The Developing Human Clinically Oriented Embryology 9th Edition By Keith L. Moore – Test Bank

The Developing Human Clinically Oriented Embryology 9th Edition By Keith L. Moore – Test Bank

Moore: The Developing Human, 9th Edition

Chapter 06: Placenta and Fetal Membranes

Test Bank

MULTIPLE CHOICE

Directions: Each group of questions below consists of a numbered list of descriptive words or phrases accompanied by a diagram with certain parts indicated by letters or by a list of lettered headings. For each numbered word or phrase, select the lettered part or heading that matches it correctly and then insert the letter in the space to the right of the appropriate number. Sometimes more than one numbered word or phrase may be correctly matched to the same lettered part or heading.

________ Decidua capsularis

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: B

The decidua capsularis is the part of the decidua (gravid endometrium) that encapsulates the luminal surface of the implanted conceptus. At the stage shown, it is fused with the smooth chorion (chorion laeve). Together the amnion and chorion form the amniochorionic membrane.

________ Ensheaths umbilical cord

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: D

As the amniotic sac enlarges, it obliterates the chorionic cavity and ensheaths the umbilical cord. The amnion becomes the epithelial covering of the cord.

________ Smooth chorion

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: C

The smooth chorion is continuous with the chorionic plate (“roof”) of the placenta. From the third to eighth weeks, the chorionic sac is covered by villi. The villi degenerate as the amniotic sac enlarges and presses the chorion against the decidua capsularis. This reduces the blood supply to the villi and results in their degeneration.

________ Decidua parietalis

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: A

The decidua parietalis refers to the endometrium lining parts of the uterus not directly involved with the conceptus (i.e., endometrium not designated as decidua capsularis or decidua basalis).

________ Maternal part of placenta

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: E

The decidua basalis forms the maternal part of the placenta. The fetal part is formed by the villous chorion (chorion frondosum). Together they form a unique fetomaternal organ, the placenta, the basic function of which is to bring the maternal and fetal circulations into proximity to permit effective exchange of materials.

6. ________ Occurs only in monozygotic twins

A.

Separate placentas and membranes

B.

Fibrinoid material

C.

Amniochorionic membrane

D.

Monochorionic placenta

E.

Syncytial knot

ANS: D

A monochorionic twin placenta, associated with twins in separate amniotic sacs, occurs only with monozygotic twins; thus, this type of placenta is diagnostic of monozygotic twinning. The twins often have a common fetal-placental circulation.

7. ________ Nuclear aggregation

A.

Separate placentas and membranes

B.

Fibrinoid material

C.

Amniochorionic membrane

D.

Monochorionic placenta

E.

Syncytial knot

ANS: E

At some sites, the syncytiotrophoblast of the placental membrane in mature placentas shows protuberances or sprouts of cytoplasm that contain aggregations of syncytiotrophoblastic nuclei—syncytial knots. Some knots break off and float in the intervillous space. They may pass into the maternal circulation through the uterine veins and lodge in the capillaries of the lungs. This occurrence is not usually considered to be of clinical significance because these nuclear masses are believed to degenerate and disappear.

8. ________ Extends into cervical canal during labor

A.

Separate placentas and membranes

B.

Fibrinoid material

C.

Amniochorionic membrane

D.

Monochorionic placenta

E.

Syncytial knot

ANS: C

The chorion, with which the amnion is fused, extends into the cervical canal during the first stage of labor and helps to dilate the cervix. When the fused layers of amnion and chorion (amniochorionic membrane) rupture, the amniotic fluid escapes through the cervix and vagina.

9. ________ Forms on the surfaces of chorionic villi

A.

Separate placentas and membranes

B.

Fibrinoid material

C.

Amniochorionic membrane

D.

Monochorionic placenta

E.

Syncytial knot

ANS: B

Fibrinoid is an eosinophilic, homogeneous substance that forms on the surfaces of chorionic villi and reduces the area of tissues through which exchange of materials between the maternal and fetal circulations may take place. It consists of fibrin and other unidentified substances.

________ Fetal capillary

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: E

The fetal capillaries, embedded in the connective tissue of the chorionic villi, are part of an arterio-capillary–venous system that carries the fetal blood. As pregnancy advances, the capillaries increase in size and their walls eventually come into intimate relation with the syncytiotrophoblast. The endothelium of the capillary is separated from the syncytiotrophoblast by only an extremely delicate network of reticular fibers.

________ Placental membrane

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: A

The placental membrane may be defined as the fetal tissues that are interposed between the fetal and placental circulations. The structure and thickness of the membrane vary at different stages of pregnancy. The placental membrane becomes extremely thin as pregnancy advances, and its permeability increases. The thickness of the membrane is also affected by the extent of distention of the capillaries in the villus.

________ Syncytial knot

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: D

Syncytial knots consist of aggregations of nuclei in protuberances of cytoplasm of the syncytiotrophoblast. They form at intervals along a villus; occasionally they break off and enter the maternal circulation. Apparently these nuclear aggregations have a short life in the maternal blood.

________ Fibrinoid material

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: B

Fibrinoid material develops as a homogeneous layer at various places on the maternal aspect of the villi. Because it is at the fetomaternal junction of tissues, fibrinoid is believed to be important in preventing rejection of the fetus by the mother. Composed of fibrin and other unidentified substances, fibrinoid decreases the permeability of the placental membrane for exchange of material between the fetal and maternal blood streams.

14. ________ Fetal surface of placenta

A.

Anchoring villi

B.

Cytotrophoblast

C.

Amnion

D.

Battledore placenta

E.

Cotyledons

ANS: C

The amnion adheres to the smooth fetal surface of the placenta and is continuous with the epithelial membrane covering the umbilical cord. The umbilical vessels radiate over the fetal surface of the placenta deep to the amnion.

15. ________ Features of maternal surface of placenta

A.

Anchoring villi

B.

Cytotrophoblast

C.

Amnion

D.

Battledore placenta

E.

Cotyledons

ANS: E

Cotyledons are characteristic features of the maternal surface of the placenta. The placental septa divide the maternal surface into 15 to 30 cotyledons, which gives the expelled placenta a cobblestone appearance. During examination of the placenta after delivery, special attention should be given to determining whether the cotyledons are all present and intact. If they are not all recognizable and complete, placental tissue may still be in the uterus and must be removed.

16. ________ Marginal attachment of umbilical cord

A.

Anchoring villi

B.

Cytotrophoblast

C.

Amnion

D.

Battledore placenta

E.

Cotyledons

ANS: D

When the umbilical cord and vessels are attached to the margin of the placenta, it is called a battledore placenta because of its resemblance to the bat used in the medieval game of battledore and shuttlecock. This is a common variation of placental form. Battledore placenta (marginal insertion of cord) has some clinical significance because slight bleeding occasionally occurs. It has also been shown that many patients with battledore placentas have premature labor.

17. ________ Forms part of early placental membrane

A.

Anchoring villi

B.

Cytotrophoblast

C.

Amnion

D.

Battledore placenta

E.

Cotyledons

ANS: B

The cytotrophoblast consists of large, pale cells with relatively large nuclei. Their cytoplasm contains vacuoles and some glycogen. The placenta synthesizes glycogen early in pregnancy, and its declining ability to perform this activity later in pregnancy may be related to the assumption of this function by the fetal liver and to the retrogression of the cytotrophoblast.

18. ________ Places of attachment to decidua basalis

A.

Anchoring villi

B.

Cytotrophoblast

C.

Amnion

D.

Battledore placenta

E.

Cotyledons

ANS: A

The main means of attachment of the conceptus to the uterus is by anchoring stem villi that pass from the chorionic plate to the decidua basalis. Columns of cytotrophoblastic cells extend through the syncytiotrophoblast at the tips of these villi and cover the maternal tissue. Soon cytotrophoblastic cells from adjacent villi join to form a cytotrophoblastic shell around the conceptus. This shell is also attached to the decidua basalis.

________ Branch villus

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: C

The main stem villi give rise to numerous branch villi that are bathed by maternal blood in the intervillous spaces. Exchange of gases, nutrients, and waste products between mother and fetus occurs between maternal blood in the intervillous space and fetal vessels in the branch villi.

________ Fetal capillaries

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: A

Fetal capillaries are tiny blood vessels in the branch villi that transport poorly oxygenated blood and waste products from the fetus and carry well-oxygenated blood and nutrients to the fetus. Exchange of material occurs between the blood in the fetal capillaries and in the intervillous space.

________ Syncytiotrophoblast

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: D

Cells from the cytotrophoblast proliferate rapidly, migrate into the syncytiotrophoblast, and lose their cell membrane. During implantation, the highly invasive syncytiotrophoblast invades the endometrial connective tissue and by the end of the second week the blastocyst is fully implanted in the endometrium.

________ Umbilical arteries

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: E

There are normally two umbilical arteries and one umbilical vein in the umbilical cord. The presence of only one umbilical artery may be associated with congenital anomalies in the fetus, often involving the heart and blood vessels. The umbilical arteries transport poorly oxygenated blood and waste products from the fetus to the placenta.

________ Arteriocapillary venous network

a.

A

b.

B

c.

C

d.

D

e.

E

ANS: B

An extensive arterio-capillary venous network is formed in the numerous villi from branches of the umbilical arteries and veins. Only the thin placental membrane separates fetal blood in the arterio-capillary venous plexus from the maternal blood in the intervillous space.