PLACENTAL FUNCTION

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PLACENTAL FUNCTION

• Transfer of nutrients and waste products b\n the
  mother fetus.
• RESPIRATORY
• EXCRETORY
• NUTRITIVE
• Produces or metabolizes the hormones enzymes
  necessary to maintain the pregnancy.

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PLACENTAL FUNCTION

• BARRIER FUNCTION
• IMMUNOLOGICAL FUNCTION

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Transfer function

• Transport is facilitated by the close
  approximation of maternal and fetal vascular
  systems within the placenta.
• It is important to recognize that there normally
  is no mixing of fetal and maternal blood within
  the placenta.

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• Respiratory functionIntake of o2 output of co2
  takes place by simple diffusion.o2 supply to
  fetus rate of 5ml/kg/min this achieved with
  cord flow of 165-330ml/min.
• Excretory functionwaste products urea, uric
  acid,creatinine are excreted to maternal blood by
  simple diffusion.

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NUTRITIVE FUNCTION

• Glucose is the major energy substrate provided to
  the placenta and fetus. It is transported across
  the placenta by facilitated diffusion via hexose
  transporters
• Although the fetus receives large amounts of
  intact glucose, a large amount is oxidized within
  the placenta to lactate, which is used for fetal
  energy production.

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• Amino acid concentrations in fetal blood are
  higher than in maternal blood. Amino acids are
  therefore transported to the fetus by active
  transport .
• LIPIDSTGs FA directly transported from mother
  to fetus in early pregnancy but synthesised in
  fetus later in pregnancy. Thus,fetal fat has got
  dual origin.

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• Water electrolytesNa,K,Cl- by simple
  diffusion.Ca,Ph,iron by active transport.
• BARRIER FUNCTION-Protective barrier to the fetus
  against noxious agents circulating in maternal
  blood.(High MW gt500daltons.

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IMMUNOLOGICAL FUNCTION

• Fetus placenta contain paternally determined
  antigens,foreign to the mother . Inspite of this
  ,no evidence of graft rejection. Probably
• Fibrinoid sialomucin coating of trophoblast
  may suppress the troblastic antigen.
• Placental hormones ,steriods,HCG have got weak
  immunosuppressive effect,may be responsible for
  producing sialomucin.

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• 3.Nitabuchs layer which intervenes b\n decidua
  basalis cytotrophoblast probably inactivates the
  antigenic property of tissue.
• 4.There is little HLA blood group antigens on
  trophoblast surface.so antigenic stimulus is
  poor.
• 5. Production of block antibodies by mother
  ,protects fetus from rejection.

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• ENDOCRINEhormones secreted internally.
• HORMONE--Any organic chemical that is secreted by
  a gland into the circulatory system and is
  transported to some target organ. The target may
  be either peripheral tissue (such as muscle or
  other gland) or brain.

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• Fetal, placental maternal compartments
• form an integrated hormonal unit
• The feto-placental-maternal (FPM) unit
• creates the
• Endocrine Environment
• that maintains and drives the processes of
  pregnancy and pre-natal development.

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PLACENTAL HORMONES

• Human Chorionic Gonadotropin (hCG
• Human Chorionic Somammotropin (hCS)or Placental
  Lactogen(hPL)
• OTHER HORMONES
• Chorionic Adrenocorticotropin
• Chorionic thyrotropin
• Relaxin
• PTH-rP
• hGH-V

• Estrogen (E)
• Progesterone (P)
• HYPOTHALAMIC-LIKE RELEASING HORMONES
• GnRH
• CRH
• cTRH
• GH-RH
• PLACENTAL PEPTIDE HORMONES
• Neuropeptide-Y
• Inhibin Activin
• ANP

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To understand the FPM one should know

• 1. The major hormones involved
• hCGn
• Progesterone
• Estrogen
• Human Chorionic Somatomammotropin (hCS)
• (placental lactogen)
• 2. How the FPM compartments work together
• to produce the steroid hormones
• 3. The transfer of hormones between
• the FPM compartments.

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Human Chorionic Gonadotropin (hCG)

• PREGNANCY HORMONE---glycoprotein
• Half life 24hrsof hCG
• Levels peak at 60-70 days then remain at a low
  plateau for the rest of pregnancy.
• Placental GnRH have control of hCG.
• FUNCTIONS
• RESCUE MAINTENANCE of function of corpus luteum.

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• Prevents degeneration of corpus luteum
• Stimulates corpus luteum to secrete E P which,
  in turn, stimulate continual growth of
  endometrium.
• 2.hCG stimulates leydig cells of male fetus to
  produce testosterone in conjunction with fetal
  pituitary gonadotrophins.Thus indirectly involed
  in development of external genitalia.
• 3. Suppresses maternal immune function
• reduces possibility of fetus immunorejection

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Human Chorionic Somammotropin (hCS)or Placental
Lactogen

• Structure similar to growth hormone
• Produced by the placenta
• Levels throughout pregnancy
• Large amounts in maternal blood but
• DO NOT reach the fetus

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Human Chorionic Somammotropin (hCS)or Placental
Lactogen

• Biological effects are reverse of those of
  insulin utilization of lipids make
  glucose more readily available to fetus, and for
  milk production.
• hCS levels proportionate to placental size
• hCS levels placental
  insuffiency

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Estrogen (E)

• FORMS-estriol,estradiol estrone .
• Estriol most important .
• Levels increase throughout pregnancy
• 90 produced by placenta.(syncytiotrophoblast)
• Placental production is transferred to both
  maternal and fetal compartments

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• Two of the principle effects of placental
  estrogens are
• Stimulate growth of the myometrium and antagonize
  the myometrial-suppressing activity of
  progesterone. In many species, the high levels of
  estrogen in late gestation induces myometrial
  oxytocin receptors, thereby preparing the uterus
  for parturition.
• Stimulate mammary gland development. Estrogens
  are one in a battery of hormones necessary for
  both ductal and alveolar growth in the mammary
  gland.

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Progesterone (P)

• Levels increase throughout pregnancy
• 80-90 is produced by placenta and secreted to
  both fetus and mother

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• Progestins, including progesterone, have two
  major roles during pregnancy
• Support of the endometrium to provide an
  environment conducive to fetal survival. If the
  endometrium is deprived of progestins, the
  pregnancy will inevitably be terminated.
• Suppression of contractility in uterine smooth
  muscle, which, if unchecked, would clearly be a
  disaster. This is often called the "progesterone
  block" on the myometrium. Toward the end of
  gestation, this myometrial-quieting effect is
  antagonized by rising levels of estrogens,
  thereby facilitating parturition.

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• Progesterone and other progestins also potently
  inhibit secretion of the pituitary gonadotropins
  luteinizing hormone and follicle stimulating
  hormone. This effect almost always prevents
  ovulation from occuring during pregnancy

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FETAL ADRENAL GLAND
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Adrenal Gland Development

• Adrenal Cortex
• Vital to organism survival
• Begins to develop at 4th week of embryonic life
• Functional around 10th to 12th week of embryonic
  life
• Enzymes necessary for biosynthesis of
  adrenocortical hormones do not develop
  simultaneously
• hCG may have a role in stimulating Adrenocortical
  development
• Adrenal Medulla
• Originates from nervous system
• Ganglia of Autonomic Nervous System

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Fetal Adrenal Cortex Function

• Adrenal Cortex
• Zona Glomerulosa
• Has enzymes to convert Pregnenalone to
• Progesterone
• Deoxycorticosterone
• Corticosterone
• Aldosterone
• Zona Fasciculata
• Converts Pregnenalone and Progesterone to
  17OH-Pre and 17OH-Pro
• 17OH-Pro is converted to cortisol (major
  glucocorticoid)
• Zona Reticularis
• Converts 17OH-Pre into DHEA and Androstenedione
  (androgens)

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