Placenta Flashcards
The fetal component of the placenta is derived from …………
The trophoblast and extraembryonic mesoderm (chorionic plate)
The maternal component of the placenta is derived from ………….?
The basal decidua of the uterine endometrium
The surface of the villi is formed by …………..
The synctium resting on a layer of cytotrophoblastic cells
How is the extraembryonic vascular system formed?
The capillary system developing in the core of the villous stems soon come in contact with capillaries of the chorionic plate and connecting stalk, thus giving rise to the extraembryonic vascular system
Maternal blood is delivered to the placenta by ……………
spiral arteries in the uterus
endovascular invasion is achieved by………….
cytotrophoblast cells.
How is endovascular invasion achieved?
cytotrophoblast cells, released from the ends of anchoring villi invade the terminal ends of spiral arteries, where they replace maternal endothelial cells in the vessels’ walls, creating hybrid vessels containing both fetal and maternal cells.
To accomplish endovascular invasion, cytotrophoblast cells undergo an …………..
epithelial-to-endothelial transition.
What is the nature of the spiral arteries after endovascular invasion?
these vessels are transformed from small-diameter, high-resistance vessels to larger-diameter, low- resistance vessels that can provide increased quantities of maternal blood to intervillous spaces.
by …………… month cytotrophoblastic cells and some connective tissue cells disappear
by the beginning of the fourth month
……………are the only layers that separate the maternal and fetal circulations by the beginning of the fourth month
The syncytium and endothelial wall of the blood vessels
What are syncytial knots?
Frequently, the syncytium becomes very thin, and large pieces containing several nuclei may break off and drop into the intervillous blood lakes. These pieces, known as syncytial knots
What is preeclampsia?
A condition characterised by maternal hypertension and proteinuria due to reduced organ perfusion.
the only portion of the chorion participating in the exchange process is the ……………..
chorion frondosum
The chorion frondosum together with the ………….. makes up the placenta.
decidua basalis
fusion of the amnion and chorion to form the ……………
amniochorionic membrane
…………. is this membrane that ruptures during labor (breaking of the water)
amniochorionic membrane
Between the chorionic and decidual plates are the ……………. spaces
intervillous spaces
Decidual septa are formed from the decidua during the ……… month
4th and 5th month
throughout pregnancy, the placenta covers approximately ………….% of the internal surface of the uterus.
15% to 30%
The increase in thickness of the placenta results from ………….
arborization of existing villi and is not caused by further penetration into maternal tissues.
Describe the full term placenta
At full term,
- the placenta is discoid
- has a diameter of 15 to 25 cm
- It is approximately 3 cm thick
- it weighs about 500 to 600 g.
What is velamentous insertion
an abnormal cord insertion in which the umbilical chord insert into the chorionic membranes outside the placenta
Intervillous spaces of a mature placenta contain approximately ………… volume of blood
150 mL
………… separates maternal and fetal blood
Placental membrane
Mention four initial layers of the placental membrane (before the fourth month)
(1) the endothelial lining of fetal vessels
(2) the connective tissue in the villus core
(3) the cytotrophoblastic layer
(4) the syncytium
Why is the human placenta considered hemochorial?
Because the maternal blood in the intervillous spaces is separated from the fetal blood by a chorionic derivative
What are the main functions of the placenta
(1) exchange of metabolic and gaseous products between maternal and fetal bloodstreams and
(2) production of hormones.
When does immunological competence begin to develop?
Late in the first trimester
……….. is an indicator of pregnancy found in the urine, during the first 2 months of pregnancy
HCG
What are the effects of somatomammotropin
- gives the foetus priority on maternal blood glucose
- makes the mother somewhat diabetogenic
- promotes breast development for milk production
Mention some hormones secreted by the placenta
Progesterone
Estrogenic hormones, predominantly estriol
HCG
Somatomammotropin, formerly known as placental lactogen
The oval line of reflection between the amnion and embryonic ectoderm is the ………….
primitive umbilical ring
………. Is the oval line of reflection at the amnio-ectodermal junction
Primitive umbilical ring
Mention the structures that pass through the primitive umbilical ring at the fifth week of development
(1) the connecting stalk, containing the allantois and the umbilical vessels, consisting of two arteries and one vein
(2) the yolk stalk (vitelline duct), accompanied by the vitelline vessels;
(3) the canal connecting the intraembryonic and extraembryonic cavities.
The chorionic cavity refers to ……….
A space between the amnion and chorionic plate
How is the primitive umbilical chord formed?
the amniotic cavity enlarges rapidly at the expense of the chorionic cavity, and the amnion begins to envelop the connecting and yolk sac stalks, crowding them together and giving rise to the primitive umbilical cord
Name the contents of the primitive umbilical cord
- Distally, the cord contains the yolk sac stalk and umbilical vessels.
- More proximally, it contains some intestinal loops and the remnant of the allantois
At the end of the …… month, the amnion has expanded so that it comes in contact with the chorion, obliterating the chorionic cavity
3rd month
What is a physiological umbilical hernia?
The abdominal cavity is temporarily too small for the rapidly developing intestinal loops, and some of them are pushed into the extraembryonic space in the umbilical cord.These extruding intestinal loops form a physiological umbilical hernia.
Mention the placental changes that occur at the end of pregnancy
(1) an increase in fibrous tissue in the core of the villus
(2) thickening of basement membranes in fetal capillaries
(3) obliterative changes in small capillaries of the villi
(4) deposition of fibrinoid on the surface of the villi in the junctional zone and in the chorionic plate.
What’s the effect of excessive fibrinoid formation?
infarction of an intervillous lake or sometimes of an entire cotyledon. The cotledon then assumes a whitish appearance.
Outline the volumes of amniotic fluid at different weeks of gestation
30 mL at 10 weeks of gestation
450 mL at 20 weeks
1,000 mL at 37 weeks.
Outline the functions of the amniotic fluid
1) absorbs jolts
2) prevents adherence of the embryo to the amnion, and
3) allows for fetal movements
How often is the volume of amniotic fluid replaced?
Every 3 hours
What’s the role of the amniochorionic membrane in parturition?
During childbirth, the amniochorionic membrane forms a hydrostatic wedge that helps to dilate the cervical canal.
The length of the umbilical cord reflects………….
the amount of intrauterine movement of the fetus
What’s the major cause of amniotic bands?
tears in the amnion result in amniotic bands
…………….. is the term used to describe an excessive amniotic fluid, whereas ………….. refers to a decreased amount
Hydramnios or polyhydramnios is the term used to describe an excessive amniotic fluid, whereas oligohydramnios refers to a decreased amount of amniotic fluid.
What is the volume of amniotic fluid in hydramnious or polyhydramnios?
> 1,500 - 2000mL
What is the volume of amniotic fluid in oligohydramnios?
<400mL
Where is placenta previa attached?
Lower segment of the uterine body, near the cervix
