Placenta and Amniotic Fluid: Structure, Function, and Abnormalities

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Questions and Answers

What is the function of the amniotic membrane in placental formation?

It separates the placenta from the fetus

It prevents excessive penetration of the decidua

It does not take part in placental formation (correct)

It takes part in placental formation

What is the layer of tissue that prevents excessive penetration of the decidua by the trophoblastic layer?

Layer of Nitabuch (correct)

Cytotrophoblastic shell

Syncytiotrophoblast

compact and spongy layer of decidua basalis

What is the structure that forms the roof of the placenta?

Basal Plate

Chorionic Plate (correct)

Intervillous Space

Amniotic Membrane

What is the function of the spiral arteries in the placenta?

They allow entry of maternal blood into the intervillous space Signup and view all the answers

What is the term for a condition where the placenta remains attached to the uterine?

Placenta Accreta Signup and view all the answers

What is the layer that consists of a compact and spongy layer of decidua?

Decidua Basalis Signup and view all the answers

What is the percentage of the placenta that is of fetal origin?

4/5 Signup and view all the answers

What is the average weight of the fully developed placenta?

500gm Signup and view all the answers

What is the function of the decidua basalis in the placenta?

It gives the placenta a shaggy appearance Signup and view all the answers

What is the characteristic of the fetal surface of the placenta?

Smooth and glistening Signup and view all the answers

How many cotyledons does the maternal surface of the placenta have?

15-20 Signup and view all the answers

What is the location of the placenta attachment in the uterus?

Upper part of the uterine body Signup and view all the answers

What is the primary function of the placenta and umbilical cord?

To form a transport system for substances between mother and fetus Signup and view all the answers

What is the approximate diameter of the mature human placenta?

20-25 cm Signup and view all the answers

What is the source of the maternal component of the placenta?

Decidua basalis Signup and view all the answers

At what stage of development does the placenta begin to form?

5-6 weeks Signup and view all the answers

What is the main function of the syncytiotrophoblast?

To cover the cytotrophoblast Signup and view all the answers

What is the result of the trophoblast eroding the maternal spiral arteries?

The flow of blood directly into the intervillous spaces Signup and view all the answers

What is the primary function of the cytotrophoblast cells?

To penetrate through the primary syncytium Signup and view all the answers

At what stage of development does the human placental development require co-ordinated interaction between the trophoblast lineages and the maternal endometrium?

Throughout the entire pregnancy Signup and view all the answers

What lines the intervillous space internally on all sides?

Syncytiotrophoblast Signup and view all the answers

What is the estimated total surface area of the villi for exchange?

4-14 sq meters Signup and view all the answers

What is the main function of the placenta in supporting fetal growth?

Providing gases and nutrients Signup and view all the answers

What is the thickness of the placental membrane or barrier?

0.025 mm Signup and view all the answers

What is the term for the structural unit of the placenta?

Fetal cotyledon Signup and view all the answers

What type of placenta is characterized by the presence of chorionic derivatives?

Haemochorial type Signup and view all the answers

What layer is lost in the placental barrier by full-term?

Cytotrophoblast Signup and view all the answers

What substances can pass through the placental barrier?

Drugs and viruses Signup and view all the answers

What is the origin of amniotic fluid?

Both from maternal circulation and fetal urine, as well as other sources Signup and view all the answers

What is the normal pH of amniotic fluid?

Faintly alkaline Signup and view all the answers

What is the volume of amniotic fluid at 36 weeks of gestation?

1 liter Signup and view all the answers

What is the osmolarity of amniotic fluid indicative of?

Fetal maturity Signup and view all the answers

What is the color of amniotic fluid in early pregnancy?

Colorless Signup and view all the answers

What is the function of amniotic fluid during labor?

To form a hydrostatic wedge to help dilatation of the cervix Signup and view all the answers

What is the significance of studying amniotic fluid?

To know the well-being and maturity of the fetus Signup and view all the answers

What is the term for excessive amniotic fluid?

Polyhydroamnios Signup and view all the answers

What is the composition of amniotic fluid?

Water, proteins, glucose, urea, and hormones Signup and view all the answers

What is the function of amniotic fluid in preventing adhesion formation?

It prevents adhesion formation between fetal parts and the amniotic sac Signup and view all the answers

Study Notes

Placenta Development

The placenta is a fetomaternal organ composed of two surfaces: maternal surface (derived from the endometrium) and fetal surface (derived from the chorionic sac)
Human placental development begins at 6 weeks and is completed by 12 weeks
The placenta develops from two sources: fetal component (chorionic frondosum) and maternal component (decidua basalis)
The umbilical cord is formed by the connection between the placenta and the fetus, forming a transport system for substances between mother and fetus

Placenta Structure

The mature human placenta is a discoid organ, 20-25 cm in diameter, 3 cm thick, and weighing 400-600g
The placenta consists of three layers: amnion (innermost), chorion membrane (middle), and decidua (outermost)
The amnion is a single layer of ectodermal epithelium, completely enclosing the embryo
The chorion membrane surrounds the amniotic sac and includes the villi and trophoblast
The decidua is the maternal endometrium, which undergoes changes to accommodate the placenta

Placenta at Term

Gross anatomy: fleshy, 15-20 cm in diameter, 2.5 cm thick, and weighing 500g
The placenta has two surfaces: maternal (rough and spongy) and fetal (smooth and glistening)
The umbilical cord is attached to the center of the fetal surface
The maternal surface has 15-20 cotyledons, separated by septa

Amniotic Membrane and Basal Plate

The amniotic membrane is a single layer of cubical epithelium, loosely attached to the chorionic plate
The basal plate forms the floor of the placenta, consisting of compact and spongy decidua basalis, Layer of Nitabuch, cytotrophoblastic shell, and syncytiotrophoblast
The Layer of Nitabuch is a fibrous layer formed at the junction of the cytotrophoblastic shell with decidua basalis

Intervillous Space and Stem Villi

The intervillous space is filled with maternal blood and stem villi with their branches
Stem villi arise from the chorionic plate and extend to the basal plate
Fetal cotyledons (60-100) are derived from one major primary stem villus and are the structural units of the placenta
Maternal cotyledons (15-20) contain 3-5 fetal cotyledons

Placental Barrier or Membrane

The placental barrier separates maternal and fetal blood, consisting of endothelial lining of fetal vessels, connective tissue of the villi, basement membrane, cytotrophoblast, and syncytiotrophoblast
The placental barrier is relatively thick in the first trimester (0-13 weeks) and much thinner at full-term (27-40 weeks)

Placental Functions

The placenta provides gases and nutrients to the fetus throughout pregnancy
It allows the exchange of substances between the maternal and fetal circulations

Amniotic Fluid

Origin: transudation from maternal circulation, active secretion from amniotic epithelium, transudation across the umbilical cord and fetal placental circulation, fetal urine, tracheobronchial secretion, and transfer across fetal skin
Composition: proteins, glucose, urea, non-protein nitrogen, uric acid, creatinine, lipids, hormones, and suspended particles
Physical features: faintly alkaline, low specific gravity, and becomes highly hypotonic to maternal serum at term pregnancy
Abnormal appearance: greenish (meconium), golden yellow (bilirubin), greenish-yellow (post-maturity), dark maroon/blood-stained (altered blood), and prune juice/dark brown (retained dead fetus)
Functions: shock absorber, temperature regulation, free movement and growth of fetus, prevents adhesion formation, and has some nutritive value
Clinical importance: study of amniotic fluid helps in knowing the well-being and maturity of the fetus

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Description

This quiz covers the development, structure, and function of the placenta, as well as its abnormalities. Learn about the maternal and fetal surfaces, and the characteristics of the mature human placenta.