placenta

Question 1

what is decidua?

Answer 1

-uterine endometrium after implantation of embryo
- gravid endometrium and the functional layer of the
endometrium.

Question 2

3 regions of decidua in relation to the implantation site are :-

Answer 2

 Decidua basalis
 Decidua capsularis
 Decidua parietalis
look at pic on slide

Question 3

Decidua formation

Answer 3

-Trophoblast secretes (HCG) which prolong the life of corpus luteum.
The corpus luteum of pregnancy continues to secrete progesterone.
increasing level of progesterone in maternal blood induces endometrial changes into decidua.

Question 4

describe Decidua basalis

Answer 4

-Part between the embryo and the myometrium
 Implantation site & site where placenta developed

Question 5

describe Decidua capsularis

Answer 5

Part between the embryo and uterine cavity
 Overlying the embryo and covering the chorionic sac

Question 6

describe Decidua parietalis

Answer 6

 Part of decidua which lines the rest of uterine cavity  Not involving in covering the embryo

Question 7

Fate of Decidua

Answer 7

The chorionic sac expands towards the cavity of the uterus due to the growth of fetus & enlargement of amniotic cavity.
 The cavity of uterus is obliterated due to fusion of chorion & amnion.
 Decidua parietalis & capsularis fuse together and disappear gradually.
 Decidua basalis persists to become the maternal part of placenta.

Question 8

describe PLACENTA

Answer 8

Discoid(shape),interstitial(implantation),deciduate(shedoff), haemochorial (maternal blood contact) and villous (chorion projection) type of organ.

• Dimension:
• Diameter - 15 to 20 cm
• Thickness - 3 cm
• Weight -500 gm
• occupies about 30% of the uterine wall.
• on upper uterine segment on the posterior wall.

Question 9

describe Maternal surface of placental surfaces

Answer 9

Rough lobulated areas-15-20 cotyledons separated by grooves containing decidual (placental) septa.
Each cotyledon formed by 3-4 stem villi with their branches.

Question 10

describe fetal surface of placenta

Answer 10

Chorionic plate which is smooth (not divided into cotyledons) and shiny due to the covering of amniotic membrane.
Umbilical cord is inserted right to its center with the umbilical vessels radiating from the cord under the amnion.
At birth, the amnion and chorion are torn from the margin of placenta.

Question 11

structure of placenta

Answer 11

Made up of chorionic plate (foetal component) & decidua basalis (maternal component)
 With an intervening choroideo- decidual space which is occupied by the villi extending from chorionic plate to basal plate.
look at pic on slide

Question 12

Fetal component of placenta (Chorionic plate and villi)

Answer 12

 The chorionic villi (which gradually progress from primary to tertiary stage) emerge from the chorion and invade the endometrium.
 allowing transfer of nutrients from the maternal blood present in the intervillous spaces to the foetus.

 Chorionic villi consists of from inside outwards:
1. Extra embryonic mesoderm with blood
vessels
2. Cytotrophoblast (CTB)
3. Syncytiotrophoblast (STB)

 Stem villi arise from the chorionic plate and extend to the basal plate.
 There are spaces between these stem villi known as inter villous spaces.
 These spaces are lined internally on all sides by the syncytiotrophoblast and is filled with maternal blood.

Question 13

Maternal component of placenta (Decidua basalis and basal plate) (from outside inward):

Answer 13

1.Decidua basalis (maternal component of the placenta)
2.Layer of fibrinoid degeneration of STB (Nitabuch’s layer)
3.Outer Cytotrophoblast(CTB) shell 4.Syncytiotrophoblast(STB)

Question 14

describe Placental barrier/membrane

Answer 14

Consists of tissues which intervene between fetal blood in the chorionic villi and maternal blood in intervillous space.
With further development of placenta, cytotrophoblast will degenerates and connective tissue disappears.
 Capillaries move towards syncytiotrophoblast.
 Barrier becomes thinner, composed only of:
I. Syncytiotrophoblast
II. Capillary endothelium
 Near term, fibrinoid material are deposited on villi decrease the maternal & fetal blood exchange.

Question 15

The layers of placental barrier/membrane?

Answer 15

I. Endothelium of chorionic villous capillary
with its basal lamina
II. Stromal/connective tissue (extra
embryonic mesodermal core)
III. Basal lamina of cytotrophoblast
IV. Cytotrophoblast
V. Syncytiotrophoblast

Question 16

state Placental barrier/membrane functions

Answer 16

Separates fetal from maternal blood & prevents mixing of them.
 Incomplete barrier because it only prevents large molecules to pass (heparin, bacteria).
 cannot prevent passage of viruses (e. g. rubella), microorganisms (e. g. toxoplasma gondii, treponema pallidum), drugs and hormones.

Question 17

state of two independent circulatory system of placental circulation and structures involved

Answer 17

 Maternal-placental circulation
1. Spiral uterine arteries
2. Uterine veins
3. Intervillous spaces

 Fetal-placental circulation
1. Umbilical arteries
2. Umbilical vein
3. Fetal capillaries

Question 18

Maternal-placental circulation- look at pic on slide

Answer 18

Oxygenated blood from mother enter the intervillous space via spiral arteries which provide a pulsatile flow of blood (spurt towards chorionic plate).

When blood pressure decreased, exchange of gases and metabolic products with the fetal blood occurs.

Deoxygenated blood flow out of intervillous spaces from the placenta to be drained by endometrial veins to uterine veins.

Question 19

Fetal-placental circulation- look at pic on slide

Answer 19

Deoxygenated blood flow out from fetus and enters umbilical arteries to the placenta.
Umbilical arteries branched before entering the villi and form an extensive arterio- capillary-venous system within villi.
provides a very large area for exchange of metabolic and gaseous products with maternal blood
Oxygenated fetal blood enters umbilical vein to the fetus.

Question 20

Placenta has 3 main functions which are:

Answer 20

 Metabolism
 Transport of substances
 Endocrine secretion

Question 21

METABOLISM

Answer 21

For synthesis of glycogen, cholesterol & fatty acids: source of nutrition & energy for embryo or fetus during early pregnancy

Question 22

TRANSPORT

Answer 22

Transport of substances in both directions between placenta & maternal blood:
* Gases: Oxygen and Carbon dioxide
* Nutritional substances: Glucose, Aminoacids, Vitamins
* Hormones: Steroid hormones (testosterone)
* Electrolytes: Na+, K+, Cl.
* Maternal antibodies: Antibodies against diphteria,
smallpox, measles

Question 23

ENDOCRINE

Answer 23

Secretion of :
* Protein hormones:
1. Human chorionic gonadotropin
2. Human placental lactogen
3. Human chorionic thyrotropin
4. Human chorionic corticotropin
5. Relaxin

• Steroid hormones:
  1. Progesterone
  2. Estrogen

Question 24

look at structur go through placenta on slide

Answer 24

-

Question 25

Fate of placenta

Answer 25

Towards the end of the pregnancy fibrinoid deposits accumulate in the placenta.
 Occurs below the chorionic plate, where they form Langhans’ fibrinoid layer (A) that lies under the chorion,
 In basal plate under the anchoring villus and cytotrophoblast layer, where the fibrin deposit forms Rohr’s fibrinoid layer (B).
 Deeper in the decidua basalis these deposits form Nitabuch’s fibrinoid layer (C). Here is where the placenta will detach at birth.

Question 26

Placental separation

Answer 26

separates after the birth of baby and line of separation is through spongy layer of decidua basalis.

Question 27

Anomalies of placenta

Answer 27

A. According to size & shape
 Placenta membranacea
 Accessory placenta

B. According to position
 Placenta previa

C. According to extension  Placenta accreta
 Placenta percreta

D. According to attachment of umbilical cord
 Battledore placenta
 Velamentous placenta

Question 28

According to size & shape

Answer 28

I. Placenta membranacea = A large placenta due to persistence of functioning villi on the entire surface of chorionic sac
II. Accessory placenta = A patch of chorionic villi persisted a short distance from main placenta

Question 29

According to position

Answer 29

I. Placenta previa = Occurs when blastocyst implants close to or overlying the internal os of uterus
Subclassified into:
i. Low implantation
ii. Marginal
iii. Partial
iv. Total

Question 30

According to extension

Answer 30

I. Placenta accreta = Chorionic villi attach to the myometrium
II. Placenta increta = Chorionic villi invade the myometrium
III. Placentapercreta=Chorionicvillipenetrate the whole thickness of myometrium and extending to perimetrium and invade adjacent organs

Question 31

According to attachment of umbilical cord

Answer 31

I.Battledore placenta = Umbilical cord is attached to the margin of placenta

II.Velamentous placenta = Umbilical cord is attached to the membranes surrounding placenta; umbilical vessels are liable to be ruptured