml 20 weeks400ml 38 weeks1000ml
The function of amniotic fluid Protect maternal
and fetal
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Maternal changes during pregnancy
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Isthmus be dialated and become soft from 1cm
pre-pregnancy a portion of the
uterus after 12
gestational weeks Cervix be soft and coloration
or stain secrete amount of
mucus avoiding the uterus
cavity suffer from infection Changes of ovary
Stop ovulation Corpus luteum formation and
maintains for 10 weeks And the function
of corpus luteum is substituted by the
placenta Corpus luteum atretic gradually after
3-4 months gestation.
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2.Changes of the circulation
Heart border become enlargement Heart rate
increased 10-15 beat per min at the
late pregnancy Heart volume
increased 10 at the late
pregnancy Cardiac output Very important
for fetal growth and development Incrased begain
10 weeks and upto the peak at 32 weeks 80ml/bp
and keeps the level to the term pregancy Changes
of blood system Volume increased (30-45 )
begain 6- 8 weeks and up to the
peak at 32-34 weeks increased
about 1500ml including plasma
1000ml and red cell 500ml
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Changes of blood component Red cell reticulocyte
increased red cell decreased
3.61012(4.21012) Hb decreased
110g/L(130g/L) WBC neutrophilic granulocyte
increased lymphocyte mild increased
no change in orther blood cells
Coagulation Hypercoagulability Factor ??? ? ? ?
increased ESR increased significantly upto
100mm/h Plasma protein albumin decreased
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THANKS FOR YOUR ATTENTION
Teng Yincheng M.D., Ph.D., Professor Dep. of
Obstet. Gynecol. Renji Hospital Affiliated to
SJTU School of Medicine