PLACENTAL FORMATION AND FUNCTION ,COMPLICATION

1. PLACENTA
 Placenta is a Latin word for pancake. It arises out of trophoblast tissue.
 It serves as the fetalLungs, Kidneys and gastro intestinal tract and as a separate endocrine organ
throughout pregnancy. It growth equally of the fetus growing
 It has 15 to 20cm in Diameter and 2 to 3cm in depth at term
 It also corer half the circle of the internal uterus
PLACENTAL CIRCULATION
 Once the fertilization is completed the zygotes migrates over next 3 to 4 days towards the body of
the uterus with the muscular contraction of the fallopian tube
 During this period miotic cell division and cleavage occurs. 1st
cleavage will occur at about 24
hrs and continue at the rate of every 22 hrs
 By the time zygote reaches the body of the uterus and it consists of 16 to 50 cells. It is called
MORULA.
 Morula is from a Latin word “ MORUS” means mulberry. It continues to multiply and free to
float in the uterine cavity for 3 or 4 days time.
 This large cell in the morula collect at the periphery and forming the inner cell mass. This
structure is called BLASTOCYST.
 Blastocyst will attaches to the endometrial layer of the uterine cavity. The cell in the enter ring is
called TROPHOBLAST. Later this trophoblast form the placenta and the membrane.
 The inner cell mass called embryo blast cells and later will form as EMBRYO.

2.  Implantation will occurs within 8-10 days after fertilization.
 With the help of trophoblast the blastocyst able to involved the endometrium. They produce
photolytic enzyme that allows the blastocyst to barrow deeply in to the endometrium and
receives the basic nourishment
 As it barrows deeper the communication network also established well with the blood
system of the endometrium.
 Occasionally a small amount of bleeding may occur at the time of implantation, because of
capillary rapture. Once implanted the zygote is called Embryo
DECIDUA
1. After fertilization the corpus luteum in the ovary continues to function because of the influence of
HCG.
2. hcG is the hormone secreted by the trophoblast uterine muscles continues to grow in thickness
and vascularity. The endometrium is called as Decidua
3. Decidua is the Latin word means “Falling off” Decidua has three layers
1. Decidua basalis – endometrium lies directly under the embryo
2. Decidua capsularis - endometrium that encapsulate the surface of trophoblast
3. Decidua vera - remaining portion of the uterine lining
CHORIONIC VILLI

3.  Once implantation occurs the trophoblastic layer of the blastocyst begins to grow rapidly. The
decidua capsularies fuses with the endometrium. At birth the entire inner surface of the uterus is
“falling off” and the organ (Uterus) is highly susceptible to haemorrhagic and infection
 11th
or 12th
day miniature villas formed called chronic villi reached into the uterine endometrum
at term more than 200 such villi have formed.
 The chorionic villi has the double layer of trophoblast cells
o Central core contain fetalcapillaries
o Outer layers instrumental in production of various
 The hormones are (placental hormones)
1. Human chorionic Gonadotrophic hormone (HCG)
2. Human placental lactogen hormone (LPL)
3. Oestrogen
4. Progression
5. Gonadotropin – releasing hormone
6. Thyrotrophic – releasing hormone
7. Corticotrophin
The inner layer cytotrophoblast present from 12th
day of gestation. It protect the growing embryo, from
infections
PLACENTA
It is a pan cake shape or flat dish shaped arises from the trophoblast tissue (chorion, chorinicvilli,
deciduabasalis)
 It serves as a fetallungs, kidneys and gastro intestinal tract.
 Acts as a endocrine organ till throughout the term
 Characteristics at term
weight - 450 – 650 gm
measures - 15 to 25.5cm Diameter
thickness - 2.5 to 3 cm
two surface - Rough surface
- maternal surface
- shiny and grey surface
- fetal surface
FUNCTIONS
1. Exchange of oxygen and nutrients from maternal circulation
2. Produce hormones - 1 – 7 hormones
3. Supplies carbohydrate, protein, fat, water,minerals and inorganic salts to fetus
4. Carries and products of fetal metabolism
5. Transfer passive immunity via maternal antibodies

4. PLACENTAL CIRCULATION
 Started from the 12th
day of pregnancy maternal blood collects in the inter villous spaces of the
endometrium
 3rd
week O2 other nutrients such as amino acids fatty acids, minerals, vitamins and water diffuse
from the maternal villi to the cell layers of the chronic villi
• Nutrients transports to the growing embryo. No direct exchange of blood between the maternal
and fetus, but there is selective osmosis through the chronicvilli
 Due to minute breaks occasionaly fetalcells and enzymes cross from mother to fetus
 Certain drugs specially alcohol crosses the placenta
 Specific mechanism helps the nutrients to cross the placenta
 With the communication network, the inter villious spaces grow larger and larger it separated by
a septa
 In a mature placenta there are 30 separate segment present called COTYLEDENS
 About 100 maternal uterine anterier supplies to the mature placenta
 The rate of uteroplacental blood flow 50ml/mt
 The maternal blood gradually loses its momentum and settled to the floor of cotyledons
 Blood vessels from the cotyledons had direct connection to the maternal circulation
 Uterine perfusion and placental circulation is most efficient while the woman is in left lateral
position

5.  At terms placental circulation increases and the placenta weighs about 400 – 600 gm; 1/6 the
weight of the baby.
COMPLICATIONS
1. small placenta indicate poor nourishment
2. bigger placenta fetus was threatened
3. diabetic mother – larger than usual placenta due to excess fluid collected