Placenta as an endocrine organ
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Transcript of Placenta as an endocrine organ
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Placenta as an endocrine organ
Dr. Sadaf Mumtaz11-2-11
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• Placenta – is fetal lung – is also the route by which all nutritive materials enters the fetus– Fetal wastes are discharged to the maternal blood
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Placenta is a unique endocrine organ
• Transient tissue• Secretion of its hormone is not subject to
extrinsic control
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hCG• Gonadotrophin secreted by placenta• Prolongs life span of corpus luteum
– Estrogen, progesterone and relaxin• Glycoprotein • Produced by syncytiotrophoblast• Two subunits – α and β
– α subunit of LH, FSH and TSH
• Primarily luteinizing and luteotrophic and has little FSH activity• Appears to act on the same receptor as LH• Detected in
– Blood 6days
– Urine 14 days
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Rates of secretion of estrogen and progesterone and concentration of hCG at different stages of pregnancy
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• In a male fetus…..Role of hCG
• Any role of hCG in inducing vomiting….
• Can ovariectomy before 6th week leads to abortion?
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• Why does’nt the developing placenta start producing estrogen and progesterone in the first place instead of secreting hCG?
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Secretion of estrogen and progesterone by placenta
Measurement of estriol levels in maternal urine can be used clinically to assess the viability of fetus
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Roles of estrogen and progesterone during Pregnancy
• Myometrium
• Breast
• Pelvic ligaments
Role of high estrogen levels
• Gap Junctions
• Increased number of oxytocin receptors
• Cervical ripening local prostaglandins cervical enzymes collagen fibers
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Human chorionic Somatomammotropin
• Secreted by syncytiotrophoblast at about fifth week• Lactogenic and growth stimulating activity• CGP [chorionic growth hormone prolactin] or human
placental lactogen (hPL) • Secretion of growth hormone is decreased by hCS• Less potent (potency is a measure of hormone activity expressed in terms of the
amount required to produce an effect of given intensity) • Decreased insulin sensitivity and glucose utilization in
mother sparing it for the fetus• Mobilizes FFA from the mother
• Low hCS levels indicate placental insufficiency
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Role of corticotropin releasing hormone
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Other Placental hormones
• POMC• GnRH and inhibin-------- regulate hCG• Leptin (Trophoblast and amnion cells)• Prorenin (Cytotrophoblast and amniotic fluid)• Relaxin
– Helps maintain pregnancy by inhibiting myometrial contractions
– Softens the cervix at the time of delivery• Human chorionic thyrotropin
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Diffusion of Oxygen
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• Diffusion of Carbon dioxide• Diffusion of Food stuff
– Facilitated diffusion of glucose
• Excretion of waste products
• A shift of oxygen Hb dissociation curve to the right in response to increase in blood CO2 and H+ ions has a significant effect by enhancing the release of oxygen from the blood in the tissues and enhancing oxgenation of blood in the lungs. Bohrs effect
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