Physiology of pregnancy

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Physiology of pregnancy

• Zhao aimin

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Definition of pregnancy

• 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

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Definition of fertilazation

• Fertilization is defined as the course of
  combination of the oocyte and sperm
• It onset 12h after ovulation usually in
  ampulla of the oviduct(fallopian tube)

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The Development of the fertilizated egg

• 3 days after ovulation, the morula (early
  blast)is fomulated
• 4 days after ovulation, the late blast is
  fomulated
• 6-7 days after ovulation, the egg imbeds in the
  uterus

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The stage of egg imbed

• Apposition
• Adhesion
• Penetration

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The necessary conditions of imbed

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

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Changes of endometrium after the egg imbed

• The endometrium changes into dicedua
• Basal decidua
• Capsular decidua
• True decidua

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Attachment of the fetal

• Placenta
• Fetal membranes
• Umbilical cord
• Amniotic fluid

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placenta

• Its an exchange organ between maternal and
  fetal
• Amniotic membrane
• chorion frondosum
• Basal decidua

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chorion frondosum

• 13-21 days after ovulation, villi fomulating
  gradually
• Grade I viili
• Grade II Iviili
• Grade III viili

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Structure of placenta

• Round
• Weight450-650g
• Diameter16-20cm
• Thickness1-3cm
• thick in center and thin in margin

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Function of placenta

• One important function of placenta is
  substance exchange between maternal and fetal

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• The position of exchange is VSM(vasculo-syncytial
  membrane)
• VSM is comprised of
• Syntrophoblastocyte
• Basal membrane of Syntrophoblastocyte
• Stroma of villi
• Basal membrane of capillary
• Endothelium of capillary

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• The way of substance exchange
• Simple diffusion
• Facilitated diffusion
• Active transportion
• phagocytosis

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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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• Fetal membrane
• Chorion
• Amnion
• Umbilical cord
• Length30-70cm average50cm
• Consist of 2 artery and 1 vein

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• Amniotic fluid
• Source early from serum dialysis
• late fron fetal urine
• Absorse by fetal membrane, fetal
• swallowing(500ml/day)
• Amniotic exchange between maternal
• and fetal 400ml/h

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• Volume of amniotic fluid
• 8 weeks5-10ml
• 10 weeks30ml
• 20 weeks400ml
• 38 weeks1000ml

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• Status of amniotic fluid
• pH7.20
• Density1.007-1.025
• Contained water(98-99)
• inorganic substance
• organic substance(1-2)

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The function of amniotic fluid Protect maternal
and fetal
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Maternal changes during pregnancy The maternal
system may produce a series of changes in order
to adapt to the needing of fetal growth and
development influenceed by placenta hormone and
neuro-endocrine
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Changes of reproductive system Uterus Body
become enlargement and soft from
75 3cm pre-pregnancy to 3525
22cm at term Volume of uterus cavity become
enlargement from 5ml pre-pregnancy to 5000ml.at
term
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Weight be increased from from 50g pre-
pregnancy to 1000g at term Wall become
thickness and the thickist at mid-
period from 1 cm pre-pregnancy to 2-2.5
cm at term Blood suplyblood flow
increased significantly
upto 500- 700ml/min,increased 4-6
times and most of blood flow is
transported to the
placenta(80-85)
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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
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• 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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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
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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
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• Blood pressure changes due to pregnancy
• No obvious change in Systolic pressure
• Mild decreased in diastolic pressure
• Vein pressure
• No significantly changes in Upper limb vein
• pressure
• Lower limb vein pressure increased because of
• the disturbance of vein reflux

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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
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Coagulation Hypercoagulability Factor ??? ? ? ?
increased ESR increased significantly upto
100mm/h Plasma protein albumin decreased