Fetal membranes and placenta Flashcards
What is the role of the placenta?
Act as respiratory organ for foetus and the nutritive support from maternal circulation, excretion of waste and endocrine ( placenta takes over p/o from corp.l)
Immune effects of the placenta?
Protects from microorganisms from crossing blood/placenta barrier- norovirus, mumps, rubella syphillis etc
What is the decidua?
CT reaction of endometrium after implantation, prepares decidua (main maternal placenta component)
How does decidua reaction take place?
Progesterone induced- inc. vascular swelling of stromal cells, accumulation of glycogen (nourishment for early embryo), prog. sprouting and ingrowth of caps.
Decidua reaction days 7 + 8
Implantatino begins via integrin connections and HB-EGF
8. amniotic sac starts to form
decidua reactions days 9 + 12
yolk sac starts to form and extraembryonic mesoderm begins to develop
12. EE mesoderms surrounds amniotic yolk and sac
yolk- EE splanchnic mesoderm
sac- EE somatic mesoderm
Day 12 of decidua reaction
Trophoblastic lacunae form syncitotropoblasts (primitive fetal vessels)
Maternal sinusoids encapsulated within syncitiotrophoblast layer (embryo w nutrients)
Extraembryonic coelom starts to appear > chorionic cavity (day 13- 16)w
What are the roles of syncitiotrophoblasts and cytotrophoblasts?
SCTB- invasive cells which get embryo to nutrient supply, target endometrium to break open sinusoids > trophoblastic lacunae
CTB- supply of syncitiotrophoblasts and produce villi in placenta
What is the significance of the trophoblastic lacunae filling with blood?
Become villi of placenta ( foeto-maternal boundary), primary v fill with mesoderm and become sec. chorionic villi
What are the differences between 1, 2 and 3 villi?
- Cytotrophoblasts
- Infiltrating extrambryonic mesoderm fills internal cavity
- Mesoderm differentiates to form small blood vessels and fetal blood
What should be done by week 3?
Connection between f and m vessels initiated
CTB start to proliferate around SCTB in collars
Chorionic cavity surround fetal tissues, connected by extraembryonic mesoderm connecting stalk
What should be done by week 5?
Tertiary villi formed
CTB have encompassed SCTB, cytotrophoblast shell
Connecting stalk mesoderm develop fetal capillaries, primitive umbilical cord
Feto-maternal exchange
CT invade endometrial spiral arteries (hybrid BV created)
Maternal blood pool in intervillous spaces (coated by SCTB), nutrients diffuse/ AT’erred into chorionic villi containing fetal capillaries and lead into vessels of C.stalk and to developing foetus.
How are villi formed?
Stem vs branch villi- start off w several layers of barrier tissue, reduced to 2 partial layers and allows for close connections of M+F blood
What are the 3 decidual layers formed?
D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo
What are the 3 layers formed from endometrium in decidual reaction?
D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo
What are the 3 decidual layers formed?
D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo
What are the 3 decidual layers formed?
D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo
How is amnion formed?
Decidua P+C fuse w. amniochorionic membrane by end of tri. 3
What is the role of amniotic fluid?
Made of water and fetal cellular debris- hydrates skin lungs and GI tract (swallowing), fluid comes from maternal cells and amnioblasts
Late gestation when urinary tract active, excretion into A.F
How do maternal spiral arteries function?
Spurt into intravillous space, bathe into branching villus which has large SA and can take up nutrients/ exchange gas quickly
Placental circulation and HDN
Rh+ blood of foetus mixing with Rh- mother- maternal immune system detects as foreign and RBC destruction
More a problem in 2nd pregnancy after AB produced from first exposure (parturition)
Placental endocrine function
Programmes maternal metabolism to ensure it meets foetal demands- HGC, progesterone, oestrogen, placental parathyroid hormone, relaxin, CRH, chorionic somatommatrophin
Role of 2 umblical arteries and 1 umbilical vein
Return deoxygenated blood with waste from foetus to placenta
Veins return oxygenated, nutrient rich blood from placenta to foetus- vessels are in Wharton’s jelly
Umbilical abnormalities
Single umbilical artery ( common w genetic conditions), Entanglement, compression or prolapse
Placental abnormalities
Shape, placenta previa, pre-eclampsia, abnormal implantation, trophoblastic disease (tumours)
PP- Blocks normal vaginal delivery, C section
Pre- eclampsia- HT and proteinuria- CTB in spiral arteries don’t invade properly- eclampsia, renal failure, PO
Implantation abnormalities
Morbidly adherent placenta, doesn’t fully detatch at parturition and severe haemorrhage/ damage to uterus
Accreta- too deep in endometrium (mm)
Increta- into myommetrium
Percretia- through perimetrium
Molar pregnancies (gestational trophoblastic disease)
Non cancerous- complete, egg w no maternal DNA or partial (triploid gestations)
Cancerous- invasive, arise if benign moles progress
