Placenta and Fetal Membranes

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Questions and Answers

What structure suspends the embryo, amniotic sac, and umbilical vesicle in the chorionic cavity?

Yolk sac stalk diverticulum

Connecting stalk (correct)

Primordial uteroplacental circulation

Secondary chorionic villi

Which of the following is NOT a derivative of the yolk sac?

Primordial germ cells

The early gut epithelium of the respiratory and digestive tracts

Epithelium of the skeletal system (correct)

Early blood cells formed from blood islands

What is the function of the yolk sac during the early stages of development?

Forms the placenta

Provides nutrition to the embryo (correct)

Forms the amniotic sac

Develops into the umbilical cord

What is the origin of the allantois?

Endodermal origin Signup and view all the answers

What is the purpose of the connecting stalk?

It suspends the embryo in the chorionic cavity Signup and view all the answers

What is the time period during which blood cell formation occurs?

Third to fifth week Signup and view all the answers

What is the name of the membrane that forms from the primary yolk sac?

Heuser's membrane Signup and view all the answers

What is the result of the second wave of cell migration?

Formation of the definitive yolk sac Signup and view all the answers

What becomes the urachus ligament that connects the belly button to the bladder?

Remnants of Allantois Signup and view all the answers

What is the function of the placenta?

To provide nutrition, oxygen, and hormones to the fetus Signup and view all the answers

What is the term for the remaining intervening parts of the decidua?

Decidua parietalis Signup and view all the answers

What is formed when the amnion and smooth chorion fuse?

Amniochorionic membrane Signup and view all the answers

What is the most common event leading to premature labor?

Preterm rupture of the amniochorionic membrane Signup and view all the answers

What are the two components of the placenta?

Fetal part and maternal part Signup and view all the answers

What happens when the amniochorionic membrane ruptures?

The amniotic fluid flows through the cervix and vagina Signup and view all the answers

How many layers does the placental membrane initially consist of?

Four Signup and view all the answers

What are the primary components of the chorion?

Extraembryonic somatic mesoderm and trophoblasts Signup and view all the answers

What is the primary function of the decidual reaction?

To provide an immunologically privileged site for the conceptus Signup and view all the answers

At what stage is the conceptus completely embedded in the endometrium?

10 days Signup and view all the answers

What is the significance of the lacunae in the formation of the uteroplacental circulation?

They represent the beginning of the primordial uteroplacental circulation Signup and view all the answers

What is the origin of the amnion?

Epiblast and extraembryonic mesoderm Signup and view all the answers

What is the characteristic of the decidual cells?

They are larger due to the accumulation of glycogen and lipid Signup and view all the answers

What is the significance of the primary chorionic villi?

They mark the beginning of the second week of development Signup and view all the answers

What is the origin of the yolk sac?

Hypoblast and extraembryonic mesoderm Signup and view all the answers

What is the primary function of the placenta regarding gases and nutrients?

Simple diffusion and pinocytosis Signup and view all the answers

Which type of immunoglobulin is transferred across the placenta to provide fetal immunity?

Immunoglobulin G Signup and view all the answers

Which viruses can pass through the placental membrane and cause fetal infection?

Cytomegalovirus, rubella, and coxsackieviruses Signup and view all the answers

What is the primary function of human chorionic gonadotropin (hCG)?

Maintaining the corpus luteum during pregnancy Signup and view all the answers

What is the primary method of waste excretion in the placenta?

Urea, uric acid, and conjugated bilirubin excretion Signup and view all the answers

What is the function of human chorionic somatomammotropin (also known as placental lactogen)?

Stimulating lactation in the mother Signup and view all the answers

Which disease does the fetus not acquire immunity to from maternal antibodies?

Pertussis (whooping cough) Signup and view all the answers

What is the primary function of the endothelium of the fetal capillaries?

Gas and nutrient exchange Signup and view all the answers

What is the primary function of amniotic fluid during fetal development?

To control embryonic body temperature Signup and view all the answers

What is the characteristic of dizygotic twins?

They have two amnions and two chorions Signup and view all the answers

What is the significance of the placenta during pregnancy?

It separates from the uterus after birth Signup and view all the answers

How do monozygotic twins develop?

From the fertilization of one oocyte Signup and view all the answers

What is the role of amniotic fluid in fetal lung development?

It permits fetal lung development Signup and view all the answers

What is the significance of human chorionic corticotropin in pregnancy?

It prevents adherence of the amnion to the embryo Signup and view all the answers

What happens during the process of parturition?

Dilation, expulsion, and placental separation occur Signup and view all the answers

What is the characteristic of monozygotic twins?

They are genetically identical Signup and view all the answers

Study Notes

Embryonic Development

By the end of the third week, a primordial uteroplacental circulation has developed.
The embryo, amniotic sac, and umbilical vesicle are suspended in the chorionic cavity by the connecting stalk.

Chorionic Villi Development

Secondary chorionic villi develop into tertiary chorionic villi.
The process is illustrated in figures A, B, C, and D, which show the development of the chorionic villi from 14 to 21 days.

Yolk Sac and Allantois

The yolk sac is formed from the hypoblast and is surrounded by the connecting stalk.
The allantois is an endodermal outpocketing of the yolk sac that invades the connecting stalk.
Blood cell formation occurs in the allantois during the third to fifth weeks.
The allantois eventually becomes the umbilical vessels and the urachus ligament.

Placenta Development

The placenta is a fetomaternal organ with two components: a fetal part from the chorionic sac and a maternal part from the endometrium.
The placenta functions in protection, nutrition, respiration, excretion of waste products, and hormone production.

Amniotic Sac and Membrane

The amniotic sac enlarges faster than the chorionic sac, causing the amnion and smooth chorion to fuse and form the amniochorionic membrane.
The amniochorionic membrane ruptures during labor, and preterm rupture can lead to premature labor.

Placental Circulation

The placental membrane consists of four layers: syncytiotrophoblast, cytotrophoblast, placenta, and fetal membranes.
There are two types of circulation: fetoplacental circulation and maternal-placental circulation.

Decidua Development

The decidua is the mucous membrane lining the uterus, and it undergoes a transformation (decidual reaction) due to cyclic adenosine monophosphate and progesterone signaling.
The decidual reaction provides an immunologically privileged site for the conceptus.

Placental Functions

The placenta functions in metabolism, transport of gases and nutrients, and excretion of waste products.
The placenta also produces hormones, such as human chorionic gonadotropin (hCG), human chorionic somatomammotropin (placental lactogen), human chorionic thyrotropin, and human chorionic corticotropin.

Amniotic Fluid Significance

Amniotic fluid permits uniform external growth of the embryo, acts as a barrier to infection, and prevents adherence of the amnion to the embryo.
It also cushions the embryo against injuries, controls embryonic body temperature, and enables fetal lung development.

Parturition

The process of childbirth includes dilation, expulsion, and placental separation.

Multiple Pregnancies

Dizygotic (DZ) twins develop from two zygotes and have two amnions and two chorions, while monozygotic (MZ) twins develop from one zygote and are genetically identical.

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Description

Learn about the structure and function of the placenta, umbilical cord, and fetal membranes. Understand the formation of amniotic cavity, embryonic disc, and umbilical vesicle. Quiz covers topics like chorion, amnion, yolk sac, and allantois.