fetal membranes, umbilical cord. structure of the placenta
TRANSCRIPT
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Fetal membranes, umbilical cord. Structure of the placenta,
placental circulation.
Emese Pálfi
Semmelweis University
Department of Anatomy, Histology and Embryology
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1. week Fertilization Implantation
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Blastocyst Endometrium
1. ZP 2. Trophoblast 3. Hypoblast 4. Blastocyst cavity 5. ICM
Criteria of implantation: • Blastula (stage) • Uterus (endometrium: 19-24. day, „window”)
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Endometrium – secretory phase 1.Proliferative 2. Secretory 3. Menstrual
Stratum functionale: • decidual transformation (enlargement of the stroma cells pseudodecidua cells)
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Fetal membranes
• Decidua
• Chorion
• Amnion
• Yolk sac
• Allantois
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Decidua decidua basalis decidua capsularis decidua parietalis
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Amnion and amniotic fluid • Amnion is attached to the embrionic disk
obliterates the chorionic cavity
enfolds the umbilican cord
• Amniotic fluid
- secreted by the amniotic cells, maternal interstitial fluid, fetal respiratory tract, urine of the fetus
- exchange in every 3 hours (also swallowed by the fetus)
- clinical relevance: oligohydraminos, polyhydraminos
amniocentesis
1. Permits symmetrical external growth 2. Enables free movment 3. Permits normal fetal lung developement 4. Acts as barrier to infections 5. Cushions embryo aganist injuries 6. Control the embryo’s bodies temperature 7. Prevents adherence of amnion
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Yolk sac • Nonfunctional in human
• Atrophies during pregnancy
detaches from the midgut loop in the 6. week
ileal diverticulum/Meckel’s diverticulum (2% of adults)
1. Transfer of nutrients to the embryo (2-3 weeks)
2. Blood developement 3. Dorsal part is
incorporated GI tract 4. Primordial germ cells
appearing in the wall
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Allantois • Nonfunctional in human
• Extraembryonic umbilical portion degenerates in the 2. month
1. Blood formation during the 3-5. week 2. Its vessels become the umbilical vessels 3. Fluid from the amniotic cavity diffuses into the umbilical vein 4. The intraemryonic portion runs from the umbilicus to the urinary bladder urachus
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Chorion 8. week smooth chorion/ chorion laeve villous chorion/ chorion frondosum
2. week
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Development of the trophoblast
Primary villus
12-14. day
Secondary villus
Chorionic cavity/ extraembryonic cavity
Tertiary villus
End of the 3. week - 20. week
Placental barrier waste products
RBC antigens nutrients
antibodies, vitamins, IgG harmful substances (drugs, alcohol) nontransferable substances (heparin, bacteria, IgS, IgM)
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Placenta Fetal part Maternal part
Amnion: covers the fetal part simple cuboidal epithelium Chorion: chorionic plate chorionic villi
Decidua basalis Placental septums
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Haemochorial placenta syncytiothophoblast- fused basal membrane - endothel
main stem villus intervillous space
endometrial veins and arteries
anchoring villus decidua basalis
myometrium
placental septum
decidua parietalis
smooth chorion amnion
chorionic plate
cytotrophoblastic shell
surface area of chorionic villi 4-14 m2
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Transport - passive diffusio n: O2, CO2, water, lipids, steroids - facilitated diffusion: glukose, aminoacids - active transport: proteins (Ig) - pinocytosis
Metabolism glycogen, cholesterol, fatty acids
Endocrine secretion hCG ( human chorion gonadotropin hormon) progestins estrogens somatomammotrop hormon
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Placental circulation Fetal placental circulation - poorly oxygenated blood in the umbilical arteries - branches in the chorionic plate - arteriocapillary-venous system wihin the villi - exchange of metabolic and gaseous products between maternal and fetal blood NO INTERMINGLING OF FETAL AND MATERNAL BLOOD - well-oxygenated blood passes into the veins - umbilical vein carries the blood to the fetus
Maternal placental circulation - 80-100 spiral arteries are opening in
the intervillous space endovascular invasion by cytotrophoblast cells gaps on the cytotrophoblastic shell
- pulsatil flow - the blood returns to the endometrial
veins - ~150 ml blood in the untervillous
space, preplenished 3-4 times/minute
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Histology of the placenta
chorionic plate with umbilical vessels
amnionepithel
tercier villi
maternal septum
decidua basalis
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Umbilical cord
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Histology of the umbilical cord
amnionepithel
Wharton’s jelly
arteries vein urachus
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János Hanics: Fetal membranes, Placenta
Andrea Székely: Placenta
Langman: Medical embryology (12th edition)
Moore and Persaud: The developing human (5th edition)