The placenta is a temporary organ that connects the developing foetus via the umbilical cord to the uterine wall to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother's blood supply; to fight against internal infection; and to produce hormones which support pregnancy. The placenta functions as a fetomaternal organ with two components: the fetal placenta which develops from the same blastocyst that forms the fetus, and the maternal placenta , which develops from the maternal uterine tissue. The placenta is expelled from the body upon birth of the fetus.
2. PLACENTAThe placenta is a temporary organ that
connects the developing foetus via
the umbilical cord to the uterine wall to allow
nutrient uptake, thermo-regulation, waste
elimination, and gas exchange via the
mother's blood supply; to fight against
internal infection; and to produce hormones
which support pregnancy. The placenta
functions as a fetomaternal organ with two
components: the fetal placenta which -
3. develops from the same blastocyst that forms the
fetus, and the maternal placenta , which develops
from the maternal uterine tissue. The placenta is
expelled from the body upon birth of the fetus.
4. Anatomy
• Circular disc with a diameter of 15-20 cm and
thickness of about 2.5 cm at its center.
• It feels spongy and weight about 500 gm.
• It presents two surfaces, fetal , maternal and
peripheral margin.
5. FETAL SURFACE (Chorionic Plate) :
• Covered by the smooth and glistening amnion with
the umbilical cord attached at or near its center.
• Branches of the umbilical vessels are visible beneath
the amnion.
• The amnion can be peeled off from the underlying
chorion except at the insertion of the cord.
• At term, about four-fifths of the placenta is of fetal
origin.
6. MATERNAL SURFACE :
• Rough and spongy• Dull red colour• A thin greyish,
layer which is the remnant of decidua basalis
(compact and spongy layer).
• Maternal surface mapped out into 15-20 convex
polygonal areas known as lobes or cotyledons which
are limited by fissures.
• Each fissure is occupied by the decidual septum.
• Only the Decidua basalis and Blood in the intervillous
space are of Maternal origin.
7. MARGIN :
• Peripheral margin of the placenta is limited by the
fused basal and chorionic plates.
• Essentially, the chorion and the placenta are one
structure but the placenta is a specialized part of
the chorion.
8. Foetal surface of placenta showing
attachment of the umbilical cord
with ramification of the umbilical
vessels.
Maternal surface of the placenta
showing shaggy look with cotyledons
limited by fissures.
9. STRUCTURES :
• Placenta consist of 2 plates,
i) Chorionic Plate –
• Lies internally, lined by amniotic membrane.
• Umbilical cord is attached to this plate.
• it consists of –
i. Primitive mesenchymal tissue containing
branches of umbilical vessels
ii. A layer of cytotrophoblast and
iii. Syncytiotrophoblast.
10. ii) BASAL PLATE
• It Lies to Maternal aspect.
• It consists of the following structures from outside
inwards.
i. Part of the compact and spongy layer of the
decidua basalis
ii. Nitabuchs layer of fibrinoid degeneration of the
outer syncytiotrophoblast at the junction of the
cytotrophoblastic shell and decidua.
iii. Cytotrophoblastic shell
iv. Syncytiotrophoblast.
11.
12. DEVELOPMENT OF PLACENTA
• Developed from two sources.• The principal
component is fetal which develops from the chorion
frondosum and the maternal component consists of
decidua basalis.
• When the Interstitial implantation is completed on
11th day, the blastocyst is surrounded on all sides by
lacunar spaces.
• Stem villi developed on13th day which connect the
chorionic plate with the basal plate.
13. • Primary, secondary and tertiary villi are successively
developed from the stem villi.
• Arterio-capillary-venous system in the mesenchymal
core of each villus is completed on 21st day.
• Simultaneously, lacunar spaces become confluent
with one another by 3rd – 4th week and form a
multilocular receptacle.
• Chorion frondosum and decidua basalis form the
discrete placenta. It begins at 6th week and is
completed by 12th week.
14. • Until end of 16th week placenta grows both in
thickness and circumference due to the growth of
chorionic villi with accompanying expansion of the
intervillous space.
15.
16. PLACENTAL FUNCTIONS :
The main functions of Placenta are –
• Transfer of nutrients and waste products between
the mother and foetus
• Endocrine Function – Placenta is an endocrine
gland , it produces both steroid and peptide
hormones to maintain pregnancy.
• Barrier Function – The Fetal membrane has long
been considered as the protective barrier to the
foetus against noxious agents circulating in the
maternal blood.
17. • Respiratory Function
Although the fetal respiratory movements are observed
as early as 11 weeks, there is no gaseous exchange.
Intake of oxygen and carbon dioxide take place by
simple diffusion across the fetal membrane.
• Excretory Function
Waste products from the foetus such as urea, uric acid
and creatinine are excreted in the maternal blood by
simple diffusion.
• Nutritive Function
The foetus obtain its nutrients from the Maternal blood
and when the diet is inadequate, then only depletion
of maternal tissue storage occurs.
