FETAL MEMBRANES Placenta Nutrition

FETAL MEMBRANES
Placenta
Nutrition
2011

Fetal membranes
Chorion
Amnion
Yolk sac
Allantois
They develop from zygote, however they
are not involved in embryo formation
except for small part of yolk sac, that
participate on gut formation

Amnion
Amnionic fluid
Amnioblasts,
interstitial fluid form
endometrium
Embryo (before skin
keratinization) –
transudation from
body
Umbilical cord
Respiratory system,
urine
10th week – 30ml
20
th
week – 350ml
37
th
week - 700-
1000ml

Function of amniotic fluid
It allows symetric growth
Protects from infection
Facilitates normal development of lung
Protects from adhesion
Protects from injury
Keeps stabile temperature
Alows free movement
Takes place in homeostasis (electrolytes)

Failures of amnionic fluid
volume
Oligohydramnion – less than 400ml -
rupture of fetal membranes, renal
agenesis – (Potter syndrome) -
pulmonary hypoplasia, pes equinovarus,
face dysmorfy
Polyhydramnion – more than 2000 ml –
malformed CNS, esofageal atresia, twins,
idiopatic

Yolk sac
Transfer and metabolism of nutrients – as
liver
Development of blood cells and vessels
-vitelline vascular system
Participation on formation of primitive
gut
Primordial gamets in endoderm of yolk
sac during 3 rd week

Allantois
Development form hindgut – evagination
into embryonic stalk - only transient
Vessels – umbilical arteries and veins for
placenta supply
Intraembryonic part – urachus, urinary
bladder ( ligamentum umbilicale
medianum)

Placenta
Fetal organ providing nutrition and many
other functions:
Function:
− Metabolism (synthesis, for example glycogen)
− Transport of gases and nutrients
− Excretion of waste products
− Production of hormones (hCG)

Embryo nutrition
Nutrients supply in yolk sac (AA, lipids)
Histiotrophe – secret from glandular cells
in fallopian tube, uterus, digestion of
endometrium
Haematotrophe – maternal blood
Organ that provide nutrition of embryo in
mammals - chorion/placenta

Placenta - structure
Fetal part – chorion – chorionic plate and
chorionic villi
Maternal part – endometrium – pars
functionalis – decidua basalis

Decidua
Zona functionalis that is changing during
pregnancy
Decidua basalis
Decidua capsularis
Decidua parietalis
Progesteron – cell in stroma (fibroblasts)
are changed in decidual cells (content of
glycogen and lipids)+ changes in vascular
supply = decidual reaction

Implantation

Implantation
During implantation embryo invades in
zona functionalis of endometrium
Trophoblast diferentiates into
syncytiotrophoblast and cytotrophoblast
Extraembryonic mesoderm adds to
cytotrophoblast
= CHORION

Development of chorionic villi
Primary: Syncytiotrophoblast and
cytotrophoblast
Secondary: Syncytiotrophoblast,
cytotrophoblast and extraembryonic
mesoderm
Tertiary: Vessels occur in mesoderm
Terctiary villi are all from 3
rd
week of
development

Placenta development
Chorion laeve
Chorion frondosum
Decidua capsularis get thiner, later
disappears, chorion laeve is on the
surface, it unites with decidua parietalis
and obliterates uterine cavity ( week 22
-24)

Intervillous space
It develops from lacunae in sytiotrophoblast
It is divided by placental septa
Maternal blood – spiral arteries in decidua basalis –
uteroplacental vessels
It wash up villi – it is drained into placental veins. Fetal
and maternal blood do not mix !!!
Hemocytoblasts (stem cells) may cross from embryonic
to maternal blood and stay there for relatively long time
(several years) -chimera

Placental circulation
Umbilical arteries
-deoxygenated
blood from
embryonic body
Chorionic arteries
branching in
chorionic plate
Capillary network
in chorionic villi

Placental membrana
Interface between maternal and fetal
blood
• Syncytiotrophoblast
• Cytotrophoblast
• Connective tissue
• Endothelium of fetal capillary
After week 12 cytotrophoblast gradually
disappears, vessels come near to surface
and get in contact with
syncytiotrophoblast

3rd trimester
Nuclei of
syncytiotrophoblast
form aggregations –
syncytial knots that
may set free
Formation of
fibrinoid – it reduces
placental transfer

Syncytiotrophoblast
– microvilli, SER,
RER, GC, mito –
active synthesis
Cytotrophoblast –
undifferentiated
cells – mitoses
Basal membrane
Continuous
endothelium

Feto-maternal junction
Different genotype – necessity to supress
imunity:
Maternal and fetal tissue are separted by the
cells that do not have typical superficial
antigens. Hormonal changes (progesteron,
glucocorticods)
– Blood - Syncytiotrophoblast
– Connective tissue – Cytotrophoblastic shell
Stem - anchoring villi attach chorion to the
decidua basalis – inside cytotrophoblastic
plug

Placenta
Placental shape – discoid (olliformis) +
haemochorial
Placental septa – rests of decidua basalis.
They separate placenta from maternal
side in lobes - cotyledons
Cotyledons – contain 2 and more
anchoring villi
Diameter – 15 -20 cm, thickness 2-3 cm,
weight 500 to 600 g

Placental transfer
Difusion
Facilitated difusion
Active transport
Pinocytosis
Other types of transfer:
Damage of placetal barrier – blood cellas
Own activity – Treponema pallidum
Damage due to infection - toxoplasmosa

Transfer
Many substances from maternal blood
may transfer placental barrier including
drugs
Nutrients – glucose, AK, fatty acids,
water, vitamines, electrolytes
Hormones – only steroid unconjugates
Maternal antibodies, transferin+ iron

Syntesis
hCG – human chorionic gonadotropin
hCS – human chorionic somatomammotropin/placental
lactogen
hCT human chorionic thyrotropin
hCACTH human chorionic corticotropin
Progesteron and estrogens

Placental abnormalities
Atypical implatation:
Placenta previa
Placenta accreta
Placenta percreta
Placenta membranacea
Placenta accessoria
Atypical attachment of umbilical cord--
marginal, velamentous

Development of mbilical cord
Connective stalk with umbilical arteries
and veins and allantois
Ductus omphaloentericus connecting gut
with yolk sac
Extraembryonic coelom
Umbilicus

Development
of umbilical
cord
• Length 50 cm