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

20th week – 350ml

37th week - 7001000ml
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 3rd 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 3rd 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